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module ActionController #:nodoc:
module Filters #:nodoc:
def self.included(base)
base.extend(ClassMethods)
base.send(: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).
#
# == Filter inheritance
#
# Controller inheritance hierarchies share filters downwards, but subclasses can also add or skip 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 are 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| 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 have 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).
#
# Please note that around_filters function a little differently than the normal before and after filters with regard to filter
# types. Please see the section dedicated to around_filters below.
#
# == 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 < ActionController::Base
# before_filter :verify_open_shop
#
# class CheckoutController < ShoppingController
# 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
#
# Around filters wrap an action, executing code both before and after.
# They may be declared as method references, blocks, or objects responding
# to #filter or to both #before and #after.
#
# To use a method as an around_filter, pass a symbol naming the Ruby method.
# Yield (or block.call) within the method to run the action.
#
# around_filter :catch_exceptions
#
# private
# def catch_exceptions
# yield
# rescue => exception
# logger.debug "Caught exception! #{exception}"
# raise
# end
#
# To use a block as an around_filter, pass a block taking as args both
# the controller and the action block. You can't call yield directly from
# an around_filter block; explicitly call the action block instead:
#
# around_filter do |controller, action|
# logger.debug "before #{controller.action_name}"
# action.call
# logger.debug "after #{controller.action_name}"
# end
#
# To use a filter object with around_filter, pass an object responding
# to :filter or both :before and :after. With a filter method, yield to
# the block as above:
#
# around_filter BenchmarkingFilter
#
# class BenchmarkingFilter
# def self.filter(controller, &block)
# Benchmark.measure(&block)
# end
# end
#
# With before and after methods:
#
# around_filter Authorizer.new
#
# class Authorizer
# # This will run before the action. Returning false aborts the action.
# def before(controller)
# if user.authorized?
# return true
# else
# redirect_to login_url
# return false
# end
# end
#
# # This will run after the action if and only if before returned true.
# def after(controller)
# end
# end
#
# If the filter has before and after methods, the before method will be
# called before the action. If before returns false, the filter chain is
# halted and after will not be run. See Filter Chain Halting below for
# an example.
#
# == Filter chain skipping
#
# Declaring a filter on a base class conveniently applies to its subclasses,
# but sometimes a subclass should skip some of its superclass' filters:
#
# class ApplicationController < ActionController::Base
# before_filter :authenticate
# around_filter :catch_exceptions
# end
#
# class WeblogController < ApplicationController
# # Will run the :authenticate and :catch_exceptions filters.
# end
#
# class SignupController < ApplicationController
# # Skip :authenticate, run :catch_exceptions.
# skip_before_filter :authenticate
# end
#
# class ProjectsController < ApplicationController
# # Skip :catch_exceptions, run :authenticate.
# skip_filter :catch_exceptions
# end
#
# class ClientsController < ApplicationController
# # Skip :catch_exceptions and :authenticate unless action is index.
# skip_filter :catch_exceptions, :authenticate, :except => :index
# end
#
# == Filter conditions
#
# Filters may be limited to specific actions by declaring the actions to
# include or exclude. Both options accept single actions (:only => :index)
# or arrays of actions (:except => [:foo, :bar]).
#
# class Journal < ActionController::Base
# # Require authentication for edit and delete.
# before_filter :authorize, :only => [:edit, :delete]
#
# # Passing options to a filter with a block.
# around_filter(:except => :index) do |controller, action_block|
# results = Profiler.run(&action_block)
# controller.response.sub! "</body>", "#{results}</body>"
# end
#
# private
# def authorize
# # Redirect to login unless authenticated.
# end
# end
#
# == Filter Chain Halting
#
# <tt>before_filter</tt> and <tt>around_filter</tt> may halt the request
# before a controller action is run. This is useful, for example, to deny
# access to unauthenticated users or to redirect from http to https.
# Simply return false from the filter or call render or redirect.
# After filters will not be executed if the filter chain is halted.
#
# Around filters halt the request unless the action block is called.
# Given these filters
# after_filter :after
# around_filter :around
# before_filter :before
#
# The filter chain will look like:
#
# ...
# . \
# . #around (code before yield)
# . . \
# . . #before (actual filter code is run)
# . . . \
# . . . execute controller action
# . . . /
# . . ...
# . . /
# . #around (code after yield)
# . /
# #after (actual filter code is run, unless the around filter does not yield)
#
# If #around returns before yielding, #after will still not be run. The #before
# filter and controller action will not be run. If #before returns false,
# the second half of #around and will still run but #after and the
# action will not. If #around fails to yield, #after will not be run.
module ClassMethods
