Kotlin-如何在"lateinit"和"lateinit"之间做出决定和“可为空的变量"? [英] Kotlin - How to decide between "lateinit" and "nullable variable"?

问题描述

我对lateinit和可为空的变量感到困惑，后者用于变量.

I am confuse for lateinit and nullable variable, which one to use for variable.

lateinit var c: String
var d: String? = null
c = "UserDefinedTarget"

// if not added initialisation for c than throws UninitializedPropertyAccessException
if (c == "UserDefinedTarget") {
    //do some stuff.
}
//not throws any exception whether d is initialise or not.
if(d == "UserDefinedTarget") {
     //do some stuff
}

推荐答案

可为空的类型就是这样，即具有有效状态为null的东西.

A type that is nullable is just that, a thing that has a valid state that is null.

不可为空的延迟初始化var表示其中null为无效状态的某些内容，但是由于某些原因，您不能在构造函数中填充它.

A non-nullable late init var represents something where null is an invalid state, but for some reason you can't populate it in the constructor.

Android活动是使用Lateinit的一个很好的例子.活动必须具有no args构造函数，并且它们的生命周期只能从onCreate()开始.

Android Activities are a good example of a use of lateinit. Activities must have a no args constructor and their lifecycle only really starts with onCreate().

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