Dynamic method call in Objective-C

Question

How can I call a selector with its name in NSString * in objective c? I also need to call the selector only if the target will accept it. e.g.

+(void) callMethod: (NSString *) method onObject: (id) object
{
    // do some magic
}

When I call callMethod: @"Foo" onObject: obj if obj implements Foo then [obj Foo] should be called, if it doesn't implement it, nothing should happen.

user557219 · Accepted Answer · 2011-06-10 23:28:09Z

16

SEL selector = NSSelectorFromString(method);
if ([object respondsToSelector:selector]) {
    [object performSelector:selector];
}

answered Jun 10, 2011 at 23:28

user557219

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Comments

Basil Bourque · Accepted Answer · 2014-03-12 23:23:03Z

6

First, you use the NSSelectorFromString() method to convert the string into a method name, like so:

SEL methodToCall = NSSelectorFromString(stringToConvertToMethod);

Then, you check for the method on the receiver and call the method if it exists:

if ([receiver respondsToSelector:methodToCall]) {

  //  Method exists, call it.
  [receiver performSelector:methodToCall];

}

Just note that a potential downside is that you will not be able to pass in arguments. For passing an argument, you would call the NSObject method performSelector:withObject:. For passing two arguments, performSelector:withObject:withObject:.

edited Mar 12, 2014 at 23:23

Basil Bourque

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answered Jun 10, 2011 at 23:31

Moshe

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