F# 探险之旅－面向对象编程（下）

类的继承
#light
type Base = class
    val state : int
    new() = { state = 0}
end

type Sub = class
    inherit Base
    val otherState : int
    new() = { otherState = 1 }
end

let myObj = new Sub()

printfn "myObj.state = %i, myObj.otherState = %i"
    myObj.state
    myObj.otherState
    
System.Console.Read()

myObj.state = 0, myObj.otherState = 1

基类具有含参的构造函数
#light
type Base = class
    val state : int
    new(st) = 
        { state = st}
        then
        printfn "Init base class"
end

type Sub = class
    inherit Base
    val otherState : int
    new() = 
        { inherit Base(0)
          otherState = 1 }
        then
        printfn "Init sub class"
end

let myObj = new Sub()

printfn "myObj.state = %i, myObj.otherState = %i"
    myObj.state
    myObj.otherState
    
System.Console.Read()

Init base class
Init sub class
myObj.state = 0, myObj.otherState = 1

类继承时的方法
#light

type Base = class
    val mutable state: int
    new() = { state = 0 }
    member x.JiggleState y = x.state <- y
    abstract WiggleState: int -> unit
    default x.WiggleState y = x.state <- y + x.state
end

type Sub = class
    inherit Base
    new() = {}
    override x.WiggleState y = x.state <- y &&& x.state
end

let myBase = new Base()
let mySub = new Sub()

let test(c: #Base) =
    c.JiggleState 1
    print_int c.state
    print_newline()
    c.WiggleState 3
    print_int c.state
    print_newline()
    
print_endline "base class: "
test myBase
print_endline "sub class: "
test mySub

base class: 
1
4
sub class: 
1
1

访问基类的成员
#light
open System
open System.Drawing
open System.Windows.Forms

type RectangleForm(color) = class
    inherit Form() as base
    override x.OnPaint(e) = 
        e.Graphics.DrawRectangle(color, 10, 10,
            x.Width - 30, x.Height - 50)
        base.OnPaint(e)
    override x.OnResize(e) =
        x.Invalidate()
        base.OnResize(e)
end

let form = new RectangleForm(Pens.Blue)

[<STAThread>]
do Application.Run(form)

定义属性
#light
open System

type Propreties() = class
    let mutable rand = new Random()
    member x.MyProp
        with get() = rand.Next()
        and set y = rand <- new Random(y)
end

let prop = new Propreties()
prop.MyProp <- 10
printfn "%d" prop.MyProp
printfn "%d" prop.MyProp

定义索引器
#light

type Indexers(vals : string[]) = class
    member x.Item
        with get(i) = vals.[i]
        and set(i, v) = vals.[i] <- v
    member x.MyString
        with get(i) = vals.[i]
        and set(i, v) = vals.[i] <- v
end

let indexer = new Indexers [| "One"; "Two"; "Three"; "Four" |]

indexer.[0] <- "Five"
indexer.Item(2) <- "Six"
indexer.MyString(3) <- "Seven"
print_endline indexer.[0]
print_endline(indexer.Item(1))
print_endline(indexer.MyString(2))
print_endline(indexer.MyString(3))

定义静态方法
#light

type MyClass = class
    static member ReverseString(s: string) =
        let chars = s.ToCharArray()
        let reversedChars = Array.rev chars
        new string(reversedChars)
end

let myString = MyClass.ReverseString "dlrow olleH"
print_string myString

Hello world

定义委托
#light

type MyDelegate = delegate of int -> unit

let myInst = new MyDelegate(fun i -> print_int i)
let intList = [1; 2; 3]
intList |> List.iter(fun i -> myInst.Invoke(i))

123

定义结构类型 
#light

type IpAddress = struct
    val first: byte
    val second: byte
    val third: byte
    val fourth: byte
    new(first, second, third, fourth) =
        { first = first;
          second = second;
          third = third;
          fourth = fourth }
    override x.ToString() =
        Printf.sprintf "%O.%O.%O.%O" x.first x.second x.third x.fourth
    member x.GetBytes() = x.first, x.second, x.third, x.fourth
end

定义枚举类型
#light

type Season =
| Spring
| Summer
| Autumn
| Winter