module ActionController #:nodoc:
module Filters #:nodoc:
def self.append_features(base)
super
base.extend(ClassMethods)
base.class_eval { include ActionController::Filters::InstanceMethods }
end
# Filters enable controllers to run shared pre and post processing code for its actions. These filters can be used to do
# authentication, caching, or auditing before the intended action is performed. Or to do localization or output
# compression after the action has been performed.
#
# Filters have access to the request, response, and all the instance variables set by other filters in the chain
# or by the action (in the case of after filters). Additionally, it's possible for a pre-processing <tt>before_filter</tt>
# to halt the processing before the intended action is processed by returning false. This is especially useful for
# filters like authentication where you're not interested in allowing the action to be performed if the proper
# credentials are not in order.
#
# == Filter inheritance
#
# Controller inheritance hierarchies share filters downwards, but subclasses can also add new filters without
# affecting the superclass. For example:
#
# class BankController < ActionController::Base
# before_filter :audit
#
# private
# def audit
# # record the action and parameters in an audit log
# end
# end
#
# class VaultController < BankController
# before_filter :verify_credentials
#
# private
# def verify_credentials
# # make sure the user is allowed into the vault
# end
# end
#
# Now any actions performed on the BankController will have the audit method called before. On the VaultController,
# first the audit method is called, then the verify_credentials method. If the audit method returns false, then
# verify_credentials and the intended action is never called.
#
# == Filter types
#
# A filter can take one of three forms: method reference (symbol), external class, or inline method (proc). The first
# is the most common and works by referencing a protected or private method somewhere in the inheritance hierarchy of
# the controller by use of a symbol. In the bank example above, both BankController and VaultController use this form.
#
# Using an external class makes for more easily reused generic filters, such as output compression. External filter classes
# are implemented by having a static +filter+ method on any class and then passing this class to the filter method. Example:
#
# class OutputCompressionFilter
# def self.filter(controller)
# controller.response.body = compress(controller.response.body)
# end
# end
#
# class NewspaperController < ActionController::Base
# after_filter OutputCompressionFilter
# end
#
# The filter method is passed the controller instance and is hence granted access to all aspects of the controller and can
# manipulate them as it sees fit.
#
# The inline method (using a proc) can be used to quickly do something small that doesn't require a lot of explanation.
# Or just as a quick test. It works like this:
#
# class WeblogController < ActionController::Base
# before_filter { |controller| return false if controller.params["stop_action"] }
# end
#
# As you can see, the block expects to be passed the controller after it has assigned the request to the internal variables.
# This means that the block has access to both the request and response objects complete with convenience methods for params,
# session, template, and assigns. Note: The inline method doesn't strictly has to be a block. Any object that responds to call
# and returns 1 or -1 on arity will do (such as a Proc or an Method object).
#
# == Filter chain ordering
#
# Using <tt>before_filter</tt> and <tt>after_filter</tt> appends the specified filters to the existing chain. That's usually
# just fine, but some times you care more about the order in which the filters are executed. When that's the case, you
# can use <tt>prepend_before_filter</tt> and <tt>prepend_after_filter</tt>. Filters added by these methods will be put at the
# beginning of their respective chain and executed before the rest. For example:
#
# class ShoppingController
# before_filter :verify_open_shop
#
# class CheckoutController
# prepend_before_filter :ensure_items_in_cart, :ensure_items_in_stock
#
# The filter chain for the CheckoutController is now <tt>:ensure_items_in_cart, :ensure_items_in_stock,</tt>
# <tt>:verify_open_shop</tt>. So if either of the ensure filters return false, we'll never get around to see if the shop
# is open or not.
#
# You may pass multiple filter arguments of each type as well as a filter block.
# If a block is given, it is treated as the last argument.
#
# == Around filters
#
# In addition to the individual before and after filters, it's also possible to specify that a single object should handle
# both the before and after call. That's especially usefuly when you need to keep state active between the before and after,
# such as the example of a benchmark filter below:
#
# class WeblogController < ActionController::Base
# around_filter BenchmarkingFilter.new
#
# # Before this action is performed, BenchmarkingFilter#before(controller) is executed
# def index
# end
# # After this action has been performed, BenchmarkingFilter#after(controller) is executed
# end
#
# class BenchmarkingFilter
# def initialize
# @runtime
# end
#
# def before
# start_timer
# end
#
# def after
# stop_timer
# report_result
# end
# end
module ClassMethods
# The passed <tt>filters</tt> will be appended to the array of filters that's run _before_ actions
# on this controller are performed.
def append_before_filter(*filters, &block)
filters << block if block_given?
