Associations join

[Timen E.]

Hey there,

Im fairly new to rails and i've tried several tutorials which taught me
how to use the associatives on a basic level(has_many => belongs_to).

However i'm trying to figure out how i can create and execute some kind
of a join. My case is:
I've got a list of playing cards in my DB that are static.
Every user can have any of those cards, even multiple times. So my
tables would look something like this:

users
id = 1
name => "Bear Grylls"

id => 2
name => "Poopypants"
----------------------
cards
id => 1
name => "Captain Carl"

id => 2
name => "Whatever"
----------------------
usercardsjoin
card_id => 1
user_id => 1

card_id => 2
user_id=> 1

card_id => 1
user_id => 2
----------------------

Although i know how it should look like because of my experience with
PHP i have absolutely no clue how i can get this one to work.

Can any of you explain this or send me a link which handles this
particular issue?

Thanks in advance,

--
Posted via http://www.ruby-forum.com/.

[Tim Shaffer]

Check out the guide to associations. It should have more information than you need...

http://guides.rubyonrails.org/association_basics.html 

[Manuel Hutter]

Hey!

Associats are covered in great detail here:
http://guides.rubyonrails.org/association_basics.html

I think what you need is a has_many :through association

-- Manuel

[Timen E.]

Thanks you guys, i've actually tried that(And failed) Perhaps you guys
can help me out.
I have to following files:

card_controller.rb
class CardController < ApplicationController
has_many :cardlevels
has_many :users, :through => :cardlevels
def show
@cards = Card.find(1)
end
end
------------------------------------------------------

cardlevel_controller.rb
class CardlevelController < ApplicationController
belongs_to :users
belongs_to :cards
end
------------------------------------------------------

user_controller.rb
class UserController < ApplicationController
has_many :cardlevels
has_many :cards, :through => :cardlevels
end
------------------------------------------------------


As you can see i'm doing @cards = Card.find(1) in the card_controller.
However i'm getting the error: "undefined method `has_many' for
CardController:Class"

[Timen E.]

I seem to have it up and running at this point. I made all the
has_many's etc. in my models. But when i try @cards.user (Or each it
first and use c.user) it says 'undefined method 'user''. So i'm assuming
i'm doing something awfully wrong.

My card_controller looks like this
def show
@cards = Card.all
end



Here are my models:
card.rb
class Card < ActiveRecord::Base

has_many :cardlevels
has_many :users, :through => :cardlevels

end
-------------------------------------------------

cardlevel.rb
class Cardlevel < ActiveRecord::Base

belongs_to :users
belongs_to :cards
end
-------------------------------------------------

user.rb
class User < ActiveRecord::Base

has_many :cardlevels
has_many :cards, :through => :cardlevels
end

-------------------------------------------------

[Colin Law]

On 19 June 2012 13:38, Timen E. <li...@ruby-forum.com> wrote:
> I seem to have it up and running at this point. I made all the
> has_many's etc. in my models. But when i try @cards.user (Or each it
> first and use c.user) it says 'undefined method 'user''. So i'm assuming
> i'm doing something awfully wrong.
>
> My card_controller looks like this
> def show
>    @cards = Card.all
>  end
>
>
>
> Here are my models:
> card.rb
> class Card < ActiveRecord::Base
>    has_many :cardlevels
>  has_many :users, :through => :cardlevels
> end
> -------------------------------------------------
>
> cardlevel.rb
> class Cardlevel < ActiveRecord::Base
>    belongs_to :users
>  belongs_to :cards

Those should both be singular (:user and :card). Each cardlevel
belongs to one user and card so they should be singular.

Colin

> end
> -------------------------------------------------
>
> user.rb
> class User < ActiveRecord::Base
>    has_many :cardlevels
>  has_many :cards, :through => :cardlevels
> end
>
> -------------------------------------------------
>
> --
> Posted via http://www.ruby-forum.com/.
>

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[Timen E.]

Colin Law wrote in post #1065209:

> On 19 June 2012 13:38, Timen E. <li...@ruby-forum.com> wrote:
>>
>> class Cardlevel < ActiveRecord::Base
>> belongs_to :users
>> belongs_to :cards
>
> Those should both be singular (:user and :card). Each cardlevel
> belongs to one user and card so they should be singular.
>
> Colin

That sounds fair indeed, however when i tried i still got the same
error. This associations got me so bloody confused :')

[Colin Law]

Post the code for the models, the code that generates the error (with
a few lines each side) and the full error message.

Colin

[Timen E.]

