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passing array as a parameter

Posted on 2004-04-12
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Last Modified: 2010-04-05
hi, everyone.

my code is this:

procedure TForm1.Beregn(var Vinner: array of TKort);
var
j: integer;
begin
SetLength(Vinner,j);
dosomething with Vinner;
SetLength(Vinner,j);
end;

I call this metdhod this way:

procedure TForm1.Test;
var
Vinner: array of TKort;
begin
Beregn(Vinner);
Continue with my Vinner array that has been changed inside Beregn-method.
end;


But the thing is... I get an error everytime i try to call the SetLength method inside the Beregn method. Incompatible types, it says. Then I thought... is this a pointer-issue?
0
Comment
Question by:Darth_helge
1 Comment
 
LVL 20

Accepted Solution

by:
Madshi earned 2000 total points
ID: 10804708
When using an open "array of" array parameter like that you can't change the length of the array. The reason is simple:

procedure TForm1.Test;
var Vinner: array [0..9] of TKort;
begin
  Beregn(Vinner);
end;

What should Delphi do now, if you call SetLength? Do you see the problem? That's why calling SetLength is not supported.

However, you can solve the problem this way:

type TVinnerArr = array of TKort;

procedure TForm1.Beregn(var Vinner: TVinnerArr);
var j: integer;
begin
  SetLength(Vinner,j);
  dosomething with Vinner;
  SetLength(Vinner,j);
end;

procedure TForm1.Test;
var Vinner: TVinnerArr;
begin
  Beregn(Vinner);
end;

This works.
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