Re: Qualifiers, many-to-many and horizontal inheritance
Re: Qualifiers, many-to-many and horizontal inheritance
- Subject: Re: Qualifiers, many-to-many and horizontal inheritance
- From: Chuck Hill <email@hidden>
- Date: Fri, 21 Jul 2006 15:03:42 -0700
You pretty much have to use some sort of extension to the qualifiers
that ship with WO. It looks like Pierre Bernard has posted updated
versions of his here:
http://www.bernard-web.com/pierre/webobjects/code.html
I use these and they are excellent!
Chuck
On Jul 21, 2006, at 2:39 PM, Timo Hoepfner wrote:
Hi,
I have some entity (Asset, representing files with added meta info)
which has a many-to-many relationship to an abstract entity
(Keyword) in a horizontal inheritance scheme (subclasses are very
heterogenous. All they have in common is a "name" attribute).
Navigating through the object graph works fine, but I have some
problem figuring out how to build qualifiers that do what I want. I
want to build qualifiers that match
1. Any Asset which has a certain filename
2. All Assets that have no associated Keyword and have a certain
filename
3. All Assets that belong to a certain Keyword and have a certain
filename
4. All Assets that belong to any Keyword in a given list of
Keywords and have a certain filename (Some of the concrete Keyword
subclasses build a tree and I want to match Assets belonging to a
certain Keyword and all of its children)
1. is trivial
2. I've built a FetchSpec utilizing raw SQL, which does the "no
associated" keyword stuff, but I have no clue how to pass bindings
to a FetschSpec when using raw SQL (to get the "match filename" stuff)
3. Can be done easily by navigating via asset.keywords, but I'd
like to build a qualifier to be able to restrict by other
attributes, too (w/o doing in-memory filtering). I haven't been
able to build an EOQualifier (w/o raw sql) which does that. I think
there should be a way... In most cases I get either NPEs, CCEs or
SQL-Exceptions, because the generated SQL tries to look into tables
which don't exist (abstract), etc. I also tried to use some of the
Wonder qualifiers, but no luck so far.
4. Basically the same situation as 3.
I'd be more than thankful for a bit of help!
Timo
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