How to handle the result of a completion block between classes

Question

Let's say I have a class UploadManager and I create an instance of it in my ViewController . UploadManager.m has a method -(void)requestData

-(void)requestData
{
    HTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] init];
    [operation setCompletionBlockWithSuccess:^(HTTPRequestOperation *operation, id responseObject){
        // Do something here
    }];
    [operation start];
}

Now I can call the requestData method from my instance of UploadManager in ViewController.m , but I'd like to do something with the responseObject inside of ViewController.m once the completion block has fired. What's the best way of doing this? I assume I could make a delegate method but I'm wondering if there's a better solution. Thanks.

Answer 1

You can use blocks structure for that

   -(void)requestDataWithHandler:(void (^)(id responceObject))handler
    {
        HTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] init];
        [operation setCompletionBlockWithSuccess:^(HTTPRequestOperation *operation, id responseObject){
            // Do something here

        if(handler)
        {
           handler(responceObject)
        }
        }];
        [operation start];
    }

In another class

 [uploadManager requestDataWithHandler:^(responceObject) {
    // here work with responeObject
    }];

Answer 2

The block-based approach will certainly work. If you want an alternate approach to blocks, you could use NSNotifications as follows:

-(void)requestDataWithHandler:(void (^)(id responseObject))handler
{
    HTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] init];
    [operation setCompletionBlockWithSuccess:^(HTTPRequestOperation *operation, id responseObject){
        // You'll probably want to define the Notification name elsewhere instead of saying @"Information updated" below.
        [[NSNotificationCenter defaultCenter] postNotificationName:@"Information updated" object:nil];
    }];
    [operation start];
}

Elsewhere in ViewController.m :

- (void)viewDidLoad
{
  [super viewDidLoad];
  [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(doSomethingUponUpdate) name:@"Information updated" object:nil];
}

-(void)dealloc
{ 
  // Don't forget to remove the observer, or things will get unpleasant
  [[NSNotificationCenter defaultCenter] removeObserver:self];
}

- (void)doSomethingUponUpdate
{
  // Something
}