Kotlin 数据类 : how to read the value of property if I don't know its name at compile time?

Question

如果属性名称仅在运行时已知，我如何读取 Kotlin 数据类实例中的属性值？

Answer 1

这是一个从给定属性名称的类的实例中读取属性的函数(如果未找到属性则抛出异常，但您可以更改该行为):

import kotlin.reflect.KProperty1
import kotlin.reflect.full.memberProperties

@Suppress("UNCHECKED_CAST")
fun <R> readInstanceProperty(instance: Any, propertyName: String): R {
    val property = instance::class.members
                     // don't cast here to <Any, R>, it would succeed silently 
                     .first { it.name == propertyName } as KProperty1<Any, *> 
    // force a invalid cast exception if incorrect type here
    return property.get(instance) as R  
}

build.gradle.kts

dependencies {
    implementation(kotlin("reflect"))
}

---

使用

// some data class
data class MyData(val name: String, val age: Int)
val sample = MyData("Fred", 33)

// and reading property "name" from an instance...
val name: String = readInstanceProperty(sample, "name")

// and reading property "age" placing the type on the function call...
val age = readInstanceProperty<Int>(sample, "age")

println(name) // Fred
println(age)  // 33