ObjectExpressions.fs

module Tests

open System
open Xunit

type IFoo =
  abstract Foo1 : string
  abstract Foo2 : unit -> string
  abstract Foo3 : string -> string
  
let useIFoo (p: IFoo) =
    Console.WriteLine p.Foo1
    Console.WriteLine (p.Foo2())
    Console.WriteLine (p.Foo3("xyz"))
    
type Int32 with
    member x.AsIFoo() = 
        { new IFoo with
                member this.Foo1 = "1-" + x.ToString()
                member this.Foo2() = "2-" + x.ToString()
                member this.Foo3(p) = "3-" + p + "-" + x.ToString()}

type String with
    member x.AsIFoo() = 
        { new IFoo with
                member this.Foo1 = "1-" + x
                member this.Foo2() = "2-" + x
                member this.Foo3(p) = "3-" + p + "-" + x}
                
[<Fact>]
let ``Use IFoo`` () =
    useIFoo <| (45).AsIFoo()
    useIFoo <| "bee".AsIFoo()