Question

class Ability
  include CanCan::Ability
  def initialize(user)
    @user = user || User.new

    can :manage, :all
    can :custom_action, User, role: 'admin'
  end
end

and in view

if can? :custom_action, @user
  SHOW SOMETHING

this if always show “SHOW SOMETHING”, don’t understood why it’s happend.

Answer 1

Well, that’s because in your ability class, you give every user all rights.

You are probably looking for something like this:

def initialize(user)
  @user = user || User.new

  can :manage, :all

  # When user is an admin, grant her extra privileges
  if @user.is_admin?
    can :custom_action
  end
end

This way, you define the abilities (by using can) conditionally