how to use array variables inside action in controller

Question

I want to fetch all posts posted by those users who have gone to same college as the current users...So inside my welcome controller i have written following code..

class WelcomesController < ApplicationController

def index

  @col = Education.select(:college_id).where(:user_id => @current_user)
  @user = Education.select(:user_id).where(:college_id => @col)
  @welcome = Welcome.where(:user_id => @user)

end

end

Following is my shema code for welcome and education model:

create_table "welcomes", :force => true do |t|
    t.text     "message"
    t.integer  "user_id"
end

create_table "educations", :force => true do |t|
    t.integer  "college_id"
    t.integer  "user_id"
end

@col = Education.select(:college_id).where(:user_id => @current_user)....this line returns college ids associated with current logged in user.This is working perfectly on my console which is returning following output..

[#<Education college_id: 1>, #<Education college_id: 2>]

but i dont know how to use this output in my next line,so i have written this statement which should return all the users whose college id is the output of prevous statement

@user = Education.select(:user_id).where(:college_id => @col)

and my last line should return all the posts posted by those users whose ids are inside the @user array:

 @welcome = Welcome.where(:user_id => @user)

but this is not working.When i run my project i cant see any output on my page and on console i am getting following output : SELECT welcomes.* FROM welcomes WHERE (welcomes.user_id IN (NULL)) which means its not getting any user ids.. How can i solve this ...

**Using bold text makes things harder to read and one does not know what is important anymore so avoid using bold text for long sentences and instead use it to emphasize content that really needs to be emphasized.** — Zabba, Apr 09 '12 at 06:33

score 0 · Accepted Answer · answered Apr 09 '12 at 06:37

You can try this:

@col = Education.select(:college_id).where(:user_id => @current_user.id).all
@users = Education.select(:user_id).where(:college_id => @col.collect(&:college_id)).all
@welcome = Welcome.where(:user_id => @users.collect(&:user_id)).all

score 0 · Answer 2 · answered Apr 09 '12 at 06:56

The best way I see to accomplish this is to set up a has_many_and_belongs_to_many relationship between your User and Education models. (Each Education will have many Users and each User may have multiple Eductions.) You will need to create a joining table in your database to support this type of relationship - see the Rails Guide for more information on this.

I would set up your models in this manner:

class User < ActiveRecord::Base
  has_one :welcome
  has_and_belongs_to_many :educations
end

class Education < ActiveRecord::Base
  has_and_belongs_to_many :users
end

class Welcome < ActiveRecord::Base
  belongs_to :user
end

The join table for the has_many_and_belongs_to_many join table migration (be sure to double check this code, not sure I got this exactly right):

def self.up
  create_table 'education_user', :id => false do |t|
    t.column :education_id, :integer
    t.column :user_id, :integer
  end
end

Your controller code is now much simpler and looks like this:

@welcomes = @current_user.eductions.users.welcome.all

In your view:

<% @welcomes.each do |welcome| %>
  <p><%= welcome.message %></p>
<% end %>

One of the more powerful features of Ruby on Rails is the model relationships. They are a little more work up front, but if you take the time to set them up correctly they can make your life much easier, as is evidenced by the simplified @welcomes query above.

score 0 · Answer 3 · answered Apr 09 '12 at 07:14

I'd recommend you to make relation between User and Collage

class User < ActiveRecord::Base
  has_many :educations
  has_many :colleges, :through => :educations
  has_many :posts

  scope :by_college_id, lambda {|cid| where("exists (select educations.id from educations where educations.user_id = users.id AND educations.college_id in (?) limit 1)", Array.wrap(cid)) }

  def college_mates
    self.class.by_college_id(self.college_ids).where("users.id != ?", id)
  end :through => :educations
end

class Education < ActiveRecord::Base
  belongs_to :user
  belongs_to :college
end

So now in your controller you can write

class WelcomesController < ApplicationController
  def index
    @posts = @current_user.college_mates.includes(:posts).map(&:posts).flatten
    # or
    @posts = Post.where(user_id: @current_user.college_mates.map(&:id))
  end
end

Second variant generates 3 sql-requests, first variant - only two. But this is same work with data, I think time will be also same. Usually controllers contain only few lines of code, all logic written in models. Ideally controller should contain only Post.by_college_mates_for(@curren_user.id)

how to use array variables inside action in controller

3 Answers3