scala - Slick 3.0 many-to-many query with the join as an iterable -

i've created many-to-many collection using slick 3.0, i'm struggling retrieve data in way want.

there many-to-many relationship between events , interests. here tables:

case class eventdao(title: string,                     id: option[int] = none)   class eventstable(tag: tag)   extends table[eventdao](tag, "events") {    def id = column[int]("event_id", o.primarykey, o.autoinc)   def title = column[string]("title")    def * = (     title,     id.?) <> (eventdao.tupled, eventdao.unapply)    def interests = eventinterestqueries.query.filter(_.eventid === id)     .flatmap(_.interestfk) }   object eventqueries {    lazy val query = tablequery[eventstable]    val findbyid = compiled { k: rep[int] =>     query.filter(_.id === k)   } } 

here's eventsinterests:

case class eventinterestdao(event: int, interest: int)   class eventsintereststable(tag: tag)   extends table[eventinterestdao](tag, "events_interests") {    def eventid = column[int]("event_id")   def interestid = column[int]("interest_id")    def * = (     eventid,     interestid) <> (eventinterestdao.tupled, eventinterestdao.unapply)    def eventfk = foreignkey("event_fk", eventid, eventqueries.query)(e => e.id)   def interestfk = foreignkey("interest_fk", interestid, interestqueries.query)(i => i.id) }   object eventinterestqueries {   lazy val query = tablequery[eventsintereststable] } 

and interests:

case class interestdao(name: string,                        id: option[int] = none)  class intereststable(tag: tag)   extends table[interestdao](tag, "interests") {    def id = column[int]("interest_id", o.primarykey, o.autoinc)   def name = column[string]("name")   def name_idx = index("idx_name", name, unique = true)    def * = (     name,     id.?) <> (interestdao.tupled, interestdao.unapply)    def events = eventinterestqueries.query.filter(_.interestid === id)     .flatmap(_.eventfk) }   object interestqueries {    lazy val query = tablequery[intereststable]    val findbyid = compiled { k: rep[int] =>     query.filter(_.id === k)   } } 

i can query , retrieve tuples of (event.name, interest) following:

val eventinterestquery = {   event <- eventqueries.query   interest <- event.interests } yield (event.title, interest.name)  await.result(db.run(eventinterestquery.result).map(println), duration.inf) 

so have.

what want able populate case class like:

case class eventdao(title: string,                 interests: seq[interestdao],                 id: option[int] = none) 

the trouble if update case class this, messes def * projection in eventstable. also, i'll have rename eventstable.interests filter eventstable.interestids bit ugly live if necessary.

also, can't find way of writing for query yields (event.name, seq(interest.name)). anyway, that's stepping stone me being able yield (eventdao, seq(interestdao)) tuple want return.

does know how can achieve these things? want able 'take' number of interests, queries returned, others first 3 be.

so after reading this page , chatting on mailing list, got working:

val eventinterestquery = {   event <- eventqueries.query   interest <- event.interests } yield (event, interest)  await.result(db.run(eventinterestquery.result   // convert interests sequence.   .map {   _.groupby(_._1)     .map {       case (k,v) => (k, v.map(_._2))   }.toseq } ), duration.inf)