Jython

Thanks for your reply, I also made it a bookmark.
I went to the site and track down enableEvents() and
found that it was a method of Component. So I imported
java.awt.Component and then qualified enableEvents with
java.awt.Component. I get an error tell me that enableEvents()
is not an attribute of Component. So I checked my spelling
ant thing look ok. Can someone tell me what I doing wrong?
Thanks.
Wayne

"O'Brien-Strain, Eamonn" wrote:

> Personally I keep a bookmark on my desktop to the Java API reference at ...
>
>   http://java.sun.com/j2se/1.3/docs/api/overview-summary.html
>
> ... to which I frequently go to answer questions like this.
>
> In this case if you go to that page, click on "Index" at the top, click on
> "E", and scroll down -- you will see that there are "enableEvents" methods
> in two different classes.  Following the links to those two methods should
> help you figure out which one to use and what to pass as its arguments.
>
> __
> Eamonn
>
> -----Original Message-----
> From: cindy [mailto:infotechsys@...]
> [...]For instance,
> one of the statements in  an example reads like this,
> "enableEvents(AWTEvent.WINDOW_EVENT_MASK)".
> How would I go about determining which class/package to
> import and  how would I know what qualifiers to us for
> "enableEvents"?
> [...]
>
> _______________________________________________
> Jython-users mailing list
> Jython-users@...
> http://lists.sourceforge.net/lists/listinfo/jython-users

In Java everything is coded as part of a class.  As an example class
take this :

public class Foo
{
    public void func1( )
    {
        System.out.println( "Hello from func1" ) ;
    }

    static public void func2( )
    {
        System.out.println( "Hello from func1" ) ;
    }
}


This class contains 2 methods, func1 and func2.  func2 is declared as
static.  That means that the following (Java) code is legal :

Foo.func2() ;
Foo f = new Foo() ;
f.func2()
f.func1()

while the following is illegal :

Foo.func1() ;


The reason is that only "static" members belong to the _class_, all
others belong to _instances_ of the class.  In order to call the
method you must first have an instance of java.awt.Component and call
it on the instance.  Note also that it will only affect the instance
you call it on, not all instances of the class.

Python's classes don't have any "static" members because Python
doesn't force you to write everything inside of a class construct.
Instead put "static" functions in the module.  (If you are trying to
use a mix of Java and Python then the java code is unable to access
module level stuff unless it goes through the interpreter directly)

-D

On Wed, Mar 28, 2001 at 06:37:53PM -0500, cindy wrote:
| Thanks for your reply, I also made it a bookmark.
| I went to the site and track down enableEvents() and
| found that it was a method of Component. So I imported
| java.awt.Component and then qualified enableEvents with
| java.awt.Component. I get an error tell me that enableEvents()
| is not an attribute of Component. So I checked my spelling
| ant thing look ok. Can someone tell me what I doing wrong?
| Thanks.
| Wayne

Hi again,
If I may reiterate what you said to help me understand.If module Foo.py
has the statement "enableEvents(AWTEvent.WINDOW_EVENT_MASK)" and
module Bar.py does a composite on module Foo.py, then I have to pass
the instance name to module Foo.py to qualify the method enableEvents()
thus
"instanceName.enableEvents(). If this is so how do I pass the instance
name
in the creation of the instance?  If I have the statement in Bar.py
"self.myInstance = Foo().
Thanks.
Wayne


D-Man wrote:

> In Java everything is coded as part of a class.  As an example class
> take this :
>
> public class Foo
> {
>     public void func1( )
>     {
>         System.out.println( "Hello from func1" ) ;
>     }
>
>     static public void func2( )
>     {
>         System.out.println( "Hello from func1" ) ;
>     }
> }
>
> This class contains 2 methods, func1 and func2.  func2 is declared as
> static.  That means that the following (Java) code is legal :
>
> Foo.func2() ;
> Foo f = new Foo() ;
> f.func2()
> f.func1()
>
> while the following is illegal :
>
> Foo.func1() ;
>
> The reason is that only "static" members belong to the _class_, all
> others belong to _instances_ of the class.  In order to call the
> method you must first have an instance of java.awt.Component and call
> it on the instance.  Note also that it will only affect the instance
> you call it on, not all instances of the class.
>
> Python's classes don't have any "static" members because Python
> doesn't force you to write everything inside of a class construct.
> Instead put "static" functions in the module.  (If you are trying to
> use a mix of Java and Python then the java code is unable to access
> module level stuff unless it goes through the interpreter directly)
>
> -D

On Tue, Apr 03, 2001 at 10:21:29PM -0400, cindy wrote:
| Hi again,
| If I may reiterate what you said to help me understand.If module Foo.py
| has the statement "enableEvents(AWTEvent.WINDOW_EVENT_MASK)" and
| module Bar.py does a composite on module Foo.py, then I have to pass
| the instance name to module Foo.py to qualify the method enableEvents()
| thus
| "instanceName.enableEvents(). If this is so how do I pass the instance
| name
| in the creation of the instance?  If I have the statement in Bar.py
| "self.myInstance = Foo().
| Thanks.
| Wayne

I'm not sure if I completely understand your goals and your design.
Also, I think you mixed up modules and classes in your description
above.

