NSOperation

// 同步执行的代码NSInvocationOperation * invocationOp = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(invocationRun) object:nil]; [invocationOp start]; NSBlockOperation * blockOp = [NSBlockOperation blockOperationWithBlock:^{        NSLog(@"blockOpRun_0");    }];[blockOp start];   

//这个是异步操作    [blockOp addExecutionBlock:^{        NSLog(@"blockOpRun_1");    }];    //这个是异步操作    [blockOp addExecutionBlock:^{        NSLog(@"blockOpRun_2");    }];    //这个是异步操作    [blockOp addExecutionBlock:^{        NSLog(@"blockOpRun_3");    }];    //这个是异步操作    [blockOp addExecutionBlock:^{        NSLog(@"blockOpRun_4");    }];    [blockOp start];