is there an objective-c "equivalent" to ruby's send method?

Question

I'm not sure this is possible, but in ruby, you can dynamically call a method using send

e.g. if I want to invoke the bar method for the object, foo, I can use

foo.send("bar")

Is there any way of doing something similar using objective-c?

tks!

Answer 1

There are several options, as far as I know

1. You could use NSObject's performSelector: method. This, however, is only really good for methods that have few or no arguments.
2. Use the NSInvocation class. This is a bit heftier, but is a lot more flexible.
3. You might be able to use objc_msgSend(), but it's probably a bad idea to call it directly, due to other stuff that the runtime might be doing behind the scenes.

Answer 2

For general use (method with a return value and any number of arguments), use NSInvocation:

if ([target respondsToSelector:theSelector]) {
    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:
        [target methodSignatureForSelector:theSelector]];
    [invocation setTarget:target];
    [invocation setSelector:theSelector];
    // Note: Indexes 0 and 1 correspond to the implicit arguments self and _cmd, 
    // which are set using setTarget and setSelector.
    [invocation setArgument:arg1 atIndex:2]; 
    [invocation setArgument:arg2 atIndex:3];
    [invocation setArgument:arg3 atIndex:4];
    // ...and so on
    [invocation invoke];
    [invocation getReturnValue:&retVal]; // Create a local variable to contain the return value.
}