Calling a VBA form from a button causes UserForm_Initialize to run twice, breaking my code? - excel

Question

Hello wonderful VBA community,
I'm still really new to vba and am trying to learn a lot. Thank you in advance for looking through my code and my description of the issue I'm facing.
I have a button on a page that calls a new Userform.
CODE SNIPPET 1:
Sub btnShowDetails_Click()
Call frmShowDeets.ShowDeets
End Sub
... which calls the next bit of code in the 'frmShowDeets' UserForm:
CODE SNIPPET 2:
Public Sub ShowDeets()
Dim frm As frmShowDeets
Set frm = New frmShowDeets 'this line triggers the Userform_Initialize() event below
frm.Show
End Sub
... triggering:
CODE SNIPPET 3:
Private Sub UserForm_Initialize()
Dim comboBoxItem As Range
For Each comboBoxItem In ContactList.Range("tblContactList[CompanyName]")
'^refers to unique values in a named range
With Me.boxCompanySelection
.AddItem comboBoxItem.Value
End With
Next comboBoxItem
End Sub
So at this point, the form I want to display has values loaded in its one combobox for user selection. The user selects a company and the Combobox_Change event triggers other routines that pull information for that company.
CODE SNIPPET 4:
Public Sub boxCompanySelection_Change()
Call frmShowDeets.PullData
End Sub
Sub PullData()
Dim numCompanies As Long
numCompanies = ContactList.Range("B6").Value 'this holds a count of the rows in the named range
Dim FoundCell As Range
Set FoundCell = ContactList.Range("tblContactList[Company Name]").Find(What:=boxCompanySelection.Text, LookIn:=xlValues, LookAt:=xlWhole)
Dim CompanyRow As Long
CompanyRow = FoundCell.Row
With ContactList
'pull a bunch of the company's details
End With
End Sub
Here is where it gets weird... Once the form is shown and the user selects one of the combo box items, triggering the Combobox_Change event the code breaks because the 'What:=boxCompanySelection.Text' part of the Range().Find method reads as "" empty (even though Code Snippet 3 is meant to load in company names and Code Snippet 4 is only triggered when the user selects one of those company names from the combobox) and I shouldn't need to build something to handle 'not found' exceptions since the only possible values should be the ones pulled in from my named range.
From stepping through the code, I have determined that for some reason, Code Snippets 2 and 3 run TWICE before Snippet 4 is run. Does anyone know what about my code is causing this to happen? I'm thinking there's a disconnect between the form that is shown and loaded with combobox values and whatever Code Snippet 4 is reading data from.
What is weirder is that if I run the code starting from Code Snippet 2 (ignoring the button call in Code Snippet 1), the form works as intended and from what I can tell 2 and 3 are only run once.
The problem is probably something simple I'm overlooking but I just cannot figure out what it is. Thanks again!

Answer 1

You have to understand that a form is an object - exactly as any other class module, except a form happens to have a designer and a base class, so UserForm1 inherits the members of the UserForm class.
A form also has a default instance, and a lot of tutorials just happily skip over that very important but rather technical bit, which takes us exactly here on Stack Overflow, with a bug involving global state accidentally stored on the default instance.
Call frmShowDeets.ShowDeets
Assuming frmShowDeets is the name of the form class, and assuming this is the first reference to that form that gets to run, then the UserForm_Initialize handler of the default instance runs when the . dot operator executes and dereferences the object. Then the ShowDeets method runs.
Public Sub ShowDeets()
Dim frm As frmShowDeets
Set frm = New frmShowDeets 'this line triggers the Userform_Initialize() event below
frm.Show
End Sub
That line triggers UserForm_Initialize on the local instance named frm - which is an entirely separate object, of the same class. The Initialize handler runs whenever an instance of a class is, well, initialized, i.e. created. The Terminate handler runs when that instance is destroyed.
So ShowDeets is acting as some kind of "factory method" that creates & shows a new instance of the frmShowDeets class/form - in other words whatever happened on the default instance is irrelevant beyond that point: the object you're working with exists in the ShowDeets scope, is named frm, and gets destroyed as soon as it goes out of scope.
Remove the ShowDeets method altogether. Replace this:
Call frmShowDeets.ShowDeets
With this:
With New frmShowDeets
.Show
End With
Now the Initialize handler no longer runs on the default instance.
What you want, is to avoid using the default instance at all. Replace all frmShowDeets in the form's code-behind, with Me (see Understanding 'Me' (no flowers, no bees)), so that no state ever accidentally gets stored in the default instance.
Call frmShowDeets.PullData
Becomes simply:
Call Me.PullData
Or even:
PullData
Since Call is never required anywhere, and the Me qualifier is always implicit when you make a member call in a class module's code.