The property delegate of CALayer cause Crash.

在非arc与arc的环境中使用时，导致程序crash.

 

 1 //当前类使用－fno-objc 编译
 2 
 3     needle_ = [[MyView alloc] init];
 4 
 5     needleLayer = [CALayer layer];    
 6     needleLayer.delegate = self.needle;
 7 
 8 
 9 - (void)dealloc
10 {    
11     [needle_ release];
12     [needleLayer release];
13     [super dealloc];   //crash
14 }
15     

 

 

1 -(void) drawLayer: (CALayer*) layer inContext: (CGContextRef) context  

 

he lightest-wight solution would be to create a small helper class in the the file as the UIView that's using the CALayer:

In MyView.h

@interfaceMyLayerDelegate:NSObject...@end

In MyView.m

@implementationMyLayerDelegate-(void)drawLayer:(CALayer*)layer inContext:(CGContextRef)ctx
{...}@end

Just place those at the top of your file, immediately below the #import directives. That way it feels more like using a "private class" to handle the drawing (although it isn't -- the delegate class can be instantiated by any code that imports the header).

 

Feedback

 

#1楼

2012-11-09 11:51 |  

needleLayer.delegate = nil;这句话写在dealloc中，因为CALayer中的delegate是assign的属性，这样你释放[needle_ release];后，deletate就是野指针了。在arc中如果有weak了，如果delegatej是weak的属性，就不会crash..

我们在程序设计中也要注意传指针。

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#2楼楼主]

2012-11-14 15:07 |  

@ 为了谁
请教一下，为什么视图已经在delloc中了，它还会访问用CALayer的delegate呢？

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