Is_a? and kind_of? for type checking in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the variable obj is a String using is_a?.

Ruby

obj = "hello"
puts obj.[1](String)

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

Ais_a?

Bkind_of?

Cinstance_of?

Dclass

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'instance_of?' which only checks exact class, not subclasses.

Using 'class' which returns the class object, not a boolean.

The is_a? method checks if an object is an instance of a class or its subclass. Here, obj.is_a?(String) returns true because obj is a String.

2fill in blank

medium

Complete the code to check if num is a Numeric type using kind_of?.

Ruby

num = 42
if num.[1](Numeric)
  puts "It's a number!"
end

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

Ais_a?

Binstance_of?

Ckind_of?

Drespond_to?

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'instance_of?' which does not consider subclasses.

Using 'respond_to?' which checks for methods, not class type.

The kind_of? method checks if an object is an instance of a class or its subclass. Here, num.kind_of?(Numeric) returns true because 42 is a Numeric.

3fill in blank

hard

Fix the error in the code to correctly check if arr is an Array using is_a?.

Ruby

arr = [1, 2, 3]
if arr.[1](Array)
  puts "It's an array!"
end

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

Ais_a

Bis_a?

Ckind_of?

Dkind_of

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the question mark in the method name.

Using 'kind_of' without question mark.

The method is_a? must include the question mark. Without it, Ruby raises a NoMethodError.

4fill in blank

hard

Fill both blanks to create a method that returns true if obj is a String or a subclass of String.

Ruby

def string_check(obj)
  obj.[1](String) || obj.[2](String)
end

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

Ais_a?

Binstance_of?

Ckind_of?

Dclass

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'instance_of?' which only checks exact class.

Using 'class' which returns the class object, not a boolean.

Both is_a? and kind_of? check if an object is an instance of a class or its subclass. Using either returns true for String or its subclasses.

5fill in blank

hard

Fill all three blanks to create a hash that maps objects to their type check results using is_a? and kind_of?.

Ruby

obj1 = [1, 2, 3]
obj2 = {a: 1}
obj3 = "test"
results = {
  obj1: obj1.[1],
  obj2: obj2.[2](Hash),
  obj3: obj3.[3](String)
}

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

Ais_a?

Bkind_of?

Cinstance_of?

Dclass

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'instance_of?' which does not consider subclasses.

Using 'class' expecting a boolean result.

Here, obj1.class returns the class of obj1, which is truthy but not a boolean. obj2.kind_of?(Hash) and obj3.is_a?(String) correctly check type including subclasses.