Can someone point me to a reference or tutorial that shows how to map foreign key relationships in the model? For example given: Users id name email Posts id user_id title How do I associate user_id with users.id in the Post and User models? has_many and belongs_to don''t seem to do it. -- Posted via http://www.ruby-forum.com/.
Arch Stanton wrote:> Can someone point me to a reference or tutorial that shows how to map > foreign key relationships in the model? > > For example given: > > Users > id > name > email > > Posts > id > user_id > title > > How do I associate user_id with users.id in the Post and User models? > has_many and belongs_to don''t seem to do it.This cheatsheet might be helpful: http://slash7.com/cheats/activerecord_cheatsheet.pdf Regards, Andre -- Posted via http://www.ruby-forum.com/.
In this case, why won''t it? In your user model, you''d say has_many :posts and in the post model you''d say belongs_to :user and that''s all you need for what you describe. What''s not working? Arch Stanton wrote:> Can someone point me to a reference or tutorial that shows how to map > foreign key relationships in the model? > > For example given: > > Users > id > name > email > > Posts > id > user_id > title > > How do I associate user_id with users.id in the Post and User models? > has_many and belongs_to don''t seem to do it.-- Posted via http://www.ruby-forum.com/.
Steve Koppelman wrote:> In this case, why won''t it? > > In your user model, you''d say > > has_many :posts > > and in the post model you''d say > > belongs_to :user > > and that''s all you need for what you describe. What''s not working? >Well in the view I get no visibility to the foreign keys. Just now I found this example: class Student < ActiveRecord::Base set_table_name "students" set_primary_key "id" belongs_to :advisor, :class_name=>"Advisor", :foreign_key => "advisor_id" belongs_to :second_advisor, :class_name=>"Advisor", :foreign_key => "sub_advisor" has_and_belongs_to_many :courses, :class_name=>"Course" end I want my posts/edit to allow me to select a user. -- Posted via http://www.ruby-forum.com/.
So that cheat sheet raised some questions. First it sounds like it is saying not to use has_many and belongs_to with foreign keys?? I guess what I want an example of is how to set my simple example up so that in the basica scaffold view I can edit/select the values for a property that is a foreign key. So from the post view I want to select/assign the user. -- Posted via http://www.ruby-forum.com/.
models:
class User < ActiveRecord::Base
has_many :posts
end
class Post < ActiveRecord::Base
beongs_to :user #
end
controller
class PostController < ApplicationController
def new
@post = Post.new
@users = User.find(:all)
end
end
view (new.rhtml)
<%= start_form_tag :action => "create" %>
...
<%= select :post, :user_id, options_from_collection_for_select(@users,
"id",
"name") %>
...
<%= end_form_tag %>
On 3/31/06, Arch Stanton <d6veteran@gmail.com>
wrote:>
> Steve Koppelman wrote:
> > In this case, why won''t it?
> >
> > In your user model, you''d say
> >
> > has_many :posts
> >
> > and in the post model you''d say
> >
> > belongs_to :user
> >
> > and that''s all you need for what you describe.
What''s not working?
> >
>
>
> Well in the view I get no visibility to the foreign keys. Just now I
> found this example:
>
> class Student < ActiveRecord::Base
> set_table_name "students"
> set_primary_key "id"
>
> belongs_to :advisor, :class_name=>"Advisor", :foreign_key
=>
> "advisor_id"
> belongs_to :second_advisor, :class_name=>"Advisor",
:foreign_key =>
> "sub_advisor"
>
> has_and_belongs_to_many :courses, :class_name=>"Course"
>
> end
>
> I want my posts/edit to allow me to select a user.
>
> --
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
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Chris Hall wrote:> models: > > class User < ActiveRecord::Base > has_many :posts > end > > class Post < ActiveRecord::Base > beongs_to :user # > end >Thanks Chris. So, what do I get from explicitly identifying the foreign key relationship in the model (like belongs_to :advisor, :class_name=>"Advisor", :foreign_key => "advisor_id")?? Thanks. -- Posted via http://www.ruby-forum.com/.
you''re not getting anything. Rails figures out that info based on the criteria you specify. if you stick to Rails conventions, you don''t have to do anything but provide the association name, rails does the rest. so in that example student belongs_to :advisor rails will make the following assumptions: students table contains an "advisor_id" column that references the id column in advisors table the associated class is named "Advisor" example 2: student belongs_to :advisor, :class_name => "Person" in this case, we must tell the model to not make the default assumptions, since our association name has nothing to do with what we really want. you have to be explicit if you don''t want to stick to Rails conventions On 3/31/06, Arch Stanton <d6veteran@gmail.com> wrote:> > Chris Hall wrote: > > models: > > > > class User < ActiveRecord::Base > > has_many :posts > > end > > > > class Post < ActiveRecord::Base > > beongs_to :user # > > end > > > > > Thanks Chris. > > So, what do I get from explicitly identifying the foreign key > relationship in the model (like belongs_to :advisor, > :class_name=>"Advisor", :foreign_key => > "advisor_id")?? > > Thanks. > > -- > Posted via http://www.ruby-forum.com/. > _______________________________________________ > Rails mailing list > Rails@lists.rubyonrails.org > http://lists.rubyonrails.org/mailman/listinfo/rails >-------------- next part -------------- An HTML attachment was scrubbed... URL: http://wrath.rubyonrails.org/pipermail/rails/attachments/20060401/e20075ee/attachment.html
Chris Hall wrote:> you''re not getting anything. Rails figures out that info based on the > criteria you specify. if you stick to Rails conventions, you don''t have > to > do anything but provide the association name, rails does the rest. >Thank you Chris that was extremely helpful. It makes sense now. -- Posted via http://www.ruby-forum.com/.
