RubyGems repository - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this RubyGems command?

Consider the following Ruby code that uses RubyGems to list installed gems. What will be printed?

Ruby

require 'rubygems'
puts Gem::Specification.find_all.map(&:name).sort.first(3).join(', ')

A A comma-separated list of the first three gem names alphabetically installed on the system

B A list of all gem names installed, unsorted

C An error because Gem::Specification.find_all is not a valid method

D An empty string because no gems are found

💡 Hint

Gem::Specification.find_all returns all installed gems as objects. Mapping &:name extracts their names.

The code lists all installed gems, sorts their names alphabetically, takes the first three, and joins them with commas.

🧠 Conceptual

intermediate

Which RubyGems command installs a gem and its dependencies?

You want to install a gem named 'nokogiri' along with all its dependencies. Which command should you use?

A gem uninstall nokogiri

B gem install nokogiri

C gem build nokogiri

D gem fetch nokogiri

💡 Hint

Installing a gem downloads and installs it with dependencies.

'gem install' downloads and installs the gem and its dependencies. 'fetch' only downloads the gem file, 'build' creates a gem from source, and 'uninstall' removes a gem.

❓ Predict Output

advanced

What error does this RubyGems code raise?

What error will this Ruby code raise when run?

Ruby

require 'rubygems'
Gem::Specification.find_by_name('nonexistent_gem')

A Gem::MissingSpecError

B NoMethodError

C ArgumentError

D RuntimeError

💡 Hint

find_by_name raises an error if the gem is not found.

If the gem name is not found, RubyGems raises Gem::MissingSpecError to indicate the gem is missing.

🚀 Application

advanced

How to programmatically list all versions of a gem installed?

You want to write Ruby code that lists all installed versions of the gem 'rake'. Which code snippet correctly does this?

A Gem::Specification.list_versions('rake')

B Gem::Specification.find_by_name('rake').version.to_s

C Gem::Specification.latest_version('rake')

D Gem::Specification.find_all_by_name('rake').map(&:version).map(&:to_s)

💡 Hint

find_all_by_name returns all specs matching the gem name.

find_all_by_name returns all installed specs for 'rake'. Mapping version and converting to string lists all installed versions.

🔧 Debug

expert

Why does this RubyGems code fail to install a gem?

This Ruby code tries to install the 'json' gem but fails with an error. What is the cause?

Ruby

require 'rubygems'
require 'rubygems/installer'
installer = Gem::Installer.new('json-2.6.1.gem')
installer.install

A Gem::Installer requires a block to run

B The gem 'json' is already installed, so install fails

C The gem file path 'json-2.6.1.gem' is missing or incorrect

D Gem::Installer cannot install gems programmatically

💡 Hint

Check if the gem file exists at the given path.

Gem::Installer expects a valid gem file path. If the file is missing or path is wrong, installation fails.