Re: [TCLCORE] TIP #320: Improved Variable Handling in the Core Object System

[Will D. <wi...@wj...>]

On Jun 14, 2008, at 8:36 AM, Arnulf Wiedemann wrote:
> Am Samstag, 14. Juni 2008 14:31:33 schrieb Donal K. Fellows:
>> PROPOSED CHANGE
>> =================
>>
>> Every object and every class will have associated with it a list of
>> variable names. This list will be configurable via a subcommand of
>> *oo::define* and introspectable. Methods (strictly, only procedure- 
>> like
>> methods, constructors and destructors) will then make those variables
>> that were declared at the same declaration level (i.e. in the same
>> class, or in the object itself for methods defined on the object)
>> available in the method body without further declaration or
>> qualification. At declaration time, the type of the variable (i.e.
>> whether it is an array or a simple variable) will not be defined;  
>> that
>> may be done in the constructor. As there is no (public) C API for
>> declaring a procedure-like method, there will not be a public C API  
>> for
>> declaring the variables either.
>>
>
> First of all, thanks for starting a tip for variables for TclOO.
>
> I think I have not yet fully understood, how that will work.
>
> For example:
> class cat has a variable cat_color defined and I have 2 objects  
> which have as
> object class cat and these are named cat1 and cat2. Will variable  
> cat_color
> be shared between the objects?
> So if I set cat1 cat_color to black with a class method, will a  
> class method
> of cat2 get back black as cat_color?
>
> Are object specific variables also accessible by class methods?

I'm equally pleased to see this; thank you, Donal.

I am curious about this point as well.  As I read it, normal variables  
declared by class cat are instance variables; cat1 and cat2 do not  
share values.  However, variables can also be declared by the class  
using "self"; in this case, the variable  is a "typevariable" in Snit  
parlance.  Is that correct?

Will such class variables be visible without declaration or  
qualification in instance methods? (I'd presume so.)

And I presume that class and instance variables declared by ancestors  
will also be accessible, but *with* qualification (mechanism clearly  
to be fleshed out later)?

Will

>
>
> Arnulf
>
>> Note that the order in which the declaration of some methods and some
>> variables for a class or object will not matter.
>>
>> DECLARATION
>> -------------
>>
>> The *oo::define* and *oo::objdefine* (and also the *self*  
>> subcommand of
>> *oo::define*) will gain a new subcommand: *variable*. This will take
>> zero or more arguments, and those arguments will form the list of
>> variables that are made available by default. Each argument will need
>> to be a valid variable local name without parentheses.
>>
>> Syntax (other uses analogous according to normal behaviour of the  
>> class
>> and object definition commands):
>>
>>       *oo::define* /class/ *variable* ?/varName .../?
>>
>> INTROSPECTION
>> ---------------
>>
>> The list of variables declared by a particular class, /class/, may be
>> retrieved by:
>>
>>       *info class variables* /class/
>>
>> The list of variables declared by a particular object, /object/,  
>> may be
>> retrieved by:
>>
>>       *info object variables* /object/
>>
>> Note that the full list of /all/ variables (matching an optional
>> pattern) in an object's namespace will be retrievable using *info
>> object vars*; this mechanism is disjoint (though *info object
>> variables* will return variables that can be returned by *info object
>> vars*).
>>
>> IMPLEMENTATION
>> ================
>>
>> Not yet done; details still to be written up here.
>>
>> COPYRIGHT
>> ===========
>>
>> This document has been placed in the public domain.
>>
>> -------------------------------------------------------------------------
>>
>> TIP AutoGenerator - written by Donal K. Fellows
>>
>> -------------------------------------------------------------------------
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>
>
>
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