Writing datas to memobox from .txt file using Lazarus freepascal? - pascal

Question

I've got a project at schools which requires to write datas from a .txt file to a "memobox" in Lazarus freepascal.
There are datas in order like this.
Budapest tomato 23
Dublin tv 45
Rosslare projector 43
etc.
I have to read these datas from a .txt file and then write them into a memobox in Lazarus freepascal.
If I am not mistaken I have already copyed the datas from the .txt file but I have no idea how to write them.
I've already written this code:
type
cityname:integer;
product:string;
quantity:integer;
var
Form1: TForm1;
ceg:array[1..5] of rektip;
db:integer;
implementation
procedure TForm1.Button1Click(Sender: TObject);
var f:textfile; i:integer; a:char;
begin
assignfile(f,'termek.txt');
reset(f);
readln(f,db);
While not eof(f) do
begin
readln(f,ceg[i].varosnev,a,ceg[i].termek,a,ceg[i].darabszam);
end;
db:=1;
closefile(f);
end;
procedure TForm1.Button2Click(Sender: TObject);
var i:integer;
begin
For i:=1 to db do
Memo1.lines.add(ceg[i].varosnev,ceg[i].termek,IntToStr(ceg[i].darabszam));
end;
end;
I would like to know how to fix it.

Answer 1

The code you posted is incomplete, so I assume:
type
rektip = record
varosnev: string;
termek: string;
darabszam: Integer;
end;
There is a lot wrong with your approach:
readln(f,db);
While not eof(f) do
begin
readln(f,ceg[i].varosnev,a,ceg[i].termek,a,ceg[i].darabszam);
end;
db:=1;
closefile(f);
end;
You are not initializing nor updating i, so you are reading all data into the same record, and you don't even know which one (i could be 100 and you'd be writing the data to somewhere unknown -- there is no ceg[100]). That results in undefined behaviour (and that can be a crash too).
Do something like:
var
ceg: array of rektip;
...
begin
AssignFile(f, 'termek.txt');
Reset(f);
Readln(f, db);
if db = 0 then
Exit;
SetLength(ceg, db);
i := 0;
while not eof(f) do
begin
Readln(f, ceg[i].varosnev, ceg[i].termek, ceg[i].darabszam);
Inc(i);
if i > High(ceg) then
Break;
end;
SetLength(ceg, i); // remove any empty slots.
CloseFile(f);
end;
Now you can put them into the TMemo:
for i := Low(ceg) to High(ceg) do
begin
Memo1.Lines.Add(Format('%s %s %d', [ceg[i].varosnev, ceg[i].termek, ceg[i].darabszam]));
end;
Note that the code above, reading from the file, assumes the file looks like:
3
Budapest tomato 23
Dublin tv 45
Rosslare projector 43
i.e. each "record" is on a line of its own and the first line contains the number of records.