Default Initializer in swift

Question

I created a swift class with string optionals (String?) and instantiated the class in a different swift file and got a compile error. When I instantiate the class within the same file, there is no error. Is there something wrong I am doing? I double checked the behaviour and this behaviour is consistent even with the class definition given in the swift documentation:

class ShoppingListItem {
    var name: String?
    var quantity = 1
    var purchased = false
}
var item = ShoppingListItem()

Excerpt From: Apple Inc. “The Swift Programming Language.” iBooks. https://itun.es/in/jEUH0.l

If the var item = ShoppingListItem() is done in the appDelegate.swift, from the function application:didFinishLaunchingWithOptions we get the error:

<class> cannot be initialised because it has no accessible initializers

OTOH, if we keep the instantiation as soon as the class declaration ends, there is no problem.

Edit: This issue is not a showstopper, the current default initialiser behaviour seems inconsistent or I need to understand it better

Also add some context around where you use the classes, I'm not sure I understand the issue. — HighFlyingFantasy
– HighFlyingFantasy, Commented Aug 15, 2014 at 14:15
@PseudoNym01 there is a compile error: <class> cannot be initialised because it has no accessible initialisers. — runios
– runios, Commented Aug 15, 2014 at 14:36
@HighFlyingFantasy I created a new swift file which would contain my model, within it I created a class (take the code above as the class for a sample). I then instantiated the class within the appDelegate - applicationdidFinishLaunchingWithOptions. Doing this gives a compile error, the error as stated above. — runios
– runios, Commented Aug 15, 2014 at 14:43

HighFlyingFantasy · Accepted Answer · 2014-08-15 15:13:56Z

32

Chances are it's an issue with the Swift compiler and access control (not pointing fingers, just trying to troubleshoot). Add an explicit initializer to the class and see if that works:

class ShoppingListItem {
    var name: String?
    var quantity = 1
    var purchased = false

    init() { }
}

If that doesn't work, then set the class to public, along with the initializer

    public class ShoppingListItem {
        var name: String?
        var quantity = 1
        var purchased = false

        public init() { }
    }

answered Aug 15, 2014 at 15:13

HighFlyingFantasy

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4 Comments

runios Over a year ago

Yes adding an explicit init() does work and thats what I did, the point of the question was me wanting to be sure that this is an issue with the compiler. From the responses so far it seems like a compiler issue. I would mark this as the answer if there are no other contradicting responses.

Eneko Alonso Over a year ago

It is not a compiler issue. All pure Swift classes (those with no parent), require at least one initializer (or initial values for all their members, including Optionals). This is not very well explained by Apple's documentation.

Christopher Wade Cantley Over a year ago

I am working with this in a Playground and turns out I also needed to make the class, init, and variables public in order to access them. Thanks for the help on this.

davis Over a year ago

Why is it that the Playground requires initializers to be public, but a subclass hierarchy with NSObject as the parent does not?

zrslv · Accepted Answer · 2014-10-08 23:55:13Z

17

Providing all members with a default value, in this case

var name: String? = nil

fixes the error.

answered Oct 8, 2014 at 23:55

zrslv

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3 Comments

Anton Over a year ago

Have just discovered the same

Iducool Over a year ago

It fixes the error but swift book is saying that "If you define an optional constant or variable without providing a default value, the constant or variable is automatically set to nil for you: ". So, why here do we need to provide explicitly nil?

user1244109 Over a year ago

didn't make a change

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