解决循环引用的问题，参考学习了ibireme大神的YYFPSLabel的实现，整理以备用
// 如果直接用 self 或者 weakSelf，都不能解决循环引用问题
_link = [CADisplayLink displayLinkWithTarget:[YYWeakProxy proxyWithTarget:self] selector:@selector(tick:)];
// _link = [CADisplayLink displayLinkWithTarget:self selector:@selector(tick:)];
// __weak typeof(self) weakSelf = self;
// _link = [CADisplayLink displayLinkWithTarget:weakSelf selector:@selector(tick:)];
[_link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
//NSDefaultRunLoopMode - 标准优先级
//NSRunLoopCommonModes - 高优先级
//UITrackingRunLoopMode - 用于UIScrollView和别的控件的动画
return self;
@interface YYWeakProxy : NSProxy /**
The proxy target.
*/
@property (nonatomic, weak, readonly) id target; /**
Creates a new weak proxy for target. @param target Target object. @return A new proxy object.
*/
- (instancetype)initWithTarget:(id)target; /**
Creates a new weak proxy for target. @param target Target object. @return A new proxy object.
*/
+ (instancetype)proxyWithTarget:(id)target; @end
@implementation YYWeakProxy
- (instancetype)initWithTarget:(id)target {
_target = target;
return self;
}
+ (instancetype)proxyWithTarget:(id)target {
return [[YYWeakProxy alloc] initWithTarget:target];
}
- (id)forwardingTargetForSelector:(SEL)selector {
return _target;
}
- (void)forwardInvocation:(NSInvocation *)invocation {
void *null = NULL;
[invocation setReturnValue:&null];
}
- (NSMethodSignature *)methodSignatureForSelector:(SEL)selector {
return [NSObject instanceMethodSignatureForSelector:@selector(init)];
}
- (BOOL)respondsToSelector:(SEL)aSelector {
return [_target respondsToSelector:aSelector];
}
- (BOOL)isEqual:(id)object {
return [_target isEqual:object];
}
- (NSUInteger)hash {
return [_target hash];
}
- (Class)superclass {
return [_target superclass];
}
- (Class)class {
return [_target class];
}
- (BOOL)isKindOfClass:(Class)aClass {
return [_target isKindOfClass:aClass];
}
- (BOOL)isMemberOfClass:(Class)aClass {
return [_target isMemberOfClass:aClass];
}
- (BOOL)conformsToProtocol:(Protocol *)aProtocol {
return [_target conformsToProtocol:aProtocol];
}
- (BOOL)isProxy {
return YES;
}
- (NSString *)description {
return [_target description];
}
- (NSString *)debugDescription {
return [_target debugDescription];
}
@endNSProxy（ /BrE ˈprɒksi/）的父类不是NSObject