# The passed <tt>filters</tt> will be appended to the filter_chain and
# will execute before the action on this controller is performed.
def append_before_filter(*filters, &block)
append_filter_to_chain(filters, :before, &block)
end
# The passed <tt>filters</tt> will be prepended to the filter_chain and
# will execute before the action on this controller is performed.
def prepend_before_filter(*filters, &block)
prepend_filter_to_chain(filters, :before, &block)
end
# Shorthand for append_before_filter since it's the most common.
alias :before_filter :append_before_filter
# The passed <tt>filters</tt> will be appended to the array of filters
# that run _after_ actions on this controller are performed.
def append_after_filter(*filters, &block)
append_filter_to_chain(filters, :after, &block)
end
# The passed <tt>filters</tt> will be prepended to the array of filters
# that run _after_ actions on this controller are performed.
def prepend_after_filter(*filters, &block)
prepend_filter_to_chain(filters, :after, &block)
end
# Shorthand for append_after_filter since it's the most common.
alias :after_filter :append_after_filter
# If you append_around_filter A.new, B.new, the filter chain looks like
#
# B#before
# A#before
# # run the action
# A#after
# B#after
#
# With around filters which yield to the action block, #before and #after
# are the code before and after the yield.
def append_around_filter(*filters, &block)
filters, conditions = extract_conditions(filters, &block)
filters.map { |f| proxy_before_and_after_filter(f) }.each do |filter|
append_filter_to_chain([filter, conditions])
end
end
# If you prepend_around_filter A.new, B.new, the filter chain looks like:
#
# A#before
# B#before
# # run the action
# B#after
# A#after
#
# With around filters which yield to the action block, #before and #after
# are the code before and after the yield.
def prepend_around_filter(*filters, &block)
filters, conditions = extract_conditions(filters, &block)
filters.map { |f| proxy_before_and_after_filter(f) }.each do |filter|
prepend_filter_to_chain([filter, conditions])
end
end
# Shorthand for append_around_filter since it's the most common.
alias :around_filter :append_around_filter
# Removes the specified filters from the +before+ filter chain. Note that this only works for skipping method-reference
# filters, not procs. This is especially useful for managing the chain in inheritance hierarchies where only one out
# of many sub-controllers need a different hierarchy.
#
# You can control the actions to skip the filter for with the <tt>:only</tt> and <tt>:except</tt> options,
# just like when you apply the filters.
def skip_before_filter(*filters)
skip_filter_in_chain(*filters, &:before?)
end
# Removes the specified filters from the +after+ filter chain. Note that this only works for skipping method-reference
# filters, not procs. This is especially useful for managing the chain in inheritance hierarchies where only one out
# of many sub-controllers need a different hierarchy.
#
# You can control the actions to skip the filter for with the <tt>:only</tt> and <tt>:except</tt> options,
# just like when you apply the filters.
def skip_after_filter(*filters)
skip_filter_in_chain(*filters, &:after?)
end
# Removes the specified filters from the filter chain. This only works for method reference (symbol)
# filters, not procs. This method is different from skip_after_filter and skip_before_filter in that
# it will match any before, after or yielding around filter.
#
# You can control the actions to skip the filter for with the <tt>:only</tt> and <tt>:except</tt> options,
# just like when you apply the filters.
def skip_filter(*filters)
skip_filter_in_chain(*filters)
end
# Returns an array of Filter objects for this controller.
def filter_chain
read_inheritable_attribute("filter_chain") || []
end
# Returns all the before filters for this class and all its ancestors.
# This method returns the actual filter that was assigned in the controller to maintain existing functionality.
def before_filters #:nodoc:
filter_chain.select(&:before?).map(&:filter)
end
# Returns all the after filters for this class and all its ancestors.
# This method returns the actual filter that was assigned in the controller to maintain existing functionality.
def after_filters #:nodoc:
filter_chain.select(&:after?).map(&:filter)
end
# Returns a mapping between filters and the actions that may run them.
def included_actions #:nodoc:
@included_actions ||= read_inheritable_attribute("included_actions") || {}
end
# Returns a mapping between filters and actions that may not run them.
def excluded_actions #:nodoc:
@excluded_actions ||= read_inheritable_attribute("excluded_actions") || {}
end
# Find a filter in the filter_chain where the filter method matches the _filter_ param
# and (optionally) the passed block evaluates to true (mostly used for testing before?
# and after? on the filter). Useful for symbol filters.
#
# The object of type Filter is passed to the block when yielded, not the filter itself.
def find_filter(filter, &block) #:nodoc:
filter_chain.select { |f| f.filter == filter && (!block_given? || yield(f)) }.first
end
# Returns true if the filter is excluded from the given action
def filter_excluded_from_action?(filter,action) #:nodoc:
case
when ia = included_actions[filter]
!ia.include?(action)
when ea = excluded_actions[filter]
ea.include?(action)
end
end
# Filter class is an abstract base class for all filters. Handles all of the included/excluded actions but
# contains no logic for calling the actual filters.
class Filter #:nodoc:
attr_reader :filter, :included_actions, :excluded_actions
def initialize(filter)
@filter = filter
end
def type
:around
end
def before?
