寓言实现外部接口编译错误

Question

TL;DR: 我正在尝试创建外部接口，但出现编译错误。我的 F# 技能还不能胜任这项任务。

我已经编写了一个 Photoshop 脚本，现在我正在尝试将该脚本转换为 Fable (F#) 以供我自己的 F# 练习使用。

旁注：我是 F# 的新手，但我有很好的 C# 背景。

要使用 photoshop 脚本库，我需要将其定义为外部接口 (http://fable.io/docs/interacting.html). I am trying to implement a small class first for testing purposes. Namely the UnitValue class (see https://wwwimages.adobe.com/content/dam/Adobe/en/products/indesign/pdfs/JavaScriptToolsGuide_CS5.pdf p.230)

我的尝试：

#r "node_modules/fable-core/Fable.Core.dll"

open System
open Fable.Core

[<Global>]
module Photoshop =
    [<Erase;StringEnum>]
    type PSUnit =
        | [<CompiledName("in")>] Inches
        | [<CompiledName("ft")>] Feet
        | [<CompiledName("yd")>] Yards
        | [<CompiledName("mi")>] Miles
        | [<CompiledName("mm")>] Millimeters
        | [<CompiledName("cm")>] Centimeters
        | [<CompiledName("m")>] Meters
        | [<CompiledName("km")>] Kilometers
        | [<CompiledName("pt")>] Points
        | [<CompiledName("pc")>] Picas
        | [<CompiledName("tpt")>] TraditionalPoints
        | [<CompiledName("tpc")>] TraditionalPicas
        | [<CompiledName("ci")>] Ciceros
        | [<CompiledName("px")>] Pixels
        | [<CompiledName("%")>] Percent

    type PSUnitValue =
        abstract ``as``: PSUnit -> float
        abstract ``value``: float with get, set
        abstract ``type``: PSUnit with get, set    

    let UnitValue : PSUnitValue = jsNative

open Photoshop

let test = new UnitValue();
test.``value`` = 12.0;
test.``type`` = Unit.Centimeters

Console.WriteLine (test.``as`` PSUnit.Millimeters)

在编译期间我得到：

C:\PsScripts>fable test.fsx
fable-compiler 0.7.28: Start compilation...
F# project contains errors:
C:\PsScripts\test.fsx(L35,15) : error FSHARP: The type 'UnitValue' is not defined
C:\PsScripts\test.fsx(L36,0) : error FSHARP: Lookup on object of indeterminate type based on information prior to this program point. A type annotation may be needed prior to this program point to constrain the type of the object. This may allow the lookup to be resolved.
C:\PsScripts\test.fsx(L37,0) : error FSHARP: Lookup on object of indeterminate type based on information prior to this program point. A type annotation may be needed prior to this program point to constrain the type of the object. This may allow the lookup to be resolved.
C:\PsScripts\test.fsx(L37,21) : error FSHARP: The field, constructor or member 'Centimeters' is not defined
C:\PsScripts\test.fsx(L39,19) : error FSHARP: Lookup on object of indeterminate type based on information prior to this program point. A type annotation may be needed prior to this program point to constrain the type of the object. This may allow the lookup to be resolved.
C:\PsScripts\test.fsx(L39,0) : error FSHARP: A unique overload for method 'WriteLine' could not be determined based on type information prior to this program point. A type annotation may be needed. Candidates: Console.WriteLine(buffer: char []) : unit, Console.WriteLine(format: string, [<ParamArray>] arg: obj []) : unit, Console.WriteLine(value: bool) : unit, Console.WriteLine(value: char) : unit, Console.WriteLine(value: decimal) : unit, Console.WriteLine(value: float) : unit, Console.WriteLine(value: float32) : unit, Console.WriteLine(value: int) : unit, Console.WriteLine(value: int64) : unit, Console.WriteLine(value: obj) : unit, Console.WriteLine(value: string) : unit, Console.WriteLine(value: uint32) : unit, Console.WriteLine(value: uint64) : unit

