Return value from a form

[John Kang]

Is there a proper technique for returning value from a form? For example,
I want the user to select something from a list of choices on a form and
return the value of what the user chose to the calling procedure/form? Do
I have to resort to using public variables?

[Jim Edgar]

John --

Add the following function to a form:

' You can add any arguments to the
' Display function that you need.
Public Function Display() As String
Me.Show vbModal
Display = m_sReturnValue
End Function

Declare a form level variable called:

m_sReturnValue

and set the value of the form level value in your code
prior to closing the form. Do not reference any control
on the form after the Me.Show vbModal line of code
or the form will reload.


To use the form do the following:

Dim frm as New MyForm, sReturn As String
sReturn = frm.Display


Hope it helps,

Jim Edgar
"John Kang" <johnchulkang@hotmail.com> wrote in message
news:3991daea$1@news.devx.com...
>
> Is there a proper technique for returning value from a form? For example,
> I want the user to select something from a list of choices on a form and
> return the value of what the user chose to the calling procedure/form? Do
> I have to resort to using public variables?

[John Kang]

Thanks Jim, your solution should work. However, what if I wanted multiple
return values from a form? How about passing an object and having it returned
back from a form? Does same technique apply for objects?

Thanks!

"Jim Edgar" <djedgar@home.com> wrote:
>John --
>
>Add the following function to a form:
>
>' You can add any arguments to the
>' Display function that you need.
>Public Function Display() As String
> Me.Show vbModal
> Display = m_sReturnValue
>End Function
>
>Declare a form level variable called:
>
>m_sReturnValue
>
>and set the value of the form level value in your code
>prior to closing the form. Do not reference any control
>on the form after the Me.Show vbModal line of code
>or the form will reload.
>
>
>To use the form do the following:
>
>Dim frm as New MyForm, sReturn As String
>sReturn = frm.Display
>
>
>Hope it helps,
>
>Jim Edgar
>"John Kang" <johnchulkang@hotmail.com> wrote in message
>news:3991daea$1@news.devx.com...
>>
>> Is there a proper technique for returning value from a form? For example,
>> I want the user to select something from a list of choices on a form and
>> return the value of what the user chose to the calling procedure/form?
Do
>> I have to resort to using public variables?
>
>

[Jim Edgar]

John --

Pass some arguments byref, ie..

Private m_sStringArg As String
Private m_iIntegerArg As Integer
Private m_dDateArg As Date
Private m_lReturnValue As Long

Public Function Display(arg1 As String, arg2 As Integer, arg3 As Date) As
Long
' Get default values for the form level variables
m_sStringArg = arg1
m_iIntegerArg = arg2
m_dDateArg = arg3
' Use your own return values to indicate the success/failure of the
' form, ie: 0 = Cancel, -1 = Success, etc...
m_lReturnValue = 0 ' Set default return value

' Show the form. The form level variables will be
' set by the user. If the user selects Cancel then
' the return value will be 0.
Me.Show vbModal

arg1 = m_sStringArg
arg2 = m_iIntegerArg
arg3 = m_dDateArg
Display = m_lReturnValue
End Function


Sample use:

Dim sStringArg As String, iIntegerArg As Integer
Dim dDateArg As Date, lRet As Long, frm As New MyForm

lRet = frm.Display(sStringArg, iIntegerArg, dDateArg)
If lRet = -1 Then ' Success
' Use the returned values here
txtMyString = sStringArg
txtMyNumber = iIntegerArg
txtMyDate = dDateArg
Else ' User cancelled the form
MsgBox "User cancelled the form."
End If


This is a pretty quick example but I think you'll get the idea. You
can also try passing references to objects if that's what you need.
Hope it helps.

Jim Edgar


"John Kang" <johnchulkang@hotmail.com> wrote in message
news:3991ea5f$1@news.devx.com...
>
> Thanks Jim, your solution should work. However, what if I wanted multiple
> return values from a form? How about passing an object and having it
returned
> back from a form? Does same technique apply for objects?
>
> Thanks!
>
> "Jim Edgar" <djedgar@home.com> wrote:
> >John --
> >
> >Add the following function to a form:
> >
> >' You can add any arguments to the
> >' Display function that you need.
> >Public Function Display() As String
> > Me.Show vbModal
> > Display = m_sReturnValue
> >End Function
> >
> >Declare a form level variable called:
> >
> >m_sReturnValue
> >
> >and set the value of the form level value in your code
> >prior to closing the form. Do not reference any control
> >on the form after the Me.Show vbModal line of code
> >or the form will reload.
> >
> >
> >To use the form do the following:
> >
> >Dim frm as New MyForm, sReturn As String
> >sReturn = frm.Display
> >
> >
> >Hope it helps,
> >
> >Jim Edgar
> >"John Kang" <johnchulkang@hotmail.com> wrote in message
> >news:3991daea$1@news.devx.com...
> >>
> >> Is there a proper technique for returning value from a form? For
example,
> >> I want the user to select something from a list of choices on a form
and
> >> return the value of what the user chose to the calling procedure/form?
> Do
> >> I have to resort to using public variables?
> >
> >
>

