RACKVOTrampoline.m
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//
// RACKVOTrampoline.m
// ReactiveCocoa
//
// Created by Josh Abernathy on 1/15/13.
// Copyright (c) 2013 GitHub, Inc. All rights reserved.
//
#import "RACKVOTrampoline.h"
#import "NSObject+RACDeallocating.h"
#import "RACCompoundDisposable.h"
#import "RACKVOProxy.h"
@interface RACKVOTrampoline ()
// The keypath which the trampoline is observing.
@property (nonatomic, readonly, copy) NSString *keyPath;
// These properties should only be manipulated while synchronized on the
// receiver.
@property (nonatomic, readonly, copy) RACKVOBlock block;
@property (nonatomic, readonly, unsafe_unretained) NSObject *unsafeTarget;
@property (nonatomic, readonly, weak) NSObject *weakTarget;
@property (nonatomic, readonly, weak) NSObject *observer;
@end
@implementation RACKVOTrampoline
#pragma mark Lifecycle
- (id)initWithTarget:(__weak NSObject *)target observer:(__weak NSObject *)observer keyPath:(NSString *)keyPath options:(NSKeyValueObservingOptions)options block:(RACKVOBlock)block {
NSCParameterAssert(keyPath != nil);
NSCParameterAssert(block != nil);
NSObject *strongTarget = target;
if (strongTarget == nil) return nil;
self = [super init];
if (self == nil) return nil;
_keyPath = [keyPath copy];
_block = [block copy];
_weakTarget = target;
_unsafeTarget = strongTarget;
_observer = observer;
[RACKVOProxy.sharedProxy addObserver:self forContext:(__bridge void *)self];
[strongTarget addObserver:RACKVOProxy.sharedProxy forKeyPath:self.keyPath options:options context:(__bridge void *)self];
[strongTarget.rac_deallocDisposable addDisposable:self];
[self.observer.rac_deallocDisposable addDisposable:self];
return self;
}
- (void)dealloc {
[self dispose];
}
#pragma mark Observation
- (void)dispose {
NSObject *target;
NSObject *observer;
@synchronized (self) {
_block = nil;
// The target should still exist at this point, because we still need to
// tear down its KVO observation. Therefore, we can use the unsafe
// reference (and need to, because the weak one will have been zeroed by
// now).
target = self.unsafeTarget;
observer = self.observer;
_unsafeTarget = nil;
_observer = nil;
}
[target.rac_deallocDisposable removeDisposable:self];
[observer.rac_deallocDisposable removeDisposable:self];
[target removeObserver:RACKVOProxy.sharedProxy forKeyPath:self.keyPath context:(__bridge void *)self];
[RACKVOProxy.sharedProxy removeObserver:self forContext:(__bridge void *)self];
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
if (context != (__bridge void *)self) {
[super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
return;
}
RACKVOBlock block;
id observer;
id target;
@synchronized (self) {
block = self.block;
observer = self.observer;
target = self.weakTarget;
}
if (block == nil || target == nil) return;
block(target, observer, change);
}
@end