I have the two following models associated:
class Post < ActiveRecord::Base
belongs_to :language
end
class Language < ActiveRecord::Base
has_many :posts
end
From a view I have a link to filter the posts by language:
<div id="english"><%= link_to "English", {:controller => 'posts', :action => 'search_result', :language => "english"} %></div>
The model language has a variable name:string which is the one i am using to make the active record query.
The doubt i have is how i can make this query from the post controller to retrieve the right posts which has a field: language.name == "english".
I tried this:
#posts = Post.all(:conditions => ["language.name = ?", params[:language]])
and also this:
#posts = Post.where(:language.name => params[:language])
Hope i have explained well the issue, i am a quite newbie yet. Ah! i would also know what would it be better in this case to use: "all" or "where" ??.
Thanks a lot in advance.
You need to do a join: http://guides.rubyonrails.org/active_record_querying.html#specifying-conditions-on-the-joined-tables
If I have understood your models/database structure correctly, the ActiveRecord call should looks something like:
Post.joins(:language).where('languages.name' => params[:language])
Hope that helps.
PS. The where call is the preferred method these days.
Related
I've implemented "following" function. Showing "people user A is following" was simple, but showing "people who are following user A" is giving me troubles.
I have follow_links, which have id, user_id, and follow_you_id column. When user A begins following user B, the columns will be like (user_id = A, follow_you_id = B).
To show users that A(#user) is following, I can simply do
#follow_yous = #user.follow_yous
But I'm not sure how to show users who are following A(#user)
To do this, I first found all the related links.
#follow_links = FollowLink.where(:follow_you_id => #user.id)
Now I thought I could just do #follow_mes = #follow_links.users, but it says user is an undefined method. So I guess I can either call user.follow_yous or follow_you.users.
My next approach was
#follow_links = FollowLink.where(:follow_you_id => #user.id)
#follow_mes = User.where(:id => #user.id, :include => #follow_links)
I intended to find all the User objects that had the provided #follow_links objects, but I think the syntax was wrong. I couldn't find a decent solution after a bit of research. I'd appreciate any help.
Update:
FollowLink model
belongs_to :user
belongs_to :follow_you, :class_name => "User"
You can use joins like this:
#users = User.joins(:follow_links).where(:follow_links => { :follow_you_id => #user.id })
you can use following:
#follow_links = FollowLink.where(:follow_you_id => #user.id)
#follow_links.collect(&:user) # :user should be the name of your relation to user in your followlink model
=> [User1, User2,...]
I am modifying a Documents table from using three columns (article1, article2, and article3) to one (articles) which has a string of comma-separated IDs stored in it (i.e., 23,4,33,2). That's all working well, but I'm trying to adjust the functions that read the three columns to read the one and I'm getting rather stuck.
In the model I have:
scope :all_articles, lambda {|p| where(:page => p) }
In the controller I have this:
#articles = (1..3).to_a.map { |i| Article.all_articles(i).reverse }
And in the view:
<% #articles.each_with_index do |a, i| %>
<%= a[i].name %>
<% end %>
It's just a bit beyond me at this point.
Cheers!
It's usually not good practice to put store the ids in a column like you have done. It is better to break that relationship out into a Has and Belongs to Many relationship. You set it up in your models like this:
class Document < ActiveRecord::Base
#...
has_and_belongs_to_many :articles
#...
end
class Article < ActiveRecord::Base
#...
has_and_belongs_to_many :documents
end
Then you will create a join table that ActiveRecord will use to store the relationships.
create_table :articles_documents, :id => false do |t|
t.integer :article_id
t.integer :document_id
end
add_index :articles_documents, [:article_id, :document_id], unique: true
This will allow you to query a lot more efficiently than you are currently doing. For example, to find all documents that have some article id. You would do:
#documents = Document.joins(:articles).where("articles.id = ?", some_article_id)
Or if you want to query for a document and return the articles with it:
#documents = Document.includes(:articles).where(some_conditions)
I am trying to create a nested attribute form to create a model which is primarily an association "connector" between two other models. In my case, the models represent books, awards, and the "connector" model book_awards. When I am editing a book, I want to be able to quickly select which awards it has won.
