Delphi TList of records

Question

I need to store a temporary list of records and was thinking that a TList would be a good way to do this? However I am unsure how to do this with a TList<

Answer 1

If using an older version of Delphi where generics isn't present, consider inheriting from TList and override Notify method. When adding an item, alloc memory, copy added pointer memory content and override content in list. When removing, just free memory.

  TOwnedList = class(TList)
  private
    FPtrSize: integer;
  protected
    procedure Notify(Ptr: Pointer; Action: TListNotification); override;
  public
    constructor Create(const APtrSize: integer);
  end;

  constructor TOwnedList.Create(const APtrSize: integer);
  begin
    inherited Create();
    FPtrSize := APtrSize;
  end;

  procedure TOwnedList.Notify(Ptr: Pointer; Action: TListNotification);
  var
    LPtr: Pointer;
  begin
    inherited;
    if (Action = lnAdded) then begin
      GetMem(LPtr, FPtrSize);
      CopyMemory(LPtr, Ptr, FPtrSize); //May use another copy kind
      List^[IndexOf(Ptr)] := LPtr;
    end else if (Action = lnDeleted) then begin
      FreeMem(Ptr, FPtrSize);
    end;
  end;

Usage:

...
LList := TOwnedList.Create(SizeOf(*YOUR RECORD TYPE HERE*));
LList.Add(*YOU RECORD POINTER HERE*);
...

• Note that where I did use CopyMemory(LPtr, Ptr, FPtrSize), you may use another copy aproach. My list is intended to store a record with pointer references, so it doesn't manage it's fields memory.