I just read the docs for java.awt.Component.enableEvents( long ) and
noticed the following :

        This method only needs to be invoked by subclasses of
        Component which desire to have the specified event types
        delivered to processEvent regardless of whether or not a
        listener is registered.

Are you trying to create a subclass of Component that needs to receive
events even if no listeners are registered?  Could you post some code
showing what it is you are currently trying to do?

If you have a class Foo that inherits from component, you could do
something like the following, but I'm not sure if it is what you are
looking for.

---- in some .py file ------
import java

class Foo( java.awt.Component ) :
    def __init__( self ) :
        # note that 'self' now refers the the instance of 'Foo' and
        # therefore is-a instance of 'Component'
        self.enableEvents( java.awt.AWTEvent.WINDOW_EVENT_MASK ) 

    def processEvent( self , event ) :
        """ 
        @sig protected void processEvent( java.awt.AWTEvent event )
        
        this method must be defined or you will end up with errors
        when the event dispatcher tries to call it
        """

        print "Found an event!"
        print event

HTH,
-D

The code is not exactly the same as the book.
In Sketcher.py I have-

import java
from SketchFrame import *

class Sketcher:
      def __init__(self):
            true = 1
            title = 'sketcher'
            self.aSketchFrame = SketchFrame(title)

            self.theKit = self.aSkechFrame.getToolkit()
            self.wndSize = setBounds(self.wndSize.width/4,
                                                     self.wndSize.height/4,
                                                     self.wndSize.width/2,
                                                     self.wndSize.height/2)
             self.aSketchFrame.setVisible(true)
if __name__ == '__maine__'
   aSketcher = Sketcher()

Here is the code for SketchFrame.

from javax import swing
import java
import java.awt.event

class SketchFrame(swing.JFrame):
        def __init__(self, title):
              // some code left out - it build a menu bar
             enableEvents(java.awt.event.WindowEvent.WINDOW_EVENT_MASK)

        def processWindowEvent(self, event):
             if (event.getID() == java.awt.event.WindowEvent.WINDOW.CLOSE):
                  java.awt.event.dispose()         # not sure if this works
yet. I haven't gotten to this point.
                  java.awt.System.exit(0)
             swing.JFrame.super.processWindowEvent(event)





> On Tue, Apr 03, 2001 at 10:21:29PM -0400, cindy wrote:
> | Hi again,
> | If I may reiterate what you said to help me understand.If module Foo.py
> | has the statement "enableEvents(AWTEvent.WINDOW_EVENT_MASK)" and
> | module Bar.py does a composite on module Foo.py, then I have to pass
> | the instance name to module Foo.py to qualify the method enableEvents()
> | thus
> | "instanceName.enableEvents(). If this is so how do I pass the instance
> | name
> | in the creation of the instance?  If I have the statement in Bar.py
> | "self.myInstance = Foo().
> | Thanks.
> | Wayne
>
> I'm not sure if I completely understand your goals and your design.
> Also, I think you mixed up modules and classes in your description
> above.
>
> I just read the docs for java.awt.Component.enableEvents( long ) and
> noticed the following :
>
>         This method only needs to be invoked by subclasses of
>         Component which desire to have the specified event types
>         delivered to processEvent regardless of whether or not a
>         listener is registered.
>
> Are you trying to create a subclass of Component that needs to receive
> events even if no listeners are registered?  Could you post some code
> showing what it is you are currently trying to do?
>
> If you have a class Foo that inherits from component, you could do
> something like the following, but I'm not sure if it is what you are
> looking for.
>
> ---- in some .py file ------
> import java
>
> class Foo( java.awt.Component ) :
>     def __init__( self ) :
>         # note that 'self' now refers the the instance of 'Foo' and
>         # therefore is-a instance of 'Component'
>         self.enableEvents( java.awt.AWTEvent.WINDOW_EVENT_MASK )
>
>     def processEvent( self , event ) :
>         """
>         @sig protected void processEvent( java.awt.AWTEvent event )
>
>         this method must be defined or you will end up with errors
>         when the event dispatcher tries to call it
>         """
>
>         print "Found an event!"
>         print event
>
> HTH,
> -D
>
> _______________________________________________
> Jython-users mailing list
> Jython-users@...
> http://lists.sourceforge.net/lists/listinfo/jython-users

The change you need to make is shown below.

In Java, C++ and Eiffel, member functions can be called on the current
object without specifying the object.  In Python, however, the object
(usually named 'self' but called 'this' in Java and C++, 'current' in
Eiffel) must be explicitly named.

The following 2 runme functions in java code are equivalent, and serve the
same purpose as the python function following it.

public class Foo
{
    public void func( )
    {
        System.out.println( "func was called" ) ;
    }

    public void runme( )
    {
        func() ;
    }

    public void runme2( )
    {
        this.func() ;
    }
}


class Foo :
    def func( self ) :
        print "func was called"

    def runme( self ) :
        func() # this won't work as you've seen in your code

    def runme2( self ) :
        self.func() # this will work as expected


Conclusion :
    As you read through sample Java code, prepend "this" (for java) or
    "self" (for python) to each method call on the current object.