我的预期输出是这样的：

var test = new UnitValue();
test.value = 12;
test.unit = "cm";
console.log(test.as("mm"));

对于那些想知道 UnitValue class 看起来如何但不想在 pdf 中查找它的人，这里我在 C# 中定义了它：

public class UnitValue
{
    // Static baseUnit not yet implemented in Fable
    public static UnitValue baseUnit { get; set; }

    // Constructors not yet implemented in Fable
    public UnitValue(float value, string unit) { }
    public UnitValue(string valueUnit) { }

    public string type { get; set; }
    public float value { get; set; }

    public float @as(string unit) { throw new NotImplementedException(); }

    // I don't use convert in my scripts, so not yet implemented in Fable as well
    public UnitValue convert(string unit) { throw new NotImplementedException(); }
}

Answer 1

您正在绑定变量 UnitValue，而不是声明类型的别名（不确定这是否是本意）。
类型和值，就像在 C# 中一样，具有不同的范围，因此就编译器而言，类型未声明。
jsNative 只是 "throw" 的 shorthand，它用于导入的 JS 结构，但您没有导入任何结构。参见 http://fable.io/docs/interacting.html
由于 JS 缺少类型，如果互操作是意图，您实际上必须自己在 F# 中定义类型。
如果互操作不是一个意图，那么写一个普通的 F# 代码，没有任何 Fable 属性，fable 会处理剩下的。

在此处为格式添加评论答案： UnitValue 需要是一个函数（构造函数）：

let UnitValue : unit->PSUnitValue = jsNative

那么你可以这样称呼它：

let test = UnitValue()

另请查看 this post 以了解有关绑定的一些背景知识。

Answer 2

在Eugene Tolmachev的帮助下：

工作（大概）代码：

#r "node_modules/fable-core/Fable.Core.dll"

open System
open Fable.Core

module Photoshop =
    [<StringEnum>]
    type PSUnit =
        | [<CompiledName("in")>] Inches
        | [<CompiledName("ft")>] Feet
        | [<CompiledName("yd")>] Yards
        | [<CompiledName("mi")>] Miles
        | [<CompiledName("mm")>] Millimeters
        | [<CompiledName("cm")>] Centimeters
        | [<CompiledName("m")>] Meters
        | [<CompiledName("km")>] Kilometers
        | [<CompiledName("pt")>] Points
        | [<CompiledName("pc")>] Picas
        | [<CompiledName("tpt")>] TraditionalPoints
        | [<CompiledName("tpc")>] TraditionalPicas
        | [<CompiledName("ci")>] Ciceros
        | [<CompiledName("px")>] Pixels
        | [<CompiledName("%")>] Percent

    type PSUnitValue =
        abstract ``as``: PSUnit -> float
        abstract ``value``: float with get, set
        abstract ``type``: PSUnit with get, set    
    let [<Global>] UnitValue : unit->PSUnitValue = jsNative

open Photoshop

let test = UnitValue();
test.``value`` <- 12.0;
test.``type`` <- PSUnit.Centimeters

Console.WriteLine (test.``as`` PSUnit.Millimeters)

输出

export var test = UnitValue(null);
test.value = 12;
test.type = "cm";
console.log(test.as("mm"));

我不知道 export 关键字在这里做什么，或者为什么 UnitValue 没有 new 关键字，但它编译并按照我的方向查找想要....

继续！

我现在在我的输出中有 new 关键字：

let [<Global;Emit("new [=12=](, )")>] UnitValue (v: float) (t: PSUnit): IUnitValue = jsNative

现在的用法是：

let test = UnitValue 12.0 PSUnit.Centimeters
Console.WriteLine (test.``as`` PSUnit.Millimeters)

寓言实现外部接口编译错误

Fable implement foreign interface compile errors

f#

fable-f#