Delphi: Use public procedures from a dynamic form - delphi

Question

I have a Delphi XE+ application with 3 forms, 2 of them created dynamically, like so:
form_main is triggering form_equip
form_equip is triggering form_certif
form_main -> form_equip -> form_certif
1'st: Open form_equip
procedure Tform_main.button_equip_addClick(Sender: TObject);
var
form_equip: Tform_equip;
begin
form_equip:= Tform_equip.Create(Self);
form_equip.equip_id:= 0;
form_equip.ShowModal;
FreeAndNil(form_equip);
end;
On form_equip I have a public procedure has_changes
2'nd: Open form_certif
procedure Tform_equip.button_certif_addClick(Sender: TObject);
var
form_certif: Tform_certif;
begin
form_certif:= Tform_certif.Create(Self);
form_certif.index:= 0;
form_certif.ShowModal;
FreeAndNil(form_certif);
end;
Now, when I press OK button from form_certif
procedure Tform_certif.button_okClick(Sender: TObject);
begin
//do something...
form_equip.has_changes; //this public procedure from form_equip is not visible because form was created as local var on form_main
end;
The question is, how can I transmit the sender/parent name to form_certif so can I see the public procedures and variables from form_equip?
A simple way is to declare inside unit_equip as global:
var
form_equip: Tform_equip
but I avoid to do this because form_equip is made to be opened dynamically in multiple windows with different names...

Answer 1

Pass all needed information from form_equip to form_certif. That way form_certif is decoupled from any dependence of form_equip.
procedure Tform_equip.button_certif_addClick(Sender: TObject);
var
form_certif: Tform_certif;
begin
form_certif:= Tform_certif.Create(nil);
try
form_certif.index:= 0;
// Pass all other needed variable values to form_certif
// including callback methods
form_certif.Has_Changes_Method := Self.Has_Changes();
if form_certif.ShowModal = mrOk then
begin
// take care of changes
end;
finally
FreeAndNil(form_certif);
end;
end;
And this is how it would look in the form_certif unit:
type
THas_Changes_Method = procedure of Object;
TForm_Certif = class(TForm)
...
private
FIndex: Integer;
FHasChanges: THas_Changes_Method;
public
property Index: Integer read FIndex write FIndex;
property Has_Changes_Method: THas_Changes_Method read fHasChanges write fHasChanges;
end;

Answer 2

Pass the information as a parameter in the constructor. Declare the constructor like this:
constructor Create(AOwner: TComponent; const ParentName: string);
In the implementation of the constructor, make a note of the name that was passed.

Answer 3

Since you are creating forms in code, you can add custom constructor to the form and pass other form as parameter.
Tform_certif = class(TForm)
...
protected
form_equip: Tform_equip;
public
constructor Create(AOwner: TComponent; Aform_equip: Tform_equip); reintroduce;
end;
constructor Tform_certif.Create(AOwner: TComponent; Aform_equip: Tform_equip);
begin
inherited Create(AOwner);
form_equip := Aform_equip;
end;
So now you can call form_equip.has_changes, because it is a field that you have initialized during construction of your Tform_certif form and it points to particular instance of Tform_equip that created this particular instance of Tform_certif.
procedure Tform_certif.button_okClick(Sender: TObject);
begin
//do something...
// test whether form_equip is assigned to avoid AV by calling methods on nil object
if Assigned(form_equip) then form_equip.has_changes;
end;
And to create your Tform_certif you would use following code
procedure Tform_equip.button_certif_addClick(Sender: TObject);
var
form_certif: Tform_certif;
begin
form_certif:= Tform_certif.Create(Self, Self);
form_certif.index:= 0;
form_certif.ShowModal;
FreeAndNil(form_certif);
end;
There is also variation of above constructor code, where you only need to send one parameter and then test in constructor whether AOwner it is of Tform_equip type and you don't need to change code in button_certif_addClick for using that kind of solution.
Tform_certif = class(TForm)
...
protected
form_equip: Tform_equip;
public
constructor Create(AOwner: TComponent); override;
end;
constructor Tform_certif.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
if AOwner is Tform_equip then form_equip := Tform_equip(AOwner);
end;