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POWhy does NSInvocation getReturnValue: lose object?
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copied!<p>I need your help. I have some problems with NSInvocation 'getReturnValue:' method. I want to create UIButton programmatically, and even more, I want to create it dynamically using NSInvocation and through passing value through the NSArray (that's why I wrapped UIButtonTypeRoundedRect).</p> <p>Listing.</p> <pre><code>NSLog(@"Button 4 pushed\n");//this code executed when button pushed Class cls = NSClassFromString(@"UIButton");//if exists {define class},else cls=nil SEL msel = @selector(buttonWithType:); //id pushButton5 = [cls performSelector:msel withObject:UIButtonTypeRoundedRect];//this code works correctly,but I want to do this by NSInvocation //--------------------------- NSMethodSignature *msignatureTMP; NSInvocation *anInvocationTMP; msignatureTMP = [cls methodSignatureForSelector:msel]; anInvocationTMP = [NSInvocation invocationWithMethodSignature:msignatureTMP]; [anInvocationTMP setTarget:cls]; [anInvocationTMP setSelector:msel]; UIButtonType uibt_ = UIButtonTypeRoundedRect; NSNumber *uibt = [NSNumber numberWithUnsignedInt:uibt_]; NSArray *paramsTMP; paramsTMP= [NSArray arrayWithObjects:uibt,nil]; id currentValTMP = [paramsTMP objectAtIndex:0];//getParam from NSArray NSInteger i=2; void* bufferTMP; //if kind of NSValue unwrapp it. if ([currentValTMP isKindOfClass:[NSValue class]]) { NSUInteger bufferSize = 0; NSGetSizeAndAlignment([currentValTMP objCType], &bufferSize, NULL); bufferTMP = malloc(bufferSize); [currentValTMP getValue:bufferTMP];//copy currentVal to bufer [anInvocationTMP setArgument:bufferTMP atIndex:i];// The +2 represents the (self) and (cmd) offsets }else { [anInvocationTMP setArgument:&currentValTMP atIndex:i];//Again,+2 represents (self) and (cmd) offsets } void* result = malloc([[cls methodSignatureForSelector:msel] methodReturnLength]); [anInvocationTMP invoke]; [anInvocationTMP getReturnValue:result]; NSLog(@"sizeof(UIButton)=%i,sizeof(result)=%i,methodreturnlength = %i,sizeof(*result)=%i",class_getInstanceSize(NSClassFromString(@"UIButton")),sizeof(result),[[cls methodSignatureForSelector:msel] methodReturnLength],sizeof(*result)); id pushButton5; pushButton5=result; //--------------------------- </code></pre> <p>NSLog output:<b> sizeof(UIButton)=140,sizeof(result)=4,methodreturnlength = 4,sizeof(*result)=1</b></p> <p>The problem is that value from NSInvocation is pointer of size 4 bytes. It should point to UIButton object,size of 140 bytes. But actually refers to 1 byte data. So what does happen with UIButton object,that should be initialized by 'buttonWithType:'?</p> <h2>Added after getting some answers:</h2> <p>To clarify: I want to get <code>UIButton</code> object, but after this code <code>id pushButton5 = (id) result;</code> ,when I try to work with <code>pushButton5</code>,it causes <code>EXC_BAD_ACCESS</code>. Can someone help me?</p> <p>Can this happen because of this? </p> <pre><code>Class cls = NSClassFromString(@"UIButton"); ... [anInvocationTMP setTarget:cls]; </code></pre> <p>It is correct, isn't it?</p>

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