ios - OC中的方法加锁

Answer 1

Method-level control has no language-level modifiers, and code blocks can be locked.

There are many ways to lock.

1. @synchronized

2. NSLock

3. pthread_mutex

4. dispatch_semaphore

5. OSSpinLock

1. @synchronized

@interface A : NSObject {
    NSObject _lock;
}

- (void)func {
    @synchronized(_lock) {
    // do something
    }
}

2. NSLock

- (void) func {
    [_lock lock];
    // do something
    [_lock unlock];
}

3. pthread_mutex

@interface A : NSObject {
    pthread_mutex_t lock;
}

- (instance)init {
    // 省略
    pthread_mutex_init(&_lock, NULL);
}

- (void)func {
    pthread_mutex_lock(&lock);
    // do something
    
    pthread_mutex_unlock(&lock);
}

4. dispatch_semaphore

@interface A : NSObject {
    dispatch_semaphore_t _semaphore; 
}

- (instance)init {
    // 省略
    _semaphore = dispatch_semaphore_create(1);
}

- (void)func {
    dispatch_semaphore_wait(_semaphore, DISPATCH_TIME_FOREVER);
    // do something
    
    dispatch_semaphore_signal(_semaphore);
}

5.OSSpinLock

Since spin lock is no longer safe in iOS, it will not be introduced here. For details, you can read this blog
OSSpinLock is no longer safe

Answer 2

GCD+block for

.