18

我正在使用串行 GCD 队列来处理领域。Realm accessed from incorrect thread当 GCD 开始为队列切换线程时，应用程序崩溃并出现异常。有没有办法使用 GCD API 将给定领域与线程绑定？

这是一个简单的例子

self.realmQueue = dispatch_queue_create("db", DISPATCH_QUEUE_SERIAL);

__block RLMRealm *realm = nil;
dispatch_async(self.realmQueue, ^{
    realm = [RLMRealm realmWithPath:[NSTemporaryDirectory() stringByAppendingPathComponent:@"temp"]];
});

self.motionManager = [[CMMotionManager alloc] init];
self.motionManager.accelerometerUpdateInterval = 0.001;
__block int i = 0;
__block BOOL shouldBeginWriteTransaction = YES;

[self.motionManager startAccelerometerUpdatesToQueue:[[NSOperationQueue alloc] init] withHandler:^(CMAccelerometerData *accelerometerData, NSError *error) {

    dispatch_async(self.realmQueue, ^{
        if (shouldBeginWriteTransaction) {
            [realm beginWriteTransaction];
            shouldBeginWriteTransaction = NO;
        }

        AccelerationEvent *event = [[AccelerationEvent alloc] init];
        event.x = accelerometerData.acceleration.x;
        event.y = accelerometerData.acceleration.x;
        event.z = accelerometerData.acceleration.y;
        event.time = [NSDate date];
        [realm addObject:event];

        if (i % 1000) {
            dispatch_async(dispatch_get_main_queue(), ^{
                self.xLabel.text = [NSString stringWithFormat:@"%f", event.x];
                self.yLabel.text = [NSString stringWithFormat:@"%f", event.y];
                self.zLabel.text = [NSString stringWithFormat:@"%f", event.z];
            });
        }

        if (i % 10000 == 0) {
            NSDate *startDate = [NSDate date];
            [realm commitWriteTransaction];
            NSLog(@"save time: %f", [[NSDate date] timeIntervalSinceDate:startDate]);
            shouldBeginWriteTransaction = YES;
        }

        i++;
    });
}];
4

1 回答 1

35

来自 Realm 文档：RLMRealm对象不是线程安全的，不能跨线程共享，因此您必须RLMRealm在要读取或写入的每个线程/dispatch_queue 中获取一个实例。

同样来自 Realm 文档：RLMRealm对象由 Realm 在内部缓存，并且在运行循环的单次迭代中在单个线程上多次调用此方法通常会返回相同的RLMRealm对象。

所以知道了这一点，我修改了您的代码示例以RLMRealm直接从dispatch_async使用它的块中获取它，而不会导致性能损失，因为它被缓存了。

我还注意到 anAccelerationEvent跨线程传递，这也是不允许的。因此，这个修改后的代码示例NSString改为跨线程传递 s。

self.realmQueue = dispatch_queue_create("db", DISPATCH_QUEUE_SERIAL);

self.motionManager = [[CMMotionManager alloc] init];
self.motionManager.accelerometerUpdateInterval = 0.001;
__block int i = 0;
__block BOOL shouldBeginWriteTransaction = YES;

[self.motionManager startAccelerometerUpdatesToQueue:[[NSOperationQueue alloc] init] withHandler:^(CMAccelerometerData *accelerometerData, NSError *error) {

    dispatch_async(self.realmQueue, ^{
        RLMRealm *realm = [RLMRealm realmWithPath:[NSTemporaryDirectory() stringByAppendingPathComponent:@"temp"]];
        if (shouldBeginWriteTransaction) {
            [realm beginWriteTransaction];
            shouldBeginWriteTransaction = NO;
        }

        AccelerationEvent *event = [[AccelerationEvent alloc] init];
        event.x = accelerometerData.acceleration.x;
        event.y = accelerometerData.acceleration.x;
        event.z = accelerometerData.acceleration.y;
        event.time = [NSDate date];
        [realm addObject:event];

        if (i % 1000) {
            NSString *xString = [NSString stringWithFormat:@"%f", event.x];
            NSString *yString = [NSString stringWithFormat:@"%f", event.y];
            NSString *zString = [NSString stringWithFormat:@"%f", event.z];
            dispatch_async(dispatch_get_main_queue(), ^{
                self.xLabel.text = xString;
                self.yLabel.text = yString;
                self.zLabel.text = zString;
            });
        }

        if (i % 10000 == 0) {
            NSDate *startDate = [NSDate date];
            [realm commitWriteTransaction];
            NSLog(@"save time: %f", [[NSDate date] timeIntervalSinceDate:startDate]);
            shouldBeginWriteTransaction = YES;
        }

        i++;
    });
}];

我还没有运行此代码来确认它是否有效，所以如果这仍然不能解决问题，请告诉我。

于 2014-09-04T16:24:00.513 回答