chapter 9 exercise

michaelcode · March 6th, 2006, 10:07 AM

Anyone give me some help on this exericse for chapter 9.

Define an Engine class, whose properties include SerialNo, Rpm, and Name (to be set by the class constructor), and whose methods include SwitchOn and SwitchOff. Now integrate it with the Car class so that you can access these properties and methods from instances of the Car class.

<script runat="server">
Public Class Car
Private _Color As String
Private _Gear As Integer
Private _Ignition As Integer
Private _Engine As Engine

Public Property MyEngine As Engine
Get
Return _Engine
End Get
Set
_Engine=value
End Set
End Property

Sub New()
_Color="Cold grey Steel"
_Ignition=IgnitionShape
End Sub

End Class

</script>

thanks.

mpressler · April 9th, 2006, 03:56 PM

Here's what I came up with. There's some extra stuff in there that you probably don't need (related to color, ignitionshape, etc.), but this demonstrates how to create the engine class and "tie" it to the car class:

<script runat=server language=vb>
Public Class Engine
    Private _SerialNum as Integer
    Private _RPM as Integer
    Private _EngineName as String
    Private _IsOn as Boolean

    Public ReadOnly Property SerialNum as Integer
        Get
            Return _SerialNum
        End Get
    End Property

    Public ReadOnly Property RPM as Integer
        Get
            Return _RPM
        End Get
    End Property

    Public ReadOnly Property EngineName as String
        Get
            Return _EngineName
        End Get
    End Property

    Public ReadOnly Property IsRunning as String
        Get
            If _IsOn then
                Return "The engine is running."
            Else
                Return "The engine is not running."
            End If
        End Get
    End Property

    Public Sub SwitchOn()
        _IsOn = true
    End Sub

    Public Sub SwitchOff()
        _IsOn = False
    End Sub

    Public Sub New()
        _SerialNum = 12223
        _RPM = 130
        _EngineName = "Ferrari 350"
    End Sub

End Class

Public Class Car
    Private _Color as String
    Private _IgnitionShape as Integer

    'This section ties the Engine Class to the Car class
    Private _Engine as Engine

    Public Property MyEngine as Engine
        Get
            Return _Engine
        End Get
        Set
            _Engine = value
        End Set
    End Property

    Public Property Color as string
        get
            Return _Color
        End Get
        Set(value as String)
            _Color = value
        End Set
    End Property
    Public Property IgnitionShape as Integer
        get
            Return _IgnitionShape
        End Get
        Set(value as Integer)
            _IgnitionShape = value
        End Set
    End Property

    Sub New(newIgnitionShape as Integer)
        _IgnitionShape = newIgnitionShape
        _Color = "cold grey steel"
    End Sub

end Class

Sub Page_Load()

    Dim MyCar as New Car(131233123)
    MyCar.MyEngine = New Engine()
    Response.write("<br><br><b>New object 'MyCar' created.</b>")
    Response.write("<br>Color: " & MyCar.Color)
    Response.write("<br>Ignition Shape: " & MyCar.IgnitionShape)
    Response.write("<br>" & MyCar.MyEngine.IsRunning)
    MyCar.MyEngine.SwitchOn
    Response.write("<br>" & MyCar.MyEngine.IsRunning)
    Response.write("<br>Serial Num: " & MyCar.MyEngine.SerialNum)
    Response.write("<br>RPM: " & MyCar.MyEngine.RPM)
    Response.write("<br>Name: " & MyCar.MyEngine.EngineName)

End Sub

</script>
<body>

</body>