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Dynamic  instantiation of classes

Posted on 2000-04-08
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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.
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Question by:mathought
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8 Comments
 
LVL 9

Accepted Solution

by:
ITugay earned 50 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
 

Author Comment

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

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