lib/cancan/ability.rb
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
# Check if the user has permission to perform a given action on an object.
#
# can? :destroy, @project
#
# You can also pass the class instead of an instance (if you don't have one handy).
#
# can? :create, Project
#
# Nested resources can be passed through a hash, this way conditions which are
# dependent upon the association will work when using a class.
#
# can? :create, @category => 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
#
# Also see the RSpec Matchers to aid in testing.
def can?(action, subject, *extra_args)
match = relevant_rules_for_match(action, subject).detect do |rule|
rule.matches_conditions?(action, subject, extra_args)
end
match ? match.base_behavior : 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.
# Here the user has the ability to update or destroy both articles and comments.
#
# can [:update, :destroy], [Article, Comment]
#
# You can pass :all to match any object and :manage to match any action. Here are some examples.
#
# can :manage, :all
# can :update, :all
# can :manage, Project
#
# You can pass a hash of conditions as the third argument. Here the user can only see active projects which he owns.
#
# can :read, Project, :active => true, :user_id => user.id
#
# See ActiveRecordAdditions#accessible_by for how to use this in database queries. These conditions
# are also used for initial attributes when building a record in ControllerAdditions#load_resource.
#
# If the conditions hash does not give you enough control over defining abilities, you can use a block
# along with any Ruby code you want.
#
# can :update, Project do |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. The downside to using a block is that it cannot be used to generate
# conditions for database queries.
#
# You can pass custom objects into this "can" method, this is usually done with a symbol
# and is useful if a class isn't available to define permissions on.
#
# can :read, :stats
# can? :read, :stats # => true
#
# IMPORTANT: Neither a hash of conditions or a block will be used when checking permission on a class.
#
# can :update, Project, :priority => 3
# can? :update, Project # => true
#
# If you pass no arguments to +can+, the action, class, and object will be passed to the block and the
# block will always be executed. This allows you to override the full behavior if the permissions are
# defined in an external source such as the database.
#
# can do |action, object_class, object|
# # check the database and return true/false
# end
#
def can(action = nil, subject = nil, conditions = nil, &block)
rules << Rule.new(true, action, subject, conditions, block)
end
# Defines 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 = nil, subject = nil, conditions = nil, &block)
rules << Rule.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]
validate_target(target)
aliased_actions[target] ||= []
aliased_actions[target] += args
end
# User shouldn't specify targets with names of real actions or it will cause Seg fault
def validate_target(target)
raise Error, "You can't specify target (#{target}) as alias because it is real action name" if aliased_actions.values.flatten.include? target
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
def model_adapter(model_class, action)
adapter_class = ModelAdapters::AbstractAdapter.adapter_class(model_class)
adapter_class.new(model_class, relevant_rules_for_query(action, model_class))
end
# See ControllerAdditions#authorize! for documentation.
def authorize!(action, subject, *args)
message = nil
if args.last.kind_of?(Hash) && args.last.has_key?(:message)
message = args.pop[:message]
end
if cannot?(action, subject, *args)
message ||= unauthorized_message(action, subject)
raise AccessDenied.new(message, action, subject)
end
subject
end
def unauthorized_message(action, subject)
keys = unauthorized_message_keys(action, subject)
variables = {:action => action.to_s}
variables[:subject] = (subject.class == Class ? subject : subject.class).to_s.underscore.humanize.downcase
message = I18n.translate(nil, variables.merge(:scope => :unauthorized, :default => keys + [""]))
message.blank? ? nil : message
end
def attributes_for(action, subject)
attributes = {}
relevant_rules(action, subject).map do |rule|
attributes.merge!(rule.attributes_from_conditions) if rule.base_behavior
end
attributes
end
def has_block?(action, subject)
relevant_rules(action, subject).any?(&:only_block?)
end
def has_raw_sql?(action, subject)
relevant_rules(action, subject).any?(&:only_raw_sql?)
end
def merge(ability)
ability.send(:rules).each do |rule|
rules << rule.dup
end
self
end
private
def unauthorized_message_keys(action, subject)
subject = (subject.class == Class ? subject : subject.class).name.underscore unless subject.kind_of? Symbol
[subject, :all].map do |try_subject|
[aliases_for_action(action), :manage].flatten.map do |try_action|
:"#{try_action}.#{try_subject}"
end
end.flatten
end
# Accepts an array of actions and returns an array of actions which match.
# This should be called before "matches?" and other checking methods since they
# rely on the actions to be expanded.
def expand_actions(actions)
actions.map do |action|
aliased_actions[action] ? [action, *expand_actions(aliased_actions[action])] : action
end.flatten
end
# Given an action, it will try to find all of the actions which are aliased to it.
# This does the opposite kind of lookup as expand_actions.
def aliases_for_action(action)
results = [action]
aliased_actions.each do |aliased_action, actions|
results += aliases_for_action(aliased_action) if actions.include? action
end
results
end
def rules
@rules ||= []
end
# Returns an array of Rule instances which match the action and subject
# This does not take into consideration any hash conditions or block statements
def relevant_rules(action, subject)
rules.reverse.select do |rule|
rule.expanded_actions = expand_actions(rule.actions)
rule.relevant? action, subject
end
end
def relevant_rules_for_match(action, subject)
relevant_rules(action, subject).each do |rule|
if rule.only_raw_sql?
raise Error, "The can? and cannot? call cannot be used with a raw sql 'can' definition. The checking code cannot be determined for #{action.inspect} #{subject.inspect}"
end
end
end
def relevant_rules_for_query(action, subject)
relevant_rules(action, subject).each do |rule|
if rule.only_block?
raise Error, "The accessible_by call cannot be used with a block 'can' definition. The SQL cannot be determined for #{action.inspect} #{subject.inspect}"
end
end
end
def default_alias_actions
{
:read => [:index, :show],
:create => [:new],
:update => [:edit],
}
end
end
end