ruby - How do I "group" sets in Rails' jbuilder? -

i've got set of "player" , "team" models in ror app (a json api) representing sports team, "roster" model acting middleman in many-to-many relationship. in "roster" view, i'm trying 'group' players team jbuilder, can't figure out proper code this.

my current jbuilder view code (index.json.jbuilder) looks this:

json.rosters @rosters |roster|     json.team_id       roster.team.team_id     json.team_name     roster.team.team_name     json.player_id     roster.player.player_id     json.first_name    roster.player.first_name     json.last_name     roster.player.last_name end 

this outputs following json:

{     "rosters": [         {             "team_id": "1",             "team_name": "dallas mavericks",             "player_id": "1",             "first_name": "dirk",             "last_name": "nowitzki"         },         {             "team_id": "1",             "team_name": "dallas mavericks",             "player_id": "2",             "first_name": "rajon",             "last_name": "rando"         }     ] } 

my question: how can jbuilder output data in format instead? :

{     "rosters": [         {             "team_id": "1",             "team_name": "dallas mavericks",             "players": [                 {                     "player_id": "1",                     "first_name": "dirk",                     "last_name": "nowitzki"                 },                 {                     "player_id": "2",                     "first_name": "rajon",                     "last_name": "rando"                 }             ]         }     ] } 

some side notes:

• for wondering why team-player relation many-to-many, it's because players allowed change teams. roster table has start- , end-date fields represent player's tenure on team, representing changing roster on time; isn't shown in above example lack-of-clutter's sake.
• i more in team view, don't want return roster information there since it's used listing teams. might end being lot of data unconditionally pull if include roster stuff each time.
• i'm using sequel orm, not activerecord, if solution involves twiddling source data before sending jbuilder, i'm not sure if ar magic apply. still rather new this.