Unable to submit add action form - Rails 4 - ruby-on-rails

Question

So my problem is more or less as follows. I have a rails applications with the following classes:
Users
Skills
Each user can have multiple skills and they are added from the users profile screen which is the show action for the users controller. Currently I have the Skills set up and able to be created but I cannot add a pre-built skill onto a users profile. When I try to submit I get the following error Empty list of attributes to change
The following is my add skill to user action:
def add_skill_to_user
user = User.find(params[:id])
user.skills.create(skill_params) #skill name, level...
#skills_options = Skill.all.map{|s| [ s.name, s.id] }
#whatever happens when this is is done, redirect, json answer etc...
if user.skills.update_all(skill_params)
flash[:success] = "Skill Added"
else
render 'add_skill_to_user'
end
end
private
# Set skills params whitelist
def skill_params
params.permit(:name, :user_id)
end
and the following to routes
post 'users/:id/add_skill_to_user' => 'users#add_skill_to_user'
And this is my form
<%= form_tag({controller: "users", action: "add_skill_to_user"}, method: "put") do %>
<%= collection_select(:skill, :name, Skill.all, :id, :name) %>
<%= submit_tag 'Submit' %>
<%end%>
Let me know any additional information you need.
---------Added Models Code------------------
User.rb
class User < ActiveRecord::Base
attr_accessor :remember_token, :activation_token, :reset_token
before_save :downcase_email
before_create :create_activation_digest
belongs_to :group
has_many :ranks
has_many :skills
has_many :mission_notes
has_and_belongs_to_many :training_events
accepts_nested_attributes_for :skills
validates :username, presence: true
validates :email, presence: true
VALID_EMAIL_REGEX = /\A[\w+\-.]+#[a-z\d\-.]+\.[a-z]+\z/i
validates :email, presence: true, length: { maximum: 255 },
format: { with: VALID_EMAIL_REGEX },
uniqueness: { case_sensitive: false }
validates :group_id, presence: true
has_secure_password
validates :password, length: { minimum: 6 }, allow_blank: true
# Returns the hash digest of the given string.
def User.digest(string)
cost = ActiveModel::SecurePassword.min_cost ? BCrypt::Engine::MIN_COST :
BCrypt::Engine.cost
BCrypt::Password.create(string, cost: cost)
end
# Returns a random token.
def User.new_token
SecureRandom.urlsafe_base64
end
# Remembers a user in the database for use in persistent sessions.
def remember
self.remember_token = User.new_token
update_attribute(:remember_digest, User.digest(remember_token))
end
# Returns true if the given token matches the digest.
def authenticated?(remember_token)
return false if remember_digest.nil?
BCrypt::Password.new(remember_digest).is_password?(remember_token)
end
# Forgets a user.
def forget
update_attribute(:remember_digest, nil)
end
# Converts email to all lower-case.
def downcase_email
self.email = email.downcase
end
# Creates and assigns the activation token and digest.
def create_activation_digest
self.activation_token = User.new_token
self.activation_digest = User.digest(activation_token)
end
# Returns true if the given token matches the digest.
def authenticated?(attribute, token)
digest = send("#{attribute}_digest")
return false if digest.nil?
BCrypt::Password.new(digest).is_password?(token)
end
# Activates an account.
def activate
update_attribute(:activated, true)
update_attribute(:activated_at, Time.zone.now)
end
# Sends activation email.
def send_activation_email
UserMailer.account_activation(self).deliver
end
# Sets the password reset attributes.
def create_reset_digest
self.reset_token = User.new_token
update_attribute(:reset_digest, User.digest(reset_token))
update_attribute(:reset_sent_at, Time.zone.now)
end
# Sends password reset email.
def send_password_reset_email
UserMailer.password_reset(self).deliver
end
def password_reset_expired?
reset_sent_at < 2.hours.ago
end
end
Skill.rb
class Skill < ActiveRecord::Base
belongs_to :user
end

Answer 1

Your collection_select will generate something like
<select name="skill[name]">
<option value="1">First Skill</option>
...
</select>
where "skill[name]" doesn't reflect what's in the option values (skill ids).
Furthermore, your params whitelist doesn't handle the fact that the POST data generated by the select is an array.
I'd suggest
<%= collection_select(:skill, :id, Skill.all, :id, :name) %>
with this whitelist filter in the controller:
params.require(:skill).permit(:id)
But your add_skill_to_user method is confusing. If all you want to do is assign pre-existing skills to a user, there is a RailsCast for that.