Kotlin和泛型，用泛型数组实现抽象泛型类(Kotlin and generics, implementing abstract generic class with generic array)

 我有以下抽象类 
 
 abstract class Vec2t<T : Number>(open var x: T, open var y: T) 
 
 由...实施 
 
 data class Vec2(override var x: Float, override var y: Float) : Vec2t<Float>(x, y) 
 
 到目前为止，一切正常 
 
 现在，我想为矩阵做类似的事情，这是我的抽象类 
 
 abstract class Mat2t<T : Number>(open var value: Array<out Vec2t<T>>) 
 
 应该通过实施 
 
 class Mat2(override var value: Array<Vec2>) : Mat2t<Float>(value) 
 
 但编译器抱怨Array<Vec2> ： 
 
 
 
 错误：（8,32）Kotlin：'value'的类型与在main.mat.Mat2t中定义的重写的var-property'public open var value：Array>的类型不匹配' 
 
 
 有人告诉我： 
 
 
 
 当我覆盖它时，我无法更改var属性的类型（但实际上我并没有真正改变它，我用一个子类型覆盖它...是同样的事情吗？） 
 
 
 mat2.value = object : Vec2t<Float>() { ... }无效， Mat2t<Float>任何子类都不一定如此 
 
 
 我怎么能克服这些问题呢？ 
 
 有没有办法让一个抽象的泛型类Mat2t与一个通用数组并用子类型数组实现它？ 

I have the following abstract class 
 
abstract class Vec2t<T : Number>(open var x: T, open var y: T)
 
implemented by 
 
data class Vec2(override var x: Float, override var y: Float) : Vec2t<Float>(x, y)
 
So far, everything works just fine
 
Now, I'd like to do something similar for the matrices, this is at the moment my abstract class
 
abstract class Mat2t<T : Number>(open var value: Array<out Vec2t<T>>)
 
that should be implemented by
 
class Mat2(override var value: Array<Vec2>) : Mat2t<Float>(value)
 
But compiler complains on Array<Vec2>:
 
 
 
Error:(8, 32) Kotlin: Type of 'value' doesn't match the type of the overridden var-property 'public open var value: Array> defined in main.mat.Mat2t'
 
 
I was told:
 
 
 
I can't change the type of a var property when I override it (but actually I am not really changing it, I am overriding it with a subtype.. is it the same thing?)
 
 
mat2.value = object : Vec2t<Float>() { ... } would not be valid, which must not be the case for any subclass of Mat2t<Float>
 
 
How may I overcome these problems? 
 
Is there a way to have an abstract generic class Mat2t with a generic array and implement it with a subtype array?

原文：https://stackoverflow.com/questions/40528739