rails add record to has_many :through join table

Question

class EventTeam < ActiveRecord::Base
  belongs_to :event
  belongs_to :team
end

class Event < ActiveRecord::Base
  has_many :event_teams
  has_many :teams, through: :event_teams
end

class Team < ActiveRecord::Base
  has_many :event_teams
  has_many :events, through: :event_teams
end

I am trying to add the :event_id and :team_id to the EventTeam join table when creating a new Event and can't seem to figure out how, despite an exhaustive search of similar questions such as: how to add records to has_many :through association in rails (I've tried all of these suggestions)

It seems that the following should work, though a NoMethodError is delivered: "undefined method `events' for #ActiveRecord::Relation []"

EventsController

def new
  @event = Event.new(:team_id => params[:team_id])
end

def create
  @team = Team.where(:id => params[:team_id])
  @event = @team.events.create(event_params)
  if @event.save
    flash[:success] = "Event created!"
    redirect_to @event
  else  
    render 'new'
  end
end

I have a similar situation in the same app with Users, Teams, and Memberships (join table). The following code automatically adds the :team_id and :user_id to the Memberships table when a user creates a new Team.

TeamsController

def new
  @team = Team.new(:user_id => params[:user_id])
end

def create
  @team = current_user.teams.create(team_params)
  if @team.save
    flash[:success] = "Team created!"
    redirect_to @team
  else
    render 'new'
  end
end

Any suggestions on how to accomplish this?

Pavan · Accepted Answer · 2016-04-26T19:41:59.763

1

undefined method `events' for #ActiveRecord::Relation []

where returns an AR relation not a single instance, so @team.events won't work. Use find instead

@team = Team.find(params[:team_id])
@event = @team.events.create(event_params)

Update

could not find Team with 'id'=

You are getting team_id inside event hash, so params[:team_id] won't work. You need to use params[:event][:team_id]

@team = Team.find(params[:event][:team_id])
@event = @team.events.create(event_params)

edited Apr 26 '16 at 19:41

answered Apr 26 '16 at 19:19

Pavan

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for some reason, I get the error "could not find Team with 'id'= When I just put 1 instead of params[:team_id], the event is created, and record added to the join table - so .find instead of .where definitely works. The strange part is, I can see team_id=1 in the url for the new_event path. – ncarroll Apr 26 '16 at 19:34
@ncarroll What are the params that are generated for that action? – Pavan Apr 26 '16 at 19:36
{"utf8"=>"✓", "authenticity_token"=>"EryBDSRyQWO3zEXCjjz0J/Y9IOy0bfCw5tVhMnN+MiG0cOyJYWIWPNVihVbyP9C36raLXZ8B2uN8HR9PlCqTzg==", "event"=>{"date"=>"2016-04-20", "name"=>"test", "location"=>"test", "venue"=>"test", "team_id"=>"1"}, "commit"=>"Create event"} – ncarroll Apr 26 '16 at 19:37
@ncarroll I've updated my answer. It should work now. – Pavan Apr 26 '16 at 19:42

score 0 · Answer 2 · answered Apr 26 '16 at 19:18

Just specify first value of the relation, since you are searching by unique index with value id, so that should be well:

@team = Team.where(id: params[:team_id]).first
@event = @team.events.create(event_params)

That is because .where, unlike find_by or find(1) returning a Relation, not a first value in it.

However, in modern version of rails I saw recommendation to use exactly where.first pair, not a find.

rails add record to has_many :through join table

2 Answers2