[Rails] Re: The need of IDs in ActiveRecord

[Eric Anderson]

Justin Rudd wrote:
> That's inheritance, not a parent/child relationship.
[...snip...]
> A parent table is one that lends its identity to a child to help
> uniquely identify the child.  I used an example of a PO and a PO Line
> item in another e-mail.  The PO Line Item is a child of the PO because
> its primary key is a the PO Number and the Line Item number.

I guess this is just difference in definition. Usually when I think of 
inheritance I think of it as a parent/child relationship. The superclass 
is the parent, the subclass is the child.

For your PO example I see those as two different objects. The PO Line 
Item is related to and dependent on the PO, but it is still it's own object.

Like I said, just a difference in definition.

Eric
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