iOS中的读写安全方案

iOS中的读写安全方案

• 同一时间，只能有一个线程进行写操作
• 同一时间，允许多个线程进行读操作
• 同一时间，不允许既有写操作，又有读操作

方案一：

pthread_rwlock

读写锁

导入头文件

#import <pthread.h>

@property (assign, nonatomic) pthread_rwlock_t lock;

- (void)viewDidLoad {
[super viewDidLoad];

// 初始化锁
pthread_rwlock_init(&_lock, NULL);

dispatch_queue_t queue = dispatch_get_global_queue(0, 0);

for (int i = 0; i < 10; i++) {
dispatch_async(queue, ^{
[self read];
});
dispatch_async(queue, ^{
[self write];
});
}
}

- (void)read {
pthread_rwlock_rdlock(&_lock);

sleep(1);
NSLog(@"%s", __func__);

pthread_rwlock_unlock(&_lock);
}

- (void)write
{
pthread_rwlock_wrlock(&_lock);

sleep(1);
NSLog(@"%s", __func__);

pthread_rwlock_unlock(&_lock);
}

- (void)dealloc
{
pthread_rwlock_destroy(&_lock);
}

方案二：

dispatch_barrier_async

异步栅栏函数

- (void)viewDidLoad {
[super viewDidLoad];

self.queue = dispatch_queue_create("rw_queue", DISPATCH_QUEUE_CONCURRENT);

for (int i = 0; i < 10; i++) {
dispatch_async(self.queue, ^{
[self read];
});

dispatch_async(self.queue, ^{
[self read];
});

dispatch_async(self.queue, ^{
[self read];
});

dispatch_barrier_async(self.queue, ^{
[self write];
});
}
}

- (void)read {
sleep(1);
NSLog(@"read");
}

- (void)write
{
sleep(1);
NSLog(@"write");
}

注意：

dispatch_barrier_async