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我想将 setter 属性添加到有区别的工会,我应该怎么做?

费:

type Factor =    
    | Value     of Object
    | Range     of String

    let mutable myProperty = 123
    member this.MyProperty
        with get() = myProperty
        and set(value) = myProperty <- value
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3 回答 3

5

以下是我可能会采用的方法:

type Value = { value: obj; mutable MyProperty: int }
type Range = { range: string; mutable MyProperty: int }

type Factor =    
    | Value     of Value
    | Range     of Range

    member this.MyProperty
        with get() = 
            match this with
            | Value { MyProperty=myProperty }
            | Range { MyProperty=myProperty } -> myProperty
        and set(myProperty) = 
            match this with
            | Value x -> x.MyProperty <- myProperty
            | Range x -> x.MyProperty <- myProperty

并像这样使用它:

let v = Value {value="hi":>obj ; MyProperty=0 }
v.MyProperty <- 2

match v with
| Value { value=value } as record ->
    printfn "Value of value=%A with MyProperty=%i" value record.MyProperty
| _ -> 
    printfn "etc."

我在与您类似的场景中使用了这种技术,并在 FsEye 的手表模型中取得了令人满意的结果:http://code.google.com/p/fseye/source/browse/tags/2.0.0-beta1/FsEye/WatchModel。 FS

于 2012-06-09T14:30:18.820 回答
2

为什么不使用类和活动模式:

type _Factor =    
    | Value_     of obj
    | Range_     of string

type Factor(arg:_Factor) =

    let mutable myProperty = 123
    member this._DU = arg
    member this.MyProperty
        with get() = myProperty
        and set(value) = myProperty <- value

let (|Value|Range|) (arg:Factor) = 
    match arg._DU with
    |Value_(t) -> Value(t)
    |Range_(t) -> Range(t)

这显然会慢得多,但它可以让你做你想做的事

于 2012-06-09T08:16:58.523 回答
1

我对 F# 还不太熟悉,但我想你不能这样做,这没有任何意义。从他们的名字可以看出,受歧视的工会是工会。它们代表了某种选择。你正试图将一些状态融入其中。你想达到什么目的?用例是什么?

也许您需要做的就是为您的 DU 添加额外的“参数”,即如果您有

type DU = 
    | A of int
    | B of string

并且您想添加 int 类型的 setter,那么您可以通过以下方式扩展 DU:

type DU = 
    | A of int * int
    | B of string * int

    member x.Set i =
        match x with
        | A(a1, a2) -> A(a1, i)
        | B(b1, b2) -> B(b1, i)
于 2012-06-09T08:19:45.703 回答