I've been using
http://railscasts.com/episodes/196-nested-model-form-part-1
to help me get started, but I'm afraid I'm pretty much stuck.
Another SO question which seems similar is
accepts_nested_attributes_for with find_or_create? Unfortunately, it's also not quite what I'm doing and I haven't been able to adapt it.
My models look like this. Each model has additional attributes and validations etc, but I've removed them for clarity.
class Book < ActiveRecord::Base
has_many :book_awards
accepts_nested_attributes_for :book_awards, :allow_destroy => true
end
class Award < ActiveRecord::Base
has_many :book_awards
end
class BookAward < ActiveRecord::Base
belongs_to :book, :award
end
In my book controller methods for edit and new, and the failure cases for create and update I have a line #awards = Award.all.
In my view, I would like to see a list of all awards with check boxes next to them. When I submit, I would like to either update, create, or destroy a book_award model. If the check box is selected, I would like to update an existing model or create a new one if it doesn't exist. If the check box isn't selected, then I would like to destroy an existing model or do nothing if the award never existed. I have a partial for book_awards. I'm not sure if the check box selector should be in this partial or not.
I think my check box will be my hook to :_destroy but with its polarity reversed. I think something like this will basically do it:
= f.check_box :_destroy, {}, 0, 1
Currently, I have this in my partial but I'm not sure where it really belongs.
Next comes my view which currently doesn't work, but maybe it will help demonstrate what I'm trying to do. I loop through the awards and use a fields_for to set nested attributes for anything that already exists. It's horribly ugly, but I think it somewhat works. However, I don't really know how to get started with the else case.
= f.label :awards
- #awards.each do |a|
- if f.object.awards && f.object.awards.include?(a)
= f.fields_for :book_awards, f.object.book_award.select{|bas| bas.award == a } do |ba|
= render 'book_awards', :f => ba, :a => a
- else
= fields_for :book_awards do |ba|
= render 'book_awards', :f => ba, :a => a
I would prefer the awards to be listed in the same order each time (my #awards assignment in the controller will probably specify the order) as opposed to listing the existing awards first or last.
I hate to answer my own question, but I finally figured out something which works. The first thing I needed to do was to update the "new" case based on the crazy object which was included in the railscast. Next, I needed to manually set the :child_index. Finally, I needed to manually set the :_destroy check box appropriately.
.field
= f.label :awards
- #awards.each_with_index do |a,i|
- if exists = (f.object.awards && f.object.awards.include?(a))
- new_ba = f.object.book_awards.select{|s| s.award == a}
- else
- new_ba = f.object.class.reflect_on_association(:book_awards).klass.new
= f.fields_for :book_awards, new_ba, :child_index => i do |ba|
= render 'book_awards', :f => ba, :a => a, :existing => exists
My partial looks like this:
.field
= f.check_box :_destroy, {:checked => existing}, 0, 1
= f.label a.name
= f.hidden_field :award_id, :value => a.id
= f.label :year
= f.number_field :year
It's not horribly pretty, but it seems to do exactly what I wanted.
Let's say I have the following classes
class SolarSystem < ActiveRecord::Base
has_many :planets
end
class Planet < ActiveRecord::Base
scope :life_supporting, where('distance_from_sun > ?', 5).order('diameter ASC')
end
Planet has a scope life_supporting and SolarSystem has_many :planets. I would like to define my has_many relationship so that when I ask a solar_system for all associated planets, the life_supporting scope is automatically applied. Essentially, I would like solar_system.planets == solar_system.planets.life_supporting.
Requirements
I do not want to change scope :life_supporting in Planet to
default_scope where('distance_from_sun > ?', 5).order('diameter ASC')
I'd also like to prevent duplication by not having to add to SolarSystem
has_many :planets, :conditions => ['distance_from_sun > ?', 5], :order => 'diameter ASC'
Goal
I'd like to have something like
has_many :planets, :with_scope => :life_supporting
Edit: Work Arounds
As #phoet said, it may not be possible to achieve a default scope using ActiveRecord. However, I have found two potential work arounds. Both prevent duplication. The first one, while long, maintains obvious readability and transparency, and the second one is a helper type method who's output is explicit.
class SolarSystem < ActiveRecord::Base
has_many :planets, :conditions => Planet.life_supporting.where_values,
:order => Planet.life_supporting.order_values
end
class Planet < ActiveRecord::Base
scope :life_supporting, where('distance_from_sun > ?', 5).order('diameter ASC')
end
Another solution which is a lot cleaner is to simply add the following method to SolarSystem
def life_supporting_planets
planets.life_supporting
end
and to use solar_system.life_supporting_planets wherever you'd use solar_system.planets.
