Kotlin使用通用化获取泛型类型类 [英] Kotlin get generic type class using reified

问题描述

我刚开始使用Kotlin而不是Java，但我正努力进行可靠的工作来检索泛型类型类.这是我的用例

I just started using Kotlin instead of Java and i'm struggling to make refied work to retrieve a generic type class. Here my use case

abstract class BaseDataFragment<VM : BaseViewModel> : BaseFragment()
{
    @Inject
    protected lateinit var viewModelProvider: ViewModelProvider
    protected lateinit var viewModel: VM

    @CallSuper
    override fun init(savedInstanceState: Bundle?)
    {
        viewModel = viewModelProvider.get(getViewModelClass())
    }

    private inline fun <reified T : ViewModel> getViewModelClass():Class<T> = T::class.java
}

不幸的是，我从getViewModelClass()收到错误消息:

Unfortunately i get an error from getViewModelClass():

不能将"VM"用作已类型化参数.改用类.

Cannot use 'VM' as reified type parameter. Use a class instead.

反正有办法使它正常工作吗?

Is there anyway to make it work?

推荐答案

reified并不是用于类型擦除的神奇解决方法. JVM上的泛型类的实例不包含有关实例化其类型参数的任何信息.因为信息不存在，所以不能使用reified来访问它.

reified is not a magical workaround for type erasure. An instance of a generic class on the JVM does not carry any information about the type parameter it was instantiated with. Because the information is not there, reified cannot be used to access it.

reified仅在编译时在调用站点知道类型信息的情况下才有效，而在这种情况下不是这样.

reified only works when the type information is known at the call site at compile time, which is not the case here.

如果您希望做到这一点，则需要将Class或KClass作为类的属性存储，或者实际上是创建用于获取Class或KClass实例的虚拟方法.每个派生类.

If you want to be able to do that, you need to store a Class or KClass as a property of your class, or indeed to create a virtual method for obtaining the Class or KClass instance for each derived class.

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