?
Solved

Dynamic  instantiation of classes

Posted on 2000-04-08
8
Medium Priority
?
167 Views
Last Modified: 2013-11-23
I have a certain class defined. Let's say:
class someClass
   constructor create(const a: integer);
   ...
end;

During runtime I need to create instances of that class, yet I cannot know until rutime how many objects will be required (of course, for each instance of the class, the constructor should be called).

What would be the best way to create instances of this class in runtime and manage a list of all the object I have created from that class so I can access their methods etc.?

Note that instances of this class shoukd be created from within a function yet remain viable after the function exits because other functions should use those objects.
0
Comment
Question by:mathought
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 3
  • 2
8 Comments
 
LVL 9

Accepted Solution

by:
ITugay earned 150 total points
ID: 2696150
uses cntnrs;

var CList : TObjectList;


procedure SomeCreate;
var I : integer;
begin
   for I:=1 to 50 do CList.Add(TYourClass.Create(I));
end;


procedure DoSomething;
begin
   TYourClass(CList[5]).YourMethod;
end;
----
Igor.

Do not forget to initialize CList;


0
 

Author Comment

by:mathought
ID: 2696637
I use Delphi 4 and:
Does not recognize "TObjectList" nor "uses cntnrs"

anyway, I used TList instead of TObjectList and it worked. (Am I missing anything?)
0
 
LVL 13

Expert Comment

by:Epsylon
ID: 2696698
That should be contnrs


Or use TList instead:

CList.Add(Pointer(TYourClass.Create));


The rest is like Igor says.

Regards,

Epsylon.
0
Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 

Author Comment

by:mathought
ID: 2696720
Helped me, but was a little bit inaccurate.
0
 
LVL 13

Expert Comment

by:Epsylon
ID: 2696740
>but was a little bit inaccurate

How about 'Thanks' or something like that? We answer questions in our own time you know...
0
 

Author Comment

by:mathought
ID: 2696745
You are right, sorry.
I truely thank you both.

But The points did belong to Igor.
0
 
LVL 13

Expert Comment

by:Epsylon
ID: 2696757
>The points did belong to Igor

No problem, I agree  :o)

Cheers,

Epsylon.
0
 
LVL 9

Expert Comment

by:ITugay
ID: 2697535
The main difference of TList and TObjectList:

----- TObjectList Delphi help --------
If the OwnsObjects property is set to True (the default), TObjectList controls the memory of its objects, freeing an object when its index is reassigned; when it is removed from the list with the Delete, Remove, or Clear method; or when the TObjectList instance is itself destroyed.
----- end------

TList did't free items automatically.

-----
Igor.
0

Featured Post

Free Tool: Subnet Calculator

The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Introduction I have seen many questions in this Delphi topic area where queries in threads are needed or suggested. I know bumped into a similar need. This article will address some of the concepts when dealing with a multithreaded delphi database…
In my programming career I have only very rarely run into situations where operator overloading would be of any use in my work.  Normally those situations involved math with either overly large numbers (hundreds of thousands of digits or accuracy re…
In this video we outline the Physical Segments view of NetCrunch network monitor. By following this brief how-to video, you will be able to learn how NetCrunch visualizes your network, how granular is the information collected, as well as where to f…
Monitoring a network: how to monitor network services and why? Michael Kulchisky, MCSE, MCSA, MCP, VTSP, VSP, CCSP outlines the philosophy behind service monitoring and why a handshake validation is critical in network monitoring. Software utilized …
Suggested Courses
Course of the Month12 days, 17 hours left to enroll

777 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question