2005 B1: Clear Link field value

Question

Hi,
I have a UDF field of type "General" and Structure "LINK" on the A/P Invoice screen. My addon requirement is
to clear this field each time a user duplicates an A/P invoice. How can I do
this via the UI API?  What object in the UI API should I associate with this
fied e.g. Edit Text, Static Text etc.
I got an error message "Item is not editable" when I tried to clear the value. See code below for the "Duplicate" menu click:
if(pVal.MenuUID=="1287")
SAPbouiCOM.Form frmAPInvoice;
frmAPInvoice=gapp.Forms.GetForm("-141",1);
frmAPInvoice.Items.Item("U_Attach").Enabled=true;
//<b>This line returns an object type of it_EDIT</b>
object s = ((SAPbouiCOM.Item)frmAPInvoice.Items.Item("U_")).Type;
// THIS LINE WORKS OK
string str = ((SAPbouiCOM.EditText)frmAPInvoice.Items.Item("U_Attach").Specific).Value;
//ERROR HAPPENS ON THIS LINE          
((SAPbouiCOM.EditText)frmAPInvoice.Items.Item("U_test").Specific).Value="";
Please advise.,

Answer 1

You get the error message because by default the UDF for a 'link' type field is not editable (ie. it is greyed out).
There are a few restrictions in the UI API for system forms which you will need to work around to get desired results:-
Limitation #1: You will not be able to change the editable property of the system item "U_test" to true.
Limitation #2: You cannot simply set the value directly on the DBDataSource in a system form.
One possible workaround for this is to use a custom edittext linked to the same underlying field(OPCH/U_test), which you can make editable and can change using the syntax .value = "".
During Form Load of the UDF Window, add a new edit text to the form, bind it to the datasource for your link field and hide it.  eg:-
    'Add own field to form, bind it to UDF and hide it
    Set sboForm = sboApp.Forms.GetForm("-141", 1)
    Set sboItem = sboForm.Items.Add("U_test2", it_EDIT)
    Set sboEdit = sboItem.Specific
    sboItem.Visible = False
    sboEdit.DataBind.SetBound True, "OPCH", "U_test"
On the duplicate menu click, make your custom field visible, blank its value and hide it again.  After doing this simply call the update method on the original UDF and it too should be blanked out.
    Set sboForm = sboApp.Forms.GetForm("-141", 1)
    Set sboItem = sboForm.Items("U_test2")
    Set sboEdit = sboItem.Specific
    'Make own field visible, blank its contents, hide it again
    sboItem.Visible = True
    sboEdit.Value = ""
    sboItem.Visible = False
    'Update original UDF
    Set sboItem = sboForm.Items("U_test")
    sboItem.Update
John.