ios swift init of uninitialized instance variable

Question

Have a simple question on Swift. I have a simple base class Base and a child class ABase:

class Base {
    var test1:Int

    init(forTest test1:Int) {
        self.test1 = test1
    }
}

class ABase : Base {
    var test3:Int

    init(forAnother test3:Int) {
        **super.init(forTest: test3)**
        self.test3 = test3
    }
}

I get a compiler error at the super.init(forTest: test3) line in my init call in ABase. The error is:

Property 'self.test3' no initialized at super.init call.

I'm trying to understand why I can't init an object with an uninitialized var in Swift?

Lou Franco · Accepted Answer · 2014-06-19 00:21:15Z

2

Swift has a two-phase init, in which you need to initialize all of your members before doing anything else.

init(forAnother test3:Int) {
    self.test3 = test3
    super.init(forTest: test3)
}

More info here:

https://developer.apple.com/library/prerelease/ios/documentation/swift/conceptual/swift_programming_language/Initialization.html

Search for two-phase init on the page.

If you needed to call super.init() (for example, if test3 depended on what it did), you could give an initial value to test3 in its declaration.

answered Jun 19, 2014 at 0:21

Lou Franco

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