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module CanCan
# This module is designed to be included into an Ability class. This will
# provide the "can" methods for defining and checking abilities.
#
# class Ability
# include CanCan::Ability
#
# def initialize(user)
# if user.admin?
# can :manage, :all
# else
# can :read, :all
# end
# end
# end
#
module Ability
attr_accessor :user
# Use to check the user's permission for a given action and object.
#
# can? :destroy, @project
#
# You can also pass the class instead of an instance (if you don't have one handy).
#
# can? :create, Project
#
# Any additional arguments will be passed into the "can" block definition. This
# can be used to pass more information about the user's request for example.
#
# can? :create, Project, request.remote_ip
#
# can :create Project do |project, remote_ip|
# # ...
# end
#
# Not only can you use the can? method in the controller and view (see ControllerAdditions),
# but you can also call it directly on an ability instance.
#
# ability.can? :destroy, @project
#
# This makes testing a user's abilities very easy.
#
# def test "user can only destroy projects which he owns"
# user = User.new
# ability = Ability.new(user)
# assert ability.can?(:destroy, Project.new(:user => user))
# assert ability.cannot?(:destroy, Project.new)
# end
#
def can?(action, noun, *extra_args)
(@can_definitions || []).reverse.each do |base_behavior, defined_action, defined_noun, defined_block|
defined_actions = expand_actions(defined_action)
defined_nouns = [defined_noun].flatten
if includes_action?(defined_actions, action) && includes_noun?(defined_nouns, noun)
result = can_perform_action?(action, noun, defined_actions, defined_nouns, defined_block, extra_args)
return base_behavior ? result : !result
end
end
false
end
# Convenience method which works the same as "can?" but returns the opposite value.
#
# cannot? :destroy, @project
#
def cannot?(*args)
!can?(*args)
end
# Defines which abilities are allowed using two arguments. The first one is the action
# you're setting the permission for, the second one is the class of object you're setting it on.
#
# can :update, Article
#
# You can pass an array for either of these parameters to match any one.
#
# can [:update, :destroy], [Article, Comment]
#
# In this case the user has the ability to update or destroy both articles and comments.
#
# You can pass a block to provide logic based on the article's attributes.
#
# can :update, Article do |article|
# article && article.user == user
# end
#
# If the block returns true then the user has that :update ability for that article, otherwise he
# will be denied access. It's possible for the passed in model to be nil if one isn't specified,
# so be sure to take that into consideration.
#
# You can pass :all to reference every type of object. In this case the object type will be passed
# into the block as well (just in case object is nil).
#
# can :read, :all do |object_class, object|
# object_class != Order
# end
#
# Here the user has permission to read all objects except orders.
#
# You can also pass :manage as the action which will match any action. In this case the action is
# passed to the block.
#
# can :manage, Comment do |action, comment|
# action != :destroy
# end
#
# You can pass custom objects into this "can" method, this is usually done through a symbol
# and is useful if a class isn't available to define permissions on.
#
# can :read, :stats
# can? :read, :stats # => true
#
def can(action, noun, &block)
@can_definitions ||= []
@can_definitions << [true, action, noun, block]
end
# Define an ability which cannot be done. Accepts the same arguments as "can".
#
# can :read, :all
# cannot :read, Comment
#
# A block can be passed just like "can", however if the logic is complex it is recommended
# to use the "can" method.
#
# cannot :read, Product do |product|
# product.invisible?
# end
#
def cannot(action, noun, &block)
@can_definitions ||= []
@can_definitions << [false, action, noun, block]
end
# Alias one or more actions into another one.
#
# alias_action :update, :destroy, :to => :modify
# can :modify, Comment
#
# Then :modify permission will apply to both :update and :destroy requests.
#
# can? :update, Comment # => true
# can? :destroy, Comment # => true
#
# This only works in one direction. Passing the aliased action into the "can?" call
# will not work because aliases are meant to generate more generic actions.
#
# alias_action :update, :destroy, :to => :modify
# can :update, Comment
# can? :modify, Comment # => false
#
# Unless that exact alias is used.
#
# can :modify, Comment
# can? :modify, Comment # => true
#
# The following aliases are added by default for conveniently mapping common controller actions.
#
# alias_action :index, :show, :to => :read
# alias_action :new, :to => :create
# alias_action :edit, :to => :update
#
# This way one can use params[:action] in the controller to determine the permission.
def alias_action(*args)
target = args.pop[:to]
aliased_actions[target] ||= []
aliased_actions[target] += args
end
# Returns a hash of aliased actions. The key is the target and the value is an array of actions aliasing the key.
def aliased_actions
@aliased_actions ||= default_alias_actions
end
# Removes previously aliased actions including the defaults.
def clear_aliased_actions
@aliased_actions = {}
end
private
def default_alias_actions
{
:read => [:index, :show],
:create => [:new],
:update => [:edit],
}
end
def expand_actions(actions)
[actions].flatten.map do |action|
if aliased_actions[action]
[action, *aliased_actions[action]]
else
action
end
end.flatten
end
def can_perform_action?(action, noun, defined_actions, defined_nouns, defined_block, extra_args)
if defined_block.nil?
true
else
block_args = []
block_args << action if defined_actions.include?(:manage)
block_args << (noun.class == Class ? noun : noun.class) if defined_nouns.include?(:all)
block_args << (noun.class == Class ? nil : noun)
block_args += extra_args
return defined_block.call(*block_args)
end
end
def includes_action?(actions, action)
actions.include?(:manage) || actions.include?(action)
end
def includes_noun?(nouns, noun)
nouns.include?(:all) || nouns.include?(noun) || nouns.any? { |c| c.kind_of?(Class) && noun.kind_of?(c) }
end
end
end
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