多线程的创建方法

- (void)viewDidLoad {
    [super viewDidLoad];
   

    //第一种开启新的线程调用 mutableTheard
    NSThread * t = [[NSThread alloc]initWithTarget:self selector:@selector(mutableTheard) object:nil];
    [t start];
    
    
    //第二种开启新的线程调用 mutableTheard
    [NSThread detachNewThreadSelector:@selector(mutableTheard) toTarget:self withObject:nil];
    
    //第三种开新的线程 mutableTheard
    [self performSelectorInBackground:@selector(mutableTheard) withObject:self];
    
    //第四种开新的线程
    NSOperationQueue *operationQueue = [[NSOperationQueue alloc]init];
    [operationQueue addOperationWithBlock:^{
        for (int i = 1; i <100; i++) {
            NSLog(@"---多线程");
        }
    }];

    
    //第五种开新的线程
    NSOperationQueue * Queue = [[NSOperationQueue alloc]init];
    //设置线程执行的并发数。
    Queue.maxConcurrentOperationCount = 2;
    //创建一个线程惭怍对象
    NSInvocationOperation * operation1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(mutableTheard) object:nil];
   //创建一个线程惭怍对象
    NSInvocationOperation *operation2 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(mutableTheard) object:nil];
    //把线程添加到队列中
    [operationQueue  addOperation:operation1];
    [operationQueue addOperation:operation2];
    
    
    
    //第六种开新的线程GCD
    dispatch_queue_t queue = dispatch_queue_create("test", NULL);
    dispatch_async(queue, ^{
        NSLog(@"我在多线程");
    });
    
    //可以使用这个方法可以回到主线程
    dispatch_sync(dispatch_get_main_queue(), ^{
        BOOL isMain = [NSThread isMainThread];
        if (isMain == YES) {
       NSLog(@"回到主线程了");
        }
        
    });
    
    
    //用过这种方法，还是同步在当前线程上
    dispatch_sync(queue, ^{
        ///当前线程
    });
    
    
}


-(void)mutableTheard
{
///创建自动释放池
    @autoreleasepool {
     
        
     [self  performSelectorOnMainThread:@selector(mainTheard) withObject:nil waitUntilDone:YES];// 回到主线程
        

    }
 }