Managing a bunch of NSOperation with dependencies

Question

I\'m working on an application that create contents and send it to an existing backend. Content is a title, a picture and location. Nothing fancy.

The backend is a bit c

Answer 1

I'm probably totally, biased - but for a particular reason - I like @Rob's approach #6 ;)

Assuming you created appropriate wrappers for your asynchronous methods and operations which return a Promise instead of signaling the completion with a completion block, the solution looks like this:

RXPromise* finalResult = [RXPromise all:@[[self filename], [self process]]]
.then(^id(id filenameAndProcessResult){
    return [self generateEntry];
}, nil)
.then(^id(id generateEntryResult){
    return [self uploadImage];
}, nil)
.thenOn(dispatch_get_main_queue() , ^id(id uploadImageResult){
    [self refreshWithResult:uploadImageResult];
    return nil;
}, nil)
.then(nil, ^id(NSError*error){
    // Something went wrong in any of the operations. Log the error:
    NSLog(@"Error: %@", error);
});

And, if you want to cancel the whole asynchronous sequence at any tine, anywhere and no matter how far it has been proceeded:

[finalResult.root cancel];

(A small note: property root is not yet available in the current version of RXPromise, but its basically very simple to implement).