Observer pattern

Observer pattern in F#

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type Subject() = 
    let mutable notify = fun _ -> ()
    member this.Subscribe (notifyFunction) = 
        let wrap f i = f(i); i
        notify <- (wrap notifyFunction) >> notify
    member this.Reset() = notify <- fun _ -> ()
    member this.SomethingHappen(k) = 
        notify k

type ObserverA() =
    member this.NotifyMe(i) = printfn "notified A %A" i
type ObserverB() = 
    member this.NotifyMeB(i) = printfn "notified B %A" i

let observer() = 
    let a = ObserverA()
    let b = ObserverB()
    let subject = Subject()
    subject.Subscribe(a.NotifyMe)
    subject.Subscribe(b.NotifyMeB)
    subject.SomethingHappen("good")

Multiple items
type Subject =
  new : unit -> Subject
  member Reset : unit -> unit
  member SomethingHappen : k:string -> unit
  member Subscribe : notifyFunction:(string -> unit) -> unit

Full name: Script.Subject

--------------------
new : unit -> Subject

val mutable notify : (string -> unit)

val this : Subject

member Subject.Subscribe : notifyFunction:(string -> unit) -> unit

Full name: Script.Subject.Subscribe

val notifyFunction : (string -> unit)

val wrap : (('a -> unit) -> 'a -> 'a)

val f : ('a -> unit)

val i : 'a

member Subject.Reset : unit -> unit

Full name: Script.Subject.Reset

member Subject.SomethingHappen : k:string -> unit

Full name: Script.Subject.SomethingHappen

val k : string

Multiple items
type ObserverA =
new : unit -> ObserverA
member NotifyMe : i:'a -> unit

Full name: Script.ObserverA

--------------------
new : unit -> ObserverA

val this : ObserverA

member ObserverA.NotifyMe : i:'a -> unit

Full name: Script.ObserverA.NotifyMe

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

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

Multiple items
type ObserverB =
new : unit -> ObserverB
member NotifyMeB : i:'a -> unit

Full name: Script.ObserverB

--------------------
new : unit -> ObserverB

val this : ObserverB

member ObserverB.NotifyMeB : i:'a -> unit

Full name: Script.ObserverB.NotifyMeB

val observer : unit -> unit

Full name: Script.observer

val a : ObserverA

val b : ObserverB

val subject : Subject

member Subject.Subscribe : notifyFunction:(string -> unit) -> unit

member ObserverA.NotifyMe : i:'a -> unit

member ObserverB.NotifyMeB : i:'a -> unit

member Subject.SomethingHappen : k:string -> unit

Raw view Test code New version

More information

Link:	http://fssnip.net/7j
Posted:	13 years ago
Author:	Tao Liu
Tags:	design patterns