VBA: Initialize object with values?
It is a pain in the neck but this is the only way to do it.
File CArticle
Option Explicit
Private pNumber As String
Private pQuantity As Double
Private Sub Class_Initialize()
pNumber = vbNullString
pQuantity = 0
End Sub
Public Sub InitializeWithValues(ByVal number As String, ByVal quantity As Double)
pNumber = number
pQuantity = quantity
End Sub
Public Sub InitializeDefaultValues()
pNumber = vbNullString
pQuantity = 99999
End Sub
and in the calling module
Dim art As New CArticle ' Initialize value to empty
art.InitializeWithValues "Bowtie", 100 ' and assign values
Set art = New CArticle ' Initialize values to empty
art.InitializeDefaultValues ' Initialize values to default
If anyone gets here by a search, as did I. I recommend looking instead at the answers in StackOverFlow: Pass arguments to Constructor in VBA
This is not my answer, it came from Bgusach. I am including it here because I see that a useful answer is more than just a link.
Pass arguments to Constructor in VBA
Here's a little trick I'm using lately and brings good results. Bgusach would like to share with those who have to fight often with VBA.
1.- Implement a public initiation subroutine in each of your custom classes. I call it InitiateProperties throughout all my classes. This method has to accept the arguments you would like to send to the constructor.
2.- Create a module called factory, and create a public function with the word "Create" plus the same name as the class, and the same incoming arguments as the constructor needs. This function has to instantiate your class, and call the initiation subroutine explained in point (1), passing the received arguments. Finally returned the instantiated and initiated method.
Example:
Let's say we have the custom class Employee. As the previous example, is has to be instantiated with name and age.
This is the InitiateProperties method. m_name and m_age are our private properties to be set.
Public Sub InitiateProperties(name as String, age as Integer)
m_name = name
m_age = age
End Sub
And now in the factory module:
Public Function CreateEmployee(name as String, age as Integer) as Employee
Dim employee_obj As Employee
Set employee_obj = new Employee
employee_obj.InitiateProperties name:=name, age:=age
set CreateEmployee = employee_obj
End Function
And finally when you want to instantiate an employee
Dim this_employee as Employee
Set this_employee = factory.CreateEmployee(name:="Johnny", age:=89)
Especially useful when you have several classes. Just place a function for each in the module factory and instantiate just by calling factory.CreateClassA(arguments), factory.CreateClassB(other_arguments), etc.
EDIT
As stenci pointed out, you can do the same thing with a terser syntax by avoiding to create a local variable in the constructor functions. For instance the CreateEmployee function could be written like this:
Public Function CreateEmployee(name as String, age as Integer) as Employee
Set CreateEmployee = new Employee
CreateEmployee.InitiateProperties name:=name, age:=age
End Function
Which is nicer.