Question

I have a problem at the moment and am not sure what I should do. It is
in regards to relationships between tables and whether I need foreign
keys.

I have two tables in my database; users and games. Users includes all
the users information (username, email, address, password etc.) Games
includes all the games information (name, genre, console user_id). As
you may have noticed the games table includes the users id in order to
associate the relationship between the two which is every game needs an
associated user.

What I wish to do is on each games show.html.erb page, I have a button
which should send an email to the owner of that game in order to let
them now that the currently signed in user is interested in trading that
game.

I am wondering how I would do this. Does the user_id automatically link
all the users associated data or just the id. If not then how would I
declare the users email as a foreign key in order for me to call the
users email to be sent to?

Any help would be much appreciated. Thank you

Christopher Jones

UPDATE

Hey I had the following in my games_controller show section and it did not work. It threw the following error: undefined method `email’ for “[e-mail]”:String.

def show
@game = Game.find(params[:id])

respond_to do |format|
  GameTrade.game_interest(@game.user.email).deliver
  format.html { redirect_to root_url }
  format.json { render json: @game }
end
end

So I changed it to the following in order to break down the problem and find out what line it broke on and it stated that the block was on line 19 which is the line g = GameTrade.game_interest(email). I got the following error:

undefined method `email’ for “[e-mail]”:String

Any ideas? the code is below

def show
  @game = Game.find(params[:id])

respond_to do |format|
  user = @game.user
  email = user.email
  g = GameTrade.game_interest(email)
  g.deliver
  format.html { redirect_to root_url }
  format.json { render json: @game }
end
end

The following code is that of my Game_trade.rb in the mailer section:

  class GameTrade < ActionMailer::Base
    default :from => "[e-mail]"

    def game_interest(user)
      @user = user
      mail :to => user.email, :subject => "Game Interest"
    end
   end

Answer 1

Take a look at this Stack Overflow question regarding Rails and referential integrity. You may want to look into the foreigner gem for adding and removing foreign keys during Rails migrations.

However, I’m curious as to why you’re creating foreign key constraints beyond the game->user constraint you already have. Is there a reason you’re denormalizing the username and email fields?