Doubts creating, manipulating and deleting form

1. How to ensure release of form from memory?

  

When creating a form, according to the code below, do I need to destroy it in some way when it is finished by the user?

     

F_PesqCli := TF_PesqCli.Create(self);

The Create default constructor of the TComponent objects in delphi is received by (AOwner: TComponent)

If you pass Owner to Self , you are saying that the current instance of where the code is is the donor of the created component, in this case TForm . So when this Owner is destroyed, the form will also be destroyed.

If you want the user to terminate a form, that it is destroyed, in the event onClose of the form you just have to set the desired action

Action := caFree;

Another measure is to manage the lifecycle of the Modal windows during their startup:

Form := TForm.Create(nil);
try
  Form.ShowModal;
finally
  Form.Free;
end;

2. How to ensure that a window is not opened doubly?

The safest way is to validate those already created in the application

function ValidaFormJaCriado(const ClassDoForm: TClass): Boolean;
var
  I: Integer;
begin
  Result := False;
  for I := 0 to Screen.FormCount - 1 do
  begin
    if Screen.Forms[I].Class = ClassDoForm then
    begin
      Result := True;
      Break;
    end;
  end;
end;

3. How do I minimize a form internally, as in the example image below?

The Main Form must be set to FormStyle property to fsMDIForm
The child forms must have the parent form as Owner and FormStyle to fsMDIChild