MustInherit and NotInheritable in VB.NET
< Continued from page 2
On the previous pages, the 'how' and 'why' of both MustInherit and NotInheritable were explained. In the application "WorkInAmerica" below, an example of both are combined in a single program. Here's the code:
Both the worker and the boss have assigned workdays of eight hours:
But the output is:
The class Employee is marked MustInherit and the doWork method is marked MustOverride so both the Boss class and the Worker class are required to have their own separate doWork procedures. The Boss class only does half the work and then adds the hours not worked to the Worker's hours. Finally, Boss class and the Worker class are both marked NotInheritable so no one can create a new class and change the way things work.
On the previous pages, the 'how' and 'why' of both MustInherit and NotInheritable were explained. In the application "WorkInAmerica" below, an example of both are combined in a single program. Here's the code:
Public Structure WorkHours Dim IWorked As Decimal Dim myBossWorked As Decimal End Structure Public Class WorkInAmerica Private Sub ADaysWork_Click( _ ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles ADaysWork.Click Dim myJob As New Worker Dim myBoss As New Boss Dim theHours As New WorkHours theHours.IWorked = 0 theHours.myBossWorked = 0 ' The workday .... myJob.doWork(8, theHours) myBoss.doWork(8, theHours) Console.WriteLine("I worked: " & _ theHours.IWorked) Console.WriteLine("My boss worked: " & _ theHours.myBossWorked) End Sub End Class Public MustInherit Class Employee MustOverride Sub doWork( _ ByVal hours As Decimal, _ ByRef theHours As WorkHours) End Class Public NotInheritable Class Worker Inherits Employee Public Overrides Sub doWork( _ ByVal hours As Decimal, _ ByRef thehours As WorkHours) thehours.IWorked += hours End Sub End Class Public NotInheritable Class Boss Inherits Employee Public Overrides Sub doWork( _ ByVal hours As Decimal, _ ByRef thehours As WorkHours) thehours.myBossWorked += (hours / 2) thehours.IWorked += (hours / 2) End Sub End Class Both the worker and the boss have assigned workdays of eight hours:
myJob.doWork(8, theHours) myBoss.doWork(8, theHours) But the output is:
I worked: 12 My boss worked: 4 The class Employee is marked MustInherit and the doWork method is marked MustOverride so both the Boss class and the Worker class are required to have their own separate doWork procedures. The Boss class only does half the work and then adds the hours not worked to the Worker's hours. Finally, Boss class and the Worker class are both marked NotInheritable so no one can create a new class and change the way things work.
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