Ruby on Rails，无法让cancan工作

Question

I have been trying to get cancan to work all day. I have started over several times using different tutorials but I keep getting the same errors.

It's pretty simple, I have User account (created with Devise) which can have one role, either Admin or User. Here is the ability class:

class Ability
  include CanCan::Ability

  def initialize(user)
    user ||= User.new
    if user.role? :admin
      can :manage, :all
    end
  end
end

In the profile controller I have the line load_and_authorize_resource , the class User contains ROLES = %w[admin user] . Going to http://localhost:3000/profiles/ gives me the error

wrong number of arguments (2 for 1) in app/models/ability.rb:6:in initialize'`

Using the alternative method user.admin? gives

undefined method `admin?' for #<User:0x5b34c10>

Googling the error above gives many results so I'm not the only person having this problem, but none of the solutions have worked for me.

And yes I have added the role column to the User table

class AddRoleToUsers < ActiveRecord::Migration
  def change
    add_column :users, :role, :string
  end
end

added the Gem, ran bundle install and restarted the server.

Answer 1

Providing you have the following this should work:

Ability.rb

class Ability
  include CanCan::Ability
  def initialize(user)
    user ||= User.new # guest user
   # raise user.role?(:administrator).inspect
    if user.role? :administrator

      can :manage, :all
      can :manage, User

    elsif user.role? :user
      can :read, :all

    end

  end
end

RoleUser.rb

class RoleUser < ActiveRecord::Base
  # attr_accessible :title, :body
  belongs_to :user
  belongs_to :role

end

Role

class Role < ActiveRecord::Base
  attr_accessible :name

  has_and_belongs_to_many :users
end

User.rb

 class User < ActiveRecord::Base

 has_and_belongs_to_many :roles

  def role?(role)
    self.roles.find_by_name(role.to_s.camelize)
  end

You need this as you are defining your roles, finding them, converting the role to a string and camelizing it.

seeds.rb

%w(Employee Administrator).each { |role| Role.create!(:name => role)}

creates an array User and Administrator .

Should you follow these steps correctly you this should work. And also ensure you have the following migrations:

class UsersHaveAndBelongsToManyRoles < ActiveRecord::Migration
  def self.up
    create_table :roles_users, :id => false do |t|
      t.references :role, :user
    end
  end

  def self.down
    drop_table :roles_users
  end
end

Then in your view you should use the can? by doing something like

<% if can? :manage, User %> 
  .......
    ....
  ...
<% end %>