Chris Hall wrote:> you''re not getting anything. Rails figures out that info based on the > criteria you specify. if you stick to Rails conventions, you don''t have > to > do anything but provide the association name, rails does the rest. > > so in that example > > student belongs_to :advisor > > rails will make the following assumptions: > > students table contains an "advisor_id" column that references the id > column > in advisors table > the associated class is named "Advisor" >I guess I do have a follow up question. In the above example, what is gained by adding a has_many relationship to Advisor? advisor has_many :students -- Posted via http://www.ruby-forum.com/.
I''m really having a hard time implementing foreign keys and I find it
odd that Rails makes so many things easy, yet foreign keys don''t seem
to
be supported. Maybe I am missing something. Here''s the revelant set
up
info:
Table Test
id
title
summary
test_type_id
---------------------
Table Test_Type
id
type_name
---------------------
class Admin::TestController < Admin::BaseController
scaffold :test
def new
@test = Test.new
@test_type = TestType.find(:all)
end
end
---------------------
class Admin::TestTypeController < Admin::BaseController
scaffold :test_type
end
---------------------
class Test < ActiveRecord::Base
has_many :questions
has_many :logged_tests
has_many :results
belongs_to :test_type
belongs_to :user
end
---------------------
class TestType < ActiveRecord::Base
has_many :tests
end
---------------------
views/admin/test/new.rhtml
<html>
<body>
<%= start_form_tag :action => "create" %>
<p>
<label for="test_title">Title</label><br />
<%= text_field_tag("test_title", nil, :size =>
"40") %></p>
<p>
<label for="test_summary">Summary</label><br />
<%= text_area_tag("test_summary", nil, :size =>
"40x20") %>
</p>
<p>
<%= select :test, :test_type,
options_from_collection_for_select(@test_types, "id",
"type_name") %>
</p>
<p>
<%= submit_tag(value = "Create New Test") %>
</p>
<%= end_form_tag() %>
<a href="/admin/test/list">Back</a>
</body>
</html>
---------------------
error:
ActionView::TemplateError (undefined method `inject'' for nil:NilClass)
on line #19 of app/views/admin/test/new.rhtml:
16: <%= text_area_tag("test_summary", nil, :size =>
"40x20") %>
17: </p>
18: <p>
19: <%= select :test, :test_type,
options_from_collection_for_select(@test_types, "id",
"type_name") %>
20: </p>
21: <p>
22: <%= submit_tag(value = "Create New Test") %>
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_view/helpers/form_options_helper.rb:141:in
`options_from_collection_for_select''
#{RAILS_ROOT}/app/views/admin/test/new.rhtml:19
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_view/base.rb:268:in
`send''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_view/base.rb:268:in
`compile_and_render_template''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_view/base.rb:244:in
`render_template''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_view/base.rb:205:in
`render_file''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/base.rb:655:in
`render_file''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/base.rb:595:in
`render_with_no_layout''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/layout.rb:228:in
`render_with_a_layout''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/base.rb:684:in
`render_with_layout''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/base.rb:645:in
`render_action''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/scaffolding.rb:153:in
`render_scaffold''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/scaffolding.rb:117:in
`new''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/base.rb:853:in
`send''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/base.rb:853:in
`perform_action_without_filters''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/filters.rb:332:in
`perform_action_without_benchmark''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/benchmarking.rb:69:in
`perform_action_without_rescue''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/benchmarking.rb:69:in
`measure''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/benchmarking.rb:69:in
`perform_action_without_rescue''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/rescue.rb:82:in
`perform_action''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/base.rb:369:in
`send''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/base.rb:369:in
`process_without_session_management_support''
/usr/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/session_management.rb:116:in
`process''
/usr/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/dispatcher.rb:38:in
`dispatch''
/usr/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/fcgi_handler.rb:141:in
`process_request''
/usr/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/fcgi_handler.rb:53:in
`process!''
/usr/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/fcgi_handler.rb:52:in
`each_cgi''
/usr/lib/ruby/1.8/fcgi.rb:597:in `each''
/usr/lib/ruby/1.8/fcgi.rb:597:in `each_cgi''
/usr/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/fcgi_handler.rb:52:in
`process!''
/usr/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/fcgi_handler.rb:22:in
`process!''
dispatch.fcgi:33
Any help appreciated.
