TList.IndexOf Method

Returns the index of the first entry in the Items array with a specified value.

Pascal

function IndexOf(Item: Pointer): Integer;

C++

__fastcall int IndexOf(void * Item);

Description

Call IndexOf to get the index for a pointer in the Items array. Specify the pointer as the Item parameter.

The first item in the array has index 0, the second item has index 1, and so on. If an item is not in the list, IndexOf returns -1. If a pointer appears more than once in the array, IndexOf returns the index of the first appearance.

C++ Examples:

Copy Code

/*
The following code adds an object to MyList if it isn’t
already in the list.
*/

#include <memory>       //for STL auto_ptr class

typedef struct AList
{
  int I;
  char C;
} TAList;

typedef AList* PAList;

TList *MyList;
PAList ARecord1, ARecord2;

void __fastcall DisplayTList(TList *theList)
{
  PAList AStruct;
  // Go through the list, writing the elements to the
  // canvas of a paintbox component.
  int Y = 10; // position on canvas
  for (int i = 0; i < theList->Count; i++)
  {
    AStruct = (PAList) theList->Items[i];
    Form1->PaintBox1->Canvas->TextOut(10, Y, IntToStr(AStruct->I));
    Y += 30;  // Increment Y Value again
    Form1->PaintBox1->Canvas->TextOut(10, Y, AStruct->C);
    Y += 30;  //Increment Y Value
  }
}

void __fastcall TForm1::Button1Click(TObject *Sender)
{
  if (MyList->IndexOf(ARecord1) == -1) MyList->Add(ARecord1);
  DisplayTList(MyList);
}

void __fastcall TForm1::Button2Click(TObject *Sender)
{
  if (MyList->IndexOf(ARecord2) == -1) MyList->Add(ARecord2);
  DisplayTList(MyList);
}

void __fastcall TForm1::Button3Click(TObject *Sender)
{
  if (MyList->Count != 0)
  {
    for (int B = MyList->Count - 1; B >= 0; B--)
    {
      PAList ARecord;
      ARecord = PAList(MyList->Items[B]);
      MyList->Remove(ARecord);
    }
  }
  Form1->PaintBox1->Repaint();
}

void __fastcall TForm1::FormCreate(TObject *Sender)
{
  static std::auto_ptr<TList> _MyListCleaner(MyList = new TList);
  static std::auto_ptr<TAList> _ARecord1Cleaner(ARecord1 = new TAList);
  ARecord1->I = 100;
  ARecord1->C = 'Z';
  static std::auto_ptr<TAList> _ARecord2Cleaner(ARecord2 = new TAList);
  ARecord2->I = 200;
  ARecord2->C = 'X';
}

Delphi Examples:

Copy Code

{
The following code adds an object to MyList if it isn’t
already in the list.
}
type
  PMyList = ^AList;
  AList = record
    I: Integer;
    C: Char;
  end;
var
  Form1: TForm1;
  MyList: TList;
  ARecord1, ARecord2: PMyList;

implementation

{$R *.dfm}

procedure DisplayTList(TheList: TList);
var
  ARecord: PMyList;
  B: Byte;
  Y: Word;
begin
    { Now paint the items onto the paintbox}
    Y := 10;             {Variable used in TextOut function}
    for B := 0 to (TheList.Count - 1) do
    begin
      ARecord := TheList.Items[B];
      Form1.PaintBox1.Canvas.TextOut(10, Y, IntToStr(ARecord^.I)); {Display I}
      Y := Y + 30;  {Increment Y Value again}
      Form1.PaintBox1.Canvas.TextOut(10, Y, ARecord^.C);  {Display C}
      Y := Y + 30;  {Increment Y Value}
    end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  if (MyList.IndexOf(ARecord1) = -1) then MyList.Add(ARecord1);
  DisplayTList(MyList);
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  if (MyList.IndexOf(ARecord2) = -1) then MyList.Add(ARecord2);
  DisplayTList(MyList);
end;

procedure TForm1.Button3Click(Sender: TObject);
var
  ARecord: PMyList;
  B: Integer;
begin
  if (MyList.Count <> 0) then
  begin
    for B := (MyList.Count - 1) downto 0 do
    begin
      ARecord := MyList.Items[B];
      MyList.Remove(ARecord);
    end;
  end;
  Form1.PaintBox1.Repaint;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  MyList := TList.Create;
  New(ARecord1);
  ARecord1^.I := 100;
  ARecord1^.C := 'Z';
  New(ARecord2);
  ARecord2^.I := 200;
  ARecord2^.C := 'X';
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  Dispose(ARecord1);
  Dispose(ARecord2);
  MyList.Free;
end;