help using dynamic array in gui application[Solved]

[jerryferry123]

Lazarus version 1.6.4, Widgetset gtk 2, fpc 3.0.2, Ubuntu 16.04

I could use some help using dynamic arrays in a gui project. I've not figured out how to declare them such that they are available from gui components on a form. All the examples I’ve found are used in terminal type applications.

[howardpc]

Save a new project in Lazarus in a suitable folder.
Double-click the form to generate an OnCreate handler, and try this:

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   SysUtils, Forms, Controls, StdCtrls;
9.  
10. type
11.  
12.   TForm1 = class(TForm)
13.     procedure FormCreate(Sender: TObject);
14.   private
15.     memo: TMemo;
16.   end;
17.  
18. var
19.   Form1: TForm1;
20.  
21. implementation
22.  
23. {$R *.lfm}
24.  
25. procedure TForm1.FormCreate(Sender: TObject);
26. var
27.   sa: TStringArray;
28.   s: String;
29. begin
30.   SetLength(sa, 4);
31.   sa:=TStringArray.create('zero','one','two','three');
32.   memo:=TMemo.Create(Self);
33.   memo.Align:=alClient;
34.   memo.Clear;
35.   for s in sa do
36.     memo.Lines.Add(s);
37.   memo.Parent:=Self;
38. end;
39.  
40. end.

[jerryferry123]

Thanks for the quick reply. I tried the example then added a button which tried to reference the sa string array from code, identifier not found.

I had hoped to find a way to define a dynamic array in such a way that it can be used by the other components of a form. 

[Thaddy]

But that is easy, very small change, declare the dynamic array in the form.:

Code: Text  [Select][+][-]

1. uses
2.   SysUtils, Forms, Controls, StdCtrls;
3.  
4. type
5.  
6.   TForm1 = class(TForm)
7.     procedure FormCreate(Sender: TObject);
8.   private
9.     memo: TMemo;
10.   protected
11.      sa: TStringArray;// declare the dynamic array here...
12.    end;
13.  
14. var
15.   Form1: TForm1;
16.  
17. implementation
18.  
19. {$R *.lfm}
20.  
21. procedure TForm1.FormCreate(Sender: TObject);
22. var
23.   s: String;
24. begin
25.   sa:=TStringArray.create('zero','one','two','three'); // no need to set length
26. // or in trunk: sa := ['zero','one','two','three']; // implicit constructor
27.   for s in sa do memo.lines.add(s);  //do not have to create dynamically, just put it on the form
28. end;
29.  
30. end.

The dynamic array is now available to all components on the form. If you make it public instead of protected it is available everywhere, not only on the form.

[jerryferry123]

Wow, thanks Thaddy for a simple explanation.

[Thaddy]

I couldn't have done it without howardpc's initial answer.
Glad to be of help.