Proxy パターン

なおこ(・∀・)さんのサイトではこちら。
代理オブジェクトが間に入り、実際のオブジェクトと変わらない動きをすると。間に一つクラスが入ることにより実際のオブジェクトは必要なときだけ使用する、といった実装になるわけですね。
なんだか面白そうなので自分でも書いてみました。

[Visual Basic]

Imports System

Imports System.Collections.Generic

 

 

 

Public Interface IRunking

 

  Function GetMusic(ByVal runk As Integer) As Music

 

End Interface

 

 

 

Public Class Proxy

  Implements IRunking

 

 

  Private _knownRunking As Dictionary(Of Integer, Music)

 

  Private _olicon As OliconRunking

 

 

  Public Sub New()

 

    Me._knownRunking = New Dictionary(Of Integer, Music)

    Me._olicon = New OliconRunking

 

  End Sub

 

 

  Public Function GetMusic(ByVal runk As Integer) As Music Implements IRunking.GetMusic

 

    If Me._knownRunking.ContainsKey(runk) Then

 

      Return Me._knownRunking.Item(runk)

 

    Else

 

      Dim realData As Music = Me._olicon.GetMusic(runk)

 

      Me._knownRunking.Add(runk, realData)

 

      Return realData

 

    End If

 

  End Function

 

 

End Class

 

 

 

Public Class OliconRunking

  Implements IRunking

 

  Private _runking As Dictionary(Of Integer, Music)

 

  Public Sub New()

 

    Me._runking = New Dictionary(Of Integer, Music)

 

    ' 2007 年 01 月 14 日 付

    Me._runking.Add(1, New Music("千の風になって", "秋川雅史"))

    Me._runking.Add(2, New Music("しるし", "Mr.Children"))

    Me._runking.Add(3, New Music("宙船（そらふね）/do! do! do!", "TOKIO"))

    Me._runking.Add(4, New Music("千の夜をこえて", "Aqua Timz"))

    Me._runking.Add(5, New Music("僕らの街で", "KAT-TUN"))

    Me._runking.Add(6, New Music("黒い涙", "ANNA TSUCHIYA inspi'NANA(BLACK STONES) "))

    Me._runking.Add(7, New Music("Man and Woman", "CHAGE and ASKA"))

    Me._runking.Add(8, New Music("関風ファイティング", "関ジャニ∞（エイト）"))

    Me._runking.Add(9, New Music("Here & There", "CHAGE and ASKA"))

    Me._runking.Add(10, New Music("ぼくはくま", "宇多田ヒカル"))

 

  End Sub

 

 

  Public Function GetMusic(ByVal runk As Integer) As Music Implements IRunking.GetMusic

 

    If Me._runking.ContainsKey(runk) Then

 

      Return Me._runking.Item(runk)

 

    Else

 

      Return Nothing

 

    End If

 

  End Function

 

 

End Class

 

 

 

Public Class Music

 

 

  Private _title As String

 

  Public ReadOnly Property Title() As String

    Get

      Return _title

    End Get

  End Property

 

 

  Private _artist As String

 

  Public ReadOnly Property Artist() As String

    Get

      Return _artist

    End Get

  End Property

 

 

  Public Sub New(ByVal title As String, ByVal artist As String)

 

    Me._title = title

    Me._artist = artist

 

  End Sub

 

 

End Class