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Delphi generics

date written: 2 years ago category: Programming Previous next Next

Just found a wonderful and deep look into generics, anonymous routines and routine references here . Written by Sébastien Doeraene.

Generics were introduced in Delphi 2009, and I'm a big fan of them, as they help me do less type casting on TObjectList's items for example.

Want to know how sorting a TObjectList<TWhatever> works? Here's how it works:

type
  TDBObject = class
    Name: String;
  end;
  TDBObjectList = TObjectList<TDBObject>;
  TDBObjectComparer = class(TComparer<TDBObject>)
    function Compare(const Left, Right: TDBObject): Integer; override;
  end;

procedure TMainform.btnOkClick(Sender: TObject);
var
  o: TDBObject;
begin
  Result := TDBObjectList.Create(TDBObjectComparer.Create);
  o := TDBObject.Create;
  o.Name := 'foo';
  Result.Add(o);
  o := TDBObject.Create;
  o.Name := 'bar';
  Result.Add(o);
end;

function TDBObjectComparer.Compare(const Left, Right: TDBObject): Integer;
begin
  Result := CompareText(Left.Name, Right.Name);
end;