一类中的多个接口 - 可飞行和可扩展

Created: November-22, 2018

使用 Flyable 示例作为起点，我们可以使用以下代码添加第二个接口 Swimmable：

Sub Swim()
    ' No code
End Sub

Duck 对象可以飞行和游泳：

Implements Flyable
Implements Swimmable

Public Sub Flyable_Fly()
    Debug.Print "Flying With Wings!"
End Sub

Public Function Flyable_GetAltitude() As Long
    Flyable_GetAltitude = 30
End Function

Public Sub Swimmable_Swim()
    Debug.Print "Floating on the water"
End Sub

Fish 类也可以实现 Swimmable：

Implements Swimmable

Public Sub Swimmable_Swim()
    Debug.Print "Swimming under the water"
End Sub

现在，我们可以看到 Duck 对象一方面可以作为 Flyable 传递给 Sub，另一方面可以传递给 Swimmable：

Sub InterfaceTest()

Dim MyDuck As New Duck
Dim MyAirplane As New Airplane
Dim MyFish As New Fish

Debug.Print "Fly Check..."

FlyAndCheckAltitude MyDuck
FlyAndCheckAltitude MyAirplane

Debug.Print "Swim Check..."

TrySwimming MyDuck
TrySwimming MyFish

End Sub

Public Sub FlyAndCheckAltitude(F As Flyable)
    F.Fly
    Debug.Print F.GetAltitude
End Sub

Public Sub TrySwimming(S As Swimmable)
    S.Swim
End Sub

此代码的输出是：

飞检…

飞翔的翅膀！

三十

乘坐喷气式飞机飞行！

10000

游泳检查……

漂浮在水面上

在水下游泳