    IMO explicit is better than implicit so I use 'this' in all my
    Java code where it won't be illegal (ie nested event handler
    classes)

HTH,
-D


On Wed, Apr 04, 2001 at 02:14:38AM -0400, cindy wrote:
| Here is the code for SketchFrame.
| 
| from javax import swing
| import java
| import java.awt.event
| 
| class SketchFrame(swing.JFrame):
|         def __init__(self, title):
|               // some code left out - it build a menu bar
|              enableEvents(java.awt.event.WindowEvent.WINDOW_EVENT_MASK)
               self.enableEvents(java.awt.event.WindowEvent.WINDOW_EVENT_MASK)
               ^^^^^
| 
|         def processWindowEvent(self, event):
|              if (event.getID() == java.awt.event.WindowEvent.WINDOW.CLOSE):
|                   java.awt.event.dispose()         # not sure if this works
| yet. I haven't gotten to this point.
|                   java.awt.System.exit(0)
|              swing.JFrame.super.processWindowEvent(event)
|

On Wed, Apr 04, 2001 at 04:24:21AM -0400, cindy wrote:
| >
| > class Foo :
| >     def func( self ) :
| >         print "func was called"
| >
| >     def runme( self ) :
| >         func() # this won't work as you've seen in your code
| >
| >     def runme2( self ) :
| >         self.func() # this will work as expected
| 
| This I undertstand, but I don't see how "self" can be used on a
| class that is inherited and that is abstract, such as Component.
| When I do "self.enableEvents(java.awt.event.WindowEvent.WINDOW_EVENT_MASK)"
| I get an AttribueError on enableEvents, which I would expect.
| Thanks.
| Wayne

I see the problem now.  The problem lies in enableEvents being
protected, and Jython's name mangling of it.  First I'll explain a
little bit about inheritance, but I'll keep everything 'public' (like
in Python).

If I make a class,

class P :
    def p_func( self ) :
        pass

and a child class

class C( P ) :
    pass

then try this

child_object = C()
dir( child_object )

I will see p_func as a member of child_object.  This is because it is
inherited.  If the parent class is 'abstract' that only means you
can't use 'new' on it.  It has no effect on inheritance.


So with that knowledge, a class that inherits from java.awt.Component
should have a member 'enableEvents'.  The problem here is it is
'protected'.  In Java that means that only subclasses and classes in
the same package can access the function.  Other classes can't call
it.  Apparently jython does some name mangling on protected members by
prefixing "super__" to it.  (I certainly hope it is mentioned in the
documentation, but like a <ahem> genius^H^H^H^H^H^Hidiot I haven't
checked ;-))

The following code worked for me :


from java.awt import Component , AWTEvent

class C( Component ) :
    def __init__( self ) :
            self.super__enableEvents( AWTEvent.WINDOW_EVENT_MASK )


I hope this clears up some confusion!  As always ask again if you have
any more problems.

-D

D-Man wrote:

> class Foo :
>     def func( self ) :
>         print "func was called"
>
>     def runme( self ) :
>         func() # this won't work as you've seen in your code
>
>     def runme2( self ) :
>         self.func() # this will work as expected

This I undertstand, but I don't see how "self" can be used on a
class that is inherited and that is abstract, such as Component.
When I do "self.enableEvents(java.awt.event.WindowEvent.WINDOW_EVENT_MASK)"
I get an AttribueError on enableEvents, which I would expect.
Thanks.
Wayne

Wayne,

You can call "self" on an abstract object, you just can't instantiate an
abstract object.  An abstract object has all the state and behaviour of
a normal, concrete object it just can't live on it's own.  It needs to
be subclassed and made abstract.  For a good example of this, check out
the java.io.* packages, in particular, either the Reader/Writer or
InputStream/OutputStream classes and their subclasses.  Look at
FileReader and you'll notice it is an implementation of the abstract
Reader class, all FileReader provides to Reader is how to get the
initial data, in this case a File.

Python really doesn't have the notion of an abstract class, in general
an abstract class or interface is implemented by defining a bunch of
methods which raise Exceptions.

So in your case, you can't instantiate a Component, but you can get
subclasses of Component and then call methods on them.

hope this helps,

brian


-----Original Message-----
From: jython-users-admin@...
[mailto:jython-users-admin@... Behalf Of cindy
Sent: Wednesday, April 04, 2001 3:48 AM
To: D-Man
Cc: Jython-users@...
Subject: Re: [Jython-users] A big problem for me!


D-Man wrote:

> class Foo :
>     def func( self ) :
>         print "func was called"
>
>     def runme( self ) :
>         func() # this won't work as you've seen in your code
>
>     def runme2( self ) :
>         self.func() # this will work as expected

This I undertstand, but I don't see how "self" can be used on a
class that is inherited and that is abstract, such as Component.
When I do
"self.enableEvents(java.awt.event.WindowEvent.WINDOW_EVENT_MASK)"
I get an AttribueError on enableEvents, which I would expect.
Thanks.
Wayne


_______________________________________________
Jython-users mailing list
Jython-users@...
http://lists.sourceforge.net/lists/listinfo/jython-users

Thanks for your time! I went the jython site and found the documentation.
the documentation has more meaning for me now, now that I had the
problem.
Wayne

> prefixing "super__" to it.  (I certainly hope it is mentioned in the
> documentation, but like a <ahem> genius^H^H^H^H^H^Hidiot I haven't
> checked ;-))
>

[D-Man]

