Gemfile for project dependencies in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Gemfile dependency version resolution?

Given this Gemfile snippet, what version of the 'rails' gem will Bundler install?

source 'https://rubygems.org'
gem 'rails', '~> 6.1.0'
gem 'rails', '>= 6.1.3'

Ruby

source 'https://rubygems.org'
gem 'rails', '~> 6.1.0'
gem 'rails', '>= 6.1.3'

A Rails version 6.2.0

B Rails version 6.1.3 or higher but less than 6.2.0

C Rails version 6.1.0

D Bundler will raise a version conflict error

💡 Hint

The '~>' operator means 'compatible with', and the '>= 6.1.3' means minimum version 6.1.3.

The '~> 6.1.0' means any version >= 6.1.0 and < 6.2.0. The '>= 6.1.3' means minimum 6.1.3. Bundler picks the intersection, so versions >= 6.1.3 and < 6.2.0.

🧠 Conceptual

intermediate

Which source declaration is correct in a Gemfile?

You want to specify the source for gems in your Gemfile. Which of these is the correct way to declare the source?

A source 'https://rubygems.org'

B set_source 'https://rubygems.org'

C gem source 'https://rubygems.org'

D source = 'https://rubygems.org'

💡 Hint

Look for the keyword used to specify gem sources in Gemfile syntax.

The correct syntax to specify the gem source is using the 'source' keyword followed by the URL in quotes.

🔧 Debug

advanced

Why does this Gemfile cause a syntax error?

Examine this Gemfile snippet and identify why it causes a syntax error:

source 'https://rubygems.org'
gem 'nokogiri', '~> 1.12.0'
gem 'puma', '~> 5.0'
gem 'rails', '~> 6.1.0'
end

Ruby

source 'https://rubygems.org'
gem 'nokogiri', '~> 1.12.0'
gem 'puma', '~> 5.0'
gem 'rails', '~> 6.1.0'
end

A The Gemfile must start with 'gemfile' keyword

B The gem versions are invalid and cause a syntax error

C Missing 'source' declaration causes syntax error

D The 'end' keyword is misplaced and causes a syntax error

💡 Hint

Check if all keywords and blocks are properly opened and closed.

There is no block opened that requires an 'end'. The 'end' keyword is extra and causes a syntax error.

🚀 Application

advanced

How to specify a gem from a Git repository in Gemfile?

You want to use a gem directly from a GitHub repository instead of RubyGems. Which Gemfile line correctly specifies this?

A gem 'mygem', git: 'https://github.com/user/mygem.git'

B gem 'mygem', source: 'https://github.com/user/mygem.git'

C gem 'mygem', repo: 'https://github.com/user/mygem.git'

D gem 'mygem', url: 'https://github.com/user/mygem.git'

💡 Hint

Look for the keyword that specifies a git repository in gem declaration.

The correct syntax uses the 'git:' option to specify the git repository URL.

❓ Predict Output

expert

How many gems will be installed by Bundler from this Gemfile?

Consider this Gemfile snippet:

source 'https://rubygems.org'
group :development, :test do
  gem 'rspec'
  gem 'pry'
end
group :production do
  gem 'puma'
end
gem 'rails'

How many gems will Bundler install when running in the test environment?

Ruby

source 'https://rubygems.org'
group :development, :test do
  gem 'rspec'
  gem 'pry'
end
group :production do
  gem 'puma'
end
gem 'rails'

A 2 gems

B 4 gems

C 3 gems

D 5 gems

💡 Hint

Bundler installs gems in the default group plus the groups for the current environment.

In the test environment, Bundler installs gems in the default group (rails) plus the :test and :development groups (rspec, pry). The :production group gems are excluded.