type == :before
end
def after?
type == :after
end
def around?
type == :around
end
def run(controller)
raise ActionControllerError, 'No filter type: Nothing to do here.'
end
def call(controller, &block)
run(controller)
end
end
# Abstract base class for filter proxies. FilterProxy objects are meant to mimic the behaviour of the old
# before_filter and after_filter by moving the logic into the filter itself.
class FilterProxy < Filter #:nodoc:
def filter
@filter.filter
end
end
class BeforeFilterProxy < FilterProxy #:nodoc:
def type
:before
end
def run(controller)
# only filters returning false are halted.
if false == @filter.call(controller)
controller.send :halt_filter_chain, @filter, :returned_false
end
end
def call(controller)
yield unless run(controller)
end
end
class AfterFilterProxy < FilterProxy #:nodoc:
def type
:after
end
def run(controller)
@filter.call(controller)
end
def call(controller)
yield
run(controller)
end
end
class SymbolFilter < Filter #:nodoc:
def call(controller, &block)
controller.send(@filter, &block)
end
end
class ProcFilter < Filter #:nodoc:
def call(controller)
@filter.call(controller)
rescue LocalJumpError # a yield from a proc... no no bad dog.
raise(ActionControllerError, 'Cannot yield from a Proc type filter. The Proc must take two arguments and execute #call on the second argument.')
end
end
class ProcWithCallFilter < Filter #:nodoc:
def call(controller, &block)
@filter.call(controller, block)
rescue LocalJumpError # a yield from a proc... no no bad dog.
raise(ActionControllerError, 'Cannot yield from a Proc type filter. The Proc must take two arguments and execute #call on the second argument.')
end
end
class MethodFilter < Filter #:nodoc:
def call(controller, &block)
@filter.call(controller, &block)
end
end
class ClassFilter < Filter #:nodoc:
def call(controller, &block)
@filter.filter(controller, &block)
end
end
class ClassBeforeFilter < Filter #:nodoc:
def call(controller, &block)
@filter.before(controller)
end
end
class ClassAfterFilter < Filter #:nodoc:
def call(controller, &block)
@filter.after(controller)
end
end
protected
def append_filter_to_chain(filters, filter_type = :around, &block)
pos = find_filter_append_position(filters, filter_type)
update_filter_chain(filters, filter_type, pos, &block)
end
def prepend_filter_to_chain(filters, filter_type = :around, &block)
pos = find_filter_prepend_position(filters, filter_type)
update_filter_chain(filters, filter_type, pos, &block)
end
def update_filter_chain(filters, filter_type, pos, &block)
new_filters = create_filters(filters, filter_type, &block)
new_chain = filter_chain.insert(pos, new_filters).flatten
write_inheritable_attribute('filter_chain', new_chain)
end
def find_filter_append_position(filters, filter_type)
# appending an after filter puts it at the end of the call chain
# before and around filters go before the first after filter in the chain
unless filter_type == :after
filter_chain.each_with_index do |f,i|
return i if f.after?
end
end
return -1
end
def find_filter_prepend_position(filters, filter_type)
# prepending a before or around filter puts it at the front of the call chain
# after filters go before the first after filter in the chain
if filter_type == :after
filter_chain.each_with_index do |f,i|
return i if f.after?
end
return -1
end
return 0
end
def create_filters(filters, filter_type, &block) #:nodoc:
filters, conditions = extract_conditions(filters, &block)
filters.map! { |filter| find_or_create_filter(filter, filter_type) }
update_conditions(filters, conditions)
filters
end
def find_or_create_filter(filter, filter_type)
if found_filter = find_filter(filter) { |f| f.type == filter_type }
found_filter
else
f = class_for_filter(filter, filter_type).new(filter)
# apply proxy to filter if necessary
case filter_type
when :before
BeforeFilterProxy.new(f)
when :after
AfterFilterProxy.new(f)
else
f
end
end
end
# The determination of the filter type was once done at run time.
# This method is here to extract as much logic from the filter run time as possible
def class_for_filter(filter, filter_type) #:nodoc:
case
when filter.is_a?(Symbol)
SymbolFilter
when filter.respond_to?(:call)
if filter.is_a?(Method)
MethodFilter
elsif filter.arity == 1
ProcFilter
else
ProcWithCallFilter
end
when filter.respond_to?(:filter)
ClassFilter
when filter.respond_to?(:before) && filter_type == :before
ClassBeforeFilter
when filter.respond_to?(:after) && filter_type == :after
ClassAfterFilter
else
raise(ActionControllerError, 'A filter must be a Symbol, Proc, Method, or object responding to filter, after or before.')