>So with that knowledge, a class that inherits from java.awt.Component
>should have a member 'enableEvents'.  The problem here is it is
>'protected'.  In Java that means that only subclasses and classes in
>the same package can access the function.  Other classes can't call
>it.  Apparently jython does some name mangling on protected members by
>prefixing "super__" to it.  (I certainly hope it is mentioned in the
>documentation, but like a <ahem> genius^H^H^H^H^H^Hidiot I haven't
>checked ;-))

It is mentioned in the section "Calling Methods in Your Superclass"

   http://www.jython.org/docs/subclassing.html

regards,
finn

( I don't mean to be condescending at all, but I want to make sure this
  doesn't cause some confusion.  )

An object can't be abstract, only classes can.  Objects also can't be
subclassed, only classes can be subclassed.  Also, 'self' hasn't been
"called", it was only used to access an attribute.  

(calling it would look like

self() or self( <some arguments here> ) and would require defining the
function  __call_

)



I think Brian knows this, but mixed a couple of terms around in
writing this.  Other than the wording issues, everything Brian said is
accurate and (hopefully) helpful to you.

-D


On Tue, Apr 03, 2001 at 03:05:05PM -0500, Brian Zimmer wrote:
| 
|    Wayne,
|    
|    You can call "self" on an abstract object, you just can't instantiate
|    an abstract object.  An abstract object has all the state and
|    behaviour of a normal, concrete object it just can't live on it's
|    own.  It needs to be subclassed and made abstract.  For a good example
|    of this, check out the java.io.* packages, in particular, either the
|    Reader/Writer or InputStream/OutputStream classes and their
|    subclasses.  Look at FileReader and you'll notice it is an
|    implementation of the abstract Reader class, all FileReader provides
|    to Reader is how to get the initial data, in this case a File.
|    
|    Python really doesn't have the notion of an abstract class, in general
|    an abstract class or interface is implemented by defining a bunch of
|    methods which raise Exceptions.
|    
|    So in your case, you can't instantiate a Component, but you can get
|    subclasses of Component and then call methods on them.
|    
|    hope this helps,
|    
|    brian

> The following code worked for me :
>
> from java.awt import Component , AWTEvent
>
> class C( Component ) :
>     def __init__( self ) :
>             self.super__enableEvents( AWTEvent.WINDOW_EVENT_MASK )

Ok. So this means that ever time I wanted to use this method, "enableEvents()" I
have to
inherit Component. But lets say that I would like to extend some other
component, like
JFrame. Then if I want to use enableEvents() in the same class that I want to
extend
JFrame, I would have to inherit Componet and do a composit on JFrame. Is this
correct?
Thanks.
Wayne

( I'm perfectly comfortable being corrected when I'm wrong. )

Point well made, I'll be more careful next time ;)

D-Man is indeed correct and offered a better explanation of object vs.
class than I did.

Sorry for any confusion and thanks for the clarification.

brian


-----Original Message-----
From: jython-users-admin@...
[mailto:jython-users-admin@... Behalf Of D-Man
Sent: Wednesday, April 04, 2001 9:30 AM
To: Jython-users@...
Subject: Re: [Jython-users] A big problem for me!



( I don't mean to be condescending at all, but I want to make sure this
  doesn't cause some confusion.  )

An object can't be abstract, only classes can.  Objects also can't be
subclassed, only classes can be subclassed.  Also, 'self' hasn't been
"called", it was only used to access an attribute. =20

(calling it would look like

self() or self( <some arguments here> ) and would require defining the
function  __call_

)



I think Brian knows this, but mixed a couple of terms around in
writing this.  Other than the wording issues, everything Brian said is
accurate and (hopefully) helpful to you.

-D


On Tue, Apr 03, 2001 at 03:05:05PM -0500, Brian Zimmer wrote:
|=20
|    Wayne,
|   =20
|    You can call "self" on an abstract object, you just can't
instantiate
|    an abstract object.  An abstract object has all the state and
|    behaviour of a normal, concrete object it just can't live on it's
|    own.  It needs to be subclassed and made abstract.  For a good
example
|    of this, check out the java.io.* packages, in particular, either
the
|    Reader/Writer or InputStream/OutputStream classes and their
|    subclasses.  Look at FileReader and you'll notice it is an
|    implementation of the abstract Reader class, all FileReader
provides
|    to Reader is how to get the initial data, in this case a File.
|   =20
|    Python really doesn't have the notion of an abstract class, in
general
|    an abstract class or interface is implemented by defining a bunch
of
|    methods which raise Exceptions.
|   =20
|    So in your case, you can't instantiate a Component, but you can get
|    subclasses of Component and then call methods on them.
|   =20
|    hope this helps,
|   =20
|    brian

_______________________________________________
Jython-users mailing list
Jython-users@...
http://lists.sourceforge.net/lists/listinfo/jython-users

On Wed, Apr 04, 2001 at 11:01:51PM -0400, cindy wrote:
| > The following code worked for me :
| >
| > from java.awt import Component , AWTEvent
| >
| > class C( Component ) :
| >     def __init__( self ) :
| >             self.super__enableEvents( AWTEvent.WINDOW_EVENT_MASK )
| 
| Ok. So this means that ever time I wanted to use this method, "enableEvents()" I
| have to
| inherit Component. But lets say that I would like to extend some other
| component, like
| JFrame. Then if I want to use enableEvents() in the same class that I want to
| extend
| JFrame, I would have to inherit Componet and do a composit on JFrame. Is this
| correct?

