forbid field name conflict in class hierarchy

[spir]

On Tue, 16 Nov 2010 05:37:52 -0500
bearophile <bearophileHUGS at lycos.com> wrote:

> spir:
> 
> > (and bug-prone, because sometimes the absence of a fields seems not caught, for any reason), so I add fields to the top type.
> 
> What do you mean? Do you have an example?
> (Adding fields to the top type doesn't look like a good idea, generally).
> 
> Bye,
> bearophile

For instance, I have 2 sub-classes of nodes: one leaf kind with element (here called slice), one branch kind with an array of (child) nodes. They are exclusive, and none of the data fields should appear on the top Node type. But everywhere the Node class must be used, since a branch (as the top tree) can indifferently hold leaves or sub-branches, right?
Each time I need to post-process results, since I apparently get Nodes (even if I know they are actually of one or the other type), I would first have to down-cast each node to the proper kind before doing anything. Else, I would get compiler errors, or plain bugs, for not having the proper field. So, I ended up setting fake fields on Node (and remove them from the sub-classes). And yes, I agree it's A Bad Thing to do. Just tell me of an elegant solution, and I apply it at once.


Denis
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vit esse estrany ☣

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