end
end
def extract_conditions(*filters, &block) #:nodoc:
filters.flatten!
conditions = filters.last.is_a?(Hash) ? filters.pop : {}
filters << block if block_given?
return filters, conditions
end
def update_conditions(filters, conditions)
return if conditions.empty?
if conditions[:only]
write_inheritable_hash('included_actions', condition_hash(filters, conditions[:only]))
elsif conditions[:except]
write_inheritable_hash('excluded_actions', condition_hash(filters, conditions[:except]))
end
end
def condition_hash(filters, *actions)
actions = actions.flatten.map(&:to_s)
filters.inject({}) { |h,f| h.update( f => (actions.blank? ? nil : actions)) }
end
def skip_filter_in_chain(*filters, &test) #:nodoc:
filters, conditions = extract_conditions(filters)
filters.map! { |f| block_given? ? find_filter(f, &test) : find_filter(f) }
filters.compact!
if conditions.empty?
delete_filters_in_chain(filters)
else
remove_actions_from_included_actions!(filters,conditions[:only] || [])
conditions[:only], conditions[:except] = conditions[:except], conditions[:only]
update_conditions(filters,conditions)
end
end
def remove_actions_from_included_actions!(filters,*actions)
actions = actions.flatten.map(&:to_s)
updated_hash = filters.inject(read_inheritable_attribute('included_actions')||{}) do |hash,filter|
ia = (hash[filter] || []) - actions
ia.empty? ? hash.delete(filter) : hash[filter] = ia
hash
end
write_inheritable_attribute('included_actions', updated_hash)
end
def delete_filters_in_chain(filters) #:nodoc:
write_inheritable_attribute('filter_chain', filter_chain.reject { |f| filters.include?(f) })
end
def filter_responds_to_before_and_after(filter) #:nodoc:
filter.respond_to?(:before) && filter.respond_to?(:after)
end
def proxy_before_and_after_filter(filter) #:nodoc:
return filter unless filter_responds_to_before_and_after(filter)
Proc.new do |controller, action|
if filter.before(controller) == false
controller.send :halt_filter_chain, filter, :returned_false
else
begin
action.call
ensure
filter.after(controller)
end
end
end
end
end
module InstanceMethods # :nodoc:
def self.included(base)
base.class_eval do
alias_method_chain :perform_action, :filters
alias_method_chain :process, :filters
end
end
protected
def process_with_filters(request, response, method = :perform_action, *arguments) #:nodoc:
@before_filter_chain_aborted = false
process_without_filters(request, response, method, *arguments)
end
def perform_action_with_filters
call_filters(self.class.filter_chain, 0, 0)
end
private
def call_filters(chain, index, nesting)
index = run_before_filters(chain, index, nesting)
aborted = @before_filter_chain_aborted
perform_action_without_filters unless performed? || aborted
return index if nesting != 0 || aborted
run_after_filters(chain, index)
end
def skip_excluded_filters(chain, index)
while (filter = chain[index]) && self.class.filter_excluded_from_action?(filter, action_name)
index = index.next
end
[filter, index]
end
def run_before_filters(chain, index, nesting)
while chain[index]
filter, index = skip_excluded_filters(chain, index)
break unless filter # end of call chain reached
case filter.type
when :before
filter.run(self) # invoke before filter
index = index.next
break if @before_filter_chain_aborted
when :around
yielded = false
filter.call(self) do
yielded = true
# all remaining before and around filters will be run in this call
index = call_filters(chain, index.next, nesting.next)
end
halt_filter_chain(filter, :did_not_yield) unless yielded
break
else
break # no before or around filters left
end
end
index
end
def run_after_filters(chain, index)
seen_after_filter = false
while chain[index]
filter, index = skip_excluded_filters(chain, index)
break unless filter # end of call chain reached
case filter.type
when :after
seen_after_filter = true
filter.run(self) # invoke after filter
else
# implementation error or someone has mucked with the filter chain
raise ActionControllerError, "filter #{filter.inspect} was in the wrong place!" if seen_after_filter
end
index = index.next
end
index.next
end
def halt_filter_chain(filter, reason)
@before_filter_chain_aborted = true
logger.info "Filter chain halted as [#{filter.inspect}] #{reason}." if logger
false
end
end
end
end
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