3 Steps To Solving RubyMotion Build Woes

December 20, 2016

Seems every few months, there is another weird build error that someone is attempting to track down when running rake to build their project in RubyMotion. The context of these errors is generally unique to the project they are running in, and often surface while compiling an included gem (ie, not in your code), and so it is difficult to Google your way to an answer on Stack Overflow ;-)

Recently Andy Stechishin discovered a pattern in his weird build problems, in which he uncovered a version mismatch with an updated version of rake.

One quick way of discovering if this is your problem, is to run:

rake --version

and

cat Gemfile.lock | grep rake

to compare your default rake with your project rake. If you have different rake versions, that could very well be the source of your build problem.

It’s all very well to discover what caused the problem, but what you really want is to know how to FIX the damn build error, so you can get back to work. The answer in this case is simple:

bundle exec rake

A more complete answer, however, involves a few steps which will make your build woes a thing of the past.

  1. Use bundler
    I know the RubyMotion Getting Started documentation doesn’t mention using bundler, but any Ruby/RubyMotion development is done using gems. And using gems without using bundler is just asking for a world of hurt.

  2. Use a Ruby version manager
    Although your Mac comes with a system version of Ruby installed, I still strongly recommend you install and use a Ruby version manager like RVM or rbenv or chruby. I personally prefer RVM. Its documentation is superior, and does not make assumptions about your wizard-like (or lack thereof) shell scripting skills. Also, with RVM you can seamlessly use gemsets, which is absolutely required, as soon as you have more than one Ruby project on the go.

  3. Include both your Ruby and Rake versions in your Gemfile
    This ensures that when you have a rake or a ruby version mismatch, bundler is going to complain about it. If you put this in your Gemfile for instance:

      ruby '2.3.3'


    then if you are using a different (system) Ruby, bundler will complain like: 

      Your Ruby version is 2.0.0, but your Gemfile specified 2.3.3

With these simple steps, you should be on your way to taking control of your RubyMotion build, and your inexplicable build failures should be a thing of the past. That’s not to say you won’t ever have more gem build failures, but they should at least be directly related to the code involved.