Common patterns and character classes in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the string contains only digits.

Ruby

if str =~ /\A[1]+\z/
  puts "Only digits"
else
  puts "Contains other characters"
end

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

A\d

B\w

C\s

D\D

Attempts:

3 left

💡 Hint

Common Mistakes

Using \w matches letters and digits, not only digits.

Using \D matches non-digit characters, which is opposite of what is needed.

The pattern \d matches any digit character. Using \A\d+\z ensures the entire string is digits only.

2fill in blank

medium

Complete the code to find all whitespace characters in the string.

Ruby

matches = str.scan(/[1]/)
puts matches

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

A\S

B\s

C\w

D\d

Attempts:

3 left

💡 Hint

Common Mistakes

Using \S which matches non-whitespace characters.

Using \w which matches letters and digits, not spaces.

The pattern \s matches any whitespace character like spaces, tabs, or newlines.

3fill in blank

hard

Fix the error in the regex to match a string that starts with a letter.

Ruby

if str =~ /^[1]/i
  puts "Starts with a letter"
else
  puts "Does not start with a letter"
end

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

A\s

B[0-9]

C\d

D[a-z]

Attempts:

3 left

💡 Hint

Common Mistakes

Using \d which matches digits, not letters.

Using [0-9] which matches digits, not letters.

The pattern [a-z] matches any letter from a to z. The i flag makes it case-insensitive.

4fill in blank

hard

Fill both blanks to create a hash with words as keys and their lengths as values, only for words longer than 3 characters.

Ruby

lengths = words.each_with_object({}) { |word, h| h[word] = word.[1] if word.[2] 3 }

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

Alength

Bsize

Clength >

Dsize >

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'length' as a method without parentheses in this context.

Using 'length >' or 'size >' as one option instead of separating method and operator.

In Ruby, word.size returns the length of the word. The condition word.size > 3 filters words longer than 3 characters.

5fill in blank

hard

Fill all three blanks to create a hash with uppercase words as keys and their lengths as values, only for words containing digits.

Ruby

result = words.each_with_object({}) { |word, h| h[word.[1]] = word.[2] if word =~ /[3]/ }

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

Aupcase

Bsize

C\d

Dlength

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'length' instead of 'size' inconsistently.

Using incorrect regex like /\w/ which matches letters and digits.

word.upcase converts the word to uppercase for the key. word.size gives the length for the value. The regex /\d/ checks if the word contains any digit.