Guard clauses pattern in Ruby - Mini Project: Build & Apply

Using Guard Clauses in Ruby

📖 Scenario: You are writing a simple program to check if a person is allowed to enter a club. The rules are simple: the person must be at least 18 years old and must have a valid ticket.

🎯 Goal: Build a Ruby program that uses guard clauses to quickly check if a person meets the entry requirements. If the person is too young or does not have a ticket, the program should stop early and print a message. Otherwise, it should welcome the person.

📋 What You'll Learn

Create a method called check_entry that takes two parameters: age and has_ticket.

Use guard clauses to check if age is less than 18 and if has_ticket is false.

Print "Entry denied: You must be at least 18 years old." if the age check fails.

Print "Entry denied: You need a valid ticket." if the ticket check fails.

If both checks pass, print "Welcome to the club!".

💡 Why This Matters

🌍 Real World

Guard clauses are used in real programs to quickly check for errors or special cases and stop processing early. This makes programs easier to understand and less error-prone.

💼 Career

Many programming jobs require writing clean, readable code. Using guard clauses is a common best practice to handle input validation and error checking efficiently.

1

Create the check_entry method with parameters

Write a method called check_entry that takes two parameters: age and has_ticket.

Ruby

def check_entry(age, has_ticket)
  # Your code here
end

Need a hint?

Define a method with def and two parameters inside parentheses.

2

Add guard clause for age check

Inside the check_entry method, add a guard clause that returns and prints "Entry denied: You must be at least 18 years old." if age is less than 18.

Ruby

def check_entry(age, has_ticket)
  # Add guard clause for age check here
end

Need a hint?

Use return puts "message" if condition to stop the method early.

3

Add guard clause for ticket check

Add another guard clause inside the check_entry method that returns and prints "Entry denied: You need a valid ticket." if has_ticket is false.

Ruby

def check_entry(age, has_ticket)
  return puts "Entry denied: You must be at least 18 years old." if age < 18
  # Add guard clause for ticket check here
end

Need a hint?

Use return puts "message" unless has_ticket to check if ticket is missing.

4

Print welcome message if all checks pass

After the guard clauses, print "Welcome to the club!" inside the check_entry method. Then call check_entry(20, true) to test.

Ruby

def check_entry(age, has_ticket)
  return puts "Entry denied: You must be at least 18 years old." if age < 18
  return puts "Entry denied: You need a valid ticket." unless has_ticket
  # Print welcome message here
end

# Call the method to test

Need a hint?

Print the welcome message only if the method did not return earlier. Then call the method with age 20 and ticket true.