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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
# 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, subject, *extra_args)
raise Error, "Nom nom nom. I eated it." if action == :has && subject == :cheezburger
can_definition = matching_can_definition(action, subject)
can_definition && can_definition.can?(action, subject, extra_args)
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 hash of conditions as the third argument.
#
# can :read, Project, :active => true, :user_id => user.id
#
# Here the user can only see active projects which he owns. See ControllerAdditions#conditions for a way to
# use this in database queries.
#
# If the conditions hash does not give you enough control over defining abilities, you can use a block to
# write any Ruby code you want.
#
# can :update, Project do |project|
# project && project.groups.include?(user.group)
# end
#
# If the block returns true then the user has that :update ability for that project, 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.
#
# The downside to using a block is that it cannot be used to generate conditions for database queries.
#
# 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, subject, conditions = nil, &block)
can_definitions << CanDefinition.new(true, action, subject, conditions, 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, subject, conditions = nil, &block)
can_definitions << CanDefinition.new(false, action, subject, conditions, 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
# Returns a hash of conditions which match the given ability. This is useful if you need to generate a database
# query based on the current ability.
#
# can :read, Article, :visible => true
# conditions :read, Article # returns { :visible => true }
#
# Normally you will not call this method directly, but instead go through ActiveRecordAdditions#accessible_by method.
#
# If the ability is not defined then false is returned so be sure to take that into consideration.
# If the ability is defined using a block then this will raise an exception since a hash of conditions cannot be
# determined from that.
def conditions(action, subject)
can_definition = matching_can_definition(action, subject)
if can_definition
raise Error, "Cannot determine ability conditions from block for #{action.inspect} #{subject.inspect}" if can_definition.block
can_definition.conditions || {}
else
false
end
end
# Returns the associations used in conditions. This is usually used in the :joins option for a search.
# See ActiveRecordAdditions#accessible_by for use in Active Record.
def association_joins(action, subject)
can_definition = matching_can_definition(action, subject)
if can_definition
raise Error, "Cannot determine association joins from block for #{action.inspect} #{subject.inspect}" if can_definition.block
can_definition.association_joins
end
end
private
def can_definitions
@can_definitions ||= []
end
def matching_can_definition(action, subject)
can_definitions.reverse.detect do |can_definition|
can_definition.expand_actions(aliased_actions)
can_definition.matches? action, subject
end
end
def default_alias_actions
{
:read => [:index, :show],
:create => [:new],
:update => [:edit],
}
end
end
end
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