Not quite.  If you look at the top of the documenation for JFrame you
will see

Class JFrame

java.lang.Object 
  |
  +--java.awt.Component 
        |
        +--java.awt.Container 
              |
              +--java.awt.Window 
                    |
                    +--java.awt.Frame 
                          |
                          +--javax.swing.JFrame 

JFrame already inherits from java.awt.Component.  The term "is-a" is
often used with inheritance.  A JFrame object is-a Component object.
If you inherit from JFrame, you are indirectly inheriting from
Component.

If you look farther down on the documentation page you will see a list
of  "Methods inherited from Frame" and "Methods inherited from Window"
and ... and "Methods inherited from Component".  Since the methods are
listed there, they exist in objects of the type "JFrame".

FYI, the documentation (for JDK1.2.2) is at

http://java.sun.com/products/jdk/1.2/docs/api/index.html

while the JFrame page is

http://java.sun.com/products/jdk/1.2/docs/api/javax/swing/JFrame.html


-D

I thought I couldn't access the method enableEvents() by inheriting JFrame.
The reason being is that this method is protected. I concluded that I have to
inherit Component to get access to this mrthod. Therefore, the tree structure
below and inheritance from JFrame wouldn't work for the method enableEvents().
Is this correct?
Wayne


D-Man wrote:

> On Wed, Apr 04, 2001 at 11:01:51PM -0400, cindy wrote:
> | > The following code worked for me :
> | >
> | > from java.awt import Component , AWTEvent
> | >
> | > class C( Component ) :
> | >     def __init__( self ) :
> | >             self.super__enableEvents( AWTEvent.WINDOW_EVENT_MASK )
> |
> | Ok. So this means that ever time I wanted to use this method, "enableEvents()" I
> | have to
> | inherit Component. But lets say that I would like to extend some other
> | component, like
> | JFrame. Then if I want to use enableEvents() in the same class that I want to
> | extend
> | JFrame, I would have to inherit Componet and do a composit on JFrame. Is this
> | correct?
>
> Not quite.  If you look at the top of the documenation for JFrame you
> will see
>
> Class JFrame
>
> java.lang.Object
>   |
>   +--java.awt.Component
>         |
>         +--java.awt.Container
>               |
>               +--java.awt.Window
>                     |
>                     +--java.awt.Frame
>                           |
>                           +--javax.swing.JFrame
>
> JFrame already inherits from java.awt.Component.  The term "is-a" is
> often used with inheritance.  A JFrame object is-a Component object.
> If you inherit from JFrame, you are indirectly inheriting from
> Component.
>
> If you look farther down on the documentation page you will see a list
> of  "Methods inherited from Frame" and "Methods inherited from Window"
> and ... and "Methods inherited from Component".  Since the methods are
> listed there, they exist in objects of the type "JFrame".
>
> FYI, the documentation (for JDK1.2.2) is at
>
> http://java.sun.com/products/jdk/1.2/docs/api/index.html
>
> while the JFrame page is
>
> http://java.sun.com/products/jdk/1.2/docs/api/javax/swing/JFrame.html
>
> -D
>
> _______________________________________________
> Jython-users mailing list
> Jython-users@...
> http://lists.sourceforge.net/lists/listinfo/jython-users

Er, no.

In Java, protected methods are available to subclasses*.  Private and
"package" (unprefixed methods, eg void myMethod()) level methods and
attributes are not.

I'd read the Java Tutorial available on the Java website if you don't want
to buy a book.  If you do want to buy a book I'd recommend Java In A
Nutshell.

* They are also available within a package, but this is dodgy, I'd stay away
from it.

Adam Burke

> -----Original Message-----
> From:	cindy [SMTP:infotechsys@...]
> Sent:	Thursday, April 05, 2001 10:11 PM
> To:	D-Man
> Cc:	Jython-users@...
> Subject:	Re: [Jython-users] A big problem for me!
> 
> I thought I couldn't access the method enableEvents() by inheriting
> JFrame.
> The reason being is that this method is protected. I concluded that I have
> to
> inherit Component to get access to this mrthod. Therefore, the tree
> structure
> below and inheritance from JFrame wouldn't work for the method
> enableEvents().
> Is this correct?
> Wayne
> 
> 
> D-Man wrote:
> 
> > On Wed, Apr 04, 2001 at 11:01:51PM -0400, cindy wrote:
> > | > The following code worked for me :
> > | >
> > | > from java.awt import Component , AWTEvent
> > | >
> > | > class C( Component ) :
> > | >     def __init__( self ) :
> > | >             self.super__enableEvents( AWTEvent.WINDOW_EVENT_MASK )
> > |
> > | Ok. So this means that ever time I wanted to use this method,
> "enableEvents()" I
> > | have to
> > | inherit Component. But lets say that I would like to extend some other
> > | component, like
> > | JFrame. Then if I want to use enableEvents() in the same class that I
> want to
> > | extend
> > | JFrame, I would have to inherit Componet and do a composit on JFrame.
> Is this
> > | correct?
> >
> > Not quite.  If you look at the top of the documenation for JFrame you
> > will see
> >
> > Class JFrame
> >
> > java.lang.Object
> >   |
> >   +--java.awt.Component
> >         |
> >         +--java.awt.Container
> >               |
> >               +--java.awt.Window
> >                     |
> >                     +--java.awt.Frame
> >                           |
> >                           +--javax.swing.JFrame
> >
> > JFrame already inherits from java.awt.Component.  The term "is-a" is
> > often used with inheritance.  A JFrame object is-a Component object.
> > If you inherit from JFrame, you are indirectly inheriting from
> > Component.
> >
> > If you look farther down on the documentation page you will see a list
> > of  "Methods inherited from Frame" and "Methods inherited from Window"
> > and ... and "Methods inherited from Component".  Since the methods are
> > listed there, they exist in objects of the type "JFrame".
> >
> > FYI, the documentation (for JDK1.2.2) is at
> >
> > http://java.sun.com/products/jdk/1.2/docs/api/index.html
> >
> > while the JFrame page is
> >
> > http://java.sun.com/products/jdk/1.2/docs/api/javax/swing/JFrame.html
> >
> > -D
> >
> > _______________________________________________
> > Jython-users mailing list
> > Jython-users@...
> > http://lists.sourceforge.net/lists/listinfo/jython-users
> 
> 
> _______________________________________________
> Jython-users mailing list
> Jython-users@...
> http://lists.sourceforge.net/lists/listinfo/jython-users

