Subclassing NSObject in Swift - Best Practice with Initializers

Woodstock picture Woodstock · Aug 16, 2014 · Viewed 39.6k times · Source

Here is the layout of an example Class, can someone guide me on what's best practice when creating a subclass of NSObject?

class MyClass: NSObject {

    var someProperty: NSString! = nil

    override init() {
        self.someProperty = "John"
        super.init()
    }

    init(fromString string: NSString) {
        self.someProperty = string
        super.init()
    }

}

Is this correct, am I following best practice here?

I wonder if I'm correctly setting up the initializers (one that sets the string to a default, and one which I can pass in a string)?

Should I call super.init() at the end of each of the initializers?

Should my more specific (the one that takes a string) initializer simply call self.init() at the end rather than super.init()?

What is the right way to set up the initializers in Swift when subclassing NSObject? - and how should I call the super init ?

This question (albeit in Objective C) suggests you should have an init, which you always call and simply set the properties in more specific inits: Objective-C Multiple Initialisers

Answer

Maxim Shoustin picture Maxim Shoustin · Aug 17, 2014

I'm not Swift ninja but I would write MyClass as:

class MyClass: NSObject {

    var someProperty: NSString // no need (!). It will be initialised from controller 

    init(fromString string: NSString) {
        self.someProperty = string
        super.init()
    }

    convenience override init() {
        self.init(fromString:"John") // calls above mentioned controller with default name
    }        
}

See the initialization section of the documentation