使用布尔值?在 if 表达式中 [英] Use of Boolean? in if expression

问题描述

如果我有一个可为空的 Boolean b，我可以在 Java 中进行以下比较:

Boolean b = ...;如果 (b != null && b) {/* 做一点事 */} 别的 {/* 做别的事情 */}

在 Kotlin 中，我可以通过使用 !! 操作符来实现相同的效果:

val b:布尔值?= ...if (b != null && b!!) {/* 做一点事 */} 别的 {/* 做别的事情 */}

然而，!! 的使用让我感觉有点粗略，绕过了零安全系统.

对此有更优雅的方法吗?

<小时>

编辑 看来我有点过于简单化了.对于局部变量，正如

解决方案

You can compare nullable boolean with true, false or null using相等运算符:

var b:布尔值?= 空如果 (b == 真) {//b 不为空且等于真}如果(b == 假){//b 是假的}如果 (b != 真) {//b 为空或假}

If I have a nullable Boolean b, I can do the following comparison in Java:

Boolean b = ...;
if (b != null && b) {
   /* Do something */
} else {
   /* Do something else */
}

In Kotlin, I can achieve the same by using the !! operator:

val b: Boolean? = ...
if (b != null && b!!) {
   /* Do something */
} else {
   /* Do something else */
}

However, the use of !! feels a bit sketchy to me, circumventing the null safety system.

Is there a more elegant approach for this?

---

Edit It seems I oversimplicated a bit. For local variables, as Banthar shows, it does work. However, my Boolean b is actually a "property with a backing field" (I'm not really up to speed yet what this imposes). This is the result:

解决方案

You can compare nullable boolean with true, false or null using equality operator:

var b: Boolean? = null
if (b == true) {
    // b was not null and equal true
} 
if (b == false) {
   // b is false 
}
if (b != true) { 
   // b is null or false 
}

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