Calling instance method during initialization in Swift

constructor, initialization, ios, swift

Solution

Convert `createY()` to a global or class function that accepts `x` as an argument and returns a `y`.

func createY(x: String) -> String {
    return x + "_test" // this computation could be much more complex
}

Then just call it normally from your `init`.

class MyClass {
  let x: String
  let y: String

  init(x: String) {
    self.x = x
    self.y = createY(x)
  }     
}

Problem

I am new to Swift and would like to initialize an object's member variable using an instance method like this: ``` class MyClass { var x: String var y: String func createY() -> String { self.y = self.x + "_test" // this computation could be much more complex } init(x: String) { self.x = x self.y = self.createY() } } ``` Basically, instead of inlining all the initialization code in `init` method, I want to extract the initialization code of `y` to a dedicated method `createY` and call this instance method `createY` in `init`. However, Swift compiler (Swift 1.2 compiler in Xcode 6.3 beta) complains: use of 'self' in method call 'xxx' before super.init initialize self Here 'xxx' is the name of the instance method (createY). I can understand what Swift compiler is complaining and the potential problem it wants to address. However, I have no idea how to fix it. What should be the correct way in Swift to call other instance method of initialization code in `init`? Currently, I use the following trick as work around but I don't think this is the idiomatic solution to this problem (and this workaround requires `y` to be declared using `var` instead of `let` which makes me feel uneasy too): ``` init(x: String) { self.x = x super.init() self.y = createY() } ``` Any comment is appreciated. Thanks.

Original source