F# Observer Pattern

Observer Pattern

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// Observer Pattern
module StringWithEvent =

    type StringChangedEvent() =
        member val RegisteredFunctions = new ResizeArray<string*string->unit>() with get
        member S.Add f = S.RegisteredFunctions.Add f

    type String( s :string ) =
        let mutable str = s
        member val Changed = new StringChangedEvent() with get
        member S.Value
            with get() = str
            and set v =
                if str <> v then
                    for f in S.Changed.RegisteredFunctions do
                        f (str,v)
                    str <- v

// Testing
let str = StringWithEvent.String("Ok")
str.Changed.Add(fun (oldStr, newStr) ->
                    printfn "String changed from %A to %A" oldStr newStr )
str.Value <- "Okey"

Multiple items
type StringChangedEvent =
  new : unit -> StringChangedEvent
  member Add : f:(string * string -> unit) -> unit
  member RegisteredFunctions : ResizeArray<(string * string -> unit)>

Full name: Script.StringWithEvent.StringChangedEvent

--------------------
new : unit -> StringChangedEvent

type ResizeArray<'T> = System.Collections.Generic.List<'T>

Full name: Microsoft.FSharp.Collections.ResizeArray<_>

Multiple items
val string : value:'T -> string

Full name: Microsoft.FSharp.Core.Operators.string

--------------------
type string = System.String

Full name: Microsoft.FSharp.Core.string

type unit = Unit

Full name: Microsoft.FSharp.Core.unit

val S : StringChangedEvent

member StringChangedEvent.Add : f:(string * string -> unit) -> unit

Full name: Script.StringWithEvent.StringChangedEvent.Add

val f : (string * string -> unit)

property StringChangedEvent.RegisteredFunctions: ResizeArray<(string * string -> unit)>

System.Collections.Generic.List.Add(item: string * string -> unit) : unit

Multiple items
module String

from Microsoft.FSharp.Core

--------------------
type String =
  new : s:string -> String
  member Changed : StringChangedEvent
  member Value : string
  member Value : string with set

Full name: Script.StringWithEvent.String

--------------------
new : s:string -> String

val s : string

val mutable str : string

val S : String

member String.Value : string with set

Full name: Script.StringWithEvent.String.Value

val set : elements:seq<'T> -> Set<'T> (requires comparison)

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

val v : string

property String.Changed: StringChangedEvent

val str : StringWithEvent.String

Full name: Script.str

module StringWithEvent

from Script

Multiple items
type String =
  new : s:string -> String
  member Changed : StringChangedEvent
  member Value : string
  member Value : string with set

Full name: Script.StringWithEvent.String

--------------------
new : s:string -> StringWithEvent.String

property StringWithEvent.String.Changed: StringWithEvent.StringChangedEvent

member StringWithEvent.StringChangedEvent.Add : f:(string * string -> unit) -> unit

val oldStr : string

val newStr : string

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

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

property StringWithEvent.String.Value: string

Raw view Test code New version

More information

Link:	http://fssnip.net/k7
Posted:	10 years ago
Author:	Evanescent Devil
Tags:	design patterns , observer pattern