--
Posted via http://www.ruby-forum.com/.
d6veteran wrote:> I''m really having a hard time implementing foreign keys and I find it > odd that Rails makes so many things easy, yet foreign keys don''t seem to > be supported. Maybe I am missing something. Here''s the revelant set up > info:You could use the scaffolding to build a working example of the logic here. Your problem on line 19, is that you have a variable @test_types, which you didn''t define in your controller. The options_from_collection_for_select calls inject on this nil object and you get this error. -- Ray
Ray Baxter wrote:> d6veteran wrote: >> I''m really having a hard time implementing foreign keys and I find it >> odd that Rails makes so many things easy, yet foreign keys don''t seem to >> be supported. Maybe I am missing something. Here''s the revelant set up >> info: > > You could use the scaffolding to build a working example of the logic > here. > > Your problem on line 19, is that you have a variable @test_types, which > you didn''t define in your controller. The > options_from_collection_for_select calls inject on this nil object and > you get this error. > > -- > > RayI thought I was using the scaffolding. So you mean in the TestTypeController I need to define @test_types? -- Posted via http://www.ruby-forum.com/.
Arch Stanton wrote:> I thought I was using the scaffolding.I was wrong about this. I thought that the scaffolding created the correct scaffolding for the associations, but it doesn''t.> So you mean in the TestTypeController I need to define @test_types?Yes. There won''t be anything in the drop down until you create some test_types though. -- Ray
Ray Baxter wrote:> Arch Stanton wrote: > >> So you mean in the TestTypeController I need to define @test_types? > > Yes. There won''t be anything in the drop down until you create some > test_types though. > > > -- > > RayThat doesn''t make any sense to me. I look through the rest of my controllers and I can access the entire model without anything more than a scaffold declaration. I understand that I should define test_type in my Type controller, as I have done here: class Admin::TestController < Admin::BaseController scaffold :test def new @test = Test.new @test_type = TestType.find(:all) end end --------------------- class Admin::TestTypeController < Admin::BaseController scaffold :test_type end Not sure why this is not working. -- Posted via http://www.ruby-forum.com/.
Arch Stanton wrote:> Not sure why this is not working.You are referencing @test_types in you view, not @test_type. You are defining @test_type in your controller, not @test_types. They need to be the same.
The point of telling Rails about the relationships between models is not because Rails will magically create scaffolding for you but because you''ll be able to access you data through the relations. For instance, once you''ve set up those two relationships in your models, you can do things like @advisor = Advisor.find(1) @students = @advisor.students and conversely, if you have a student selected into @student, you can get the advisor''s name simply via @student.advisor.name Or if you''re updating a student''s attributes in a controller action, if you set some of @student.advisor''s attributes, the changes to the advisor will also get saved when you simply call @student.save and all sorts of stuff like that. Arch Stanton wrote:> Chris Hall wrote:.... snip ...>> so in that example >> >> student belongs_to :advisor >> >> rails will make the following assumptions: >> >> students table contains an "advisor_id" column that references the id >> column >> in advisors table >> the associated class is named "Advisor" >> > > > I guess I do have a follow up question. > > In the above example, what is gained by adding a has_many relationship > to Advisor? > > advisor has_many :students-- Posted via http://www.ruby-forum.com/.
Steve Koppelman wrote:> The point of telling Rails about the relationships between models is not > because Rails will magically create scaffolding for you but because > you''ll be able to access you data through the relations. > > For instance, once you''ve set up those two relationships in your models, > you can do things like > > @advisor = Advisor.find(1) > @students = @advisor.students > > and conversely, if you have a student selected into @student, you can > get the advisor''s name simply via @student.advisor.name > > Or if you''re updating a student''s attributes in a controller action, if > you set some of @student.advisor''s attributes, the changes to the > advisor will also get saved when you simply call @student.save > > and all sorts of stuff like that. >Thanks for the reply. I cleaned up my typos and tried calling @test.test_type.id and it works. That is cool. -- Posted via http://www.ruby-forum.com/.
associations are a two way street.
in the student advisors example
# student belongs_to :advisor
s = Student.find(1, :include => :advisor) # find student with id = 1
puts s.advisor.name # print name of the student''s advisor
# advisor has_many :students
a = Advisor.find(1, :include => :students) # find advisor with id = 1
a.students.each { |s| puts s.name } # print all the names of the students
for this advisor
On 3/31/06, Arch Stanton <d6veteran@gmail.com>
wrote:>
> Chris Hall wrote:
> > you''re not getting anything. Rails figures out that info
based on the
> > criteria you specify. if you stick to Rails conventions, you
don''t have
> > to
> > do anything but provide the association name, rails does the rest.
> >
> > so in that example
> >
> > student belongs_to :advisor
> >
> > rails will make the following assumptions:
> >
> > students table contains an "advisor_id" column that
references the id
> > column
> > in advisors table
> > the associated class is named "Advisor"
> >
>
>
> I guess I do have a follow up question.
>
> In the above example, what is gained by adding a has_many relationship
> to Advisor?
>
> advisor has_many :students
>
> --
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
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