Creating a gem basics in Ruby - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a new Ruby gem module named MyGem.

Ruby

module [1]
  # gem code goes here
end

Drag options to blanks, or click blank then click option'

AMyModule

BGemfile

CGem

DMyGem

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase or incorrect module names.

Confusing the gem name with the Gemfile.

The module name for a gem should be a unique name, usually capitalized. Here, MyGem is the correct module name.

2fill in blank

medium

Complete the code to create a gemspec file with the gem name my_gem.

Ruby

Gem::Specification.new do |spec|
  spec.name = [1]
  spec.version = '0.1.0'
end

Drag options to blanks, or click blank then click option'

A'my_gem'

B:MyGem

C:my_gem

D"MyGem"

Attempts:

3 left

💡 Hint

Common Mistakes

Using symbols instead of strings for the gem name.

Capitalizing the gem name incorrectly.

The gemspec name should be a string representing the gem's name, here 'my_gem'.

3fill in blank

hard

Fix the error in the gemspec code to correctly set the author email.

Ruby

spec.authors = ['Jane Doe']
spec.email = [1]

Drag options to blanks, or click blank then click option'

A'[e-mail]'

[e-mail]

C:[e-mail]

D['[e-mail]']

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the email string.

Using symbols or arrays instead of a string.

The email field must be a string with quotes, not a bare word or symbol.

4fill in blank

hard

Fill both blanks to create a gemspec that sets the summary and homepage URL.

Ruby

spec.summary = [1]
spec.homepage = [2]

Drag options to blanks, or click blank then click option'

A"A simple Ruby gem"

BA simple Ruby gem

C"https://example.com/my_gem"

Dhttps://example.com/my_gem

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes for string values.

Using bare words or URLs without quotes.

Both summary and homepage must be strings enclosed in quotes.

5fill in blank

hard

Fill all three blanks to define a gem module with a version constant.

Ruby

module [1]
  VERSION = [2]
end

puts [3]::VERSION

Drag options to blanks, or click blank then click option'

AMyGem

B"0.1.0"

DMyGemModule

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatching module names.

Not quoting the version string.

Using wrong module name when printing.

The module name is MyGem, the version is a string "0.1.0", and to print the version we use MyGem::VERSION.

Practice

1. What is the main purpose of a Ruby gem?

easy

A. To compile Ruby code into machine language

B. To package and share reusable Ruby code

C. To create graphical user interfaces

D. To manage Ruby versions on your system

Solution

1. Step 1: Understand what a gem is

   A gem is a package that contains Ruby code that can be reused in different projects.

2. Step 2: Identify the main purpose

   The main purpose is to share and reuse code easily across Ruby projects.

3. Final Answer:

   To package and share reusable Ruby code -> Option B

4. Quick Check:

   Gem = reusable Ruby package [OK]

Hint: Gems are for sharing code, not compiling or GUIs [OK]

Common Mistakes:

• Thinking gems compile Ruby code
• Confusing gems with Ruby version managers
• Assuming gems create user interfaces

2. Which file is essential to define a Ruby gem's metadata and dependencies?

easy

A. README.md

B. Gemfile

C. Rakefile

D. gemspec

Solution

1. Step 1: Identify gem metadata file

   The gemspec file (.gemspec) defines the gem's name, version, authors, and dependencies.

2. Step 2: Differentiate from other files

   Gemfile manages project dependencies, Rakefile defines tasks, README.md is documentation.

3. Final Answer:

   gemspec -> Option D

4. Quick Check:

   Metadata and dependencies = gemspec [OK]

Hint: gemspec holds gem info; Gemfile is for app dependencies [OK]

Common Mistakes:

• Confusing Gemfile with gemspec
• Thinking README.md defines dependencies
• Assuming Rakefile holds gem metadata

3. Given this gemspec snippet, what is the gem's version?

Gem::Specification.new do |spec|
  spec.name        = "my_gem"
  spec.version     = "0.2.5"
  spec.summary     = "A sample gem"
end

medium

A. "0.2.5"

B. "2.5"

C. "0.2.0"

D. "1.0.0"

Solution

1. Step 1: Locate the version assignment

   The line spec.version = "0.2.5" sets the gem's version.

2. Step 2: Confirm the exact version string

   The version is exactly "0.2.5" as given in the code.

3. Final Answer:

   "0.2.5" -> Option A

4. Quick Check:

   Version in gemspec = "0.2.5" [OK]

Hint: Look for spec.version assignment in gemspec [OK]

Common Mistakes:

• Picking partial version like "0.2.0"
• Confusing version with gem name
• Assuming default version "1.0.0"

4. This gemspec file has an error. What is it?

Gem::Specification.new do |spec|
  spec.name = "example_gem"
  spec.version = 1.0.0
  spec.summary = "Example gem"
end

medium

A. Version should be a string, not a number

B. Missing spec.authors field

C. spec.name cannot have underscores

D. spec.summary must be longer than 20 characters

Solution

1. Step 1: Check version format

   The version is written as 1.0.0 without quotes, which Ruby treats as a numeric expression causing error.

2. Step 2: Correct version format

   Version must be a string like "1.0.0" with quotes to be valid.

3. Final Answer:

   Version should be a string, not a number -> Option A

4. Quick Check:

   Version must be string in gemspec [OK]

Hint: Always quote version strings in gemspec [OK]

Common Mistakes:

• Leaving version unquoted
• Thinking underscores are invalid in gem names
• Assuming summary length is strictly enforced

5. You want to create a gem that provides a method greet returning "Hello!". Which file structure and code snippet is correct? Options: A)

my_gem/
  lib/
    my_gem.rb
  my_gem.gemspec

# lib/my_gem.rb
module MyGem
  def self.greet
    "Hello!"
  end
end

B)

my_gem/
  src/
    greet.rb
  gemspec.rb

# src/greet.rb
class Greet
  def greet
    puts "Hello!"
  end
end

C)

my_gem/
  lib/
    greet.rb
  my_gem.gemspec

# lib/greet.rb
module Greet
  def greet
    "Hello!"
  end
end

D)

my_gem/
  lib/
    my_gem.rb
  my_gem.gemspec

# lib/my_gem.rb
def greet
  "Hello!"
end

hard

A. Wrong file name and missing self for method

B. Wrong folder and gemspec name; greet is instance method

C. Correct structure with module and class method greet

D. Method defined outside module, no namespacing

Solution

1. Step 1: Check folder and file structure

   Ruby gems use lib/ folder and a gemspec named after the gem. Correct structure with module and class method greet uses lib/my_gem.rb and my_gem.gemspec, which is correct.

2. Step 2: Verify code correctness

   Correct structure with module and class method greet defines a module MyGem with a class method self.greet returning "Hello!", which is the right way to provide a gem method.

3. Final Answer:

   Correct structure with module and class method greet -> Option C

4. Quick Check:

   lib folder + module + self method = correct gem code [OK]

Hint: Use lib folder and module with self.method for gem code [OK]

Common Mistakes:

• Using wrong folder names like src
• Defining instance instead of class methods
• Not namespacing methods inside a module