使用“大于"，“小于"的正确方法是什么? Kotlin中可空整数的比较? [英] What is the right way of using "greater than", "less than" comparison on nullable integers in Kotlin?

问题描述

var _age: Int? = 0

public var isAdult: Boolean? = false
   get() = _age?.compareTo(18) >= 0 

这仍然给我提供了一个空安全的编译错误，但是在这种情况下如何使用>，<，> =或< =?

This still gives me a null-safety, compile error, but how can I use >, <, >= or <= in this matter?

推荐答案

var age : Int? = 0

public val isAdult : Boolean?
    get() = age?.let { it >= 18 }

另一种解决方案是使用委托:

The other solution would be using delegates:

var age : Int by Delegates.notNull()
public val isAdult : Boolean
    get () = age >= 18

因此，如果您尝试获取年龄或在实际分配年龄之前检查isAdult，则会获得异常而不是null.

So if you try to get age or check isAdult before age was actually assigned then you'll get exception instead of null.

无论如何，我认为年龄= 0是某种魔术，有一天可能会导致问题(甚至是产品问题).

Anyway I believe age = 0 is some kind magic that one day may lead to issue (even prod issue).

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