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() = ...

但是获取错误：只包含没有隐式构造函数的结构和类，可能会给出'StructLayout‘属性

所以我意识到一定有相似之处：

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

但这样我就失去了我的界面。例如，在C#中，对这类类添加type:StructLayout是可能的(我认为)。如何重构代码以避免此错误？

Answer 1

正如错误消息所述，StructLayout应该与显式构造函数一起工作。

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有任何进一步的问题，请查看代码示例这里。