问题描述

我是 Swift 新手，想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，我不想在 init 方法中内联所有初始化代码，而是想将 y 的初始化代码提取到专用方法 createY 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).

我可以理解 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 var 声明 ycode> 而不是 let 这让我也感到不安):

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
}

然后从你的 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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