Register class at run time

Hi,

I'm not sure if I can do this, but I wanted to know if I can derive a new class from a base registered class just by using a string.
I want to load a list of classes into a stringlist, register each one based on TMyBaseObjectClass, so that further on I can use GetClass to instantiate a specific class type.
Hope I've explained this enough, but basically I want to remove the 2 marked lines below, but still be able to use GetClass in DoSomethingString to create objects for use.

uses
  Classes;

type
  TMyBaseObject = class(TPersistent)

  end;
  TMyBaseObjectClass = class of TMyBaseObject;

  TMyNewClass = class(TMyBaseObject); // REMOVE THIS LINE

  procedure DoSomethingClass(pClass: TMyBaseObjectClass);
  procedure DoSomethingString(pClassString: String);

var
  FMyNewObject: TMyBaseObject;

implementation

procedure DoSomethingClass(pClass: TMyBaseObjectClass);
begin
  FMyNewObject := pClass.Create();
end;

procedure DoSomethingString(pClassString: String);
var
  FClass: TMyBaseObjectClass;
begin
  FClass := TMyBaseObjectClass(GetClass('TMyNewClass'));
  FMyNewObject := FClass.Create();
end;

initialization
  RegisterClass(TMyBaseObject);
  RegisterClass(TMyNewClass); // REMOVE THIS LINE

end.
LVL 15
Mike LittlewoodEngineerAsked:
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.

Mike LittlewoodEngineerAuthor Commented:
Forgot to say Delphi 2006 version
0
Geert GOracle dbaCommented:
you  can pass any class derived TMyBaseObject
these are basic principles of OOP  (nice feature of using "class of 'class' ")

type
  TDummy = class(TMyBaseObject)

i don't see why you need to register the class to use it ?
>> why do you need that ?
0
Mike LittlewoodEngineerAuthor Commented:
Ah I think I can only do this sort of thing from delphi 2010 with all the new RTTI stuff.
I think I need to manually register each class, no way round it as far as I can see.
Or am I wrong?
0
Become a CompTIA Certified Healthcare IT Tech

This course will help prep you to earn the CompTIA Healthcare IT Technician certification showing that you have the knowledge and skills needed to succeed in installing, managing, and troubleshooting IT systems in medical and clinical settings.

Geert GOracle dbaCommented:
oh yeah, descendants of TDummy would work too :)
and descendants of those descendants ... and so on
0
Mike LittlewoodEngineerAuthor Commented:
Hey Geert,

I want to be able to use the GetClass function, but you can only do this is you register the class in the first place.
I want, in your example, to create a class called TDummy, without actually having an object defined called TDummy.
I want to take a string, create a class at run time called TDummy which inherits from TMyBaseObject.
0
Geert GOracle dbaCommented:
aren't you looking for the datasnap technology ?
http://edn.embarcadero.com/article/images/39227/The-New-Datasnap-in-Delphi-2009_WP.pdf

i saw a demo for 2009 of passing "classes" as dataobjects with datasnap technology
they recreated the DBexpress for this
only available since the D2009 version
0
Mike LittlewoodEngineerAuthor Commented:
Possibly, but isn't that 2009 onwards only? I'm only on 2006.
0
Geert GOracle dbaCommented:
yep, that's the bad news

what are you trying to do ?
dbexpress datasnap is for client-server system ...
0
Mike LittlewoodEngineerAuthor Commented:
Its ok Geert, I don't think I am able to do what I want on the current version I have.
Think I can do this a less elegant way for now, might look at updating the software at a later date.

Thanks anyway
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
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.