IRB for interactive exploration in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start the interactive Ruby shell (IRB).

Ruby

system('[1]')

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

Airb

Bruby

Crails

Dgem

Attempts:

3 left

💡 Hint

Common Mistakes

Typing 'ruby' instead of 'irb' starts the Ruby interpreter but not the interactive shell.

Using 'rails' or 'gem' commands won't open IRB.

Typing irb in the terminal starts the interactive Ruby shell where you can try Ruby commands live.

2fill in blank

medium

Complete the code to assign the value 10 to variable x inside IRB.

Ruby

x [1] 10

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

A==

B!=

C=

D=>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' which is a comparison operator, not assignment.

Using '=>' which is used in hashes, not for assignment.

Use the single equals sign = to assign a value to a variable in Ruby.

3fill in blank

hard

Fix the error in the IRB command to print 'Hello World'.

Ruby

puts [1]Hello World[1]

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

A"

B'

C`

D:

Attempts:

3 left

💡 Hint

Common Mistakes

Using backticks which execute shell commands.

Using colon which is invalid syntax here.

In Ruby, double quotes " or single quotes ' can be used for strings. Here, double quotes are correct to enclose the string.

4fill in blank

hard

Fill both blanks to create a hash with key :name and value 'Alice' in IRB.

Ruby

person = [1] => [2]

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

A:name

B"Alice"

C'Alice'

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using plain word 'name' without colon for key.

Using double quotes for key which is less common for symbols.

In Ruby, symbols like :name are used as keys in hashes. Strings can be enclosed in single quotes like 'Alice'.

5fill in blank

hard

Fill all three blanks to create an array of numbers from 1 to 5 and print each number in IRB.

Ruby

numbers = ([1]..[2]).to_a
numbers.each do |[3]|
  puts [3]
end

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

A1

B5

Cnum

Di

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 or 6 instead of 1 or 5 for range boundaries.

Using 'i' as block variable when 'num' is expected here.

The range 1..5 creates numbers from 1 to 5. to_a converts it to an array. The block variable num is used to print each number.

Practice

1. What is the main purpose of using irb in Ruby?

easy

A. To debug Ruby code with a graphical interface

B. To run Ruby code interactively and test snippets quickly

C. To create Ruby project files automatically

D. To compile Ruby code into an executable file

Solution

1. Step 1: Understand what IRB stands for

   IRB means Interactive Ruby Shell, which lets you type and run Ruby code line by line.

2. Step 2: Identify the main use of IRB

   It is mainly used to quickly test and explore Ruby code without creating files.

3. Final Answer:

   To run Ruby code interactively and test snippets quickly -> Option B

4. Quick Check:

   IRB = Interactive Ruby Shell for quick code testing [OK]

Hint: IRB runs code live, no files needed [OK]

Common Mistakes:

• Thinking IRB compiles code
• Confusing IRB with project setup tools
• Assuming IRB has a graphical interface

2. Which command correctly starts the IRB session in your terminal?

easy

A. ruby irb

B. start irb

C. run ruby

D. irb

Solution

1. Step 1: Recall the command to launch IRB

   The IRB session is started simply by typing irb in the terminal.

2. Step 2: Check other options for correctness

   Commands like ruby irb, start irb, or run ruby are incorrect for starting IRB.

3. Final Answer:

   irb -> Option D

4. Quick Check:

   Type irb to start IRB [OK]

Hint: Just type 'irb' to start interactive Ruby [OK]

Common Mistakes:

• Adding extra words like 'ruby' before irb
• Using 'start' or 'run' commands incorrectly
• Confusing IRB start with running Ruby files

3. What will be the output when you enter this in IRB?

5.times { |i| puts i }

medium

A. 5 times printed on one line

B. 1 2 3 4 5 (each on a new line)

C. 0 1 2 3 4 (each on a new line)

D. Error: undefined method 'times'

Solution

1. Step 1: Understand the times method

   The times method runs the block 5 times, with i from 0 to 4.

2. Step 2: Check what puts i does inside the block

   It prints each value of i on a new line, so output is 0,1,2,3,4 each on separate lines.

3. Final Answer:

   0 1 2 3 4 (each on a new line) -> Option C

4. Quick Check:

   5.times counts from 0 to 4 [OK]

Hint: times starts counting from zero [OK]

Common Mistakes:

• Thinking times starts at 1
• Expecting output on one line
• Assuming times is undefined in IRB

4. You typed this in IRB:

puts 'Hello

What is the error and how do you fix it?

medium

A. SyntaxError due to missing closing quote; add a closing '

B. NameError because 'Hello' is undefined; define it first

C. No error; it prints Hello

D. RuntimeError because puts is not allowed in IRB

Solution

1. Step 1: Identify the syntax problem

   The string started with a single quote but has no closing quote, causing a SyntaxError.

2. Step 2: Fix the error by adding the missing quote

   Adding the closing single quote after Hello fixes the syntax and allows the code to run.

3. Final Answer:

   SyntaxError due to missing closing quote; add a closing ' -> Option A

4. Quick Check:

   Strings need matching quotes [OK]

Hint: Check for matching quotes in strings [OK]

Common Mistakes:

• Ignoring missing quote errors
• Thinking puts can't be used in IRB
• Confusing SyntaxError with NameError

5. You want to quickly test a method in IRB that returns the square of a number. Which of these is the correct way to define and test it?

hard

A. def square(x); x * x; end; square(4)

B. def square x x * x end square 4

C. def square(x) { return x * x }; square(4)

D. def square(x): return x * x end; square(4)

Solution

1. Step 1: Check correct Ruby method syntax

   Ruby methods use def name(params); body; end syntax. def square(x); x * x; end; square(4) follows this correctly.

2. Step 2: Verify method call syntax

   Calling square(4) is correct. The other options have syntax errors or wrong Ruby style.

3. Final Answer:

   def square(x); x * x; end; square(4) -> Option A

4. Quick Check:

   Method def/end with parentheses is correct [OK]

Hint: Use def ... end with parentheses for methods [OK]

Common Mistakes:

• Using braces {} for method body
• Omitting parentheses incorrectly
• Using Python-like syntax with colons