VirtualProxy

• Quickly build virtual proxies.
• Messages sent to these proxies are forwarded to custom lazily-evaluated subjects.
• Based on the GoF proxy pattern.
• Uses Ruby's Delegator library to avoid method_missing gotchas.

Add this line to your application's Gemfile:

gem 'virtual_proxy'

And then execute:

$ bundle

Or install it yourself as:

$ gem install virtual_proxy

# Create a proxy to some subject
proxy = VirtualProxy.to { ExpensiveObject.new } # => VirtualProxy::Proxy
proxy.expensive_object_method

# Get the subject directly
proxy.__getobj__ # => ExpensiveObject instance

# Dynamically set a new subject
proxy.__setobj__ { OtherExpensiveObject.new }
proxy.other_expensive_object_method

# Extend any class with proxy construction capabilities
class ExpensiveObject
  extend VirtualProxy

  attr_reader :name
  def initialize(name:)
    @name = name
  end
end

proxy = ExpensiveObject.build_lazy(name: 'fubar')
proxy.foo # => 'fubar'

# Use it for any expensive code
proxy = VirtualProxy.to { perform_intensive_task }
proxy.generate_report

# Avoid method_missing gotchas
proxy = VirtualProxy.to { [1, 2, 3] }
proxy == [1, 2, 3] # => true
proxy.methods # => [..., :push, :append, :pop, :shift, ...]
proxy.respond_to?(:sort) # => true
# NOTE: introspective methods such as :respond_to? require the subject to be evaluated

Note that the Ruby Delegator class uses method_missing under the hood.

This benchmark suggests that the Delegator approach taken in this gem, when compared against a simpler but more limited approach, incurs a %1.28 performance penalty:

                   user     system      total        real
virtual_proxy  6.834716   0.000324   6.835040 (  6.849857)
simple_proxy   6.754349   0.000008   6.754357 (  6.763423)

To run this benchmark,

chmod +x ./bin/benchmark
./bin/benchmark

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/johnc219/virtual_proxy.

The gem is available as open source under the terms of the MIT License.