User has several skills - ruby-on-rails

Question

I want my users to have many skills. I do have a users and skills database table.
I used has_many_and_belongs_to association in user.rb
has_many :skills
which I am not sure if its correct. And in skill.rb
has_and_belongs_to_many :users
I also created a migration like that:
def change
create_table :user_skills do |t|
t.belongs_to :users
t.belongs_to :skills
end
Is this correct?
So IF this is correct, how do I add new skills to my user? What is the general approach?
What I thought of,
In my users controller on update action I will be updating user's skill and update the user_skills table.
How is this done?
Also How do I iterate through my user_skills table for a specific user? (in view)
Any guidance, resource, tip will be great help for me as its the first time i do something like this in Rails.
Thanks

Answer 1

In Rails, most would prefer to use has_many :through over habtm associations. Here's a guide on how to use it: ActiveRecord guide.
A has_many through association for users and skills would look like this in your relevant models:
class User < ActiveRecord::Base
has_many :user_skills
has_many :skills, through: :user_skills
end
class UserSkill < ActiveRecord::Base
belongs_to :user
belongs_to :skill
end
class Skill < ActiveRecord::Base
has_many :user_skills
has_many :users, through: :user_skills
end
Your migration would look like:
def change
create_table :user_skills do |t|
t.references :user, index: true
t.references :skill, index: true
end
end
The indexes in the migration are for faster look-ups for using the reference_id. It's advisable to do that for all references.
To add new skills to your user, you can refer to this SO answer.
To update a user's skill, you could do this:
#skill = #user.skills.find(params[:skill_id])
#skill.update(skill_params)
To create a user's skill, you could do this:
#user.skills.create(skill_params)
To add a skill to user, you could do this in your update action:
#user.update(user_params)
#app/views/users/edit.html.erb
<%= f.select :skill_ids, Skill.all.collect {|x| [x.name, x.id]}, {}, :multiple => true %>
When working with has_many through, you won't need to go through the user_skills table to get a specific user. You would, however, might need to get a specific user from a skill. To do this:
#skill.users.find(user_id)
Hope that helps!

Answer 2

If you set user to have_and_belong_to_many :skills also then this will work.
To create a new skill for a user do
user.skills.create!{...}
or to associate an existing skill with a user do
user << skill
"In my users controller on update action I will be updating user's skill and update the user_skills table. How is this done?"
user = User.find params[:id]
skills = user.skills
You can then do what you like to users skills
"Also How do I iterate through my user_skills table for a specific user? (in view)"
user.skills.each do |skill|
...
end
for more on HABTM association see http://guides.rubyonrails.org/association_basics.html#has-and-belongs-to-many-association-reference

Answer 3

Forgive me If I get it wrong, try to fill in the gaps but I think you want something that looks like this.
controller
def index
#to fetch all skills associated to users (add where u.id=? to fetch for a single user)
#users = User.select("u.name, s.name").
from("users u, skills s, users_skills us").
where("u.id = us.user_id").
where("s.id = us.skill_id")
end
def new
#user = User.new
#skills = Skill.all
end
def create
#user = User.new(params[:user])
...............................
end
in the create form
<%= form_for #user do |f| %>
<%= f.collection_select(:skill_ids, #skills,:id,:name)%>
<%= f.submit "Save" %>
<% end %>

Answer 4

In order to use HABTM you need a join table named either users_skills or skills_users (not sure it matters). It should contain two integer columns named user_id and skill_id. You should create indices for them as well. In your User model you want has_and_belongs_to_many :skills and in your Skill model you want has_and_belongs_to_many :users.

Answer 5

You need has_and_belongs_to_many on both sides of the realtionship.
class User
has_and_belongs_to_many :skills
class Skill
has_and_belongs_to_many :users
Alternatively (and better, in my opinion) would be to use has_many :through:
class User
has_many :user_skills
has_many :skills, through: :user_skills
class Skill
has_many :user_skills
has_many :users, through: :user_skills