xmlvm-users

[xmlvm-users] error when intializing variables

[Panayotis K. <pan...@pa...>]

there is something missing when variables are initialized outsize the constructor.

As a minium program to display this error, have a look at this: instead of printing "hello", it prints "null", since this is not initialized.




package my.testmem;

import org.xmlvm.iphone.UIApplication;
import org.xmlvm.iphone.UIApplicationDelegate;

public class Main extends UIApplicationDelegate {

    String test = "hello";
    
    @Override
    public void applicationDidFinishLaunching(UIApplication app) {
        System.out.println(test);
    }

    public static void main(String[] args) {
        UIApplication.main(args, null, Main.class);
    }
}

Re: [xmlvm-users] error when intializing variables

[Arno P. <ar...@pu...>]

that is a known issue. The code that XMLVM generates is correct. The 
problem is that certain classes (such as UIAppication*) are instantiated 
by Cocoa and Cocoa doesn't know about the __init__*() constructors that 
were generated by XMLVM. The initialization of 'test' in your example 
will end up in the default constructor for class Main and since Cocoa 
doesn't call it, it won't get initialized.

This will work perfectly fine for any other class (that is handled by 
XMLVM). It is just this special case when Cocoa instantiates a Java 
object. Back then I couldn't think of a solution for this. I'll revisit 
this with the C backend. Here we might have more hooks to solve this 
problem.

Arno


On 11/11/10 7:08 AM, Panayotis Katsaloulis wrote:
> there is something missing when variables are initialized outsize the constructor.
>
> As a minium program to display this error, have a look at this: instead of printing "hello", it prints "null", since this is not initialized.
>
>
>
>
> package my.testmem;
>
> import org.xmlvm.iphone.UIApplication;
> import org.xmlvm.iphone.UIApplicationDelegate;
>
> public class Main extends UIApplicationDelegate {
>
>      String test = "hello";
>
>      @Override
>      public void applicationDidFinishLaunching(UIApplication app) {
>          System.out.println(test);
>      }
>
>      public static void main(String[] args) {
>          UIApplication.main(args, null, Main.class);
>      }
> }
>
>
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Re: [xmlvm-users] error when intializing variables

[Panayotis K. <pan...@pa...>]

On Nov 11, 2010, at 6:56 PM, Arno Puder wrote:

> 
> that is a known issue. The code that XMLVM generates is correct. The 
> problem is that certain classes (such as UIAppication*) are instantiated 
> by Cocoa and Cocoa doesn't know about the __init__*() constructors that 
> were generated by XMLVM. The initialization of 'test' in your example 
> will end up in the default constructor for class Main and since Cocoa 
> doesn't call it, it won't get initialized.
> 
> This will work perfectly fine for any other class (that is handled by 
> XMLVM). It is just this special case when Cocoa instantiates a Java 
> object. Back then I couldn't think of a solution for this. I'll revisit 
> this with the C backend. Here we might have more hooks to solve this 
> problem.
> 
> Arno

I actually found that problem in another, more complex structure that wasn't based on UIApplicationDelegate.

In any case, you are right, probably we should push our efforts more in favor of C backend (although I believe the ObjC backend should  not become obsolete)