Calling a method by using variables in the method name?

Question

I have a situation in objective-c, specifically for iOS app development, that a particular method will execute and return a number, from 01 - 20. Also, I have 20 different methods, name m01, m02, m03, etc.

How can I program my code so that my first method calls another method that corresponds to the returned number from the first method?

Something like this:

[self m[NSStringWithFormat=@"%i", myOutputFromMethod1];

Can someone please help me get this to work?

score 5 · Accepted Answer · answered Jun 13 '13 at 05:00

5

You can get the name of a selector using NSSelectorFromString([NSString stringWithFormat:@"m%i", myOutputFromMethod1]) and then perform it using [self performSelector:].

answered Jun 13 '13 at 05:00

borrrden

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Great, I'll give it a try. Thanks! – jake9115 Jun 13 '13 at 05:01
Be aware, though, that the method *must* return an objective-c object (i.e. `NSNumber` as opposed to `int`) – borrrden Jun 13 '13 at 05:02
oh thanks for pointing that out! – jake9115 Jun 13 '13 at 05:02
See my updated answer, you just insert what you were trying to create in your question. – borrrden Jun 13 '13 at 05:03
Awesome! A bit off topic, instead of [self method], how can I call a method from another .h/.m file? Would I need to import something? – jake9115 Jun 13 '13 at 05:05
Oh, it can also return `void` just to be clear, but if it does return it has to return an object. – borrrden Jun 13 '13 at 05:05
You can use `performSelector:` on *any* valid objective-c object that inherits from `NSObject` (which is virtually everything). – borrrden Jun 13 '13 at 05:06
Awesome! It is working great, but I received a warning: "PerformSelector may cause a leak because its selector is unknown". Is this something to worry about? Also, will Appel reject apps that have warnings? – jake9115 Jun 13 '13 at 05:38
http://stackoverflow.com/a/7017537/1155387 – borrrden Jun 13 '13 at 05:59

score 2 · Answer 2 · answered Jun 13 '13 at 05:01

2

SEL s = NSSelectorFromString([NSString NSStringWithFormat:@"m%i", myOutputFromMethod1]);
[anObject performSelector:s];

answered Jun 13 '13 at 05:01

Vinayak Kini

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Usman.3D · Answer 3 · 2013-06-13T06:21:19.643

Using dozens of methods depending upon a returning value is definitely not a good programming practice, (unless you have some very special requirements which I'm not aware of). You can call the same method but pass a paramter to it. That parameter can be put into a switch statement, then you can write a 'case' for each value of parameter. For example

-(void) method_m :(int)mNum
{
    switch(mNum)
    {
        case 0:
            //your code for method 00
            break;
        case 1:
            //your code for method 01
            break;
        default:
            break;
    }
}

I hope it helps.

score 0 · Answer 4 · answered Jun 13 '13 at 05:21

0

SEL s = NSSelectorFromString([NSString NSStringWithFormat: @"m%i", myOutputFromMethod1]);

if ([anObject respondsToSelector: s])
{
    [anObject performSelector: s];
}

answered Jun 13 '13 at 05:21

stosha

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Calling a method by using variables in the method name?

4 Answers4