Kotlin:在构造函数中初始化类属性 [英] Kotlin: Initialize class attribute in constructor

问题描述

我创建一个带有class属性的Kotlin类，该属性要在构造函数中初始化:

I create a Kotlin-class with a class attribute, which I want to initialize in the constructor:

public class TestClass {

    private var context : Context? = null // Nullable attribute

    public constructor(context : Context) {
       this.context = context
    }

    public fun doSomeVoodoo() {
       val text : String = context!!.getString(R.string.abc_action_bar_home_description)
    }
}

不幸的是，我必须使用?"将属性声明为Nullable.符号，尽管该属性将在构造函数中初始化.将此属性声明为Nullable-attribute，总是必须用"!!"强制使用NonNull值.或提供带有?"的空检查.

Unfortunately I have to declare the attribute as Nullable with the "?" sign, although the attribute will be initialized in the constructor. Declaring this attribute as Nullable-attribute makes it always necessary to force an NonNull-value with "!!" or to provide a Null-check with "?".

如果将在构造函数中初始化class属性，有什么办法可以避免这种情况?我想感谢这样的解决方案:

Is there any way to avoid this, if the class attribute will be initialized in the constructor? I would like to appreciate a solution like this one:

public class TestClass {

    private var context : Context // Non-Nullable attribute

    public constructor(context : Context) {
       this.context = context
    }

    public fun doSomeVoodoo() {
       val text : String = context.getString(R.string.abc_action_bar_home_description)
    }
}

推荐答案

如果您在构造函数中唯一要做的事情是赋值， 那么您可以将主构造函数与私有属性一起使用.

If the only thing you are doing in the constructor is an assignment, then you could use the Primary Constructor with a private Property.

例如:

public class TestClass(private val context: Context) {

  public fun doSomeVoodoo() {
     val text = context.getString(R.string.abc_...)
  }
}

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