"findobj" for user defined class?

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Song on 23 Jul 2015
Commented: Song on 28 Jul 2015
Does anyone has an idea whether is there a way to fetch all instances of certain class from a up-level instance of different classes?
For example, instance A1 of Class A and instance B1 of Class B both contain instances of Class C. Is there a way to call something like "findobj" to get all instances of Class C from A1 and B1?
  1 Comment
per isakson
per isakson on 25 Jul 2015
AFAIK: No, there isn't!

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Accepted Answer

Muthu Annamalai
Muthu Annamalai on 27 Jul 2015
While @Steve Lord has answered the question "why you shouldn't do this," I'll go ahead and try to answer how you can do this, and possibly shoot yourself in the foot - due to inconsistent state.
To do this, you want to use a factory design pattern and keep a log of all instantiated objects in a singleton.
  1 Comment
Song on 28 Jul 2015
actually, I came to this workaround by myself too :)

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More Answers (1)

Steven Lord
Steven Lord on 27 Jul 2015
No, not unless the classes themselves define such a way (via a method or a property.)
Suppose instance A1 of class A has an instance of class C stored as a private property, intended to be accessed only by methods of class A and not by users. Granting users unrestricted access to that contained object of class C could render A1 no longer a valid instance of class A, if class A further restricts the values properties of class C can take.
For instance, consider class A representing an Outlook meeting invitation. It has a property representing whether a meeting requires videoconferencing (abbreviated from now on as VC.) It also has a property of class C representing the room in which the meeting is to be held, and the rooms have a property indicating whether the room is VC capable. Meetings that require VC can only be held in rooms that are VC capable. If you can change the VC property of the room stored in the meeting invitation class without going through or informing the invitation object, you could end up with a meeting that requires VC but is being held in a room that is not VC capable.


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