80 lines
2.3 KiB
Markdown
80 lines
2.3 KiB
Markdown
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---
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title: Managing Ruby versions
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---
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## Ruby has changed over time
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Ruby was been in constant development since the 1990s, and like many languages,
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there have been syntax changes across versions, so it is important to be clear
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about which Ruby version your code expects.
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Probably the most visible change came with Ruby 1.9; previously, we wrote
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hashes like this:
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```ruby
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{ :one => 1, :two => 2, :three => 3 }
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```
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This use of the 'hashrocket' operator (`=>`) was so common, that Ruby 1.9
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provided a shorthand:
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```
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{ one: 1, two: 2, three: 3 }
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```
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This older code run on any version, but the newer syntax will only run on Ruby 1.9+.
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## How does this cause problems?
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For example, you might have decided to use a Gem which internally relies on
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Ruby 1.9 features; this means that your project now also relies on Ruby 1.9
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features.
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If you don't specify which version of Ruby your project needs, it can be very
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confusing when code works on one machine, but not another.
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As with most languages, it's considered good practice to specify the version of
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Ruby that your code expects. This makes it much easier to manage multiple
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projects on your development machine, each expecting a different version of
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Ruby.
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## How do I specify my Ruby version?
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There are a couple of tools which are popular for this, but both have agreed to
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share a common file. Many Ruby (or Rails) projects will include a simple
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`.ruby-version` file, which simply specifies a version number, _eg_:
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```
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2.4.2
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```
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Popular tools to help you manage your Ruby version are:
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* [Ruby Version Manager (RVM)](https://rvm.io)
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* [rbenv](https://github.com/rbenv/rbenv)
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Let's look at RVM.
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### Using RVM
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RVM is typically installed ([link](https://rvm.io)) on a Linux, Unix or MacOS
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machine, and is very convenient as it hooks into the `cd` (`c`hange `d`irectory)
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command so when you move to a new project, your `.ruby-version` is read
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automatically, and you're automatically switched to the correct version of Ruby
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before you start working.
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For example, you might have this sequence:
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```shell
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% cd ~/projects/older-project
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% ruby --version
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ruby 2.3.5p376 (2017-09-14 revision 59905) [x86_64-darwin16]
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% cd ~/projects/newer-project
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% ruby --version
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ruby 2.4.2p198 (2017-09-14 revision 59899) [x86_64-darwin16]
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```
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(These examples are from a MacOS machine)
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