Binding Button action to close an App

I'm very much new to the world of cocoa, and I'm trying out small programs to get the hang of the mvc concept. Right now, I'm trying to close an app when I click a button on my app. Like having an 'Exit' button on your app.

In my controller.h, I have created this

Code:

- (IBAction) exitApp : (NSButton*) sender;

In my controller.m,

Code:

- (IBAction) exitApp : (NSButton*) sender {

// what should I write inside to close an app on click of a button ?

}

Can someone please help?