[Eric Litwin]

"John Kang" <johnchulkang@hotmail.com> wrote:
>
>Is there a proper technique for returning value from a form? For example,
>I want the user to select something from a list of choices on a form and
>return the value of what the user chose to the calling procedure/form?
Do
>I have to resort to using public variables?

You can have multiple Property Gets on the form that return the values of
private variables.

For example, Form A has:
Private mlngSelectedId As Long

Public Property Get SelectedId() As Long
' mlngSelectedId is set in another procedure
SelectedId = mlngSelectedId
End Property

A method in Form B might do the following:
Dim frm As FormA
Set frm = New FormA

frm.Show vbModal
MsgBox "SelectedId = " & frm.SelectedId
Unload frm

You can add as many properties to Form A as you need. Just don't unload Form
A until you've read all the properties you are interested in.

[Andrew]

"Eric Litwin" <eric_litwin@countrywide.com> wrote:
>
>You can have multiple Property Gets on the form that return the values of
>private variables.
>
>For example, Form A has:
>Private mlngSelectedId As Long
>
>Public Property Get SelectedId() As Long
> ' mlngSelectedId is set in another procedure
> SelectedId = mlngSelectedId
>End Property
>
>A method in Form B might do the following:
>Dim frm As FormA
>Set frm = New FormA
>
>frm.Show vbModal
>MsgBox "SelectedId = " & frm.SelectedId
>Unload frm
>
>You can add as many properties to Form A as you need. Just don't unload
Form
>A until you've read all the properties you are interested in.


Eric,
The idea of using Property Get to pass the variable seems a nicer, more object
oriented approach. But I was just wondering what the difference is between
using Property Get to return a private variable or making a public variable
within the Form to do the same thing. The syntax to get at the variable
from another Form is the same:

--Your example:
dim mlngSelectedId as Long

Public Property Get SelectedId() As Long
' mlngSelectedId is set in another procedure
SelectedId = mlngSelectedId
End Property

--Or Public variable:
Public SelectedId as Long


--Usage for either:

Dim frm As FormA
Set frm = New FormA

frm.Show vbModal
MsgBox "SelectedId = " & frm.SelectedId
Unload frm



Just curious.
Thanks,

Andrew.

[Jim Pragit]

John,

I asked myself the same question a while back. I tried a couple different
methods and this is the one I finally settled upon. Here's step by step
instructions:

First, you create a property for this form called DialogResult. Here's the
code to do that:

Private mvarDialogResult As VbMsgBoxResult 'general declarations

Public Property Get DialogResult() As VbMsgBoxResult
DialogResult = mvarDialogResult
End Property

The idea behind using a DialogResult property is that you can easily distinguish
between the user pressing the OK button and the Cancel button (or the Yes
and No buttons, which ever your form is using).

Note that I intentionally declare DialogResult as VbMsgBoxResult. This gives
you a nice IntelliSense popup list when you're coding. Very nice

Then I default to mvarDialogResult to vbCancel in the Form_Load event (this
is in case the user closes the form by clicking the X button in the upper
right hand corner of the form):

Private Sub Form_Load()
'default to cancel
mvarDialogResult = vbCancel
End Sub

And then simply set it in the OK and Cancel button's click events:

Private Sub cmdOK_Click()
mvarDialogResult = vbOK
Unload Me
End Sub

Private Sub cmdCancel_Click()
mvarDialogResult = vbCancel
Unload Me
End Sub

To simplify things further, you can create a template form with all this
code already written for you.

Now, create a property for every value you want the user to enter. So if
this were a form where the user you enter their age, you would code this:

Private mvarAge As Long 'general declarations

Public Property Get Age As Long
Age = mvarAge
End Property

In the Form_Load event, default mvarAge to zero:

mvarAge = 0

In the cmdOK event, set mvarAge to whatever the user typed in:

mvarAge = CLng(txtAge.Text)

There, now your dialog form is done. You call it like this:

Dim lngAge As Long

frmGetAge.Show vbModal
If frmGetAge.DialogResult = vbOK Then
lngAge = frmGetAge.Age
MsgBox "The user is " & CStr(lngAge) & " years old"
Else
MsgBox "The user pressed Cancel"
End If

Like I said, I tried a couple different methods and I found this one to be
the best.

