TStrings property in custom component

Hi

I am writing my first visual component, and struck against a problem with creating and using a property of type TStrings. Below are the relevant excerpts from my code.

type
  TMyMenu = class(TCustomControl)
  private
    FItems : TStrings;
    procedure SetItems(AItem : TStrings);

  published
    property Items : TStrings read FItems write SetItems;

implementation

procedure TMyMenu.SetItems(AItem : TStrings);
begin
     FItems := AItem;
end;


(I also found, quite by accident, a mention of array properties in the help files - but I couldn't get that to work either :(     )

I would appreciate any help with this, maybe an example or links to examples. Even better, a tutorial or how-to guide.

Thanks
sderaadtAsked:
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

x
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

interCommented:
Hi

If the problem is just using TStirngs, here are the guidlines, but if you are problem with deriving custom control please indicate what exactly you want:

1 - TStrings has just a wrapper to the strings allocated as TStringList. So it has no storage abitliy. But it is assignement compatible with TStringList which can store the strings.
2 - So you can declare your components private variable as FStrings : TStrings but to be able to store strings in it you should do
   FStrings := TStringList.Create;
Actually, if you have the VCL source code just look at the TListBox implementation and see how it stores the list of items in its TStrings field.
3 - The following example you gave is problematic.
    procedure TMyMenu.SetItems(AItem : TStrings);
    begin
         FItems := AItem;
    end;
If you do such thing you loose some memory since the items you have already created are not disposed off from the memory. Instead, the components and classes that store something has a method called Assign(..): The correct code for it is as follows:

    procedure TMyMenu.SetItems(AItem : TStrings);
    begin
         FItems.Assign(AItem);
    end;

4 - When  creating  a new component ALWAYS override the constructor and destructor even if you do not do anything in them

May these help
Regards,
Igor
0
ronit051397Commented:
Igor I right. Use TStringList instead of TStrings.
0
ZifNabCommented:
Well, nothing to be said anymore.... Everything is said. And now I've said my part too... C.U.
0
Become a Microsoft Certified Solutions Expert

This course teaches how to install and configure Windows Server 2012 R2.  It is the first step on your path to becoming a Microsoft Certified Solutions Expert (MCSE).

sderaadtAuthor Commented:
Thankyou inter

I've solved the problem, thanks to your tips.

You need to answer the question so you can get the points - or shall I delete the question?
0
interCommented:
Dear sderaadt,

If you lack of points, you may delete the question. No problem for me just notify to do so...

Sincerely,
Igor
0
sderaadtAuthor Commented:
inter

I have enough points and you deserve them, since you solved the problem :)

sderaadt
0
interCommented:
Dear sderaadt,

Sorry for misinterpreting your comment before


Thanks
Igor

0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
sderaadtAuthor Commented:
inter

Thats alright :)

Thanks for the tips.

sderaadt
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Delphi

From novice to tech pro — start learning today.