Hi.

cindy wrote:
> 
> I thought I couldn't access the method enableEvents() by inheriting JFrame.
> The reason being is that this method is protected. I concluded that I have to
> inherit Component to get access to this mrthod. Therefore, the tree structure
> below and inheritance from JFrame wouldn't work for the method enableEvents().
> Is this correct?
> Wayne
> 
> D-Man wrote:

You seem quite confused.
You really need to go through some reference material about java,
asking about every bit of java/jython semantic here is painful
and not really efficient for you...

regards.

In the jython doc , under Calling Methods in your Superclass", I quote
"In Pyhton, if I want to call the foo method in my superclass, I use the
following
SuperClass.foo(self)
This works with the majority of methods, but protected methods can not
be called from subclasses in this way. Instead you have to use the
"self.super_foo()" call style."  I beleave the latter syntax is telling me
I have to use inheritance. Am I wrong?
Wayne
P.S.   I have several books in which I'm using to learn java. What I thought
I do to learn jython was rewite all the examples in the book in jython. This
is how my problen came about. My the way the book is, "Beiginning Java"
by Ivor Horton

Adam Burke wrote:

> Er, no.
>
> In Java, protected methods are available to subclasses*.  Private and
> "package" (unprefixed methods, eg void myMethod()) level methods and
> attributes are not.
>
> I'd read the Java Tutorial available on the Java website if you don't want
> to buy a book.  If you do want to buy a book I'd recommend Java In A
> Nutshell.
>
> * They are also available within a package, but this is dodgy, I'd stay away
> from it.
>
> Adam Burke
>
> > -----Original Message-----
> > From: cindy [SMTP:infotechsys@...]
> > Sent: Thursday, April 05, 2001 10:11 PM
> > To:   D-Man
> > Cc:   Jython-users@...
> > Subject:      Re: [Jython-users] A big problem for me!
> >
> > I thought I couldn't access the method enableEvents() by inheriting
> > JFrame.
> > The reason being is that this method is protected. I concluded that I have
> > to
> > inherit Component to get access to this mrthod. Therefore, the tree
> > structure
> > below and inheritance from JFrame wouldn't work for the method
> > enableEvents().
> > Is this correct?
> > Wayne
> >
> >
> > D-Man wrote:
> >
> > > On Wed, Apr 04, 2001 at 11:01:51PM -0400, cindy wrote:
> > > | > The following code worked for me :
> > > | >
> > > | > from java.awt import Component , AWTEvent
> > > | >
> > > | > class C( Component ) :
> > > | >     def __init__( self ) :
> > > | >             self.super__enableEvents( AWTEvent.WINDOW_EVENT_MASK )
> > > |
> > > | Ok. So this means that ever time I wanted to use this method,
> > "enableEvents()" I
> > > | have to
> > > | inherit Component. But lets say that I would like to extend some other
> > > | component, like
> > > | JFrame. Then if I want to use enableEvents() in the same class that I
> > want to
> > > | extend
> > > | JFrame, I would have to inherit Componet and do a composit on JFrame.
> > Is this
> > > | correct?
> > >
> > > Not quite.  If you look at the top of the documenation for JFrame you
> > > will see
> > >
> > > Class JFrame
> > >
> > > java.lang.Object
> > >   |
> > >   +--java.awt.Component
> > >         |
> > >         +--java.awt.Container
> > >               |
> > >               +--java.awt.Window
> > >                     |
> > >                     +--java.awt.Frame
> > >                           |
> > >                           +--javax.swing.JFrame
> > >
> > > JFrame already inherits from java.awt.Component.  The term "is-a" is
> > > often used with inheritance.  A JFrame object is-a Component object.
> > > If you inherit from JFrame, you are indirectly inheriting from
> > > Component.
> > >
> > > If you look farther down on the documentation page you will see a list
> > > of  "Methods inherited from Frame" and "Methods inherited from Window"
> > > and ... and "Methods inherited from Component".  Since the methods are
> > > listed there, they exist in objects of the type "JFrame".
> > >
> > > FYI, the documentation (for JDK1.2.2) is at
> > >
> > > http://java.sun.com/products/jdk/1.2/docs/api/index.html
> > >
> > > while the JFrame page is
> > >
> > > http://java.sun.com/products/jdk/1.2/docs/api/javax/swing/JFrame.html
> > >
> > > -D
> > >
> > > _______________________________________________
> > > Jython-users mailing list
> > > Jython-users@...
> > > http://lists.sourceforge.net/lists/listinfo/jython-users
> >
> >
> > _______________________________________________
> > Jython-users mailing list
> > Jython-users@...
> > http://lists.sourceforge.net/lists/listinfo/jython-users
>
> _______________________________________________
> Jython-users mailing list
> Jython-users@...
> http://lists.sourceforge.net/lists/listinfo/jython-users

