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

问题描述

我刚开始使用Swift，并且想要使用如下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，不是内联 init 方法中的所有初始化代码，我想提取 y 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测试版中的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:

在超级.init initialize 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编译器的抱怨和潜在的问题。但是，我不知道如何解决它。 Swift中正确的方法应该是在 init ？

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?

中调用初始化代码的其他实例方法。使用以下技巧作为工作，但我不认为这是这个问题的惯用解决方案（和这个解决方法要求使用声明 y var 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。感谢。

推荐答案

将 createY（）转换为全局或类函数接受 x 作为参数，并返回 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，通常从 init 中调用它。

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)
  }     
}

这篇关于在Swift初始化期间调用实例方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！