For example, based on the type of representation, we can name visual and non-visual components. Such a methodology presupposes that Delphi apps are composed of separate â€œbricksâ€ that are known as components.ĭelphi components can be classified based on different parameters. If you are familiarized with the Delphi app development process, you definitely know that it is based on the components methodology which ensures seamless and fast creation of applications. Any attempt to use the global variable will likely crash the application.Simple custom visual component for Delphi: how to create After the event-handler terminates, the global variable no longer points to a valid form. The auto-created instance still exists, but the application can no longer access it. Specifically, if you create the new form without deleting the form of the same name from the list, Delphi creates the form at startup and this event-handler creates a new instance of the form, overwriting the reference to the auto-created instance. Note If you create a form using its constructor, be sure to check that the form is not in the Auto-create forms list on the Project OptionslForms page. If the form were displayed using Show you could not delete the form within the event handler because Show returns while the form is still open. The event handler in the example deletes the form after it is closed, so the form would need to be recreated if you needed to use ResultsForm elsewhere in the application.

Putting in the line ResultsForm.Free in the finally clause ensures that the memory for the form is freed even if the form raises an exception. In the above example, note the use of try.finally. Procedure TMainForm.Button1Click(Sender: TObject) begin ResultsForm := TResultForm.Create(self) try Note that ResultsForm is a modal form so the handler uses the ShowModal method. One way to invoke the result form is to use the global variable as follows. As an alternative, you can manually remove the following line from program's main entry point:Īpplication.CreateForm(TResultsForm, ResultsForm) ģ Invoke the form when desired by using the form's Show method, if the form is modeless, or ShowModal method, if the form is modal.Īn event handler for the main form must create an instance of the result form and destroy it.

This removes the form's invocation at startup. To create a form at a different stage during execution using the IDE, you:ġ Select the Filel Newl Form from the main menu to display the new form.Ģ Remove the form from the Auto-create forms list of the Projectl Options l Forms page. For example, a dialog box needs to be in memory only during the time a user interacts with it.

To reduce the amount of memory required at load time, you may want to create some forms only when you need to use them. You may not always want all your application's forms in memory at once.

Delphi create form template