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This project presents a way for Ruby coders to keep method_missing and respond_to_missing? in sync.


The whole idea of finding a way to automagically keep method_missing and respond_to_missing? in sync, was originally inspired by Avdi Grimm's blog post about the need to sync them. I came up with a quick and dirty hack, and a still-hacky improvement that seems to have been mangled by a blog platform change or some such.

Then at RubyConf 2014, Betsy Haibel gave a talk on metaprogramming, including the need. That inspired me to take another whack at it, this time using the different approach shown in this repo (essentially, a decorator class).

I got some suggestions and other help from Chris Hoffman, mainly in figuring out that I shouldn't do the in-block object access the way I was trying to! :-)


This requires the Ruby version to be at least 1.9. Eventually I might put some work into figuring out why many tests fail with 1.8, but for now, call it a Ruby 1.9+ gem. Check its Travis CI status page to see which versions of Ruby it has been tested against; currently that's 1.9.2, 1.9.3, 2.0.0, 2.1.0, 2.1.1, 2.1.2, JRuby in 1.9 mode, and Rubinius 2.1.1.


Add this line to your application's Gemfile:

gem 'hook_lying_syncer'

And then execute:

$ bundle

Or install it yourself as:

$ gem install hook_lying_syncer


Create a HookLyingSyncer by passing it something to wrap, a lambda to extract the the subparts of interest from a method name (passed to method_missing or respond_to_missing?), and a block to execute when there are matches.

  • The "something to wrap" can be any object, even a class. Note however that if you wrap a class, that will not affect its instances! You can affect future instances by using a wrapper to override .new, but if you need to affect extant instances, you have to wrap them yourself.

  • The lambda must return an Array with some truthy content (or at least something that responds positively to #any?) if the method name is one you're interested in, and either an empty Array (or at least something that responds negatively to #any?) or something falsey (i.e., false or nil) otherwise. If you are not comfortable making lambdas, feel free to copy the lambda_maker method in the tests.

  • The block will be called when the lambda indicates that a method of interest has been called. The block will receive three arguments: the original object the HookLyingSyncer wrapped, the matches returned by the lambda, and the list of arguments (if any) passed in the method call.

See the tests for examples.

Also, please remember, just because you can use this, doesn't mean you should! Ask your doctor if metaprogramming is right for you. Side effects may include difficulty debugging and loss of greppability.


Version Change
0.0.1 Initial release
0.0.2 Better compatibility w/ 1.9; declare 1.8 incompatible in README
0.0.3 Declare 1.8 incompatible in gemspec (duh!)
0.0.4 Fix poorly written dependency versions in gemspec


  1. Fork it ( )
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request


Ruby gem to keep method_missing and respond_to_missing? in sync







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