Re: [xmlvm-users] General questions wrt. Java iPhone development with XMLVM

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

On 1/21/11 11:40 AM, Panayotis Katsaloulis wrote:
>
> On Jan 21, 2011, at 6:31 PM, Arno Puder wrote:
>
>> he Objective-C backend still relies on
>> reference counting and it happens *very* quickly that your application
>> contains a cycle in the data structure and therefore leaks memory. These
>> are just two things where the new backend is superior.
>
>
> I have a question with the GC.
>
> There are some selectors in iOS which return an autoreleased object. This is not really the problem.
> The problem is if this object is released later on, for example after an animation cycle.
> I can't think right now of a working test example, but I'd like to hear how well the GC behaves in such mixed situations.

As an example, here is how it is done for [UIButton buttonWithType:...]:

JAVA_OBJECT org_xmlvm_iphone_UIButton_buttonWithType___int(JAVA_INT n1)
{
     if (!__TIB_org_xmlvm_iphone_UIButton.classInitialized) 
__INIT_org_xmlvm_iphone_UIButton();
     //XMLVM_BEGIN_WRAPPER[org_xmlvm_iphone_UIButton_buttonWithType___int]
     NSAutoreleasePool* p = [[NSAutoreleasePool alloc] init];
     UIButton* objcBtn = [UIButton buttonWithType: (UIButtonType) n1];
     [objcBtn retain];
     [p release];
	
     JAVA_OBJECT b = __NEW_org_xmlvm_iphone_UIButton();
     org_xmlvm_iphone_UIControl_INTERNAL_CONSTRUCTOR(b, objcBtn);
     return b;
     //XMLVM_END_WRAPPER
}

You are right: so-called convenience methods in Cocoa place the 
newly-created object automatically in the autorelease pool. You can see 
above that we create a temporary autorelease pool that we release again 
immediately. When the GC reclaims the C version of UIButton, it will 
call a finalizer (the __DELETE_* functions) that will do a 'release' in 
the wrapped Objective-C UIButton.

Arno