- Jim

"John Kang" <johnchulkang@hotmail.com> wrote:
>
>Is there a proper technique for returning value from a form? For example,
>I want the user to select something from a list of choices on a form and
>return the value of what the user chose to the calling procedure/form?
Do
>I have to resort to using public variables?

[mrfelis]

Andrew <andybecker@earthlink.net> wrote in message
news:39920093$1@news.devx.com...
> Eric,
> The idea of using Property Get to pass the variable seems a nicer, more
object
> oriented approach. But I was just wondering what the difference is
between
> using Property Get to return a private variable or making a public
variable
> within the Form to do the same thing. The syntax to get at the variable
> from another Form is the same:
>

Andrew,

A public variable is Read/Write. This allows other programmers in the
project (or yourself at a later date) to subvert the variable to do
different things. While this subversion isn't as bad as a Global variable
in a Standard Module, it is still a bad implementation for a return value. A
Property Get (with out the related Property Let/Set) is Read Only, and can
only be modified by code inside the form itself. This encourages using the
variable for only what you intended it for.

In a large project, subverted variables tend to cause bugs. The design may
be a difficult one to locate and impossible to fix.

Case in point: a project I, and about 4 or 5 other programmers, currently
work on has a Global variable gbCancel as Boolean. In some places this value
is set to True and not reset back to False at the end of the operation. This
causes other features to react as if the user canceled a dialog even when he
clicks OK.

