已定义 class 的可区分联合

Question

我有学校 class（有 2 个构造函数）：

type School(name, antiquity) = 
    member this.Name: string = name
    member this.Antiquity: int = antiquity

    new(name) = School(name, 0)

以及建筑类型：

type Building =
| House
| School of School

我想知道具有"knowType"功能的建筑物是什么类型：

let knowType building =
    match building with
    | House -> "A house!"
    | School -> "A school" // Error

"knowType"中的错误是第二种情况："The constructor is applied to 0 arguments, but expect 1".

Answer 1

应该是

let knowType building =
    match building with
    | House -> "A house!"
    | School _ -> "A school"

您需要为 of School 部分提供一个变量。 _ 就是忽略

Discriminated union with an already defined class