Ternary operator usage in Ruby - Mini Project: Build & Apply

Ternary Operator Usage

📖 Scenario: You are creating a simple program to check if a number is even or odd. This is like deciding if a number is like a pair of shoes (even) or a single shoe (odd).

🎯 Goal: Build a Ruby program that uses the ternary operator to decide if a number is even or odd and prints the result.

📋 What You'll Learn

Create a variable called number with the value 7.

Create a variable called result that uses the ternary operator to check if number is even or odd.

Print the result variable.

💡 Why This Matters

🌍 Real World

Ternary operators help write short and clear decisions in code, like quickly choosing between two options.

💼 Career

Many programming jobs require writing clean and concise code. Using ternary operators is a common skill for making decisions in your programs.

1

DATA SETUP: Create the number variable

Create a variable called number and set it to 7.

Ruby

# Create a variable called number and set it to 7
# Your code here

Hint

Use = to assign the value 7 to the variable number.

2

CONFIGURATION: Prepare the ternary operator

Create a variable called result that uses the ternary operator to check if number is even. If it is even, set result to "Even", otherwise set it to "Odd".

Ruby

number = 7
# Use the ternary operator to set result to "Even" or "Odd" based on number
# Your code here

Hint

Use condition ? value_if_true : value_if_false format. The condition here is number.even?.

3

CORE LOGIC: Use the ternary operator correctly

Make sure the ternary operator uses number.even? as the condition, and assigns "Even" or "Odd" to result accordingly.

Ruby

number = 7
result = number.even? ? "Even" : "Odd"
# Your code here

Hint

Check that the ternary operator is written exactly as number.even? ? "Even" : "Odd".

4

OUTPUT: Print the result

Write a puts statement to print the value of result.

Ruby

number = 7
result = number.even? ? "Even" : "Odd"
# Print the result
# Your code here

Hint

Use puts result to show the output.

Practice

1. What does the ternary operator condition ? value_if_true : value_if_false do in Ruby?

easy

A. It chooses one of two values based on the condition's truth.

B. It creates a loop that runs twice.

C. It defines a new method with two parameters.

D. It comments out the code after the colon.

Solution

1. Step 1: Understand the ternary operator format

   The ternary operator uses a condition followed by a question mark, then two values separated by a colon.

2. Step 2: Identify its purpose

   It returns the first value if the condition is true, otherwise the second value.

3. Final Answer:

   It chooses one of two values based on the condition's truth. -> Option A

4. Quick Check:

   condition ? true_value : false_value = chooses value [OK]

Hint: Think: condition true? pick first value, else second [OK]

Common Mistakes:

• Confusing ternary with loops
• Thinking it defines methods
• Misunderstanding the colon as comment

2. Which of the following is the correct syntax for a ternary operator in Ruby?

easy

A. condition ? value_if_true : value_if_false

B. condition : value_if_true ? value_if_false

C. condition ? value_if_true ; value_if_false

D. condition ? value_if_true, value_if_false

Solution

1. Step 1: Recall ternary operator syntax

   The correct syntax places a question mark after the condition, then the true value, a colon, then the false value.

2. Step 2: Compare options

   Only condition ? value_if_true : value_if_false matches the correct format: condition ? true_value : false_value.

3. Final Answer:

   condition ? value_if_true : value_if_false -> Option A

4. Quick Check:

   Syntax = condition ? true : false [OK]

Hint: Remember: question mark before true, colon before false [OK]

Common Mistakes:

• Swapping question mark and colon
• Using semicolon instead of colon
• Separating values with comma

3. What is the output of this Ruby code?

age = 20
puts age >= 18 ? "Adult" : "Minor"

medium

A. Minor

B. 20

C. SyntaxError

D. Adult

Solution

1. Step 1: Evaluate the condition

   The condition age >= 18 is true because age is 20.

2. Step 2: Apply ternary operator

   Since the condition is true, the expression returns "Adult".

3. Final Answer:

   Adult -> Option D

4. Quick Check:

   20 >= 18 ? "Adult" : "Minor" = "Adult" [OK]

Hint: Check condition true? pick first value, else second [OK]

Common Mistakes:

• Choosing the false value by mistake
• Printing the variable instead of result
• Expecting syntax error

4. Identify the error in this Ruby code using a ternary operator:

score = 85
result = score > 60 ? "Pass" "Fail"
puts result

medium

A. Missing question mark after condition

B. Missing colon between true and false values

C. Ternary operator cannot be used with strings

D. Wrong variable name 'score'

Solution

1. Step 1: Check ternary operator syntax

   The ternary operator requires a colon between the true and false values.

2. Step 2: Identify missing colon

   The code has "Pass" "Fail" without a colon, causing a syntax error.

3. Final Answer:

   Missing colon between true and false values -> Option B

4. Quick Check:

   Syntax = condition ? true_value : false_value [OK]

Hint: Always put colon between true and false parts [OK]

Common Mistakes:

• Omitting colon
• Using comma instead of colon
• Forgetting question mark

5. Given this Ruby code, what will be the output?

values = [0, 1, nil, 5]
results = values.map { |v| v ? "Yes" : "No" }
puts results.inspect

hard

A. ["No", "Yes", "No", "Yes"]

B. ["No", "No", "No", "No"]

C. ["Yes", "Yes", "No", "Yes"]

D. ["Yes", "No", "Yes", "No"]

Solution

1. Step 1: Understand truthiness in Ruby

   In Ruby, 0 and 1 are truthy, nil is falsy.

2. Step 2: Apply ternary operator to each element

   For each value: 0 (truthy) -> "Yes", 1 (truthy) -> "Yes", nil (falsy) -> "No", 5 (truthy) -> "Yes".

3. Step 3: Check mapped results

   The results array is ["Yes", "Yes", "No", "Yes"].

4. Final Answer:

   ["Yes", "Yes", "No", "Yes"] -> Option C

5. Quick Check:

   Truthy values = "Yes", nil = "No" [OK]

Hint: Remember: only nil and false are falsey in Ruby [OK]

Common Mistakes:

• Thinking 0 is falsy
• Confusing nil with false
• Misreading map block