Re: Help: ?Cyclic? Many to Many relationship

From: Andrus Adamchik (andru..bjectstyle.org)
Date: Mon Oct 20 2003 - 12:49:20 EDT

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    Hi Noel,

    Attached is a little sample app that I wrote for your case. It works
    traversing from child or from parent. The only caveat is that the modeler
    does not allow you to "flatten" the relationship, so I had to map a join
    table as an ObjEntity. Aside from a small inconvenience this creates,
    everything works as expected.

    I guess we need to see if we should allow flattened relationships for this
    case, but this shouldn't be a show stopper for you.

    Andrus

    > Hello,
    >
    > I've been trying to use cayenne for a few days now and I've come across
    > a problem I just can't seem to get around / figure out.
    >
    > I have 2 tables. One called Person, the other called Parent_Child. The
    > structure of each is:
    >
    > **Person**
    > ID -> Integer (Primary Key)
    > Name -> varchar
    >
    > **Parent_Child**
    > parent_id -> Integer
    > child_id -> Integer
    >
    > As you may have guessed, each row of the parent_child table simply
    > stores the Person_IDs of a parent and child.
    >
    > So, using the modeler, how do you set this up? I can't seem to get it
    > right to save my life. I want to have a method on my resulting Person
    > Object called, "getChildren" which returns all of the children for the
    > given person AND I want a method called "getParents" which would return
    > a list of the parents for the given person. The best I've been able to
    > get to happen is either the list is null or I get the root person back
    > (i.e. when i ask for my children, I get myself, etc).
    >
    > Can anyone help me? The tutorials (in their current state), don't have
    > an example of this.
    >
    > Noel Murphy





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