Neither answers the question so I just put them here as work arounds should anyone else encounter this situation.
In Rails 4, Associations have an optional scope parameter that accepts a lambda that is applied to the Relation (cf. the doc for ActiveRecord::Associations::ClassMethods)
class SolarSystem < ActiveRecord::Base
has_many :planets, -> { life_supporting }
end
class Planet < ActiveRecord::Base
scope :life_supporting, -> { where('distance_from_sun > ?', 5).order('diameter ASC') }
end
In Rails 3, the where_values workaround can sometimes be improved by using where_values_hash that handles better scopes where conditions are defined by multiple where or by a hash (not the case here).
has_many :planets, conditions: Planet.life_supporting.where_values_hash
In Rails 5, the following code works fine...
class Order
scope :paid, -> { where status: %w[paid refunded] }
end
class Store
has_many :paid_orders, -> { paid }, class_name: 'Order'
end
i just had a deep dive into ActiveRecord and it does not look like if this can be achieved with the current implementation of has_many. you can pass a block to :conditions but this is limited to returning a hash of conditions, not any kind of arel stuff.
a really simple and transparent way to achieve what you want (what i think you are trying to do) is to apply the scope at runtime:
# foo.rb
def bars
super.baz
end
this is far from what you are asking for, but it might just work ;)
I am finishing up my first RoR project, and am working on a leaderboard system that shows the number of points users have accrued for correctly answering quiz questions.
I am getting all of the users that have answered at least one question correct, grouping them by user_id, and displaying them in descending order by most correct using this:
#users = Point.find(:all,
:group => 'user_id',
:order => 'correct DESC', :conditions => { :correct => "yes"})
In my view, I am using this to iterate through the results:
<% #users.each_with_index do |user, index| %>
However, I am not able to get the number of correct answers per user. I tried:
user.count
but that doesn't work. How do I get the number of items per group?
You're on the right track. Seems like you would be better off using the all command with the count condition within it as opposed to the count command. Something like this:
Point.all(:select => 'user_id, count(id) as point_count', :group => :user_id, :conditions => { :correct => 'yes' }, :order => 'point_count desc', :limit => 10)
This will return 10 limited Point objects with a user_id attribute (so you can still access the user relationship), and a point_count attribute with the number of correct points said user has obtained.
Note: you could change the limit to be however many users you wanted to display in your leaderboard. This example would return 10.
It might make more sense to have your code look like this:
#points = Point.all(:select => 'user_id, count(id) as point_count', :group => :user_id, :conditions => { :correct => 'yes' }, :order => 'point_count desc', :limit => 10)
And as I said in a comment below, you could iterate through them by doing something like this (this would assume that your User model has a name attribute):
<table>
<% #points.each do |point| %>
<tr>
<td><%= point.user.name %></td>
<td><%= point.point_count %></td>
</tr>
<% end %>
</table>
I think the problem may be that you think you're getting an Array back, but you actually get a Hash back.
Try doing:
p #users
(which is equivalent to puts #users.inspect). You'll probably see it's more so something like:
{ "1" => [UserObject, UserObject], "2" => `[UserObject] }
You can even do p #users.class and you'll see it's not an array.
When you loop with a .each_with_index on a Hash, you need to do:
#users.each_with_index do |(key, value), index|
Then you can do #users[key].count or value.count.
Figured out how to get the correct count:
#users = Point.count(:group => :user_id, :conditions => { :correct => "yes"})
The most simple way should be:
#user.points.where(:correct => "yes").count
Though this will only work if have defined your associations in the user and point model like
class User < ActiveRecord::Base
has_many :points
class Point < ActiveRecord::Base
belongs_to :user
(personally I would have used a bool flag (smallint) instead of string for the "correct" column.