如何在F＃中聲明循環相關的抽象類

Question

考慮兩個抽象類alpha和beta：

[<AbstractClass>]  
type alpha () =
    abstract member foo: beta->beta

[<AbstractClass>] 
and beta () = //***
    abstract member bar: alpha

如果我嘗試編譯，我得到一個錯誤，在* * *指示的行上：

error FS0010: Unexpected keyword 'and' in interaction

如果我寫：

[<AbstractClass>]  
type alpha () =
    abstract member foo: beta->beta

and beta () =
    abstract member bar: alpha

然后我得到：

error FS0365: No implementation was given for 'abstract member beta.bar : alpha'

以及我應該添加AbstractClass屬性的提示

那么我如何聲明循環定義的抽象類？

Answer 1

將屬性放在'and'關鍵字后面：

[<AbstractClass>]
type alpha () =
    abstract member foo : beta -> beta

and [<AbstractClass>]  beta () =
    abstract member bar : alpha