处理大量的能力

一旦能力定义的数量开始增加，处理 Ability 文件就变得越来越困难。

处理这些问题的第一个策略是将能力转换为有意义的方法，如下例所示：

class Ability
  include CanCan::Ability

  def initialize(user)
    anyone_abilities 

    if user
      if user.admin?
        admin_abilities
      else
        authenticated_abilities
      end
    else
      guest_abilities
    end
  end

  private
  
  def anyone_abilities
    # define abilities for everyone, both logged users and visitors
  end

  def guest_abilities
    # define abilities for visitors only
  end

  def authenticated_abilities
    # define abilities for logged users only
  end

  def admin_abilities
    # define abilities for admins only
  end
end

一旦这个类变得足够大，你可以尝试将它分成不同的类来处理不同的职责，如下所示：

# app/models/ability.rb
class Ability
  include CanCan::Ability

  def initialize(user)
    self.merge Abilities::Everyone.new(user)

    if user
      if user.admin?
        self.merge Abilities::Admin.new(user)
      else
        self.merge Abilities::Authenticated.new(user)
      end
    else
      self.merge Abilities::Guest.new(user)
    end
  end
end

然后将这些类定义为：

# app/models/abilities/guest.rb
module Abilities
  class Guest
    include CanCan::Ability

    def initialize(user)
      # Abilities for anonymous visitors only
    end
  end
end

与 Abilities::Authenticated，Abilities::Admin 或其他任何其他人一样。