A procedure that is made a member of a class is called a method.
To create a method, in the body of a class, use the same formula we learned in Lesson 5. For example, to create a sub procedure, you use the following formula: Class Class Name
Sub ProcedureName()
End Sub
End Class
Here is an example: Private Class Rectangle
Sub Show()
End Sub
End Class
In the body of the method, do whatever you want. For example, you can call the MsgBox() function to display a message. Here is an example: Private Class Rectangle
Sub Show()
MsgBox("Whatever")
End Sub
End Class
To access a method outside of its class, you can use the period operator as we saw for the member variables. Here is an example Public Module Exercise
Private Class Rectangle
Sub Show()
MsgBox("Whatever")
End Sub
End Class
Public Function Main() As Integer
Dim Recto As Rectangle
Recto = New Rectangle
Recto.Show()
Return 0
End Function
End Module
In the same way, you can use a With statement to access a method of a class.
In the previous sections, we saw how to create member variables inside of a class. Here is an example: Class Rectangle
Length As Double
Height As Double
Sub Show()
End Sub
End Class
When you have created a member variable in a class, it is available to all methods of the same class. This means that, to use it from a method of the same class, you do not have to declare a variable for the class. Here is an example: Public Module Exercise
Private Class Rectangle
Public Length As Double
Friend Height As Double
Sub Show()
MsgBox("=-= Rectangle Characteristics =-=" & vbCrLf & _
"Length: " & vbTab & Length & vbCrLf & _
"Height: " & vbTab & Height)
End Sub
End Class
Public Function Main() As Integer
Dim Recto As Rectangle
Recto = New Rectangle
Recto.Length = 24.55 : Recto.Height = 20.75
Recto.Show()
Return 0
End Function
End Module
Notice that the Length and the Height member variables are accessed inside of the Show() method without an instance of the Rectangle class.
So far, we have seen how to create sub procedure in a class, which is a method that does not return a value. Like a normal procedure, a method can be made to return a value, in which case it would be a function. To create a method as a function, use the same techniques we have used so far to create a function. Here is an example:
Friend Class Rectangle
Public Length As Double
Public Height As Double
Function Assign() As Double
End Function
End Class
After declaring a procedure, in its body, you can implement the expected behavior. As seen for a sub procedure, when a method has been created, it has access to all of the other members of the same class. This means that you don't have to re-declare a member of a class to access it in a method. Based on this, you can manipulate any member variable of the same class as you wish. This means that, naturally, you do not have to create a function method to change the value of a member variable. A normal sub procedure can take care of this. Instead, you would create a method if you need to perform a calculation and get a value from it instead of storing that value in one of the member variables. Here is an example: Friend Class Rectangle
Public Length As Double
Public Height As Double
Function Assign() As Double
End Function
Function Perimeter() As Double
End Function
End Class
Therefore, in the body of the function, you can access a member variable, you can call another method of the same class, or you can use an external value as you see fit. When the function exits, make sure it returns the appropriate value based on its type. Like the member variables, the methods can be accessed outside of the class using the period operator. Here is an example: Public Module Exercise
Friend Class Rectangle
Public Length As Double
Public Height As Double
Function Perimeter() As Double
Return (Length + Height) * 2
End Function
Function Area#()
Return Length * Height
End Function
End Class
Public Function Main() As Integer
Dim Recto As Rectangle
Recto = New Rectangle
Recto.Length = 42.58 : Recto.Height = 28.08
MsgBox("=-= Rectangle Characteristics =-=" & vbCrLf & _
"Length: " & vbTab & vbTab & Recto.Length & vbCrLf & _
"Height: " & vbTab & vbTab & Recto.Height & vbCrLf & _
"Perimeter: " & vbTab & Recto.Perimeter() & vbCrLf & _
"Area: " & vbTab & vbTab & Recto.Area())
Return 0
End Function
End Module
This would produce:
Like a sub procedure that is created as a method, a member function of a class can be made private, public, or friendly. It follows the exact same rules we reviewed early.
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