Here's a clarifying example (I hope):

<A.java>
public class A {

 protected void prot1() {
   System.out.println("java prot1");
  
 }
 
 protected void prot2() {
   System.out.println("java prot2");
 }

 public static void invoke_prot2(A a) {
   a.prot2();
 }


}
</A.java>

<ex.py>

import A

class Apy(A):
  def invoke_prot1(self):
     self.prot1()
  # note: self.super__prot1() won't work because prot1 is not overriden
      
  def invoke_super_prot2(self):
    self.super__prot2()
    
  def prot2(self):
    print "Apy prot2"
    
print "-- Apy --"
print dir(Apy) # notice that there's no super__prot1

a=Apy()
a.invoke_prot1()
a.invoke_super_prot2()
a.prot2()
A.invoke_prot2(a)  

</ex.py>

You can just try it. 

regards.

Thanks Samuele, I tried your example and study it and it works
and I beleave I understand what it does.
I guess I'm not making myself clear. I just want to find away
of not having to inherit Component to use enableEvents() method.
Its obvious that I'm making some people upset. So I'll it let go.
Thanks all for being patient.
Wayne

Samuele Pedroni wrote:

> Here's a clarifying example (I hope):
>
> <A.java>
> public class A {
>
>  protected void prot1() {
>    System.out.println("java prot1");
>
>  }
>
>  protected void prot2() {
>    System.out.println("java prot2");
>  }
>
>  public static void invoke_prot2(A a) {
>    a.prot2();
>  }
>
> }
> </A.java>
>
> <ex.py>
>
> import A
>
> class Apy(A):
>   def invoke_prot1(self):
>      self.prot1()
>   # note: self.super__prot1() won't work because prot1 is not overriden
>
>   def invoke_super_prot2(self):
>     self.super__prot2()
>
>   def prot2(self):
>     print "Apy prot2"
>
> print "-- Apy --"
> print dir(Apy) # notice that there's no super__prot1
>
> a=Apy()
> a.invoke_prot1()
> a.invoke_super_prot2()
> a.prot2()
> A.invoke_prot2(a)
>
> </ex.py>
>
> You can just try it.
>
> regards.
>
> _______________________________________________
> Jython-users mailing list
> Jython-users@...
> http://lists.sourceforge.net/lists/listinfo/jython-users

On Thu, Apr 05, 2001 at 08:10:50AM -0400, cindy wrote:
| I thought I couldn't access the method enableEvents() by inheriting JFrame.
| The reason being is that this method is protected. I concluded that I have to
| inherit Component to get access to this mrthod. Therefore, the tree structure
| below and inheritance from JFrame wouldn't work for the method enableEvents().
|
| Is this correct?

Mostly.  'protected' (in Java, it is slightly different in C++) means
that only subclasses and classes in the same package can access it.
JFrame is a subclass of Component, and your class is a subclass of
JFrame, therefore your class is a subclass of Component.  You are
correct up to the point where you say "inheritance from JFrame
wouldn't work".

If you've done some work in discrete math or logic this is basically
the following axiom :

if A -> B and B -> C then A -> C


Here is an example :

>>> import javax
>>> import java
>>> class MyFrame( javax.swing.JFrame ) :
...     def __init__( self ) :
...             self.super__enableEvents( java.awt.AWTEvent.WINDOW_EVENT_MASK )
...     def processEvent( self , event ) :
...             print "got an event"
...
>>> aframe = MyFrame()
>>> aframe.getContentPane().add( javax.swing.JLabel( "Jython is cool" ) )
javax.swing.JLabel[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=null,border=,flags
=0,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,horizonta
lAlignment=,horizontalTextPosition=,iconTextGap=4,labelFor=,text=Jython is cool,
verticalAlignment=CENTER,verticalTextPosition=CENTER]
>>> aframe.show()
got an event
>>> got an event
got an event


This was an interactive interpreter session of mine.  As you can see
here, I didn't define getContentPane or setVisible, but they worked.
This is because MyFrame is-a JFrame (is-a JComponent ... is-a
Component ...).  Through inheritance, instances of MyFrame ('aframe')
have all of those public and protected members (functions and data).
Also, at the end there you can see that processEvent was called when
the frame was shown, when I gave it the focus (with the mouse) and
when I removed the focus (I clicked in the terminal window to copy the
text from).


