As you may pointed our earlier. Properties is like a function. So how can we know when we must implement property or a function. To tell you honestly, their is no universal rule concerning this scenario, but usually programmer implement a properties when a routine serves mostly to return a value stored inside the class and can be quickly and easily reevaluated. When the routine servers mostly to evaluate a complex value, they use function. If programmer thinks that in the future the value returned by the routine could be assigned to, they use Property Get procedure and gives them a chance to add a Property Let when its time to implement one.
Let's make an example. Earlier we implement a Property Get procedure for our class member FullName. How can we make our class more useable in a long run by providing a Property Let. This way we can have two way of assign a value to FirstName and LastName property. A possible solution might look like this:
Property Let FullName(ByVal strNewValue As String)
' Return the full name of Student object
Dim aStrName() As String
' Split the argument pass (strNewValue)
aStrName() = Split(strNewValue)
' Raise an error if an FirstName or LastName is empty
If UBound(aStrName) = 0 Then Err.Raise 5
FirstName = aStrName(0)
LastName = aStrName(1)
End Property
|
You can directly assign a value to FirstName and LastName property as shown below:
objStudent.FullName = "Cathrina Anniversario" 'try getting the Student property FirstName and LastName MsgBox objStudent.FirstName 'Invoke Property Get FirstName MsgBox objStudent.LastName 'Invoke Property Get LastName |
As you can see, even if we didn't assign a value to the Student FirstName and LastName property explicitly, our new FullName property does the job. This is other nice thing you can do with class property
Comments