Like many people I'm interested on Objective - C and Cocoa programming. I know conceptually what a delegate it is but I don't understand how to use them or when to use them. Here is some example code:

#import "AppControler.h"


@implementation AppControler

-(id)init
{
    [super init];
    NSLog(@"init");

    speechSynth = [[NSSpeechSynthesizer alloc] initWithVoice:nil];
    //
    [speechSynth setDelegate:self];
    voiceList = [[/Applications/Google Chrome.app availableVoices] retain];

    return self;
}

I'm setting the AppControler to be the delegate of the speechSynthasizer. Which means that the speechSynthasizer is telling hte AppControler what to do. But I don't understand this line: [speechSynth setDelegate:self];