RubyGems repository - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a RubyGems repository?

A RubyGems repository is a storage place on the internet where Ruby libraries (called gems) are kept. Developers can download and share these gems easily.

beginner

How do you install a gem from a RubyGems repository?

You use the command gem install gem_name in your terminal. This downloads the gem from the RubyGems repository and installs it on your computer.

beginner

What is the default RubyGems repository URL?

The default RubyGems repository URL is https://rubygems.org. This is where most gems are hosted and downloaded from.

intermediate

How can you specify a custom RubyGems repository?

You can specify a custom repository by using the --source option with the gem command, like gem install gem_name --source https://custom.repo.url.

intermediate

What is the purpose of the gem push command?

The gem push command uploads your gem to a RubyGems repository so others can use it. You need to be logged in to the repository to push gems.

What command installs a gem from the default RubyGems repository?

A gem remove gem_name

B gem push gem_name

C gem update gem_name

D gem install gem_name

The gem install gem_name command downloads and installs a gem from the default repository.

What is the default URL for the RubyGems repository?

A https://rubygems.org

B https://gems.ruby.com

C https://rubyrepo.net

D https://gemstore.com

The official RubyGems repository is hosted at https://rubygems.org.

Which command uploads your gem to a RubyGems repository?

A gem install

B gem push

C gem fetch

D gem build

Use gem push to upload your gem to a repository.

How do you install a gem from a custom repository?

A gem install gem_name --source https://custom.repo.url

B gem push gem_name --source https://custom.repo.url

C gem update gem_name --source https://custom.repo.url

D gem remove gem_name --source https://custom.repo.url

The --source option with gem install lets you specify a custom repository URL.

Before pushing a gem to RubyGems, what must you do?

A Update RubyGems

B Install the gem locally

C Build the gem with <code>gem build</code>

D Remove old gems

You must build your gem package first using gem build before pushing it.

Explain what a RubyGems repository is and how it helps Ruby developers.

Think about where Ruby code libraries are kept online.

Describe the steps to publish your own gem to a RubyGems repository.

Consider what commands you run before and during publishing.

Practice

1. What is the primary purpose of the RubyGems repository?

easy

A. To store and share Ruby libraries called gems

B. To compile Ruby code into machine language

C. To run Ruby programs faster

D. To create graphical user interfaces in Ruby

Solution

1. Step 1: Understand what RubyGems stores

   RubyGems repository is known for storing Ruby libraries called gems.

2. Step 2: Identify the main function

   Its main function is to share these gems so developers can reuse code easily.

3. Final Answer:

   To store and share Ruby libraries called gems -> Option A

4. Quick Check:

   RubyGems = Ruby libraries storage [OK]

Hint: RubyGems = place for Ruby code packages [OK]

Common Mistakes:

• Thinking RubyGems compiles code
• Confusing RubyGems with Ruby interpreter
• Assuming RubyGems runs programs

2. Which command correctly installs a gem named rails from the RubyGems repository?

easy

A. gem install rails

B. install gem rails

C. ruby gem add rails

D. gem add rails

Solution

1. Step 1: Recall the correct gem installation syntax

   The standard command to install a gem is gem install gem_name.

2. Step 2: Match the command with the gem name

   For the gem named rails, the command is gem install rails.

3. Final Answer:

   gem install rails -> Option A

4. Quick Check:

   Install gem = gem install [OK]

Hint: Use 'gem install gemname' to add gems [OK]

Common Mistakes:

• Swapping 'install' and 'gem' order
• Using 'gem add' instead of 'gem install'
• Adding extra words like 'ruby' before command

3. What will be the output of this Ruby code if the gem 'json' is installed?

require 'json'
puts JSON.generate({name: 'Ruby', type: 'language'})

medium

A. SyntaxError

B. {name: Ruby, type: language}

C. {"name":"Ruby","type":"language"}

D. nil

Solution

1. Step 1: Understand the require statement

   The code requires the 'json' gem, which provides JSON methods.

2. Step 2: Analyze JSON.generate output

   JSON.generate converts the Ruby hash to a JSON string with keys and values in quotes.

3. Final Answer:

   {"name":"Ruby","type":"language"} -> Option C

4. Quick Check:

   JSON.generate outputs JSON string [OK]

Hint: JSON.generate outputs string with quotes [OK]

Common Mistakes:

• Expecting Ruby hash syntax as output
• Confusing JSON.generate with JSON.parse
• Ignoring quotes around keys and values

4. Identify the error in this Ruby code snippet that tries to use the 'httparty' gem:

require 'httparty'
response = HTTParty.get('https://api.example.com/data')
puts response.body

medium

A. Missing parentheses in the require statement

B. The method 'get' does not exist in HTTParty

C. Cannot call 'body' on response

D. The gem 'httparty' is not installed

Solution

1. Step 1: Check if 'httparty' gem is installed

   If the gem is not installed, require will fail or HTTParty will be undefined.

2. Step 2: Verify method and usage

   HTTParty.get is a valid method, and response.body is valid if response is returned.

3. Final Answer:

   The gem 'httparty' is not installed -> Option D

4. Quick Check:

   Missing gem causes require failure [OK]

Hint: Install gem before requiring it [OK]

Common Mistakes:

• Assuming require adds gem automatically
• Thinking 'get' method is invalid
• Ignoring gem installation step

5. You want to create a Ruby script that uses the 'colorize' gem to print text in red. Which sequence of steps is correct?

hard

A. Run require 'colorize', then gem install colorize, then use puts 'text'.colorize(:red)

B. Run gem install colorize, then require 'colorize', then use puts 'text'.colorize(:red)

C. Use puts 'text'.colorize(:red) directly without installing or requiring

D. Run gem add colorize, then require 'colorize', then use puts 'text'.colorize(:red)

Solution

1. Step 1: Install the gem first

   You must install the gem using gem install colorize before using it.

2. Step 2: Require the gem in your script

   Use require 'colorize' to load the gem's code.

3. Step 3: Use the gem's method to color text

   Call puts 'text'.colorize(:red) to print red text.

4. Final Answer:

   Run gem install, then require, then use colorize method -> Option B

5. Quick Check:

   Install -> require -> use gem [OK]

Hint: Install gem before require and usage [OK]

Common Mistakes:

• Requiring gem before installing
• Using 'gem add' instead of 'gem install'
• Trying to use gem methods without require