This module encapsulates the functionality for building interceptor chains.

Methods
Classes and Modules
Class Needle::InterceptorChainBuilder::InterceptedServiceProxy
Class Needle::InterceptorChainBuilder::InterceptorChainElement
Class Needle::InterceptorChainBuilder::ProxyObjectChainElement
Constants
InvocationContext = Struct.new( :sym, :args, :block, :data )
  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 Instance methods
build( point, service, interceptors )

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
103:     def build( point, service, interceptors )
104:       return service if interceptors.nil? || interceptors.empty?
105: 
106:       ordered_list =
107:         interceptors.sort { |a,b|
108:           a.options[:priority] <=> b.options[:priority] }
109: 
110:       chain = ProxyObjectChainElement.new( service )
111: 
112:       ordered_list.reverse.each do |interceptor|
113:         factory = interceptor.action.call( point.container )
114:         instance = factory.new( point, interceptor.options )
115:         element = InterceptorChainElement.new( instance )
116:         element.next = chain
117:         chain = element
118:       end
119: 
120:       # FIXME: should inherited methods of "Object" be interceptable?
121:       methods_to_intercept = ( service.class.instance_methods( true ) -
122:                                Object.instance_methods +
123:                                service.class.instance_methods( false ) ).uniq
124: 
125:       service = InterceptedServiceProxy.new( chain )
126:       singleton = class << service; self; end
127: 
128:       methods_to_intercept.each do |method|
129:         next if method =~ /^__/
130: 
131:         if singleton.instance_methods(false).include? method
132:           singleton.send( :remove_method, method )
133:         end
134: 
135:         singleton.class_eval "def \#{method}( *args, &block )\ncontext = InvocationContext.new( :\#{method}, args, block, Hash.new )\n@chain.process_next( context )\nend\n"
136:       end
137: 
138:       # allow the interceptor to intercept methods not explicitly
139:       # declared on the reciever.
140:       if singleton.instance_methods(false).include? "method_missing"
141:         singleton.send( :remove_method, :method_missing )
142:       end
143: 
144:       singleton.class_eval "def method_missing( sym, *args, &block )\ncontext = InvocationContext.new( sym, args, block, Hash.new )\n@chain.process_next( context )\nend\n"
145: 
146:       return service
147:     end