Why regex is powerful in Ruby - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby regex code?

Look at this Ruby code using regex. What will it print?

Ruby

text = "Hello Ruby 2024!"
match = text.match(/Ruby (\d{4})/)
puts match[1]

A 2024

B Ruby 2024

C Hello

D nil

💡 Hint

Remember, parentheses in regex capture groups. What does match[1] return?

The regex /Ruby (\d{4})/ looks for 'Ruby ' followed by exactly 4 digits. The parentheses capture those digits. match[1] returns the first captured group, which is '2024'.

🧠 Conceptual

intermediate

Why is regex powerful in Ruby for text processing?

Choose the best reason why regex is powerful in Ruby.

A Ruby requires external libraries to use regex.

B Regex in Ruby only works with strings longer than 10 characters.

C Ruby integrates regex directly into its syntax with easy methods like <code>=~</code> and <code>match</code>.

D Ruby does not support regex backreferences.

💡 Hint

Think about how Ruby lets you use regex without extra setup.

Ruby has built-in regex support with special syntax and methods, making it easy and powerful for text matching and extraction.

🔧 Debug

advanced

What error does this Ruby regex code raise?

Find the error when running this Ruby code:

Ruby

pattern = /\d{3}-\d{2}-\d{4}/
text = "My number is 123-45-6789"
match = text.match(pattern)
puts match[5]

A SyntaxError

B IndexError

C TypeError

D NoMethodError

💡 Hint

Check what match[5] means if the regex has fewer capture groups.

The regex has no capture groups, so match[5] tries to access a non-existent group index, causing an IndexError.

📝 Syntax

advanced

Which option correctly uses regex to find all words starting with 'a' in Ruby?

Choose the Ruby code that correctly finds all words starting with 'a' in a string.

A text.scan(/\w*a\b/)

B text.scan(/a\w*\b/)

C text.scan(/\b\w*a/)

D text.scan(/\ba\w*/)

💡 Hint

Remember, \b means word boundary and \w* means zero or more word characters.

Option D matches a word boundary, then 'a', then zero or more word characters, correctly capturing words starting with 'a'.

🚀 Application

expert

What is the value of 'result' after running this Ruby code?

This Ruby code uses regex with named capture groups. What is the value of result?

Ruby

text = "User: alice, ID: 42"
pattern = /User: (?<name>\w+), ID: (?<id>\d+)/
match = text.match(pattern)
result = {user: match[:name], id: match[:id].to_i}

A {user: "alice", id: 42}

B {:user=>"alice", :id=>42}

C {user: "alice", id: "42"}

D {"user"=>"alice", "id"=>42}

💡 Hint

Look at how the hash keys and values are created and the use of to_i.

The code creates a Ruby hash with symbol keys :user and :id. The id value is converted to an integer with to_i. So the result is {user: "alice", id: 42}.