NSOperationQueue 依赖操作

NSOperationQueue * operationQueue = [[NSOperationQueue alloc]init];    NSInvocationOperation * invocationOp = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(invocationRun) object:nil];    NSBlockOperation * blockOp = [NSBlockOperation blockOperationWithBlock:^{        NSLog(@"blockOpRun_0");    }];    //invocationOp 依赖 blockOp => 也就是说 先执行 blockOp 然后再执行invocationOp    [invocationOp addDependency:blockOp];    [operationQueue addOperation:invocationOp];    [operationQueue addOperation:blockOp];