I've just got a really basic setup to see if i got it working:

card.rb
class Card < ActiveRecord::Base

attr_accessible :attack, :defense, :name

has_many :cardlevels
has_many :users, :through => :cardlevels
end

cardlevel.rb
class Cardlevel < ActiveRecord::Base

attr_accessible :card_id, :level, :user_id
belongs_to :user
belongs_to :card
end

user.rb
class User < ActiveRecord::Base

attr_accessible :name
has_many :cardlevels
has_many :cards
end
-----------------------------------------------------

card_controller.rb
class CardController < ApplicationController
def show
@card = Card.all
end
end

User & cardlevel are empty for now
-----------------------------------------------------

<h1>Card#show</h1>
<p>Find me in app/views/card/show.html.erb</p>
<%= @card.user %>
Where i tried eaching the @card, tried @card.users, @card.user.name etc.
etc.
-----------------------------------------------------

The error:
Showing c:/tuts/kaartje/app/views/card/show.html.erb where line #3
raised:

undefined method `user' for #<Array:0x3c81ac8>
Extracted source (around line #3):

1: <h1>Card#show</h1>
2: <p>Find me in app/views/card/show.html.erb</p>
3: <%= @card.user %>
Rails.root: c:/tuts/kaartje

Application Trace | Framework Trace | Full Trace
app/views/card/show.html.erb:3:in
`_app_views_card_show_html_erb___1042037435_30519240'
Request

Parameters:

{"id"=>"show"}
-----------------------------------------------------

[Michael Pavling]

On 20 June 2012 08:51, Timen E. <li...@ruby-forum.com> wrote:
> #card_controller.rb

> class CardController < ApplicationController
>  def show
>    @card = Card.all
>  end
> end
>

> <h1>Card#show</h1>
> <p>Find me in app/views/card/show.html.erb</p>
> <%= @card.user %>
>

> undefined method `user' for #<Array:0x3c81ac8>
> Extracted source (around line #3):

@card is a collection of cards (that's how you populate it in the
"show" action. If it needs to be a single card, you need to find it by
ID (or some other attribute), if it's supposed to be a collection of
every card, you need to iterate it in the view and print the user for
each card.

[Colin Law]

On 20 June 2012 08:51, Timen E. <li...@ruby-forum.com> wrote:

You would have been better to put @cards = Card.all as the result will
be be an (effectively) an array of cards not a single one.

>  end
> end
>
> User & cardlevel are empty for now
> -----------------------------------------------------
>
> <h1>Card#show</h1>
> <p>Find me in app/views/card/show.html.erb</p>
> <%= @card.user %>
> Where i tried eaching the @card, tried @card.users, @card.user.name etc.
> etc.
> -----------------------------------------------------
>
> The error:
> Showing c:/tuts/kaartje/app/views/card/show.html.erb where line #3
> raised:
>
> undefined method `user' for #<Array:0x3c81ac8>

The clue is in the error message, as is often the case, it says that
@card is an Array and the Arrray class does not have a method user.
You can only call user on an individual card.

Colin

> Extracted source (around line #3):
>
> 1: <h1>Card#show</h1>
> 2: <p>Find me in app/views/card/show.html.erb</p>
> 3: <%= @card.user %>
> Rails.root: c:/tuts/kaartje
>
> Application Trace | Framework Trace | Full Trace
> app/views/card/show.html.erb:3:in
> `_app_views_card_show_html_erb___1042037435_30519240'
> Request
>
> Parameters:
>
> {"id"=>"show"}
> -----------------------------------------------------
>
> --
> Posted via http://www.ruby-forum.com/.
>

[Timen E.]

Michael Pavling wrote in post #1065301:

aaah i see, nonetheless i noticed that i turned it around. I need to get
the user with it's cards, haha!

What you mentioned did work but it doesn't seem to 'associate' the right
way around because i'm getting the error SQLite3::SQLException: no such
column: cards.user_id: SELECT "cards".* FROM "cards" WHERE
"cards"."user_id" = 1"".
Shouldn't he query through cardlevels instead of cards?

[Timen E.]

Still got one(Hopefuly last for now) question, guys.

I've got the above data now and i can access my cards through users that
are joined by the cardlevel. I'm trying to loop through all the cards a
user has as such:
<% @user.cards.each do |c| %>
<%= c.name %><br>
<% end %>

And this works great. However i'd like to get some extra info about this
card from my cardlevel array, but i can't seem to access it like this. I
can however loop it in a seperate each, but i don't want that obviously.

Any ideas?

Thanks

[Colin Law]

On 20 June 2012 09:32, Timen E. <li...@ruby-forum.com> wrote:

> Still got one(Hopefuly last for now) question, guys.
>
> I've got the above data now and i can access my cards through users that
> are joined by the cardlevel. I'm trying to loop through all the cards a
> user has as such:
> <% @user.cards.each do |c| %>
>  <%= c.name %><br>
> <% end %>
>
> And this works great. However i'd like to get some extra info about this
> card from my cardlevel array, but i can't seem to access it like this. I
> can however loop it in a seperate each, but i don't want that obviously.

You have not explained well what you are trying to do, but possibly
you want to loop through the cardlevels instead of the cards, then for
each cardlevel you can obtain the card aswell as the other data, so
something like

<% @user.cardlevels.each do |cl| %>
<%= cl.card.name %><br>
<%= cl.other_data %>
<% end %>

You might need to check for cl.card nil though.

Colin

[Timen E.]

Colin Law wrote in post #1065311:

You're my savior, thanks alot! It's more the train of thought that needs
correcting than my code i guess.