A2 AQA Computing | Section 2.1: Programming paradigms | Exercises in OOP programming | Exercise 2

Employee.vb

Public Class Employee
    ' These private variables cannot be accessed outside the class
    ' This means that in Module1.vb, we can't do emp.EmployeeID
    ' The only time we really need to do this is when validating data
    ' See the comments for each function to see how they *could* be validated
    Private EmployeeID As String
    Private DateOfBirth As String
    Private JobTitle As String

    '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
    '' Here is the set of functions to get the individual fields ''
    '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
    Function GetEmployeeID() As String
        Return EmployeeID
    End Function

    Function GetDateOfBirth() As String
        Return DateOfBirth
    End Function

    Function GetJobTitle() As String
        Return JobTitle
    End Function

    '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
    '' Here is the set of subroutines to set the individual fields ''
    '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
    Sub SetEmployeeID(ByVal id As String)
        ' employee ID's could be of a specific form'
        ' something like ISBN's from last year, if you remember?
        ' they could be validated using a special algorithm
        EmployeeID = id
    End Sub

    Sub SetDateOfBirth(ByVal dob As String)
        ' you could check if it's not in the future
        ' tbh it's better to use the DateTime class instead
        ' of a string, but a string is much simpler
        DateOfBirth = dob
    End Sub

    Sub SetJobTitle(ByVal title As String)
        ' you could check to make sure the title
        ' is a real title in a special list you make
        JobTitle = title
    End Sub
End Class

Module1.vb

Module Module1

    Sub Main()
        ' Create a new employee object from our class
        Dim emp As New Employee

        EnterDataForEmployee(emp)
        PrintDataForEmployee(emp)

        Console.ReadLine()
    End Sub

    ' For objects you mostly want to use references
    ' The reason for this because you are setting data
    ' If you didn't use a ByRef, the data would not change outside the function
    ' You can test it out by using ByVal and see what the program does
    ' edit: in theory it should do something else, but in vb it does the same thing
    '       oh well, doesn't really matter anyway
    Sub EnterDataForEmployee(ByRef person As Employee)
        Console.Write("Enter employee ID: ")
        Dim id As String = Console.ReadLine()
        person.SetEmployeeID(id)

        Console.Write("Enter employee's date of birth: ")
        Dim dob As String = Console.ReadLine()
        person.SetDateOfBirth(dob)

        Console.Write("Enter employee's job title: ")
        person.SetJobTitle(Console.ReadLine()) ' This does the same thing as the other lines
        ' The only difference is that it doesn't create a new variable, and 
        ' that is okay, because we don't need to use that variable anywhere else!
    End Sub

    ' Here it doesn't matter if we use ByVal or ByRef (functionality wise)
    ' rule of thumb: if you don't need to edit it, a ByVal will work fine
    '                if you need to edit it, you probably need ByRef
    ' sometimes you do need to use a ByRef even if you're not editing it,
    ' but that doesn't really matter
    Sub PrintDataForEmployee(ByVal person As Employee)
        Dim id As String = person.GetEmployeeID()
        Console.WriteLine("ID: " & id)

        Console.WriteLine("Date Of Birth: " & person.GetDateOfBirth())

        Console.WriteLine("Job Title: {0}", person.GetJobTitle())
    End Sub

End Module