接口是一个模板,用于声明该类必须实现并公开的方法。
接口指定其他类实现的相关成员集,它具有以下语法-
//接口声明: [ attributes ] type interface-name = [ interface ] [ inherit base-interface-name ...] abstract member1 : [ argument-types1 -> ] return-type1 abstract member2 : [ argument-types2 -> ] return-type2 ... [ end ] //在类类型定义中实现: interface interface-name with member self-identifier.member1 argument-list=method-body1 member self-identifier.member2 argument-list=method-body2 //通过使用对象表达式实现: [ attributes ] let class-name (argument-list) = { new interface-name with member self-identifier.member1 argument-list=method-body1 member self-identifier.member2 argument-list=method-body2 [ base-interface-definitions ] } member-list
如,
type IPerson = abstract Name : string abstract Enter : unit -> unit abstract Leave : unit -> unit
调用接口方法
接口方法是通过接口而不是通过类或类型实现接口的实例调用的,要调用接口方法,请使用:>运算符将其强制转换为接口类型。
(s :> IPerson).Enter() (s :> IPerson).Leave()
以下示例说明了概念-
type IPerson = abstract Name : string abstract Enter : unit -> unit abstract Leave : unit -> unit type Student(name : string, id : int) = member this.ID = id interface IPerson with member this.Name = name member this.Enter() = printfn "Student entering premises!" member this.Leave() = printfn "Student leaving premises!" type StuffMember(name : string, id : int, salary : float) = let mutable _salary = salary member this.Salary with get() = _salary and set(value) = _salary <- value interface IPerson with member this.Name = name member this.Enter() = printfn "Stuff member entering premises!" member this.Leave() = printfn "Stuff member leaving premises!" let s = new Student("Zara", 1234) let st = new StuffMember("Rohit", 34, 50000.0) (s :> IPerson).Enter() (s :> IPerson).Leave() (st :> IPerson).Enter() (st :> IPerson).Leave()
编译并执行程序时,将产生以下输出-
Student entering premises! Student leaving premises! Stuff member entering premises! Stuff member leaving premises!
接口继承
以下示例显示了概念-
type Interface1 = abstract member doubleIt: int -> int type Interface2 = abstract member tripleIt: int -> int type Interface3 = inherit Interface1 inherit Interface2 abstract member printIt: int -> string type multiplierClass() = interface Interface3 with member this.doubleIt(a) = 2 * a member this.tripleIt(a) = 3 * a member this.printIt(a) = a.ToString() let ml = multiplierClass() printfn "%d" ((ml:>Interface3).doubleIt(5)) printfn "%d" ((ml:>Interface3).tripleIt(5)) printfn "%s" ((ml:>Interface3).printIt(5))
编译并执行程序时,将产生以下输出-
10 15 5