HLWeakProxy

HLWeakProxy.h

NS_ASSUME_NONNULL_BEGIN

/**
 A proxy used to hold a weak object.
 It can be used to avoid retain cycles, such as the target in NSTimer or CADisplayLink.
 
 sample code:
 
 @implementation MyView {
 NSTimer *_timer;
 }
 
 - (void)dealloc {
     [_timer invalidate];
 }
 
 - (void)initTimer {
 _timer = [NSTimer timerWithTimeInterval:0.1 target:[self weakProxy] selector:@selector(tick:) userInfo:nil repeats:YES];
 }
 
 - (void)tick:(NSTimer *)timer {...}
 @end
 */

@interface HLWeakProxy : NSProxy
@property (nullable, nonatomic, weak, readonly) id target;

- (id)initWithTarget:(id)target;
@end

@interface NSObject (HLWeakProxy)
- (HLWeakProxy *)weakProxy;
@end

NS_ASSUME_NONNULL_END

HLWeakProxy.m

@implementation HLWeakProxy

- (id)initWithTarget:(id)target
{
    _target = target;
    return self;
}

- (id)forwardingTargetForSelector:(SEL)selector
{
    return self.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 [self.target respondsToSelector:aSelector];
}

- (BOOL)isEqual:(id)object
{
    return [self.target isEqual:object];
}

- (NSUInteger)hash
{
    return [self.target hash];
}

- (Class)superclass
{
    return [self.target superclass];
}

- (Class)class
{
    return [self.target class];
}

- (BOOL)isKindOfClass:(Class)aClass
{
    return [self.target isKindOfClass:aClass];
}

- (BOOL)isMemberOfClass:(Class)aClass
{
    return [self.target isMemberOfClass:aClass];
}

- (BOOL)conformsToProtocol:(Protocol *)aProtocol
{
    return [self.target conformsToProtocol:aProtocol];
}

- (BOOL)isProxy
{
    return YES;
}

- (NSString *)description
{
    return [self.target description];
}

- (NSString *)debugDescription
{
    return [self.target debugDescription];
}

@end

@implementation NSObject (HLWeakProxy)

- (HLWeakProxy *)weakProxy
{
    return [[HLWeakProxy alloc] initWithTarget:self];
}

@end