Example exam paper

On question 4.2 (tut letter 103), how does one decide when to use direct data members or pointer? I have an idea, but not to sure.

Hope someone can help

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Don't be different...be the one making a difference

Ask yourself how the data members must be created and destroyed. That should help you.

Well, I have to consider two factors: Dynamic memory allocation and Polymorphisim

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Don't be different...be the one making a difference

Polymorphism is irrelevant.

You should be considering object ownership. By that, I mean which object is responsible for destroying the child objects. When it comes to aggregation, the ownership does not lie with the parent object, thus the parent object must not attempt to destroy the child objects. In this case, you would only have pointers to the child objects.

If you have a composition pattern, then ownership rests with the parent object. The parent can either create the child objects itself or acquire child objects during it's lifetime. If the children are to be acquired later, then a pointer would be necessary. In composition, the parent is responsible for destroying all the children.

In composition, if the child objects are not publicly accessible, you can choose when to have them statically or dynamically created. The choice depends on how many children there are and whether the number of children will change during the lifetime of the parent object.

Ok, but what if you have an hierarchy of classes, and you want the contained class to be an instance of some class in the hierarchy? Most definitely will need to use pointers.

_______________________________________
Don't be different...be the one making a difference

Hi all

Can anyone please mail me the tut103? jean.fourie@bcx.co.za.

Thanks.

email sent to you Jean.

@xtoor - ta

can someone email me me tut letter 103 2010?

44699530@mylife.unisa.ac.za