RACSerialDisposable.m
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//
// RACSerialDisposable.m
// ReactiveCocoa
//
// Created by Justin Spahr-Summers on 2013-07-22.
// Copyright (c) 2013 GitHub, Inc. All rights reserved.
//
#import "RACSerialDisposable.h"
#import <libkern/OSAtomic.h>
@interface RACSerialDisposable () {
// The receiver's `disposable`. This variable must only be referenced while
// _spinLock is held.
RACDisposable * _disposable;
// YES if the receiver has been disposed. This variable must only be modified
// while _spinLock is held.
BOOL _disposed;
// A spinlock to protect access to _disposable and _disposed.
//
// It must be used when _disposable is mutated or retained and when _disposed
// is mutated.
OSSpinLock _spinLock;
}
@end
@implementation RACSerialDisposable
#pragma mark Properties
- (BOOL)isDisposed {
return _disposed;
}
- (RACDisposable *)disposable {
RACDisposable *result;
OSSpinLockLock(&_spinLock);
result = _disposable;
OSSpinLockUnlock(&_spinLock);
return result;
}
- (void)setDisposable:(RACDisposable *)disposable {
[self swapInDisposable:disposable];
}
#pragma mark Lifecycle
+ (instancetype)serialDisposableWithDisposable:(RACDisposable *)disposable {
RACSerialDisposable *serialDisposable = [[self alloc] init];
serialDisposable.disposable = disposable;
return serialDisposable;
}
- (id)initWithBlock:(void (^)(void))block {
self = [self init];
if (self == nil) return nil;
self.disposable = [RACDisposable disposableWithBlock:block];
return self;
}
#pragma mark Inner Disposable
- (RACDisposable *)swapInDisposable:(RACDisposable *)newDisposable {
RACDisposable *existingDisposable;
BOOL alreadyDisposed;
OSSpinLockLock(&_spinLock);
alreadyDisposed = _disposed;
if (!alreadyDisposed) {
existingDisposable = _disposable;
_disposable = newDisposable;
}
OSSpinLockUnlock(&_spinLock);
if (alreadyDisposed) {
[newDisposable dispose];
return nil;
}
return existingDisposable;
}
#pragma mark Disposal
- (void)dispose {
RACDisposable *existingDisposable;
OSSpinLockLock(&_spinLock);
if (!_disposed) {
existingDisposable = _disposable;
_disposed = YES;
_disposable = nil;
}
OSSpinLockUnlock(&_spinLock);
[existingDisposable dispose];
}
@end