Custom Object Initialization in Objective-C

I created a custom object in Objective-C. Now I want to create a custom initializer. The object has two properties, name and score. 开发者_高级运维So my initializer is as follows:

- (id)initWithName:(NSString *)playerName {

    if ((self = [super init])) {
        self.name = [playerName retain];
        self.score = [NSNumber numberWithInt:0];
    }

    return self;
}

Am I using retain here properly? Or can I just make it something like self.name = playerName;?

Furthermore, assume I want another initializer, but keep the initWithName:playerName the designated initializer. How would I make the second initializer call the first?

And for the last question, I know I need to override the - (id)init method too. However, what do I do there? Just assign test properties incase the class was initialized with init only?

Thank you!

Am I using retain here properly?

No you are not. You should either use

self.name = playerName;

as you suggested, or (as recommended by Apple)

name = [playerName copy];

It is not recommended to use accessors in -init because subclasses might override them.

Also, note that as NSString implements NSCopying you should use a copy property, not a retain property.

Furthermore, assume I want another initializer, but keep the initWithName:playerName the designated initializer. How would I make the second initializer call the first?

Using -init as an example (because you must override the super class's designated initialiser if your designated initialiser is not the same)

-(id) init
{
    return [self initWithName: @"Some default value"];
}

you could keep self.name = playerName; if you have declared name as retained property in .h class and have also @synthesized in .m file.

For the initialization you could put the belwo two line of code in separate method.

-(void) initializeWithName:(NSString*) aName withNumber:(int) aNumber
{
  self.name = aName;
  self.score = [NSNumber numberWithInt:aNumber];
}

Lets you have three Initialization method.

- (id)initWithName:(NSString *)playerName {

    if ((self = [super init])) {
      [self initializeWithName:playerName withNumber:0]
    }

    return self;
}


- (id)initWithNumber:(int*) aNumber {

    if ((self = [super init])) {
       [self initializeWithName:nil withNumber:aNumber]
    }

    return self;
}


- (id)init{

    if ((self = [super init])) {
        [self initializeWithName:nil withNumber:0]
    }

    return self;
}

For what's it's worth to the rest of us newbies:

In normal languages, can simply define arguments when instantiating the class:

public final class MakeBed {

    private var foo:Object;
    public var bar:Array;

    public function MakeBed(_foo:Object, _bar:Array) {
        // Do stuff
        foo = _foo;
        bar = _bar;
    }

}

Then when we want to instantiate the class it's as simple as:

var myBeadMaker:MakeBed = new MakeBed({}, []);

In objc everything is backasswards.

You can create your custom initializer similar to:

// These @properties go into the header.h file
@property (nonatomic, retain) NSString *foo;
@property (nonatomic, retain) NSString *bar;

// This is in your implimentation.m file
- (id) initWithInfo:(NSObject*)foo withBar:(NSArray *)bar {
    _foo = foo;
    _bar = bar;
}

Objc automatically "synthesizes" the getters and setters and automatically creates a new variable "blindly" using the same _name _but _with _an _underscore in front when you do the @property thing -- it's magic -- bordering on the "almost too helpful" side of things.

Handy for non-newbies, but incredibly confusing for newbies -- just believe that the getter and setter is made and that a _new _var _is _available.

And the clincher that everyone forgets to mention...

When you want to instantiate the class with your custom initializer you do this:

MakeBed myBedMaker = [[MakeBed alloc] initWithInfo:*foo withBar:*bar];