vb.net教程之类的派生与继承

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  • vb.net教程之类的派生与继承

  • 2015-01-24 13:05 来源:www.js333com
类的派生与继承(相关vb.net教程)
上面mydate类中,如果要增加时、分、秒的处理又该如何呢?此时只需在前面的基础上增加三个成员m_hour m_minute m_second及其处理程序。这样便产生一个派生类mydatetime。总的操作步骤为:
1、在派生类mydatetime中加入语句:inherits mydate,以示派生关系。
2、同时,派生类的构造函数new()new(y,m,d,h,mi,s)中分别加入mybase.new()mybase.new(y,m,d)
3、原类的show函数与派生类的show函数前中分别加入:overridableoverrides
程序见,mydate的派生类mydatetime,程序如下:
Public Class mydate
    Public m_year, m_month, m_day As Integer
    Public Sub New()
        m_year = Microsoft.VisualBasic.Year(Now)
        m_month = Microsoft.VisualBasic.Month(Now)
        m_day = Microsoft.VisualBasic.Day(Now)
    End Sub
    Public Sub New(ByVal y As Integer, ByVal m As Integer, ByVal d As Integer)
        m_year = y : m_month = m : m_day = d
    End Sub
    Public Overridable Sub show()
          Dim s As String
        s = Str(m_year) + "-" + Str(m_month) + "-" + Str(m_day)
        MsgBox(s, MsgBoxStyle.OkOnly, "日期")
    End Sub
End Class
Public Class mydatetime
    Inherits mydate
    Private m_hour, m_minute, m_second
    Public Overrides Sub show()
        Dim s As String
        s = Str(m_year) + "-" + Str(m_month) + "-" + Str(m_day)
        s = s + Str(m_hour) + ":" + Str(m_minute) + ":" + Str(m_second)
        MsgBox(s, MsgBoxStyle.OkOnly, "时间日期")
    End Sub
    Public Sub setsystemtime()
        m_hour = Microsoft.VisualBasic.Hour(Now)
        m_minute = Microsoft.VisualBasic.Minute(Now)
        m_second = Microsoft.VisualBasic.Second(Now)
    End Sub
    Public Sub New()
        MyBase.New()
        setsystemtime()
    End Sub
    Public Sub New(ByVal y As Integer, ByVal m As Integer, ByVal d As Integer, ByVal h As Integer, ByVal mi As Integer, ByVal s As Integer)
        MyBase.New(y, m, d)
        m_hour = h : m_minute = mi : m_second = s
    End Sub
End Class
测试类为:
Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim a As New mydatetime
        Dim b As New mydatetime(2008, 5, 1, 11, 30, 40)
        a.show()
        b.show()
    End Sub
End Class
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