Difference between revisions of "Testing, if form exists"

From Free Pascal wiki
Line 16: Line 16:
 
begin
 
begin
 
   CloseAction := caFree;
 
   CloseAction := caFree;
 +
  MyForm := nil;
 
End;
 
End;
 
</syntaxhighlight>
 
</syntaxhighlight>

Revision as of 23:28, 1 January 2014

Sometimes a form may be launched from several places in a program. If it already exists, it only needs to be brought to the front. If not, it needs to be created.

This method is only needed if the form is not auto created. (It should be listed under Project|Project Options|Forms|Available forms.)

The easiest way is:

if (MyForm = nil) then Application.CreateForm(TMyForm, MyForm);
MyForm.Show;

Use CloseAction := caFree in the form's OnClose event.

 procedure TMyForm.Formclose(Sender: Tobject; var Closeaction: Tcloseaction);
begin
  CloseAction := caFree;
  MyForm := nil;
End;

This method is taken from forum discussions.