module Needle::InterceptorChainBuilder
This module encapsulates the functionality for building interceptor chains.
Constants
- InvocationContext
The context of a method invocation. This is used in an interceptor chain to encapsulate the elements of the current invocation. sym: the name of the method being invoked args: the argument list being passed to the method block: the reference to the block attached to the method invocation data: a hash that may be used by clients for storing arbitrary data in
the context.
Public Class Methods
This will apply the given interceptors to the given service by first ordering the interceptors based on their relative priorities, and then dynamically modifying the service's methods so that the chain of interceptors sits in front of each of them.
The modified service is returned.
# File lib/needle/interceptor-chain.rb, line 103 def build( point, service, interceptors ) return service if interceptors.nil? || interceptors.empty? ordered_list = interceptors.sort { |a,b| a.options[:priority] <=> b.options[:priority] } chain = ProxyObjectChainElement.new( service ) ordered_list.reverse.each do |interceptor| factory = interceptor.action.call( point.container ) instance = factory.new( point, interceptor.options ) element = InterceptorChainElement.new( instance ) element.next = chain chain = element end # FIXME: should inherited methods of "Object" be interceptable? methods_to_intercept = ( service.class.instance_methods( true ) - Object.instance_methods + service.class.instance_methods( false ) ).uniq service = InterceptedServiceProxy.new( chain ) singleton = class << service; self; end methods_to_intercept.each do |method| next if method =~ /^__/ if singleton.instance_methods(false).include? method singleton.send( :remove_method, method ) end singleton.class_eval <<-EOF def #{method}( *args, &block ) context = InvocationContext.new( :#{method}, args, block, Hash.new ) @chain.process_next( context ) end EOF end # allow the interceptor to intercept methods not explicitly # declared on the reciever. if singleton.instance_methods(false).include? "method_missing" singleton.send( :remove_method, :method_missing ) end singleton.class_eval <<-EOF def method_missing( sym, *args, &block ) context = InvocationContext.new( sym, args, block, Hash.new ) @chain.process_next( context ) end EOF return service end
Private Instance Methods
This will apply the given interceptors to the given service by first ordering the interceptors based on their relative priorities, and then dynamically modifying the service's methods so that the chain of interceptors sits in front of each of them.
The modified service is returned.
# File lib/needle/interceptor-chain.rb, line 103 def build( point, service, interceptors ) return service if interceptors.nil? || interceptors.empty? ordered_list = interceptors.sort { |a,b| a.options[:priority] <=> b.options[:priority] } chain = ProxyObjectChainElement.new( service ) ordered_list.reverse.each do |interceptor| factory = interceptor.action.call( point.container ) instance = factory.new( point, interceptor.options ) element = InterceptorChainElement.new( instance ) element.next = chain chain = element end # FIXME: should inherited methods of "Object" be interceptable? methods_to_intercept = ( service.class.instance_methods( true ) - Object.instance_methods + service.class.instance_methods( false ) ).uniq service = InterceptedServiceProxy.new( chain ) singleton = class << service; self; end methods_to_intercept.each do |method| next if method =~ /^__/ if singleton.instance_methods(false).include? method singleton.send( :remove_method, method ) end singleton.class_eval <<-EOF def #{method}( *args, &block ) context = InvocationContext.new( :#{method}, args, block, Hash.new ) @chain.process_next( context ) end EOF end # allow the interceptor to intercept methods not explicitly # declared on the reciever. if singleton.instance_methods(false).include? "method_missing" singleton.send( :remove_method, :method_missing ) end singleton.class_eval <<-EOF def method_missing( sym, *args, &block ) context = InvocationContext.new( sym, args, block, Hash.new ) @chain.process_next( context ) end EOF return service end