使用隐式构造函数将 StructLayout 属性添加到 F# 类型

Question

我有：

type Package =
    abstract member Date : int
    abstract member Save : unit -> unit

[<type:StructLayout(LayoutKind.Sequential, Pack=1, CharSet=CharSet.Ansi)>]
type Instant(date : int, value : int) =
    let mutable _date = date
    let mutable _value = value
    member X.Value : int = _value
    interface Package with    
        member X.Date : int = _date
        member X.Save() = ...

但出现错误：只有没有隐式构造函数的结构和类才能被赋予“StructLayout”属性

所以我意识到它一定是相似的：

type Instant =
    struct
        val Date : byte array
        ...

但是这样我就失去了我的界面。例如，在 C# 中，可以为这种类型的类添加 type:StructLayout（我认为）。我必须如何重构我的代码以避免此错误？

Answer 1

正如错误消息所说，StructLayout 应该与explicit constructors 一起使用：

type Package =
    abstract member Date : int
    abstract member Save : unit -> unit

[<type:StructLayout(LayoutKind.Sequential, Pack=1, CharSet=CharSet.Ansi)>]
type Instant =
    val mutable Date: int
    val mutable Value: int
    new(date, value) = {Date = date; Value = value}

    interface Package with
        member x.Date = x.Date
        member x.Save() = x.Value |> ignore

如果您对FieldOffset 有任何其他问题，请查看代码示例here。