Method chaining patterns in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to chain methods that convert a string to uppercase.

Ruby

"hello".[1]

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

Areverse

Bupcase

Cdowncase

Dcapitalize

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'downcase' which makes letters lowercase.

Using 'capitalize' which only changes the first letter.

The upcase method converts all letters in the string to uppercase.

2fill in blank

medium

Complete the code to chain methods that remove whitespace and then reverse the string.

Ruby

"  ruby  ".[1].reverse

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

Achomp

Bstrip!

Cstrip

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'strip!' which modifies the string in place and returns nil if no changes.

Using 'chomp' which removes newline characters only.

The strip method removes leading and trailing whitespace without changing the original string.

3fill in blank

hard

Fix the error in the method chain that tries to convert a string to an integer and then add 5.

Ruby

"10".[1] + 5

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

Ato_s

Bto_sym

Cto_f

Dto_i

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'to_s' which keeps it a string and causes an error when adding a number.

Using 'to_sym' which converts to a symbol, not a number.

The to_i method converts the string to an integer so you can add numbers.

4fill in blank

hard

Fill both blanks to chain methods that split a sentence into words and then sort them alphabetically.

Ruby

"hello world ruby".[1]([2]).sort

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

Asplit

B" "

C,

Djoin

Attempts:

3 left

💡 Hint

Common Mistakes

Using ',' as a separator which does not split words correctly.

Using 'join' which combines words instead of splitting.

The split method breaks the string into words using a space (" ") as the separator, then sort arranges them alphabetically.

5fill in blank

hard

Fill all three blanks to chain methods that remove vowels from a string, convert it to uppercase, and then reverse it.

Ruby

"example".[1]([2]).[3].reverse

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

Adelete

B"aeiou"

Cupcase

Ddowncase

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'downcase' instead of 'upcase' changes case incorrectly.

Not specifying vowels correctly in the delete method.

The delete method removes all vowels specified in "aeiou", then upcase converts the result to uppercase, and finally reverse reverses the string.

Practice

1. What is the main purpose of method chaining in Ruby?

easy

A. To call multiple methods on the same object in one line

B. To create new objects automatically

C. To run methods in parallel threads

D. To convert objects into strings

Solution

1. Step 1: Understand method chaining concept

   Method chaining allows calling several methods one after another on the same object without repeating the object name.

2. Step 2: Identify the main purpose

   The main goal is to write shorter, cleaner code by linking method calls in one line.

3. Final Answer:

   To call multiple methods on the same object in one line -> Option A

4. Quick Check:

   Method chaining = calling multiple methods on one object [OK]

Hint: Method chaining links calls on one object in one line [OK]

Common Mistakes:

• Thinking it creates new objects automatically
• Confusing with threading or parallel execution
• Believing it converts objects to strings

2. Which of the following is the correct syntax for method chaining in Ruby?

easy

A. object|method1|method2|method3

B. object.method1.method2.method3

C. object::method1::method2::method3

D. object->method1->method2->method3

Solution

1. Step 1: Recall Ruby method call syntax

   In Ruby, methods are called on objects using dot notation: object.method.

2. Step 2: Identify chaining syntax

   Method chaining uses multiple dots to call methods one after another on the same object.

3. Final Answer:

   object.method1.method2.method3 -> Option B

4. Quick Check:

   Ruby chaining uses dots between methods [OK]

Hint: Use dots (.) to chain methods in Ruby [OK]

Common Mistakes:

• Using arrows (->) which is not Ruby syntax
• Using double colons (::) which are for constants or modules
• Using pipes (|) which are not method call operators

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

class Box
  def initialize(value)
    @value = value
  end

  def add(x)
    @value += x
    self
  end

  def multiply(x)
    @value *= x
    self
  end

  def value
    @value
  end
end

box = Box.new(2)
result = box.add(3).multiply(4).value
puts result

medium

A. 20

B. 14

C. 10

D. 8

Solution

1. Step 1: Trace the add method

   Start with @value = 2. add(3) adds 3: 2 + 3 = 5, returns self.

2. Step 2: Trace the multiply method

   multiply(4) multiplies @value by 4: 5 * 4 = 20, returns self.

3. Step 3: Call value method

   value returns @value which is 20.

4. Final Answer:

   20 -> Option A

5. Quick Check:

   2 + 3 = 5; 5 * 4 = 20 [OK]

Hint: Follow each method step-by-step, remember self returns object [OK]

Common Mistakes:

• Forgetting that add and multiply return self
• Calculating operations in wrong order
• Returning intermediate values instead of final

4. Identify the error in the following Ruby code that tries to chain methods:

class Person
  def initialize(name)
    @name = name
  end

  def greet
    puts "Hello, #{@name}!"
  end

  def farewell
    puts "Goodbye, #{@name}!"
  end
end

p = Person.new("Sam")
p.greet.farewell

medium

A. initialize method missing return statement

B. farewell method is misspelled

C. Cannot create Person object with new

D. greet method does not return self, so chaining fails

Solution

1. Step 1: Check method return values

   greet prints a message but returns nil (default for puts).

2. Step 2: Understand chaining requirement

   For chaining, greet must return self to allow calling farewell next.

3. Final Answer:

   greet method does not return self, so chaining fails -> Option D

4. Quick Check:

   Method chaining needs methods to return self [OK]

Hint: Ensure methods return self to chain calls [OK]

Common Mistakes:

• Assuming puts returns self
• Thinking initialize needs explicit return
• Believing object creation is the problem

5. You want to create a Ruby class TextFormatter that allows chaining methods to transform a string. The methods are:
- upcase: converts text to uppercase
- reverse: reverses the text
- append(str): adds str to the end

Which implementation correctly supports chaining all these methods and returns the final string with result?

hard

A. Each method prints the modified string and returns nil

B. Each method returns the modified string directly without returning self

C. Each method modifies @text, returns self; add a result method returning @text

D. Each method returns a new TextFormatter object with modified text

Solution

1. Step 1: Understand chaining requirements

   To chain methods, each must return self (the object) so next method can be called.

2. Step 2: Provide final output method

   Since methods return self, a separate method (like result) should return the final string.

3. Final Answer:

   Each method modifies @text, returns self; add a result method returning @text -> Option C

4. Quick Check:

   Return self to chain, separate method to get final string [OK]

Hint: Return self in methods, separate method returns final value [OK]

Common Mistakes:

• Returning strings breaks chaining
• Printing inside methods returns nil
• Returning new objects breaks original chain