Objective-C equivalent to Java's anonymous classes in class methods

As JeremyP has rightly said, There are no anonymous classes in Objective C like there are in Java.

But in Java, anonymous classes are mostly used to implement single method interface or what we also call as a functional interface.

We do it to avoid having to implement the interface** in a class **just for one method implementation which is most commonly used for Listeners, Observers and event handlers.

This is mostly done because of **lack of anonymous first class functions in Java (prior to version 8 and project lambda).

Objective C has something called as blocks, where you can directly pass a block which contains the implementation of that single method rather than an empty class wrapping it up.

Example:

A use of Anonymous Class in Java

//Functional interface
interface SomethingHandler 
{
  void handle(Object argument);
}

//a method that accepts the handler in some other class
class SomeOtherClass
{ 
  void doSomethingWithCompletionHandler(SomethingHandler h){
      // do the work that may consume some time in a separate thread may be.
      // when work is done call the handler with the result which could be any object
      h.handler(result);
  };
}

// Somewhere else in some other class, in some other code
// passing the handler after instantiating someObj as an object of SomeOtherClass which can use the handler as needed
SomeOtherClass someObj = new SomeOtherClass();
someObj.doSomethingWithCompletionHandler( new SomethingHandler()
                        {
                              void handle(Object argument)
                              {
                                // handle the event using the argument
                              }
                         });

In Objective C

// declare the handler block 
typedef void (^SomethingHandler)(id argument){}

// this interface is different than Java interface