> There are a few possible ways to go about this. One is the manual
> way, where you actually instantiate and them modify the map record
> separately, as shown here:
...
> Finally, you could forego the many-to-many relationship definition and
> instead (or "also") defined it as chain of relationships that
> explicitly includes the mapping table:
Thanks for the quick and extremely thorough response. I ended up using a
combination of these two methods, depending on whether I was creating a
new set of tags for a project, or just adding a single tag to an
existing project.
Thanks again,
- jud
John Siracusa wrote:
> On 11/7/06, Jud Dagnall <[EMAIL PROTECTED]> wrote:
>
>>In my application, there is are projects, tags, and profiles (users).
>>Projects can be tagged by multiple profiles. Each tag has a many-to-many
>>relationship both projects and profiles. There's a mapping table
>>(tag_project_profile_map) with a 3-column primary key that relates those
>>three tables.
>>[...]
>>I'd like to be able to add tags to a project as follows (specifying the
>>missing primary key value):
>>
>>$project->tags( { name = 'cool_stuff', profile_id => 1 } );
>>$project->save;
>>
>>However, this gives me an error because the 'tags' table doesn't
>>actually have a profile_id, only the mapping table does.
>
>
> There are a few possible ways to go about this. One is the manual
> way, where you actually instantiate and them modify the map record
> separately, as shown here:
>
>
>>my $mapping = TagProjectProfileMap->new(
>> {project_id => 1,
>> tag_id => 2,
>> profile_id => 3});
>>$mapping->save;
>
>
> (Although the argument to new() should not be a hashref.)
>
> Another way is to set the tags, use the Manager to re-fetch them,
> modify the map records, and then re-save them:
>
> $project->new(id => 1)->load;
> $project->tags(...);
> $project->save;
>
> $project =
> Project::Manager->get_prouducts(
> with_objects => [ 'tags' ],
> with_map_records => 1,
> query => [ id => 1 ])->[0];
>
> foreach my $tag ($project->tags)
> {
> $tag->map_record->profile_id(...);
> $tag->map_record->save;
> }
>
> That's a save(), load(), and then re-save() for each map record, however.
>
> The next method I can think of is to split up your single mapping
> table into two mapping tables, e.g.. project_tag_map table and a
> project_profile_map. Then you could just do:
>
> $project->tags(...);
> $project->profiles(...);
> $project->save;
>
> Maybe that's not exactly in keeping with what you're trying to model,
> but the three-way tag_project_profile_map mapping table is a bit odd.
> The concept of a map table in RDBO is supposed to be part of a
> many-to-many relationship between two classes, not three. As you've
> discovered, it'll pretty much still work with three, but there's a bit
> of a mismatch in intent.
>
> Finally, you could forego the many-to-many relationship definition and
> instead (or "also") defined it as chain of relationships that
> explicitly includes the mapping table:
>
> Project
> |
> one to many <- rel name: tag_profile_map_records
> |
> v
> TagProjectProfileMap
> / \
> foreign key foreign key
> / \
> v v
> Tag Profile
>
> Then do:
>
> $project->new(id => 1)->load;
>
> $project->tag_profile_map_records
> (
> {
> tag => { name => 'foo', ... },
> profile => { username => 'bar', ... },
> },
> {
> tag => { name => 'baz', ... },
> profile => { username => 'blee', ... },
> },
> ...
> );
>
> $project->save;
>
>
>>I looked at trying define a custom primary_key_generator() function in
>>my TagProjectProfileMap, but I didn't see that I could get the
>>additional parameters.
>
>
> A pk generator is definitely not the right approach to this problem.
>
> -John
>
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>
--
Jud Dagnall
Technical Yahoo! Platform Engineering
[EMAIL PROTECTED] PH: +1 (408) 349-4478
Bugzilla questions?
http://twiki.corp.yahoo.com/view/Bugzilla/BugzillaFAQ
-------------------------------------------------------------------------
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done quickly with pre-integrated technology to make your job easier
Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
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