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Ruby for iOS Developers - Managing Ruby Versions

Like it or not Ruby plays a big part in most iOS and Mac developers life. Tools we depend upon like CocoaPods, Fastlane, and XCPretty are written in this language. With Swift going open source and getting more mature we can expect this situation to change, but is not going to be any time soon.

While being incredibly versatile, easy to pick up, and optimized for developers' happiness, Ruby has some pitfalls when it comes to managing versions and gems, Ruby's name for libraries.

How many time did you sudo gem install? Have you ever bumped into a gem that wasn't behaving properly due to your Ruby setup? Or a pod install being corrupted because your teammates were on a different version of CocoaPods? All these problems are due to system Ruby.

Working with system Ruby is a problem for two reasons: you need root access to install gems, and if you decide, or need, to upgrade Ruby all the other tools will need to be upgraded as well, and might break. This article by Thoughtbot, one of the leading Ruby agencies with a great list of open source libraries, explains the problem in more details.

Spending 5 minutes setting up your Ruby will save you hours of issues down the track.

In this and the next post we'll take a look at how to install and manage Ruby versions on your Mac, and how to make sure every team member is using the same gem versions.

Not all Rubies are made equal

Mac OS X Ruby set up requires you to use sudo for every gem install. This is something that gets in your way. On top of that Macs ship with Ruby version 2.0.0, but the latest version of the programming language is 2.3.0. I don't know about you, but this bothers me like me this bothers you.

To take back control of our Rubies we need a way to download new versions, and optionally switch between them.

The developer community might not have reached an agreement on the best Rubies version manager yet, but on thing is for sure, system Ruby isn't it.

Probably the most streamlined and less invasive way to manage your Rubies is using chruby and ruby-install.

These two tools follow the Unix philosophy of doing only one thing and being composable. ruby-install allows you to download and install Ruby versions, and chruby to switch between them.

Let's see how to set them up... At the end of this process you'll have a development environment in which you can safely install gems without sudo or permission issues, and where multiple versions of Ruby can live together in harmony.

ruby-install setup

Both ruby-install and chruby can be easily installed via Homebrew.

brew install ruby-install

You can now easily install versions of Ruby system wise like this:

ruby-install --system ruby 2.3.0

You can leave the --system option out if want to install it only for your local user.

Pro-tip: ruby-install --system --latest ruby will install the latest version.

Installing Rubies is only half of our job, now we need to reliably set the proper version and swap between them. This is chruby's job.

chruby setup

brew install chruby

Once brew has installed chruby, open your .bashrc or .zshrc and paste these two lines at the bottom. If you don't know what those files are you should read this first.

source /usr/local/opt/chruby/share/chruby/chruby.sh
source /usr/local/opt/chruby/share/chruby/auto.sh

The first line will make sure that chruby is loaded in your shell. The second makes chruby automatically switch Ruby version based on the content of the .ruby-version file in the current directory. Automatically switching is an optional feature that you might not need as an iOS developer, but I still think it can be useful.

Since you just edited the configuration of your shell you will need to open a new terminal window to load them. Alternatively you can source ~/.bashrc.

Congratulations, you can now set and change your Ruby version using:

chruby 2.3.0

That's it.


This post showed you how to gain control on your Ruby so that you can reliably choose which version to use, and install gems without worry. In the next post we'll look at how to manage the Ruby tools our projects depend upon, so that we can rest assured that every team member and CI box will be using the same version. Signup to the newsletter to be the first to now when its published.

I hope you found this article useful. Feel free to get in touch on Twitter @mokagio if you have questions, suggestions, or need help with your Rubies, or leave a comment below.

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