Each for iteration in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print each number in the array.

Ruby

numbers = [1, 2, 3]
numbers.[1] do |num|
  puts num
end

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

Areduce

Beach

Cmap

Dselect

Attempts:

3 left

💡 Hint

Common Mistakes

Using map instead of each when you only want to print values.

Using select which filters elements instead of iterating all.

The each method iterates over each element in the array and executes the block for each element.

2fill in blank

medium

Complete the code to print each word in uppercase.

Ruby

words = ['cat', 'dog', 'bird']
words.[1] do |word|
  puts word.upcase
end

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

Amap

Bselect

Creduce

Deach

Attempts:

3 left

💡 Hint

Common Mistakes

Using map which returns a new array instead of just printing.

Using select which filters elements.

The each method is used to perform an action on each element without changing the original array.

3fill in blank

hard

Fix the error in the code to correctly iterate over the hash and print keys and values.

Ruby

person = {name: 'Alice', age: 30}
person.[1] do |key, value|
  puts "#{key}: #{value}"
end

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

Aselect

Bmap

Ceach

Dreduce

Attempts:

3 left

💡 Hint

Common Mistakes

Using map which returns a new array instead of just iterating.

Using select which filters elements.

The each method correctly iterates over key-value pairs in a hash.

4fill in blank

hard

Fill both blanks to create a hash with words as keys and their lengths as values.

Ruby

words = ['apple', 'banana', 'cherry']
lengths = words.map { |word| [[1], [2]] }.to_h

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

Aword

Blen(word)

Cword.length

Dword.size

Attempts:

3 left

💡 Hint

Common Mistakes

Using Python's len() function instead of Ruby's length method.

Using word.size as key instead of value.

In Ruby, word.length returns the length of the string word. Use word as key and word.length as value.

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 longer than 5 letters.

Ruby

words = ['apple', 'banana', 'cherry', 'date']
lengths = words.select { |word| word.length [3] 5 }.map { |word| [[1], [2]] }.to_h

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

Aword.upcase

Bword.length

C>

Dword.size

Attempts:

3 left

💡 Hint

Common Mistakes

Using Python syntax like len(word) instead of Ruby methods.

Using < instead of > in the condition.

The key is the uppercase version of the word using word.upcase. The value is the length of the word with word.length. The condition filters words longer than 5 letters using >.

Practice

1. What does the each method do in Ruby when used with an array?

easy

A. It removes duplicate elements from the array.

B. It runs the given block once for every element in the array.

C. It sorts the array in ascending order.

D. It returns the length of the array.

Solution

1. Step 1: Understand the purpose of each

   The each method is used to loop over every element in a collection like an array.

2. Step 2: Identify what happens inside the block

   The block given to each runs once for each element, allowing actions on each item.

3. Final Answer:

   It runs the given block once for every element in the array. -> Option B

4. Quick Check:

   each repeats actions per item [OK]

Hint: Remember: each runs code for every item in the list [OK]

Common Mistakes:

• Confusing each with sorting or filtering methods
• Thinking each returns a new array
• Assuming each counts elements

2. Which of the following is the correct syntax to iterate over an array numbers using each in Ruby?

easy

A. numbers.each do num puts num end

B. each numbers do |num| puts num end

C. numbers.each { |num| puts num }

D. numbers.each(num) { puts num }

Solution

1. Step 1: Recognize correct each syntax

   The each method is called on the array, followed by a block with a parameter inside pipes.

2. Step 2: Check block format

   numbers.each { |num| puts num } uses curly braces with a block parameter |num| and a valid block body puts num.

3. Final Answer:

   numbers.each { |num| puts num } -> Option C

4. Quick Check:

   Correct block syntax = numbers.each { |num| puts num } [OK]

Hint: Use .each with {|var| ...} or do |var| ... end [OK]

Common Mistakes:

• Placing the variable outside the pipes
• Calling each without a block
• Using parentheses incorrectly with each

3. What will be the output of this Ruby code?

fruits = ['apple', 'banana', 'cherry']
fruits.each do |fruit|
  puts fruit.upcase
end

medium

A. APPLE
BANANA
CHERRY

B. apple
banana
cherry

C. APPLE BANANA CHERRY

D. ['APPLE', 'BANANA', 'CHERRY']

Solution

1. Step 1: Understand the each loop behavior

   The code loops over each fruit and prints the uppercase version using puts fruit.upcase.

2. Step 2: Determine output format

   puts prints each string on a new line, so each fruit name appears uppercase on its own line.

3. Final Answer:

   APPLE BANANA CHERRY -> Option A

4. Quick Check:

   each + puts prints each item on a new line [OK]

Hint: puts prints each item on a new line inside each [OK]

Common Mistakes:

• Expecting output on one line
• Confusing puts with print
• Not applying upcase method

4. Identify the error in this Ruby code snippet:

numbers = [1, 2, 3]
numbers.each do num
  puts num * 2
end

medium

A. Missing pipes around the block variable 'num'.

B. Incorrect method name; should be 'for' instead of 'each'.

C. Missing parentheses after 'each'.

D. Using 'puts' inside the block is not allowed.

Solution

1. Step 1: Check block variable syntax

   In Ruby, block variables must be enclosed in pipes like |num| when using do...end.

2. Step 2: Identify the missing pipes

   The code uses do num instead of do |num|, causing a syntax error.

3. Final Answer:

   Missing pipes around the block variable 'num'. -> Option A

4. Quick Check:

   Block variables need pipes |var| [OK]

Hint: Always put block variables inside |pipes| with do...end [OK]

Common Mistakes:

• Omitting pipes around block variables
• Thinking parentheses are required after each
• Believing puts cannot be used inside blocks

5. Given a hash scores = { alice: 10, bob: 15, carol: 12 }, how can you use each to print each name and score in the format Name: Score?

hard

A. scores.each { |name| puts "#{name.capitalize}: #{score}" }

B. scores.each { |score, name| puts "#{name}: #{score}" }

C. scores.each do |name| puts "#{name}: #{scores[name]}" end

D. scores.each do |name, score| puts "#{name.capitalize}: #{score}" end

Solution

1. Step 1: Understand hash iteration with each

   When iterating a hash with each, two block variables receive the key and value respectively.

2. Step 2: Use correct variable order and string formatting

   scores.each do |name, score| puts "#{name.capitalize}: #{score}" end correctly uses |name, score| and prints with #{name.capitalize}: #{score}.

3. Final Answer:

   scores.each do |name, score| puts "#{name.capitalize}: #{score}" end -> Option D

4. Quick Check:

   Hash each uses two vars: key, value [OK]

Hint: Hash each needs two vars: |key, value| [OK]

Common Mistakes:

• Swapping key and value variables
• Using only one block variable for hash
• Not capitalizing the name correctly