How to properly subclass SKNode when there is no init method?

Question

SKNode only offers +node method.

If you do this:

+ (instancetype)node {
    CustomNode *body = [CustomNode node]; // infinite loop
}

If you do this:

+ (instancetype)node {
    CustomNode *body = [super node]; // instance of SKNode, not CustomNode
}

How do you subclass a class that only has a convenience constructor in such way that you can override the constructor? Or is it best practice to create your own +customNode method?

Answer 1

No one's saying you can't use [... alloc] init] on an SKNode subclass. After all, SKNode is a subclass of NSObject. +node is just a convenience method.

+ (instancetype)node {
    CustomNode *body = [[self alloc] init];
    return body;
}

There's nothing wrong with this.

Answer 2

+ (instancetype)node {
    CustomNode *body = [CustomNode node]; // infinite loop
}

And infinite loop is the expected result, since you are calling the same method. As for the other one:

+ (instancetype)node {
    CustomNode *body = [super node]; // instance of SKNode, not CustomNode
}

The goal here is for you to make your CustomNode get initialised as expected. It's the same thing when you create a UIViewController for example:

if ( self == [super initWithNibName:nibName bundle:bundle])

You want to do the standard initialisation. What you do after, is what makes your CustomNode a custom node. :)

+ (instancetype)node {
    CustomNode *body = [super node];
    // My own logic goes here

   return body;
}

Answer 3

The solution is actually to do nothing. The default implementation of +[SKNode node] returns an instance of whatever class or subclass it is called on.

Don't override +[SKNode node] in your subclass. Instantiate instances of your class as in the following example:

// In MyScene.m
// MyNode is a SKNode subclass

- (void)createNewNode
{
    MyNode *node = [MyNode node]; // node is of type MyNode

    [self addChild:node];
}