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dyn. array as parameter of a procedure

Posted on 2001-09-18
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Medium Priority
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Last Modified: 2010-04-06
I need a procedure to fill a dyn. array. How to do that? The following example cause an error at "SetLength(v, 10);". Can you correct the example?

procedure FillArray(var v:array of integer);
begin
  SetLength(v, 10);
  v[5]:=12;
end;

procedure TForm1.Button1Click(Sender: TObject);
var v:array of integer;
begin
  FillArray(v);
  if v[5]=12 then beep;
end;
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Comment
Question by:bengore
3 Comments
 
LVL 20

Accepted Solution

by:
Madshi earned 200 total points
ID: 6489779
When you declare a function like...

procedure FillArray(var v: array of xxx);

... you can't change the length of the array, because you can also call "FillArray" with a static array parameter. How shall FillArray know whether the parameter is a static or a dynamic one?

You have to declare a dynamic array type like this:

type TDAInteger = array of integer;

procedure FillArray(var v: TDAInteger);
begin
  SetLength(v, 10);
  v[5] := 12;
end;

procedure TForm1.Button1Click(Sender: TObject);
var v : TDAInteger;
begin
  FillArray(v);
  if v[5] = 12 then beep;
end;

Regards, Madshi.
0
 
LVL 7

Expert Comment

by:Motaz
ID: 6489786
You must allocate space befor pass it to your fill procedure:

procedure FillArray(var v:array of integer);
begin
 v[5]:=12;
end;

procedure TForm1.Button1Click(Sender: TObject);
var v:array of integer;
begin
 SetLength(V, 10);
 FillArray(v);
 if v[5]=12 then beep;
end;


Motaz
0
 

Author Comment

by:bengore
ID: 6489801
Thank you Madshi!
0

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