Using Gems in Your Code

To use a gem, you simply require the gem in your code, which is similar to how you would include a module. Consider the following example:

user = { name: 'John Smith', age: '35', address: { home: '1 kings cross road' }}
puts JSON.pretty_generate(user)
# NameError (uninitialized constant JSON)
require 'json'
puts JSON.pretty_generate(user)
{
  "name": "John Smith",
  "age": "35",
  "address": {
    "home": "1 kings cross road"
  }
}

In the preceding example, we create a simple hash containing some user information and we attempt to convert it to JSON and display it in a formatted way using the JSON.pretty_generate function.

We can then see that it throws a NameError error because the JSON gem has not been required and is, therefore, not available. This is very much like trying to use...