Proxy を Ruby で

# The Subject interface declares common operations for both RealSubject and the # Proxy. As long as the client works with RealSubject using this interface, # you'll be able to pass it a proxy instead of a real subject. class Subject # @abstract def request raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'" end end # The RealSubject contains some core business logic. Usually, RealSubjects are # capable of doing some useful work which may also be very slow or sensitive - # e.g. correcting input data. A Proxy can solve these issues without any changes # to the RealSubject's code. class RealSubject < Subject def request puts 'RealSubject: Handling request.' end end # The Proxy has an interface identical to the RealSubject. class Proxy < Subject # @param [RealSubject] real_subject def initialize(real_subject) @real_subject = real_subject end # The most common applications of the Proxy pattern are lazy loading, caching, # controlling the access, logging, etc. A Proxy can perform one of these # things and then, depending on the result, pass the execution to the same # method in a linked RealSubject object. def request return unless check_access @real_subject.request log_access end # @return [Boolean] def check_access puts 'Proxy: Checking access prior to firing a real request.' true end def log_access print 'Proxy: Logging the time of request.' end end # The client code is supposed to work with all objects (both subjects and # proxies) via the Subject interface in order to support both real subjects and # proxies. In real life, however, clients mostly work with their real subjects # directly. In this case, to implement the pattern more easily, you can extend # your proxy from the real subject's class. def client_code(subject) # ... subject.request # ... end puts 'Client: Executing the client code with a real subject:' real_subject = RealSubject.new client_code(real_subject) puts "\n" puts 'Client: Executing the same client code with a proxy:' proxy = Proxy.new(real_subject) client_code(proxy) 

Client: Executing the client code with a real subject: RealSubject: Handling request. Client: Executing the same client code with a proxy: Proxy: Checking access prior to firing a real request. RealSubject: Handling request. Proxy: Logging the time of request.