Switching between forms

I'm having some trouble switching between forms when I use .destroy. If I only use .hide or .close, I end up increasing the memory usage of my app each time I switch.

I have a button in form 2 which, when clicked, destroys form 2 and shows form 1. How can I access form 2 again (from form 1) if I've destroyed it? I keep getting "Abstract Error" after the second time I click the second button.
Here's the code:

procedure TForm1.Button1Click(Sender: TObject); //in unit1
var j:byte;
begin
assignfile(f,'dif.txt');
rewrite(f);
write(f,'1');
closefile(f);
assignfile(g,'backclicked.txt');
reset(g);
read(g,i); // f,g and i are public in unit1
closefile(g);
if i<>1 then
begin
form1.hide;
form2.show;
end else
begin
form2:=TForm2.Create(self);
form2.show;
form1.hide;
end;
end;

procedure TForm2.BackClick(Sender: TObject); //in unit2
var f:textfile;
begin
assignfile(f,'backclicked.txt');
rewrite(f);
write(f,'1');
closefile(f);
form1.show;
form2.destroy;
end;

PLease: look the help for more explanation



Look: you ALWAYS CREATE form2 if not exists! one ERROR coding, normaly, you create only one time (in a place out the procedure that you avaliable the your existence.

try use one function, as:
function havetheformx(xFormClass:TCustomForm):boolean;
var
i:integer;
begin
for i:0 to Screen.Forms.count-1 do
if screen.forms[i].class IS "or = xFormClass then
begin //already exist
result:=true;
exit;
end;
end;


if havetheformx( TForm2 ) then
if not Form2.showing then
form2.showmodal;

------------------
application form main or for example one unit (with no forms)

unit

uses
uform2, etc.......

interface
....

var
xform2:tform2;


implementation


...

initialization
xform2:=tform2.create(application or nil or self)
finalization
xform2.free;
end.

-------------------
when you ute NIL = the form is responsable for your destory
SELF = the Owner destroy the component (form2)
application = the application destroy when terminate
-------------------

in form2 on event Onclosequery
Action = cafree = destroy the form (see help for another options)
------------------

if you needed to use very time the FORM2, so, dont destroy it (free), just HIDE

my sugestion:

if you use on DataModule, make the form2 in!

procedure datamodule.oncreate;
begin
form2:= tform2.create(self); //datamodule destroy
end; // self = datamodule component here

if = nil, so

procedure datamodule.ondestroy;
begin
if Assigned( form2 ) then
form2.free;
end;


--------------
in code normal, use FORM2.hide for hide it!

for use a bit memory try make the form2 all the time that need!

procedure tformX.buttonclickevent
var
xform2:tform2;
begin
try
try
xform2:=nil; // for assigned function better action
xform2:= tform2.create(nil); //you destroy it
x.form2.showmodal;
except
on e:exception do showmessage('error: '+e.message);
end;
finally
if assigned(xform2) then
FreeAndNil( xform2 ) ; //see help for freeandnil
end;