Kotlin的平等 [英] Equality in Kotlin

问题描述

我正在学习Kotlin，具有C ++和Java背景。我期待以下内容打印 true ，而不是 false 。我知道 == 映射到等于。 的默认实现是否等于不比较每个成员，即 firstName 和 lastName ？如果是这样，它不会看到字符串值相等（因为 == 再次映射到等于）？显然有一些与平等和身份相关的东西，我还没有在Kotlin中找到。

I'm learning Kotlin, with a C++ and Java background. I was expecting the following to print true, not false. I know that == maps to equals. Does the default implementation of equals not compare each member, i.e. firstName and lastName? If so, wouldn't it see the string values as equal (since == maps to equal again)? Apparently there's something related to equality versus identity that I haven't got right in Kotlin yet.

class MyPerson(val firstName: String, val lastName: String)

fun main(args: Array<String>) {
   println(MyPerson("Charlie", "Parker") == MyPerson("Charlie", "Parker"))
}

推荐答案

默认您描述的等于实现仅存在于数据类中。不适用于从 Object 继承实现的常规类，只需使对象等于它自己。

The default equals implementation you're describing exists only for data classes. Not for regular classes where the implementation is inherited from Object, and just make the object equal to itself.

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