DIContainers: Wiki

Two DIContainers classes are available to replace Delphi's TList class:

• TDIPointerVector – stores simple pointers very much like TList.
• TDIObjectVector – stores instances of TObject, quite like TObjectList.

Both containers can be configured to “own” their data, so any stored memory or object is automatically freed when an item is deleted. This is achieved by using a different constructor function:

• NewDIPointerVector vs. NewDIPointerOwnerVector
• NewDIObjectVector vs. NewDIObjectOwnerVector

A small console application to demonstrate TDIPointerVector without and with owning its pointer data.

program PointerVector;
 
{$APPTYPE Console}
{$I DI.inc}
 
uses
  DIPointerVector, DIPointerOwnerVector;
 
type
  TDataRec = record
    Data: Integer;
  end;
  PDataRec = ^TDataRec;
 
  //------------------------------------------------------------------------------
 
procedure UsePointerVector(const APointerVector: TDIPointerVector);
var
  i: Integer;
  p: PDataRec;
begin
  { Add a few pointers to the vector. }
  for i := 1 to 10 do
    begin
      New(p);
      p^.Data := i;
      APointerVector.InsertPointerLast(p);
    end;
 
  { Retrieve all stored pointers and write their data. }
  for i := 0 to APointerVector.Count - 1 do
    begin
      p := APointerVector.PointerAt[i];
      WriteLn(p.Data);
    end;
end;
 
//------------------------------------------------------------------------------
 
var
  i: Integer;
  pv: TDIPointerVector;
begin
  { Create a TDIPointerVector container. This does not "own" the memory pointed to.
    We must free them manually (below). }
  pv := NewDIPointerVector;
  UsePointerVector(pv);
  { Free the stored Pointers and the container. }
  for i := 0 to pv.Count - 1 do
    FreeMem(pv.PointerAt[i]);
  pv.Free;
 
  //------------------------------------------------------------------------------
 
  { Create a TDIPointerVector container which "owns" its memory. }
  pv := NewDIPointerOwnerVector;
  UsePointerVector(pv);
  { No need to free the stored Pointers. The container frees them automatically
    when it deletes items. }
  pv.Free;
end.

A small console application to demonstrate TDIObjectVector without and with owning its objects.

program ObjectVector;
 
{$APPTYPE Console}
{$I DI.inc}
 
uses
  DIObjectVector, DIObjectOwnerVector;
 
type
  TDataObject = class
  private
    FData: Integer;
  public
    property Data: Integer read FData write FData;
  end;
 
  //------------------------------------------------------------------------------
 
procedure UseObjectVector(const AObjectVector: TDIObjectVector);
var
  i: Integer;
  o: TDataObject;
begin
  { Add a few objects to the vector. }
  for i := 1 to 10 do
    begin
      o := TDataObject.Create;
      o.Data := i;
      AObjectVector.InsertObjectLast(o);
    end;
 
  { Retrieve all stored objects and write their data. }
  for i := 0 to AObjectVector.Count - 1 do
    begin
      o := AObjectVector.ObjectAt[i] as TDataObject;
      WriteLn(o.Data);
    end;
end;
 
//------------------------------------------------------------------------------
 
var
  i: Integer;
  ov: TDIObjectVector;
begin
  { Create a TDIObjectVector container. this does not "own" its objects.
    We must free them manually (below). }
  ov := NewDIObjectVector;
  UseObjectVector(ov);
  { Free the stored objects and the container. }
  for i := 0 to ov.Count - 1 do
    ov.ObjectAt[i].Free;
  ov.Free;
 
  //------------------------------------------------------------------------------
 
  { Create a TDIObjectVector container which "owns" its objects. }
  ov := NewDIObjectOwnerVector;
  UseObjectVector(ov);
  { No need to free the stored objects. The container frees them automatically
    when it deletes items. }
  ov.Free;
end.