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Calling methods within a TList

Posted on 2000-03-29
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Last Modified: 2010-04-04
My TList contains a list of TTimeRecord objects, the TTimeRecord objects contain sevgeral properties and methods (Read and write). What I want to be able to do is call the methods and access the properties of a particular item in the TList by calling the TList such as:

TList.Items[3].read;

I know I can create an instance of the TTime Record and point this to the item in the TList and call it that way but this seems messy and I'm sure you should be able to do it directly in the same way as you would call an array.

Of course the TList doesn't know it's a list of TTimeRecord so this me be the problem.

Any ideas how to do this?
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Question by:mike_tipping
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3 Comments
 
LVL 13

Accepted Solution

by:
Epsylon earned 100 total points
ID: 2666408
Try this:

type
  TMyRecord = record
                f: function: Integer;
                .....
              end;

function f1: Integer;
begin
  Result := 24;
end;

procedure TForm1.Button1Click(Sender: TObject);
var r: TMyRecord;
    l: TList;
begin
  r.f := f1;
  l := TList.Create;
  l.Add(@r);
  ShowMessage(IntToStr(TMyRecord(l.Items[0]^).f));
  l.Free;
end;
0
 
LVL 12

Expert Comment

by:rwilson032697
ID: 2667541
I think he means this: (Borrowing Epsylons code...)

type
  TMyRecord = class(TObject)
                f: function: Integer;
                .....
              end;

procedure TForm1.Button1Click(Sender: TObject);
var r: TMyRecord;
    l: TList;
begin
  l := TList.Create;
  l.Add(TMyRecord.Create);
  ShowMessage(IntToStr(TMyRecord(l[0]).f));
  l.Free;
end;

You can make this slicker again by creating your own list desencdent like this:

  TMyList = class(TObjectList)
    protected
      Function Get(Index : Integer) : TMyRecord;
      procedure Put(Index: Integer; const Value: TMyRecord);

    public
      property Items[Index : Integer] : TMyRecord read Get write Put;
  end;


function TMyList.Get(Index: Integer): TMyRecord;
begin
  Result := Inherited Get(Index);
end;


procedure TMyList.Put(Index: Integer;
                                       const Value: TMyRecord);
begin
  Inherited Put(Index, Value);
end;


Then Button1Click looks like this:

procedure TForm1.Button1Click(Sender: TObject);
var r: TMyRecord;
    l: TMyList;
begin
  l := TMyList.Create;
  l.Add(TMyRecord.Create);
  ShowMessage(IntToStr(l[0].f));
  l.Free;
end;

Cheers,

Raymond.

0
 

Author Comment

by:mike_tipping
ID: 2707311
Sorry, but I think Epsylon gave me the answer I wanted first
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