The bug is small and has proved itself to be extremely difficult to find.
The manager doesn't want to waste more resources on finding it. So the bug
has been there for more than 3 years (as long as I've worked at this
company.)
--
~~~
C'Ya,
mrfelis
mrfelis@yahoo.NOSPAM.com
just remove the spam

[Andrew]

>A Property Get (with out the related Property Let/Set) is Read Only, and
can
>only be modified by code inside the form itself.

Ah, I see the difference now. I am going to start using Property Gets!

Thanks mrfelis!
Andrew.

[John Kang]

Thanks Jim & Eric. You guys both supplied same techinique for what I wanted
so I guess it wins by default. Seriously, I really like this approach a
lot 'cause it's so logically easy to understand and implement.

Thanks guys!

"Jim Pragit" <James.Pragit@BakerNet.com> wrote:
>
>John,
>
>I asked myself the same question a while back. I tried a couple different
>methods and this is the one I finally settled upon. Here's step by step
>instructions:
>
>First, you create a property for this form called DialogResult. Here's the
>code to do that:
>
> Private mvarDialogResult As VbMsgBoxResult 'general declarations
>
> Public Property Get DialogResult() As VbMsgBoxResult
> DialogResult = mvarDialogResult
> End Property
>
>The idea behind using a DialogResult property is that you can easily distinguish
>between the user pressing the OK button and the Cancel button (or the Yes
>and No buttons, which ever your form is using).
>
>Note that I intentionally declare DialogResult as VbMsgBoxResult. This
gives
>you a nice IntelliSense popup list when you're coding. Very nice
>
>Then I default to mvarDialogResult to vbCancel in the Form_Load event (this
>is in case the user closes the form by clicking the X button in the upper
>right hand corner of the form):
>
> Private Sub Form_Load()
> 'default to cancel
> mvarDialogResult = vbCancel
> End Sub
>
>And then simply set it in the OK and Cancel button's click events:
>
> Private Sub cmdOK_Click()
> mvarDialogResult = vbOK
> Unload Me
> End Sub
>
> Private Sub cmdCancel_Click()
> mvarDialogResult = vbCancel
> Unload Me
> End Sub
>
>To simplify things further, you can create a template form with all this
>code already written for you.
>
>Now, create a property for every value you want the user to enter. So if
>this were a form where the user you enter their age, you would code this:
>
> Private mvarAge As Long 'general declarations
>
> Public Property Get Age As Long
> Age = mvarAge
> End Property
>
>In the Form_Load event, default mvarAge to zero:
>
> mvarAge = 0
>
>In the cmdOK event, set mvarAge to whatever the user typed in:
>
> mvarAge = CLng(txtAge.Text)
>
>There, now your dialog form is done. You call it like this:
>
> Dim lngAge As Long
>
> frmGetAge.Show vbModal
> If frmGetAge.DialogResult = vbOK Then
> lngAge = frmGetAge.Age
> MsgBox "The user is " & CStr(lngAge) & " years old"
> Else
> MsgBox "The user pressed Cancel"
> End If
>
>Like I said, I tried a couple different methods and I found this one to
be
>the best.
>
>- Jim
>
>"John Kang" <johnchulkang@hotmail.com> wrote:
>>
>>Is there a proper technique for returning value from a form? For example,
>>I want the user to select something from a list of choices on a form and
>>return the value of what the user chose to the calling procedure/form?

>Do
>>I have to resort to using public variables?
>

[Jim Edgar]

John --

Be careful with this technique because it may produce some unexpected
results.

> >There, now your dialog form is done. You call it like this:
> >
> > Dim lngAge As Long
> >
> > frmGetAge.Show vbModal
> > If frmGetAge.DialogResult = vbOK Then
> > lngAge = frmGetAge.Age
> > MsgBox "The user is " & CStr(lngAge) & " years old"
> > Else
> > MsgBox "The user pressed Cancel"
> > End If
> >

Calling the property gets after unloading the form causes the form to
remain in memory (although invisible to the user) and the form level
variables retain whatever value you have given them. Try changing
the following line in Jim's example and you'll see what I mean:

Private Sub Form_Load()
'default to cancel
mvarDialogResult = vbCancel
' Change the following line
' mvarAge = 0
' to
txtAge = mvarAge
End Sub

You'll see that each time you show the form the mvarAge variable
retains the value from the previous time the form was displayed
because the form never fully unloads.

This technique is fine as long as you remember to initialize all of
the variables during form_load and you don't mind the form residing
in memory after you have used it. I used to use this technique myself
until I got burned by not re-initializing one of the variables and my
program kept updating the database with a wrong value. That's why
I went to the style of passing arguments by reference in a public
'Display' function. I can set default values for the arguments and when
the form unloads I set it to nothing so it is removed from memory. The
'Display' function can return an error code or you can use Jim's idea
of VbMsgBoxResult if you don't need to return any codes. Anyway,
just be aware of the variable issue when using this style.

Hope it helps,

Jim Edgar

[Jim Pragit]

Jim,

The problem you mention isn't really a problem. Simply set the form to nothing
when you're done with it:

Set frmAge = Nothing

Sorry, I just forgot to mention this. BTW, this should be standard practice
for all forms, not just dialogs.

- Jim

"Jim Edgar" <djedgar@home.com> wrote:
>John --
>
>Be careful with this technique because it may produce some unexpected
>results.
>
>> >There, now your dialog form is done. You call it like this:
>> >
>> > Dim lngAge As Long
>> >
>> > frmGetAge.Show vbModal
>> > If frmGetAge.DialogResult = vbOK Then
>> > lngAge = frmGetAge.Age
>> > MsgBox "The user is " & CStr(lngAge) & " years old"
>> > Else
>> > MsgBox "The user pressed Cancel"
>> > End If
>> >
>
>Calling the property gets after unloading the form causes the form to
>remain in memory (although invisible to the user) and the form level
>variables retain whatever value you have given them. Try changing
>the following line in Jim's example and you'll see what I mean:
>
> Private Sub Form_Load()
> 'default to cancel
> mvarDialogResult = vbCancel
> ' Change the following line
> ' mvarAge = 0
> ' to
> txtAge = mvarAge
> End Sub
>
>You'll see that each time you show the form the mvarAge variable
>retains the value from the previous time the form was displayed
>because the form never fully unloads.
>
>This technique is fine as long as you remember to initialize all of
>the variables during form_load and you don't mind the form residing
>in memory after you have used it. I used to use this technique myself
>until I got burned by not re-initializing one of the variables and my
>program kept updating the database with a wrong value. That's why
>I went to the style of passing arguments by reference in a public
>'Display' function. I can set default values for the arguments and when
>the form unloads I set it to nothing so it is removed from memory. The
>'Display' function can return an error code or you can use Jim's idea
>of VbMsgBoxResult if you don't need to return any codes. Anyway,
>just be aware of the variable issue when using this style.
>
>Hope it helps,
>
>Jim Edgar
>
>

[Jim Pragit]

For clarity's sake, here's the corrected code for calling the dialog form:

Dim lngAge As Long

frmGetAge.Show vbModal
If frmGetAge.DialogResult = vbOK Then
lngAge = frmGetAge.Age
MsgBox "The user is " & CStr(lngAge) & " years old"
Else
MsgBox "The user pressed Cancel"
End If
Set frmGetAge = Nothing

Everything's the same as my original post except for the last line which
is new.

- Jim