kotlin - 使用反射在Kotlin中按字符串设置属性？

Question

我有一个对象:

class User {
  var id: String? = null
  var name: String? = null
}

和对列表:

val fieldsToChange = listOf<Pair<String, String>>(Pair("name", "foo"), Pair("id", "bar"))

我想迭代成对的低谷列表，并使用反射为给定的属性设置适当的值。

Answer 1

给定类实例obj，我们可以使用obj::class.memberProperties提取具有名称的属性。

我们可以构造从属性名称到属性的映射:

val nameToProperty = obj::class.memberProperties.associateBy(KProperty<*>::name)

然后，我们可以遍历fieldsToChange并检索属性并进行设置:

fieldsToChange.forEach { (propertyName, propertyValue) ->
   nameToProperty[propertyName]
       .takeIf { it is KMutableProperty<*> } // take only "settable" (var) properties
       ?.let { it as KMutableProperty<*> } // cast it to mutable property so we can access setter
       ?.let { it.setter.call(obj, propertyValue) } // call the setter
}

另外，我们可以使这个通用:

fun setFields(obj: Any, fieldsToChange: List<Pair<String, Any?>>) {
    val nameToProperty = obj::class.memberProperties.associateBy(KProperty<*>::name)
    fieldsToChange.forEach { (propertyName, propertyValue) ->
        nameToProperty[propertyName]
                .takeIf { it is KMutableProperty<*> }
                ?.let { it as KMutableProperty<*> }
                ?.let { it.setter.call(obj, propertyValue) }
    }
}

val user = User()
setFields(user, fieldsToChange)

assert(user.name == "foo")
assert(user.id == "bar")

可能的改进是优化nameToProperty以仅包含已经转换为KMutableProperty的MutableProperty