在 Swift 中初始化期间调用实例方法 [英] Calling instance method during initialization in Swift

问题描述

我是 Swift 的新手，想使用这样的实例方法初始化对象的成员变量:

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()
  }     
}

基本上，我想将y的初始化代码提取到专用方法createYinit方法中的所有初始化代码> 并在 init 中调用此实例方法 createY.但是，Swift 编译器(Xcode 6.3 beta 中的 Swift 1.2 编译器)抱怨:

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:

在 super.init 初始化 self 之前在方法调用 'xxx' 中使用 'self'

use of 'self' in method call 'xxx' before super.init initialize self

这里的'xxx'是实例方法的名称(createY).

Here 'xxx' is the name of the instance method (createY).

我能理解 Swift 编译器在抱怨什么以及它想要解决的潜在问题.但是，我不知道如何解决它.在 Swift 中调用 init 中初始化代码的其他实例方法的正确方法应该是什么?

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?

目前，我使用以下技巧作为解决方法，但我认为这不是解决此问题的惯用方法(并且此解决方法需要使用 varycode> 而不是 let 这也让我感到不安):

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()
} 

感谢任何评论.谢谢.

推荐答案

将 createY() 转换为接受 x 作为参数并返回一个全局或类函数y.

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
}

然后只需从您的 init 正常调用它.

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)
  }     
}

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