Question

Summarization:
1. Manual typecast when debugging, as LachlanG and Ken pointed out.
2. Make use of the concept of Debugger Visualizers introduced since Delphi 2010.
3. Switch to generics counterparts.

=========================================

Take the following code for example:

If breakpoints are set at the end of TestRegular, and at the end of TestGenerics, respectively, one can see the items of the generic list(and even the content of the items) through the debug inspector, but nothing meaningful (not even the count) for the regular tobjectlist, when one hovers the mouse on the tmp variable. I am wondering if there is some way to achieve similar debug-time functionality for regular tobjectlist?

    unit Unit2;

    interface

    uses
      Contnrs, Generics.Collections,
      Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
      Dialogs;

    type
      TMyItem = class;
      TMyItemList = class;
      TForm2 = class;

      TMyItem = class
      private
        fname: string;
      public
        property name: string read fname;
        constructor Create(aName: string);
      end;

      TMyItemList = class(TObjectList)
      protected
        procedure SetObject (Index: Integer; Item: TMyItem);
        function GetObject (Index: Integer): TMyItem;
      public
        function Add (Obj: TMyItem): Integer;
        procedure Insert (Index: Integer; Obj: TMyItem);
        property Objects [Index: Integer]: TMyItem
          read GetObject write SetObject; default;
      end;

      TForm2 = class(TForm)
        procedure FormCreate(Sender: TObject);
      private
        { Private declarations }
        procedure TestRegular;
        procedure TestGenerics;
      public
        { Public declarations }
      end;

    var
      Form2: TForm2;

    implementation

    {$R *.dfm}

    { TMyItem }

    constructor TMyItem.Create(aName: string);
    begin
      fname := aName;
    end;

    { TMyItemList }

    function TMyItemList.Add(Obj: TMyItem): Integer;
    begin
      Result := inherited Add (Obj);
    end;

    procedure TMyItemList.SetObject(Index: Integer; Item: TMyItem);
    begin
      inherited SetItem (Index, Item);
    end;

    function TMyItemList.GetObject(Index: Integer): TMyItem;
    begin
      Result := inherited GetItem (Index) as TMyItem;
    end;

    procedure TMyItemList.Insert(Index: Integer; Obj: TMyItem);
    begin
      inherited Insert(Index, Obj);
    end;

    {TForm2}

    procedure TForm2.FormCreate(Sender: TObject);
    begin
      TestGenerics;
      TestRegular;
    end;

    procedure TForm2.TestRegular;
    var
     tmp: TMyItemList;
    begin
     tmp := TMyItemList.Create;
     tmp.Add(TMyItem.Create('1'));
     tmp.Add(TMyItem.Create('2'));
     tmp.Free;
    end;

    procedure TForm2.TestGenerics;
    var
     tmp: TObjectList<TMyItem>;
    begin
     tmp := TObjectList<TMyItem>.Create;
     tmp.Add(TMyItem.Create('1'));
     tmp.Add(TMyItem.Create('2'));
     tmp.Free;
    end;

    end.

Answer 1

I don’t think you’ll be able to improve what appear in the mouse cursor hover hint.

You can however use typecasts inside Debug windows just as you can within source code.

For example you could typecast the tmp variable to TObjectList(tmp) from within the Evaluation Window (Ctrl F7) or create a Watch (Ctrl F5) on the typecasted variable.