iOS - how to specify a callback from another class?

Question

I am an iOS newbie. I want to specify a success callback for an Http execution. However, that is in another class. How would I specify it? I tried the following -

[request setDidFinishSelector: @selector([[MyHttpCallbacks get] successHttpMethod]:)];

The callback functions are defined in the MyHttpCallbacks. This does not work. If I define the methods in the same class and use it like this it works fine -

[request setDidFinishSelector: @selector(successHttpMethod:)];

Any help would be appreciated.

msk · Accepted Answer · 2012-09-13 19:28:32Z

4

MyHttpCallbacks *callbacks = [[MyHttpCallbacks alloc] init];
request.delegate = callbacks;

answered Sep 13, 2012 at 19:28

msk

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1 Comment

Till Over a year ago

It is indeed as simple as that.

hol · Accepted Answer · 2012-09-13 19:29:54Z

I had the same problem and I made the HTTP handling class (ServerComm in my case) to call a delegate method.

ServerComm.h I added at the end

@interface NSObject (ServerCommDelegate)
- (void)finishedLoading:(NSString*)result success:(BOOL)success;
@end

ServerComm.m

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    ...

    if ( [delegate respondsToSelector:@selector(finishedLoading:success:)] ) {
        [delegate finishedLoading:aStr success:YES];
    }    
}

In the main class after creating the instance

serverCommObj.delegate = self;

and then the method

- (void)finishedLoading:(NSString*)result success:(BOOL)success 
{
    if (!success) {
        ...
    } else {
        ...
    }    
}

Steven · Accepted Answer · 2012-09-13 19:24:25Z

I believe natively what you want to achieve is not possible (unless someone have a hack and I am unaware). I had this problem many times that I had to change my design and include the callback in the same class as where it is created.

Although, come to think of it. (This is a suggestion that I didn't try myself) You could have your callback class "include" in the main and then from there, call a selector function that calls the function inside the callback. Not a very efficient hack, but i think it will work.

So something like this:

[request setDidFinishSelector: @selector(callbackFunction)];

With the call back in the same class:

- (void)callbackFunction {
    [MyHttpCallbacks get] successHttpMethod];
}

Where successHttpMethod reside in another class and you include it as an import.

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