Question

对于标量（即非数组式）可选参数，我将使用以下模式：

[<ExcelFunction(Category= "Test", Description= "Test optional arguments.")>]
let test_test1 ([<ExcelArgument(Description= "Optional. This is a double. Default is 42.0.")>] arg1 : obj) : double = 
    match arg1 with
    | :? ExcelMissing -> 42.0  // the argument was missing
    | :? double as d  -> d     // the argument was a double
    | _               -> -1.0  // otherwise

我不确定在Excel-Dna / F＃中此代码是否“惯用”，但似乎“可行”。

但是，我不确定如何继续执行类似数组的可选参数。例如：

[<ExcelFunction(Category= "Test", Description= "Test optional arguments.")>]
let test_test2 ([<ExcelArgument(Description= "Optional. This is a double. Default is [42, 42].")>] arg1 : obj[]) : double[] = 
    match arg1.[0] with
    | :? ExcelMissing -> [42.0; 42.0] |> List.toArray // the argument was missing OR it was an empty array
    | :? double as d  -> arg1 |> castToDouble         // the argument was an array and its first argument was a double
    | _               -> Array.empty                  // otherwise

以上似乎适用于大多数情况，但不允许正确处理边缘情况：例如，如果arg1是一个空数组。（castToDouble是自定义的obj[] -> double[]转换函数）

在F＃/ Excel-Dna中处理可选双数组的正确/惯用方式是什么，然后我该如何重写test_test2？

===========编辑===

按照Govert的建议，我尝试了以下方法：

[<ExcelFunction(Category= "Test", Description= "Test optional arguments.")>]
let test_test3 ([<ExcelArgument(Description= "Optional. This is a double. Default is [42, 42].")>] arg1 : obj) : double[] = 
    match arg1 with
    | :? (double[]) as ds  -> [1.0; 2.0] |> List.toArray   // the argument was a array of double elements
    | :? ExcelMissing      -> [42.0; 42.0] |> List.toArray // the argument was missing OR it was an empty array
    | _                    -> Array.empty                  // otherwise

...但是不幸的是，当我传递一个双精度数组（或其他任何数组）时，得到了#NUM!输出。只有当我什么都不做时，我才能正确地获得[42.0，42.0]数组。

Answer 1

这涵盖了所有可能性：


[<ExcelFunction("describes the input argument")>]
let describe(arg1 : obj) : string =
    match arg1 with
        | :? double as d        -> sprintf "Double: %f" d
        | :? string as s        -> "String: " + s
        | :? bool as b          -> sprintf "Boolean: %b" b
        | :? ExcelError as err  -> sprintf "ExcelError: %A" err
        | :? (obj[,]) as arr    -> sprintf "Array[%i, %i]" (Array2D.length1 arr) (Array2D.length2 arr)
        | :? ExcelEmpty         -> "<<Empty>>"
        | :? ExcelMissing       -> "<<Missing>>"
        | _                     -> "!? Unheard of ?!"

ExcelDna F＃和可选参数

1 个答案: