Share Variables Between Multiple Apps

Share Variables Between Multiple Apps

Sometimes it’s necessary to share variables between multiple instances of an application. For example, you might want to share a database connection. Here’s how: Create an ActiveX EXE with an exposed MultiUse class named Class1. An ActiveX DLL won’t work because it’s running in-process within each client. Include a module in the project and declare the required variable you want to share in this module as a public variable.

The code in an ActiveX DLL looks like this:

 '**** Module code *****Global gCon As DatabaseGlobal glngNrOfObjects As Long'**** Code in Class ****Public Property Set DBConn(Con As Database)	Set gCon = ConEnd PropertyPublic Property Get DBConn() As Database	Set DBConn = gConEnd PropertyPrivate Sub Class_Initialize()	' this variable keeps count of objects created	glngNrOfObjects = glngNrOfObjects + 1End SubPrivate Sub Class_Terminate()	' decrease object count	glngNrOfObjects = glngNrOfObjects - 1	' if no objects exist, close the connection	If glngNrOfObjects = 0 Then		If Not gCon Is Nothing Then			gCon.Close			Set gCon = Nothing		End If	End IfEnd Sub

Now reference this ActiveX EXE in your project and use it. Here’s how I did it:

 '** Code in application using the ActiveX EXE **Dim clsDBConn As Class1Private Sub Form_Load()	Set clsDBConn = New Class1	' set the connection, when first object is 	' created	If clsDBConn.DBConn Is Nothing Then		Set clsDBConn.DBConn = _			Workspaces(0).OpenDatabase( _			"	empdb1.mdb")		End IfEnd SubPrivate Sub Form_Unload(Cancel As Integer)	Set clsDBConn = NothingEnd Sub

You don’t need to include the code to count the object instances and close the database if your variable is a simple one-that is, if it’s not an object reference. Also, in that case, change the Property Set to Property Let.

Both the projects have a reference to DAO because they’re using the database object.


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