F#动态操作符,提供对函数和函数名的访问

下面是一些示例代码,展示了其中的一些内容。我用 D 作为“动态”访问 Checks 模块加函数名。

module Checks = 
    let test1(x) = printfn "test1 %d" x
    let test2(x,y) = printfn "test2 %s %d" x y

type MyDynamic() = class end
let D = new MyDynamic()
let (?) (md:MyDynamic) fname : (string * ('a -> 'r)) =
    let a = md.GetType().Assembly
    let t = a.GetType("Program+Checks")
    let m = t.GetMethod(fname)
    let f arg = 
        let at = arg.GetType()
        let fsharpArgs = 
            if at.IsGenericType && at.GetGenericTypeDefinition().FullName.StartsWith("System.Tuple`") then
                Microsoft.FSharp.Reflection.FSharpValue.GetTupleFields(arg)
            else
                [| box arg |]
        unbox(m.Invoke(null, fsharpArgs))
    fname, f

let Main() =
    let x = 42
    let s = "foo"
    let name, func = D?test1 
    assert(name = "test1") 
    assert(func(x) = Checks.test1(x))

    let name, func = D?test2
    assert(name = "test2") 
    assert(func(s,x) = Checks.test2(s,x))

    System.Console.ReadKey()

Main()

您不能使用 ? 运算符访问模块中的函数,因为 Checks?test1 语法不正确(这将被翻译为 (?) Checks "test"

但是,对于使用对象实例的类型成员(例如。 obj?test ? 然后查找模块并搜索模块中的静态成员。

最简单的实现(第一种情况)如下所示:

let (?) obj s = 
  let memb = obj.GetType().GetMethod(s)
  // Return name and a function that runs the method
  s, (fun args -> memb.Invoke(obj, args))

// Type that contains tests as members    
type Check() = 
  member x.test1 () = 32

// We need to create instance in order to use '?'
let ch = Check()
let s,f = ch?test1

// Function 'f' takes array of objects as an argument and
// returns object, so the call is not as elegant as it could be
let n = ((f [| |]) :?> int)

您还可以添加一些包装,以使函数“f”更好一点,但我希望这能证明这一点。不幸的是,这不能用于模块。