iOS 6.0中的CADisplayLink不保留目标 [英] CADisplayLink at iOS 6.0 not retaining target

问题描述

我有这样的代码：

NSInvocation* invocation = [NSInvocation invocationWithMethodSignature:[self methodSignatureForSelector:@selector(updateFrame)]];
[invocation setTarget:self];
[invocation setSelector:@selector(updateFrame)];
displayLink_ = [[CADisplayLink displayLinkWithTarget:invocation selector:@selector(invoke)] retain];
[displayLink_ setFrameInterval:1];
[displayLink_ addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];

在这个代码调用我有两个变种的iOS 6.0（在5.1中，这段代码可以正常工作）：EXC_BAD_ACCESS或'调用无法识别的选择器'调用'。似乎displayLinkWithTarget：selector：方法不保留目标。当我添加[invocation retain]行时，代码变得正常工作。这是iOS 6.0的错误吗？

At iOS 6.0 (in 5.1 this code works ok) when this code calling I have two variants: EXC_BAD_ACCESS or 'call to unrecognized selector "invoke"'. It is seem that displayLinkWithTarget:selector: method doesn't retain target. When i add [invocation retain] line, code become to work ok. Is it bug of iOS 6.0?

推荐答案

这是有用的相关信息，而不是答案。

而不是使用 NSInvokation 你可以使用弱代理，就像我在这个问题的实际答案中所做的那样。这很简单，这是代码：

Rather than use NSInvokation you can use a weak proxy as I have done in my actual answer to this question. It's very simple, here's the code:

JAWeakProxy.h：

#import <Foundation/Foundation.h>

@interface JAWeakProxy : NSObject

@property (weak, nonatomic) id  target;

+ (JAWeakProxy*)weakProxyWithTarget:(id)target;

@end

JAWeakProxy.m：

#import "JAWeakProxy.h"

@implementation JAWeakProxy

+ (JAWeakProxy*)weakProxyWithTarget:(id)target
{
    JAWeakProxy* newObj = [self new];
    newObj.target = target;
    return newObj;
}

- (BOOL)respondsToSelector:(SEL)sel
{
    return [_target respondsToSelector:sel] || [super respondsToSelector:sel];
}

- (id)forwardingTargetForSelector:(SEL)sel
{
    return _target;
}

@end

注意：这是ARC代码，如果不使用ARC，你需要在 weakProxyWithTarget：中 autorelease 。

NOTE: This is ARC code, you'll need to autorelease in weakProxyWithTarget: if not using ARC.

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