## Ruby

### Installation

Now, you are ready to install the latest [ruby](https://www.ruby-lang.org/en/) version and set it as the default version.

Run this command, it will **take a while (5-10 minutes)**

```bash
rbenv install <RUBY_SETUP_VERSION>
```

Once the ruby installation is done, run this command to tell the system
to use the <RUBY_SETUP_VERSION> version by default.

```bash
rbenv global <RUBY_SETUP_VERSION>
```

**Reset** your terminal and check your Ruby version:

```bash
exec zsh
```

Then run:

```bash
ruby -v
```

:heavy_check_mark: If you see something starting with `ruby <RUBY_SETUP_VERSION>` then you can proceed :+1:

:x: If not, **ask a teacher**

### Installing some gems

<details>
  <summary>If you are in <bold>China</bold> 🇨🇳 click here</summary>

  :warning: If you are in China, you should update the way we'll install gem with the following commands.

```bash
# China only!
gem sources --remove https://rubygems.org/
gem sources -a https://gems.ruby-china.com/
gem sources -l
# *** CURRENT SOURCES ***
# https://gems.ruby-china.com/
# Ruby-china.com must be in the list now
```
</details>

**Everyone, in China or not**, continue here to install gems.

In the ruby world, we call external libraries `gems`: they are pieces of ruby code that you can download and execute on your computer. Let's install some!

First, we'll update `bundler`, which is what lets us install gems:

```bash
gem update bundler
```

In your terminal, copy-paste the following command:

```bash
gem install <GEMS>
```

:heavy_check_mark: If you get `xx gems installed`, then all good :+1:

:x: If you encounter the following error:

```bash
ERROR: While executing gem ... (TypeError)
incompatible marshal file format (can't be read)
format version 4.8 required; 60.33 given
```

Run the following command:
```bash
rm -rf ~/.gemrc
```

Rerun the command to install the gems.

:warning: **NEVER** install a gem with `sudo gem install`! Even if you stumble upon a Stackoverflow answer (or the terminal) telling you to do so.