Microsoft Access 2010 Bible

Part IV: Professional Database Development

998

FIGURE 28.11

The Class_Initialize event procedure runs whenever an object is instantiated from the class module.

Consumer Code

Set objProduct = New Product

objProduct.ProductName = “Beans”

A

Product Class

Private Sub Class_Initialize

End Sub

m_ProductID = -1

m_ProductName = vbNullString

m_SupplierID = -1

m_CategoryID = -1

m_QuantityPerUnit = vbNullString

m_UnitPrice = -1

m_UnitsInStock = -1

m_UnitsOnOrder = -1

m_ReorderLevel = -1

m_Discontinued = False

B

C

D

In this small example, you’ll notice that numeric property variables are set to –1, rather than VBA’s

default of zero for numeric variables. This is because certain logic in the class module uses –1 to

determine when certain states — such as when the user is entering a new product — are in effect.

The Class_Terminate event procedure

The opposite of the Initialize event is the Terminate event. The Terminate event fires

whenever an object created from the class is set to Nothing, or goes out of scope. In the following

code fragment, the Class_Terminate event procedure runs when the object is set to Nothing:

Set objProduct = Nothing

Use the Terminate event to clean up your class module. For example, if a Database or

Recordset object has been opened but hasn’t been closed by the class, use the Terminate

event to perform these operations.

The Terminate event fires as the statement dismissing the object runs, not after. VBA processes

one statement at a time, no matter where the statement takes the execution point. Therefore, when

the Set objProduct = Nothing executes, the Class_Terminate event procedure runs

before the statement ends. This sequence ensures that the class is cleaned up before execution is

returned to the code using the class. This process is illustrated in Figure 28.12.