With ManyToMany the join table is defined by you, manually as a regular mapper.
You have to tell MappedManyToMany about it and its foreign keys.
I will try to find time to make the wiki entry more clear.
Also, if the scaladocs are lacking let me know how they could be improved.
-------------------------------------
Matyjas<maty...@gmail.com> wrote:
My entities are like Programmers and Projects. There is a many to many
relationship between Programmers and Projects, but the relationship
has an attribute for type. Examples of relationship types are
Develops, Manages, Maintains, Tests, etc. In a traditional relational
db there would be a join table containing the type of relationship as
well as foreign keys to both Programmer and Project. I would like to
run queries such as "what projects does this programmer develop?"
which loosely translates to the following SQL:
SELECT * FROM projects WHERE programmer.id ==
programmer_project.programmer_id && programmer_project.project_id ==
project.id && programmer_project.type == "Develops" && programmer.id
== thisProgrammerId;
So far, I gave up on the ManyToMany Mapper because I could not figure
out how to add an attribute to the join table. The join table seemed
to be hidden away.
What I have now is both Programmer and Project extending OneToMany,
where the many side is a ProgrammerProject class. Something like:
...
class Programmer extends LongKeyedMapper[Programmer] with
OneToMany[Long, Programmer] {
...
object programmerProjects extends MappedOneToMany(ProgrammerProject,
ProgrammerProject.programmer) with Owned[ProgrammerProject] with
Cascade[ProgrammerProject]
...
}
...
class Project extends LongKeyedMapper[Project] with OneToMany[Long,
Project] {
...
object programmerProjects extends MappedOneToMany(ProgrammerProject,
ProgrammerProject.project) with Owned[ProgrammerProject] with
Cascade[ProgrammerProject]
...
}
object RelationshipType extends Enumeration {
val Develops = new Val(1, "Develops")
val Manages = new Val(2, "Manages")
}
...
class ProgrammerProject extends LongKeyedMapper[ProgrammerProject] {
...
object relationshipType extends MappedEnum(this, RelationshipType)
object programmer extends LongMappedMapper(this, Programmmer)
object project extends LongMappedMapper(this, Project)
}
This arrangement isnt terrific, but it would be okay if I could
construct valid QueryParams. I would expect something like the
following to work:
Project.findAll(In(Project.id, ProgrammerProject.project,
In(ProgrammerProject.programmer,
Programmer.id,
By(ProgrammerProject.relationshipType,
RelationshipType.Develops))))
But it doesnt. Any advice would be most appreciated
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