属性包含/排除Kotlin数据类 [英] Property include/exclude on Kotlin data classes

问题描述

假设我只希望在生成的equals和hashCode实现中包含一个或两个字段(或者排除一个或多个字段).对于简单的课程，例如:

Suppose I only want one or two fields to be included in the generated equals and hashCode implementations (or perhaps exclude one or more fields). For a simple class, e.g.:

data class Person(val id: String, val name: String)

Groovy有这个:

Groovy has this:

@EqualsAndHashCode(includes = 'id')

龙目岛有这个:

@EqualsAndHashCode(of = "id")

在Kotlin中惯用的方式是什么?

What is the idiomatic way of doing this in Kotlin?

data class Person(val id: String) {
   // at least we can guarantee it is present at access time
   var name: String by Delegates.notNull()

   constructor(id: String, name: String): this(id) {
      this.name = name
   }
}

虽然感觉很不对...我真的不希望name是可变的，并且额外的构造方法定义很丑.

Just feels wrong though... I don't really want name to be mutable, and the extra constructor definition is ugly.

推荐答案

我使用了这种方法.

data class Person(val id: String, val name: String) {
   override fun equals(other: Person) = EssentialData(this) == EssentialData(other)
   override fun hashCode() = EssentialData(this).hashCode()
   override fun toString() = EssentialData(this).toString().replaceFirst("EssentialData", "Person")
}

private data class EssentialData(val id: String) {
   constructor(person: Person) : this(id = person.id) 
}

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