Perhaps the following tutorial sections may help you?

http://python.org/doc/current/tut/node11.html

http://www.crosswinds.net/~agauld/tutclass.htm


HTH,
-D

On Thu, Apr 05, 2001 at 10:26:14PM -0400, cindy wrote:
| I guess I'm not making myself clear. I just want to find away
| of not having to inherit Component to use enableEvents() method.

You can't.  That is what 'protected' means.  (actually ... jython has
the option to ignore java accessability modifiers, but that's
different issue altogether and there is no need to make things extra
complicated now).  Umm, also,  java allows other classes in the
package to access it but that is a bad part of java's design.  Don't
go there.  (for really cool access modifier semantics, check out
Eiffel,  but don't overload yourself with too many languages at once)

| Its obvious that I'm making some people upset. So I'll it let go.
| Thanks all for being patient.

No problem.  If you want to learn more python, try the tutor list
(tutor@...).  

-D

On Thu, Apr 05, 2001 at 05:41:05PM -0400, cindy wrote:
| In the jython doc , under Calling Methods in your Superclass", I quote
| "In Python, if I want to call the foo method in my superclass, I use the
| following
|
| SuperClass.foo(self)
|
| This works with the majority of methods, but protected methods can not
| be called from subclasses in this way. Instead you have to use the
| "self.super_foo()" call style."  I beleave the latter syntax is telling me
| I have to use inheritance. Am I wrong?

Both syntaxes use inheritance.

| Wayne
|
| P.S.   I have several books in which I'm using to learn java. What I thought
| I do to learn jython was rewite all the examples in the book in jython. This
| is how my problen came about. My the way the book is, "Beiginning Java"
| by Ivor Horton


The problem you are seeing here comes from mixing Python and Java
semantics and syntax together without first understanding either of
them.  

In Python, all functions are "public", and to call an overridden
method in a superclass you use the SuperClass.function( self ) syntax
('SuperClass' isn't a keyword).  In Java it is simply super.function()
('super' is a keyword).  Also, java has "public" "protected" and
"private" attributes which complicates the Python<->Java bridging.  

I would highly recommend that you learn one language first, then the
other language, then put them together.  The combined semantics make
much more sense when you understand each language's semantics.

IMO Python is much simpler and easier to learn (while being more
powerful at a high level) than Java, so I would recommend learning
python first.  The tutor list is great at helping new people learn the
basics of programming in a python environment (tutor@...).

Once you know python or java fairly well the hoops jython jumps
through to provide as simple and clean as possible bridge between the
two makes much more sense and is easier to grasp.

-D

Thanks, Thanks, and Thanks. I notice in the example below that your
inheritance was different than mine. I did "from java.awt import swing"
I changed it to "import javax" and modified my class statement to look
like D- Man's example. Bingo, it works.
Wayne


D-Man wrote:

> On Thu, Apr 05, 2001 at 08:10:50AM -0400, cindy wrote:
> | I thought I couldn't access the method enableEvents() by inheriting JFrame.
> | The reason being is that this method is protected. I concluded that I have to
> | inherit Component to get access to this mrthod. Therefore, the tree structure
> | below and inheritance from JFrame wouldn't work for the method enableEvents().
> |
> | Is this correct?
>
> Mostly.  'protected' (in Java, it is slightly different in C++) means
> that only subclasses and classes in the same package can access it.
> JFrame is a subclass of Component, and your class is a subclass of
> JFrame, therefore your class is a subclass of Component.  You are
> correct up to the point where you say "inheritance from JFrame
> wouldn't work".
>
> If you've done some work in discrete math or logic this is basically
> the following axiom :
>
> if A -> B and B -> C then A -> C
>
> Here is an example :
>
> >>> import javax
> >>> import java
> >>> class MyFrame( javax.swing.JFrame ) :
> ...     def __init__( self ) :
> ...             self.super__enableEvents( java.awt.AWTEvent.WINDOW_EVENT_MASK )
> ...     def processEvent( self , event ) :
> ...             print "got an event"
> ...
> >>> aframe = MyFrame()
> >>> aframe.getContentPane().add( javax.swing.JLabel( "Jython is cool" ) )
> javax.swing.JLabel[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=null,border=,flags
> =0,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,horizonta
> lAlignment=,horizontalTextPosition=,iconTextGap=4,labelFor=,text=Jython is cool,
> verticalAlignment=CENTER,verticalTextPosition=CENTER]
> >>> aframe.show()
> got an event
> >>> got an event
> got an event
>
> This was an interactive interpreter session of mine.  As you can see
> here, I didn't define getContentPane or setVisible, but they worked.
> This is because MyFrame is-a JFrame (is-a JComponent ... is-a
> Component ...).  Through inheritance, instances of MyFrame ('aframe')
> have all of those public and protected members (functions and data).
> Also, at the end there you can see that processEvent was called when
> the frame was shown, when I gave it the focus (with the mouse) and
> when I removed the focus (I clicked in the terminal window to copy the
> text from).
>
> Perhaps the following tutorial sections may help you?
>
> http://python.org/doc/current/tut/node11.html
>
> http://www.crosswinds.net/~agauld/tutclass.htm
>
> HTH,
> -D
>
> _______________________________________________
> Jython-users mailing list
> Jython-users@...
> http://lists.sourceforge.net/lists/listinfo/jython-users