Local variables and naming conventions in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assign the value 10 to a local variable named count.

Ruby

count = [1]

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

ACount

B"10"

Cten

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around numbers, which makes them strings.

Starting variable names with uppercase letters, which makes them constants.

The local variable count is assigned the integer value 10. Using quotes would make it a string, and variable names are case-sensitive.

2fill in blank

medium

Complete the code to print the value of the local variable named total.

Ruby

total = 25
puts [1]

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

Atotal

BTotal

C"total"

DTOTAL

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase letters which refer to constants, not local variables.

Using quotes which print the string instead of the variable's value.

Variable names are case-sensitive. The local variable is total in lowercase, so we use total to print its value.

3fill in blank

hard

Fix the error in the code by completing the variable name correctly.

Ruby

user_name = "Alice"
puts [1]

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

AUserName

BuserName

Cuser_name

Dusername

Attempts:

3 left

💡 Hint

Common Mistakes

Changing the case or removing underscores from variable names.

Using camelCase instead of snake_case for local variables.

The variable is named user_name with an underscore and all lowercase letters. Ruby is case-sensitive and exact with variable names.

4fill in blank

hard

Fill both blanks to create a local variable named age and assign it the value 30.

Ruby

[1] = [2]

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

Aage

B30

C"30"

DAge

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase letters for variable names.

Putting numbers inside quotes, making them strings.

The local variable age is assigned the integer value 30. Variable names start with lowercase letters and numbers are written without quotes.

5fill in blank

hard

Fill all three blanks to create a local variable named full_name and assign it the string "John Doe".

Ruby

[1] = [2] + " " + [3]

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

AFullName

B"John"

C"Doe"

Dfull_name

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase letters for variable names.

Forgetting quotes around strings.

Not adding spaces between names.

The local variable full_name is assigned by joining two strings with a space. Variable names start lowercase, and strings are in quotes.

Practice

1. Which of the following is a valid local variable name in Ruby?

easy

A. user_name

B. UserName

C. user-name

D. 1username

Solution

1. Step 1: Check the first character of each variable name

   Local variables must start with a lowercase letter or underscore. 'user_name' starts with 'u' which is lowercase.

2. Step 2: Check for invalid characters

   Variable names cannot contain hyphens or start with numbers. 'user-name' has a hyphen and '1username' starts with a number, so they are invalid.

3. Final Answer:

   user_name -> Option A

4. Quick Check:

   Valid local variable = user_name [OK]

Hint: Local variables start lowercase or underscore, no hyphens or digits first [OK]

Common Mistakes:

• Starting variable names with uppercase letters
• Using hyphens instead of underscores
• Starting variable names with numbers

2. Which of these Ruby variable names will cause a syntax error?

easy

A. temp-var

B. tempVar2

C. _tempVar

D. temp_var

Solution

1. Step 1: Identify invalid characters in variable names

   Ruby variable names can only contain letters, digits, and underscores. Hyphens are not allowed.

2. Step 2: Check each option for invalid characters

   temp-var has a hyphen, which causes a syntax error. The others are valid.

3. Final Answer:

   temp-var -> Option A

4. Quick Check:

   Hyphens cause syntax errors in variable names [OK]

Hint: No hyphens allowed in variable names, use underscores instead [OK]

Common Mistakes:

• Using hyphens instead of underscores
• Confusing uppercase and lowercase letters
• Starting variable names with digits

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

def greet
  name = "Alice"
  Name = "Bob"
  puts name
end
greet

medium

A. name

B. Alice

C. Bob

D. Name

Solution

1. Step 1: Understand variable naming and scope

   In Ruby, local variables start with lowercase letters, constants start with uppercase. 'name' is local variable, 'Name' is a constant.

2. Step 2: Check which variable is printed

   The code prints 'name', which is "Alice". The constant 'Name' is not used in the puts statement.

3. Final Answer:

   Alice -> Option B

4. Quick Check:

   Local variable 'name' prints "Alice" [OK]

Hint: Local variables lowercase, constants uppercase; puts prints local variable [OK]

Common Mistakes:

• Confusing constants with local variables
• Assuming uppercase variable prints
• Ignoring case sensitivity

4. Identify the error in this Ruby code snippet:

def calculate
  total = 10
  Total = 20
  puts Total + total
end
calculate

medium

A. SyntaxError due to variable naming

B. Runtime error: undefined variable

C. No error, outputs 30

D. No error, outputs 10

Solution

1. Step 1: Analyze variable types and naming

   'total' is a local variable, 'Total' is a constant. Both are defined before use.

2. Step 2: Evaluate the expression in puts

   Adding 'Total' (20) and 'total' (10) results in 30. No syntax or runtime errors occur.

3. Final Answer:

   No error, outputs 30 -> Option C

4. Quick Check:

   Constant + local variable sums correctly [OK]

Hint: Constants uppercase, locals lowercase; both can be used together [OK]

Common Mistakes:

• Assuming case-insensitive variables
• Expecting syntax error from uppercase variable
• Confusing constants with local variables

5. You want to create a local variable to store a user's age in Ruby. Which of these variable names follows best naming conventions and is clear to other programmers?

hard

A. UserAge

B. userAge

C. user-age

D. user_age

Solution

1. Step 1: Check Ruby naming conventions for local variables

   Local variables should start with lowercase letters or underscores and use underscores to separate words for clarity.

2. Step 2: Evaluate each option for clarity and convention

   'user_age' uses lowercase and underscores, making it clear and conventional. 'UserAge' starts uppercase (looks like constant), 'user-age' has invalid hyphen, 'userAge' uses camelCase which is less common in Ruby.

3. Final Answer:

   user_age -> Option D

4. Quick Check:

   Use lowercase with underscores for clear local variables [OK]

Hint: Use lowercase and underscores for clear Ruby local variables [OK]

Common Mistakes:

• Using camelCase instead of snake_case
• Starting variable names with uppercase letters
• Using hyphens in variable names