Objective-C passing methods as parameters Objective-C passing methods as parameters ios ios

Objective-C passing methods as parameters


The type you are looking for is selector (SEL) and you get a method's selector like this:

SEL littleSelector = @selector(littleMethod);

If the method takes parameters, you just put : where they go, like this:

SEL littleSelector = @selector(littleMethodWithSomething:andSomethingElse:);

Also, methods are not really functions, they are used to send messages to specific class (when starting with +) or specific instance of it (when starting with -). Functions are C-type that doesn't really have a "target" like methods do.

Once you get a selector, you call that method on your target (be it class or instance) like this:

[target performSelector:someSelector];

A good example of this is UIControl's addTarget:action:forControlEvents: method you usually use when creating UIButton or some other control objects programmatically.


Another option is to look at blocks. It allows you to pass a block of code (a closure) around.

Here's a good write up on blocks:

http://pragmaticstudio.com/blog/2010/7/28/ios4-blocks-1

Here's the apple docs:

http://developer.apple.com/library/ios/#documentation/cocoa/Conceptual/Blocks/Articles/00_Introduction.html


Objective C makes this operation relatively easy. Apple provides this documentation.

To directly address your question, you are not calling a function, but a selector. Here is some sample code:

Big Function:

+ (void)theBigFunction:(SEL)func fromObject:(id) object{    [object preformSelector:func]}

Then for class B:

- (void)littleBFunction {    NSLog(@"classB little function");}// somewhere else in the class[ClassA theBigFunction:@selector(littleBFunction) fromObject:self]

Then for class C:

- (void)littleCFunction {    NSLog(@"classC little function");}// somewhere else in the class[ClassA theBigFunction:@selector(littleCFunction) fromObject:self]

EDIT: Fix selectors sent (remove the semicolon)


matomo