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Code Problem

Posted on 2001-09-17
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Last Modified: 2010-04-06
howdy...

could someone please inspect the following code, and tell me why the program just hangs on the line "Categories[0].Items[0].Create;"?

maybe im doing something wrong, but im not extirely sure if what im doing is correct way either...

Basically i need to have an array [0..5] each element containing an array of TStrings.

if there is a better way of doing that, i'd apprecaite being filled in! :P

Thanks

X

-----------------------

unit mainform;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;

type
  TCategoryItems = record
    Items: array of TStringList;
  end;


type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    Categories: array[0..5] of TCategoryItems;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

uses StringRoutines;

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
var
  Count1, Count2, Count3 : integer;
begin
  SetLength(Categories[0].Items, 6);
  SetLength(Categories[1].Items, 6);
  SetLength(Categories[2].Items, 6);
  SetLength(Categories[3].Items, 6);
  SetLength(Categories[4].Items, 6);
  SetLength(Categories[5].Items, 6);

  Categories[0].Items[0].Create;
  Categories[0].Items[0].Add('HEH!');

  Categories[2].Items[5].Create;
  Categories[2].Items[5].Add('wei');
  Categories[2].Items[5].Add('diddy');

  Showmessage('Category 0, Item 0 is ' + Categories[0].Items[0].Strings[0]);
  Showmessage('Category 2, Item 5 is ' + Categories[0].Items[2].Strings[0]);
  Showmessage('Category 2, Item 5 is ' + Categories[0].Items[2].Strings[1]);

{  try
    for Count1 := 0 to High(Categories) do
      for Count2 := 0 to High(Categories[Count1].Items) do
        if Assigned(Categories[Count1].Items[Count2]) then
          for Count3 := 0 to Categories[Count1].Items[Count2].Count do
            if Categories[Count1].Items[Count2].Strings[Count3] <> '' then
              Showmessage('Category ' + IntToStr(Count1) + ', Item ' + IntToStr(Count2) + ' is ' + Categories[Count1].Items[Count2].Strings[Count3]);
  except
    showmessage('we died');
  end;
}
end;

end.
0
Comment
Question by:X_Kalibur
  • 2
  • 2
  • 2
  • +1
7 Comments
 
LVL 1

Author Comment

by:X_Kalibur
Comment Utility
note that the second array of TStringList needs to be a dynamic resizable array...

the values of 6 for the size of the arrays were just something i set for testing purposes.
0
 
LVL 17

Accepted Solution

by:
geobul earned 200 total points
Comment Utility
Hi,
I think:

Categories[0].Items[0] := TStringList.Create;

Regards, Geo
0
 
LVL 22

Expert Comment

by:mnasman
Comment Utility
Hello

  You need to call create method for each Categories[?].items[?] before you can use it

  and items is TStringList, so you need to create it as Geo  suggested to you

 also you try to access items not added in some Categories

you added items to  Categories[2].Items[5]
 Categories[2].Items[5].Add('wei');
 Categories[2].Items[5].Add('diddy');

but u try to access to
 Showmessage('Category 2, Item 5 is ' + Categories[0].Items[2].Strings[0]);

so change it to
 Showmessage('Category 2, Item 5 is ' + Categories[2].Items[5].Strings[0]);
 Showmessage('Category 2, Item 5 is ' + Categories[2].Items[5].Strings[1]);


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LVL 22

Expert Comment

by:mnasman
Comment Utility
also  change this line
for Count3 := 0 to Categories[Count1].Items[Count2].Count
to
for Count3 := 0 to Categories[Count1].Items[Count2].Count -1 // count -1

ur code will look like this after the few modifications

procedure TForm1.Button1Click(Sender: TObject);
var
 Count1, Count2, Count3 : integer;
begin
 SetLength(Categories[0].Items, 6);
 SetLength(Categories[1].Items, 6);
 SetLength(Categories[2].Items, 6);
 SetLength(Categories[3].Items, 6);
 SetLength(Categories[4].Items, 6);
 SetLength(Categories[5].Items, 6);

 Categories[0].Items[0] :=TStringList.Create;

 Categories[0].Items[0].Add('HEH!');

 Categories[2].Items[5] :=TStringList.Create;;
 Categories[2].Items[5].Add('wei');
 Categories[2].Items[5].Add('diddy');

 Showmessage('Category 0, Item 0 is ' + Categories[0].Items[0].Strings[0]);
 Showmessage('Category 2, Item 5 is ' + Categories[2].Items[5].Strings[0]);
 Showmessage('Category 2, Item 5 is ' + Categories[2].Items[5].Strings[1]);

 try
   for Count1 := 0 to High(Categories) do
     for Count2 := 0 to High(Categories[Count1].Items) do
       if Assigned(Categories[Count1].Items[Count2]) then
         for Count3 := 0 to Categories[Count1].Items[Count2].Count -1 do
           if Categories[Count1].Items[Count2].Strings[Count3] <> '' then
             Showmessage('Category ' + IntToStr(Count1) + ', Item ' + IntToStr(Count2) + ' is ' + Categories[Count1].Items[Count2].Strings[Count3]);
 except
   showmessage('we died');
 end;

end;
0
 
LVL 14

Expert Comment

by:AvonWyss
Comment Utility
You may also want to enable the range checks in the compiler options while developing such stuff, it will detect bounds errors in arrays.

Very important, create the TStringList's as shown by geobul:
    Categories[0].Items[0] := TStringList.Create;
instead of
    Categories[0].Items[0].Create;

Why do you need as many TStringList's for anyways?
0
 
LVL 1

Author Comment

by:X_Kalibur
Comment Utility
Thanks!

You wouldnt belive it, but this was the second time ive done something stupid like that ever, and posted a question on EE, cause i overlooked it each time!!


Basically i need to maintain a list of categories which will be read in from a file...and each category will have a variable list of sub-categories - hence the array of dynamic array..


Thanks everyone for all your help!
0
 
LVL 14

Expert Comment

by:AvonWyss
Comment Utility
I would have solved this by makinc a custom TStringList descendant which has another TStringList assigned to each string... this would allow to build a "tree" of TStringLists without the hassle of mixing arrays and lists.
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