append_filter_to_chain("before", filters)
end
# The passed <tt>filters</tt> will be prepended to the array of filters that's run _before_ actions
# on this controller are performed.
def prepend_before_filter(*filters, &block)
filters << block if block_given?
prepend_filter_to_chain("before", filters)
end
# Short-hand for append_before_filter since that's the most common of the two.
alias :before_filter :append_before_filter
# The passed <tt>filters</tt> will be appended to the array of filters that's run _after_ actions
# on this controller are performed.
def append_after_filter(*filters, &block)
filters << block if block_given?
append_filter_to_chain("after", filters)
end
# The passed <tt>filters</tt> will be prepended to the array of filters that's run _after_ actions
# on this controller are performed.
def prepend_after_filter(*filters, &block)
filters << block if block_given?
prepend_filter_to_chain("after", filters)
end
# Short-hand for append_after_filter since that's the most common of the two.
alias :after_filter :append_after_filter
# The passed <tt>filters</tt> will have their +before+ method appended to the array of filters that's run both before actions
# on this controller are performed and have their +after+ method prepended to the after actions. The filter objects must all
# respond to both +before+ and +after+. So if you do append_around_filter A.new, B.new, the callstack will look like:
#
# B#before
# A#before
# A#after
# B#after
def append_around_filter(filters)
for filter in [filters].flatten
ensure_filter_responds_to_before_and_after(filter)
append_before_filter { |c| filter.before(c) }
prepend_after_filter { |c| filter.after(c) }
end
end
# The passed <tt>filters</tt> will have their +before+ method prepended to the array of filters that's run both before actions
# on this controller are performed and have their +after+ method appended to the after actions. The filter objects must all
# respond to both +before+ and +after+. So if you do prepend_around_filter A.new, B.new, the callstack will look like:
#
# A#before
# B#before
# B#after
# A#after
def prepend_around_filter(filters)
for filter in [filters].flatten
ensure_filter_responds_to_before_and_after(filter)
prepend_before_filter { |c| filter.before(c) }
append_after_filter { |c| filter.after(c) }
end
end
# Short-hand for append_around_filter since that's the most common of the two.
alias :around_filter :append_around_filter
# Returns all the before filters for this class and all its ancestors.
def before_filters #:nodoc:
read_inheritable_attribute("before_filters")
end
# Returns all the after filters for this class and all its ancestors.
def after_filters #:nodoc:
read_inheritable_attribute("after_filters")
end
private
def append_filter_to_chain(condition, filters)
write_inheritable_array("#{condition}_filters", filters)
end
def prepend_filter_to_chain(condition, filters)
write_inheritable_attribute("#{condition}_filters", filters + read_inheritable_attribute("#{condition}_filters"))
end
def ensure_filter_responds_to_before_and_after(filter)
unless filter.respond_to?(:before) && filter.respond_to?(:after)
raise ActionControllerError, "Filter object must respond to both before and after"
end
end
end
module InstanceMethods # :nodoc:
def self.append_features(base)
super
base.class_eval {
alias_method :perform_action_without_filters, :perform_action
alias_method :perform_action, :perform_action_with_filters
}
end
def perform_action_with_filters
return if before_action == false
perform_action_without_filters
after_action
end
# Calls all the defined before-filter filters, which are added by using "before_filter :method".
# If any of the filters return false, no more filters will be executed and the action is aborted.
def before_action #:doc:
call_filters(self.class.before_filters)
end
# Calls all the defined after-filter filters, which are added by using "after_filter :method".
# If any of the filters return false, no more filters will be executed.
def after_action #:doc:
call_filters(self.class.after_filters)
end
private
def call_filters(filters)
filters.each do |filter|
if Symbol === filter
if self.send(filter) == false then return false end
elsif filter_block?(filter)
if filter.call(self) == false then return false end
elsif filter_class?(filter)
if filter.filter(self) == false then return false end
else
raise(
ActionControllerError,
"Filters need to be either a symbol, proc/method, or class implementing a static filter method"
)
end
end
end
def filter_block?(filter)
filter.respond_to?("call") && (filter.arity == 1 || filter.arity == -1)
end
def filter_class?(filter)
filter.respond_to?("filter")
end
end
end
end
