iOS arc和mrc下重写set方法

ARC下
@property (nonatomic, weak/assign) id<PPWebViewDataDelegate> delegate;
相当于
- (void)setDelegate:(id<PPWebViewDataDelegate>)delegate
{
    if (_delegate != delegate) {
        _delegate = delegate;
    }
}



MRC下
@property (nonatomic, strong/retain/copy) id<PPWebViewDataDelegate> delegate;
相当于

- (void)setDelegate:(id<PPWebViewDataDelegate>)delegate
{
    if (_delegate != delegate) {
        [_delegate release];
        _delegate = [delegate retain/copy];
    }
}