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Command Pattern - Simple

A simple implementation of a very basic command pattern that is being submitted to an Android app called GoF Design Patterns by Poash - highly recommended btw. This is imperative/oop in style, hope it helps someone. It is my first submission and I'm an F Sharp newbie!

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open System.IO
    type ICommandListener =
        abstract member Execute : unit -> unit
              
    type Application() =
        member x.OpenFile() = 
             printfn "[Application] OpenFile"
        //Implementation
    //Other Methods

    type OpenFileCommand(app: Application) =  //implied constructor
        member x._app = app
        interface ICommandListener with
            member x.Execute() = 
             printfn "[OpenFileCommand] Execute"
             x._app.OpenFile()

    type Widget(listener : ICommandListener) =
        member x._listener = listener
        member x.SendClick() = 
             printfn "[Widget] SendClick"
             x._listener.Execute()
    
let main() = 
    let app = new Application()
    let cmd = new OpenFileCommand(app)    
    let w = new Widget(cmd)
  
    //Simulate a button click
    w.SendClick()
    printfn "done"

main()

namespace System

namespace System.IO

type ICommandListener =
  interface
    abstract member Execute : unit -> unit
  end

Full name: Script.ICommandListener

abstract member ICommandListener.Execute : unit -> unit

Full name: Script.ICommandListener.Execute

type unit = Unit

Full name: Microsoft.FSharp.Core.unit

Multiple items
type Application =
new : unit -> Application
member OpenFile : unit -> unit

Full name: Script.Application

--------------------
new : unit -> Application

val x : Application

member Application.OpenFile : unit -> unit

Full name: Script.Application.OpenFile

val printfn : format:Printf.TextWriterFormat<'T> -> 'T

Full name: Microsoft.FSharp.Core.ExtraTopLevelOperators.printfn

Multiple items
type OpenFileCommand =
  interface ICommandListener
  new : app:Application -> OpenFileCommand
  member _app : Application

Full name: Script.OpenFileCommand

--------------------
new : app:Application -> OpenFileCommand

val app : Application

val x : OpenFileCommand

member OpenFileCommand._app : Application

Full name: Script.OpenFileCommand._app

override OpenFileCommand.Execute : unit -> unit

Full name: Script.OpenFileCommand.Execute

property OpenFileCommand._app: Application

member Application.OpenFile : unit -> unit

Multiple items
type Widget =
  new : listener:ICommandListener -> Widget
  member SendClick : unit -> unit
  member _listener : ICommandListener

Full name: Script.Widget

--------------------
new : listener:ICommandListener -> Widget

val listener : ICommandListener

val x : Widget

member Widget._listener : ICommandListener

Full name: Script.Widget._listener

member Widget.SendClick : unit -> unit

Full name: Script.Widget.SendClick

property Widget._listener: ICommandListener

abstract member ICommandListener.Execute : unit -> unit

val main : unit -> unit

Full name: Script.main

val cmd : OpenFileCommand

val w : Widget

member Widget.SendClick : unit -> unit

Raw view Test code New version

More information

Link:	http://fssnip.net/hJ
Posted:	11 years ago
Author:	Richard Griffiths - SoulFireMage
Tags:	design pattern , command pattern , imperative , oop