Method declaration with def in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What keyword is used to declare a method in Ruby?

The keyword def is used to declare a method in Ruby.

beginner

How do you end a method declaration in Ruby?

You end a method declaration with the keyword end.

beginner

What is the correct way to declare a method named greet that prints 'Hello'?

Use:

def greet
  puts 'Hello'
end

intermediate

Can Ruby methods return values? How?

Yes, Ruby methods return the value of the last executed expression automatically.

intermediate

What happens if you call a method without parentheses in Ruby?

Ruby allows calling methods without parentheses if there are no arguments, making code look cleaner.

Which keyword starts a method declaration in Ruby?

A def

B function

C method

D declare

In Ruby, def is the keyword used to start a method declaration.

How do you end a method declaration in Ruby?

A stop

B end

C finish

D close

Ruby uses the keyword end to close blocks including method declarations.

What will this Ruby method return?

def add
  2 + 3
end

A 5

B 2 + 3

C nil

D Error

Ruby methods return the last evaluated expression automatically, so this returns 5.

Which of these is a valid method call in Ruby?

A greet()

B greet

C None

D Both A and B

Ruby allows calling methods with or without parentheses if there are no arguments.

What is the output of this code?

def say_hi
  puts 'Hi!'
end
say_hi

A say_hi

B nil

C Hi!

D Error

The method prints 'Hi!' to the screen when called.

Explain how to declare a simple method in Ruby using def and end.

Think about the start and end keywords and what goes in between.

Describe how Ruby methods return values and how you can call them.

Remember Ruby's automatic return and flexible syntax.

Practice

1. What keyword do you use in Ruby to start defining a method?

easy

A. method

B. function

C. define

D. def

Solution

1. Step 1: Understand Ruby method syntax

   In Ruby, methods start with the keyword def and end with end.

2. Step 2: Identify the correct keyword

   The correct keyword to start a method is def, not function, method, or define.

3. Final Answer:

   def -> Option D

4. Quick Check:

   Method start keyword = def [OK]

Hint: Remember: Ruby methods start with 'def' and end with 'end' [OK]

Common Mistakes:

• Using 'function' like in JavaScript
• Using 'method' keyword which doesn't exist
• Forgetting to use 'def' to start method

2. Which of the following is the correct way to declare a method named greet in Ruby?

easy

A. def greet puts "Hello"

B. function greet() { puts "Hello" }

C. def greet() puts "Hello" end

D. method greet() puts "Hello" end

Solution

1. Step 1: Check Ruby method syntax

   Ruby methods start with def method_name() and end with end. Parentheses are optional but allowed.

2. Step 2: Identify correct syntax

   def greet() puts "Hello" end uses def greet() puts "Hello" end, which is correct Ruby syntax. Options B and D use wrong keywords, and C misses end.

3. Final Answer:

   def greet() puts "Hello" end -> Option C

4. Quick Check:

   Correct Ruby method syntax = def greet() puts "Hello" end [OK]

Hint: Use 'def name() ... end' to declare methods in Ruby [OK]

Common Mistakes:

• Forgetting the 'end' keyword
• Using JavaScript style 'function' keyword
• Missing parentheses or using wrong keywords

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

def add(a, b)
  a + b
end

puts add(3, 4)

medium

A. 7

B. 34

C. a + b

D. Error

Solution

1. Step 1: Understand method parameters and return

   The method add takes two parameters a and b and returns their sum a + b.

2. Step 2: Calculate the method call result

   Calling add(3, 4) returns 3 + 4 = 7, which is printed by puts.

3. Final Answer:

   7 -> Option A

4. Quick Check:

   3 + 4 = 7 [OK]

Hint: Method returns last expression value; 3 + 4 = 7 [OK]

Common Mistakes:

• Thinking it concatenates as strings
• Expecting explicit return keyword
• Confusing output with code text

4. Identify the error in this Ruby method declaration:

def say_hello
  puts "Hello"

medium

A. Missing 'end' keyword to close method

B. Missing parentheses after method name

C. Incorrect use of puts inside method

D. Method name cannot have underscore

Solution

1. Step 1: Check method structure

   Ruby methods must start with def and end with end. This code misses the end keyword.

2. Step 2: Identify the missing part

   Without end, Ruby will raise a syntax error because the method is not properly closed.

3. Final Answer:

   Missing 'end' keyword to close method -> Option A

4. Quick Check:

   Every method needs 'end' [OK]

Hint: Always close methods with 'end' keyword [OK]

Common Mistakes:

• Forgetting 'end' after method body
• Thinking parentheses are mandatory
• Assuming underscores are invalid in names

5. You want to create a method greet_person that takes a name and returns a greeting like "Hello, Alice!". Which code correctly does this?

hard

A. def greet_person(name)
puts "Hello, #{name}!"
end

B. def greet_person(name)
"Hello, " + name + "!"
end

C. def greet_person(name)
return puts "Hello, " + name + "!"
end

D. def greet_person(name)
print "Hello, " + name + "!"
end

Solution

1. Step 1: Understand method return vs output

   To return a greeting string, the method should produce the string as its last expression or use return. Using puts or print outputs to console but returns nil.

2. Step 2: Analyze each option

   def greet_person(name) "Hello, " + name + "!" end returns the greeting string correctly. def greet_person(name) puts "Hello, #{name}!" end prints but returns nil. def greet_person(name) return puts "Hello, " + name + "!" end returns nil because puts returns nil. def greet_person(name) print "Hello, " + name + "!" end prints but does not return the string.

3. Final Answer:

   def greet_person(name) "Hello, " + name + "!" end -> Option B

4. Quick Check:

   Return string, not print it [OK]

Hint: Return string directly; puts prints but returns nil [OK]

Common Mistakes:

• Using puts instead of returning string
• Returning result of puts (which is nil)
• Confusing print with return