Question

This is just a very simple question to which i can’t find a good clear answer to. I don’t quite have the time to read all the documentation for this since i’m in a time crunch.

But here it is.

I have made a new class on top of my TForm class like so:

 Bucket = Class
   glass: Integer;
   steel: Integer;
 End;

I then create a couple of objects in a method which belongs to TForm1

procedure TForm1.getMarbles;
var
  objPlastic: Bucket;
  objAlu: Bucket;

begin
  // Initialize objects
  objPlastic := Bucket.Create;
  objAlu := Bucket.Create;

  // Get Values from edtBox
  val(Edit1.Text, objPlastic.steel, code);
  val(Edit2.Text, objAlu.steel, code);
  val(Edit3.Text, objPlastic.glass, code);
  val(Edit4.Text, objAlu.glass, code);
end; 

My problem is that I don’t know how to use these objects in other methods. I tried defining them in every way i know so far in the other methods I want to use them in, but I can’t get it to work.

Here is the method and what I have it currently set to (which returns 0 all the time):

procedure TForm1.marbleDrop(kind: string);
var
  objPlastic: Bucket;
  I: Integer;
begin
  objPlastic := Bucket.Create;
  if kind= 'plastic' then // the function is receiving this parameter
  begin
    for I := 0 to objPlastic.glass do
    begin
      showmessage(inttostr(objPlastic.glass)); //returns 0
    end;
  end;

end;

Sorry for this kind of question, but i couldn’t find a better way.

BTW, this is a simplified version of the code I am using. I did my best to get out any typos since it’s a translation of what I am actually using, but it’s mainly about the idea. I don’t have typos in my code in delphi.

Answer 1

In other to access the objects across methods, you have to either:

1. declare the objects as members of the Form class:

   type
     TForm1 = class(TForm);
     ...
     private
       objPlastic: Bucket;
       objAlu: Bucket;
     ...
     end;
   
   procedure TForm1.getMarbles;
   begin
     // Initialize objects
     if objPlastic = nil then objPlastic := Bucket.Create;
     if objAlu = nil then objAlu := Bucket.Create;
   
     // Get Values from edtBox
     objPlastic.steel := StrToIntDef(Edit1.Text, 0);
     objAlu.steel := StrToIntDef(Edit2.Text, 0);
     objPlastic.glass := StrToIntDef(Edit3.Text, 0);
     objAlu.glass := StrToIntDef(Edit4.Text, 0);
   end;
   
   procedure TForm1.marbleDrop(kind: string);
   begin
     if (kind = 'plastic') and (objPlastic <> nil) then
     begin
       ShowMessage(IntToStr(objPlastic.glass));
     end;
   end;
   

2. pass them as parameters of the methods themselves:

   procedure TForm1.getMarbles(objPlastic, objAlu: Bucket);
   begin
     // Get Values from edtBox
     if objPlastic <> nil then
     begin
       objPlastic.steel := StrToIntDef(Edit1.Text, 0);
       objPlastic.glass := StrToIntDef(Edit3.Text, 0);
     end;
     if objAlu <> nil then
     begin
       objAlu.steel := StrToIntDef(Edit2.Text, 0);
       objAlu.glass := StrToIntDef(Edit4.Text, 0);
     end;
   end;
   
   procedure TForm1.marbleDrop(objWhichKind: Bucket);
   begin
     if objWhichKind <> nil then
     begin
       ShowMessage(IntToStr(objWhichKind.glass));
     end;
   end;
   
   procedure TForm1.someMethod();
   var
     objPlastic: Bucket;
   begin
     objPlastic := Bucket.Create;
     getMarbles(objPlastic, nil);
     marbleDrop(objPlastic);
     objPlastic.Free;
   end;