type ICache =
        abstract member AddForever: string -> obj -> unit
        abstract member Get: string -> obj

type WebCache() =
    interface ICache with
        member this.AddForever key value =
            printf "adding key %s" key
        member this.Get string =
            box "someobject"

type TheOneCache() =
    static let caches:list<ICache> = []
    static member AddCache(c:ICache) =
        caches = c :: caches
    static member AddForever key value =
        List.iter<ICache> (fun c -> c.AddForever key value) caches