String methods (upcase, downcase, strip) in Ruby - Mini Project: Build & Apply

Using String Methods: upcase, downcase, strip

📖 Scenario: You work at a small online store. Customers enter their names and messages, but sometimes they add extra spaces or use different letter cases. You want to clean up their input before saving it.

🎯 Goal: You will write a Ruby program that takes a customer's name and message, removes extra spaces, and changes the text to uppercase or lowercase as needed.

📋 What You'll Learn

Create variables with exact names and values as instructed

Use the Ruby string methods upcase, downcase, and strip

Print the final cleaned and formatted strings exactly as shown

💡 Why This Matters

🌍 Real World

Cleaning and formatting user input is important in many apps to keep data consistent and easy to read.

💼 Career

Knowing how to manipulate strings is a basic skill for programming jobs, especially in web development and data processing.

1

Create the initial strings

Create two string variables: customer_name with the value " Alice " and customer_message with the value "Hello, I LOVE your store! ".

Ruby

# Create the variables customer_name and customer_message with the exact values
# Your code here

Hint

Use double quotes for the strings and include the spaces exactly as shown.

2

Add variables for cleaned strings

Create two new variables: clean_name by removing spaces from customer_name using strip, and message_lower by converting customer_message to lowercase using downcase.

Ruby

customer_name = "  Alice  "
customer_message = "Hello, I LOVE your store!  "
# Create clean_name by stripping spaces from customer_name
# Create message_lower by converting customer_message to lowercase
# Your code here

Hint

Use .strip to remove spaces and .downcase to make all letters lowercase.

3

Create an uppercase message

Create a variable message_upper by converting customer_message to uppercase using upcase.

Ruby

customer_name = "  Alice  "
customer_message = "Hello, I LOVE your store!  "

clean_name = customer_name.strip
message_lower = customer_message.downcase
# Create message_upper by converting customer_message to uppercase
# Your code here

Hint

Use .upcase to make all letters uppercase.

4

Print the cleaned and formatted strings

Print the variables clean_name, message_lower, and message_upper each on its own line, in that order.

Ruby

customer_name = "  Alice  "
customer_message = "Hello, I LOVE your store!  "

clean_name = customer_name.strip
message_lower = customer_message.downcase

message_upper = customer_message.upcase
# Print clean_name, message_lower, and message_upper each on a new line
# Your code here

Hint

Use puts to print each variable on its own line.

Practice

1. What does the Ruby method upcase do to a string?

easy

A. Converts all letters in the string to lowercase

B. Converts all letters in the string to uppercase

C. Removes spaces from the start and end of the string

D. Reverses the string

Solution

1. Step 1: Understand the method name

   The method upcase suggests making letters uppercase.

2. Step 2: Recall the method effect on strings

   upcase changes all letters to uppercase, not lowercase or trimming spaces.

3. Final Answer:

   Converts all letters in the string to uppercase -> Option B

4. Quick Check:

   upcase = uppercase letters [OK]

Hint: Remember: upcase = uppercase letters [OK]

Common Mistakes:

• Confusing upcase with downcase
• Thinking upcase removes spaces
• Assuming upcase reverses the string

2. Which of the following is the correct syntax to remove spaces from the start and end of a string str in Ruby?

easy

A. str.strip()

B. str.upcase()

C. strip(str)

D. str.trim()

Solution

1. Step 1: Identify the method to remove spaces

   The Ruby method to remove spaces at start and end is strip, called on the string object.

2. Step 2: Check correct method call syntax

   In Ruby, methods are called with dot notation: str.strip(). There is no trim method in Ruby.

3. Final Answer:

   str.strip() -> Option A

4. Quick Check:

   strip method called with dot = str.strip() [OK]

Hint: Use dot notation: string.strip() removes spaces [OK]

Common Mistakes:

• Using strip as a standalone function
• Using trim instead of strip
• Calling upcase to remove spaces

3. What is the output of the following Ruby code?

str = "  Hello World  "
puts str.strip.upcase

medium

A. " HELLO WORLD "

B. " hello world "

C. "hello world"

D. "HELLO WORLD"

Solution

1. Step 1: Apply strip to the string

   strip removes spaces at the start and end, so " Hello World " becomes "Hello World".

2. Step 2: Apply upcase to the stripped string

   upcase converts all letters to uppercase, so "Hello World" becomes "HELLO WORLD".

3. Final Answer:

   "HELLO WORLD" -> Option D

4. Quick Check:

   strip + upcase = "HELLO WORLD" [OK]

Hint: strip removes spaces, upcase makes uppercase [OK]

Common Mistakes:

• Forgetting strip removes spaces
• Applying upcase before strip
• Expecting original spaces to remain

4. The following Ruby code is intended to convert a string name to lowercase and remove spaces at the start and end. What is wrong?

name = "  RubyLang  "
name.downcase.strip

medium

A. The method strip does not exist

B. The methods are called in the wrong order

C. The result is not saved or printed

D. The string should be converted to uppercase instead

Solution

1. Step 1: Check method calls and order

   Both downcase and strip are valid methods and can be chained in any order.

2. Step 2: Check if result is used

   The code calls methods but does not save or print the result, so the original string remains unchanged.

3. Final Answer:

   The result is not saved or printed -> Option C

4. Quick Check:

   Method calls without assignment or output do nothing visible [OK]

Hint: Always save or print method results to see changes [OK]

Common Mistakes:

• Thinking method order matters here
• Assuming methods change string in place
• Confusing strip with a non-existent method

5. You have a list of names with inconsistent spacing and letter cases:

names = ["  Alice", "BOB  ", "  cHaRlie  "]

Which Ruby code correctly cleans this list by removing spaces and making all names lowercase?

hard

A. clean_names = names.map { |n| n.strip.downcase }

B. clean_names = names.map { |n| n.downcase.chomp }

C. clean_names = names.map { |n| n.strip.upcase }

D. clean_names = names.map { |n| n.downcase }

Solution

1. Step 1: Understand the goal

   We want to remove spaces and convert all names to lowercase.

2. Step 2: Check each option

   clean_names = names.map { |n| n.strip.downcase } uses strip then downcase, which removes spaces first, then lowercases. clean_names = names.map { |n| n.downcase.chomp } uses chomp after downcase, but chomp removes only trailing newlines, not spaces, so spaces remain. clean_names = names.map { |n| n.strip.upcase } uses upcase which is wrong. clean_names = names.map { |n| n.downcase } does not remove spaces.

3. Step 3: Choose best practice

   The code that uses strip to remove whitespace and downcase to lowercase correctly cleans the names.

4. Final Answer:

   clean_names = names.map { |n| n.strip.downcase } -> Option A

5. Quick Check:

   strip then downcase cleans names correctly [OK]

Hint: Strip spaces first, then change case for clean strings [OK]

Common Mistakes:

• Using upcase instead of downcase
• Confusing chomp with strip
• Forgetting to map over the list