Open classes (reopening classes) in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to reopen the String class and add a method.

Ruby

class String
  def [1]
    "Hello, " + self
  end
end

puts "World".greet

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

Agreet

Bhello

Csay_hello

Dgreeting

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name different from the one called on the string.

Forgetting to reopen the class before defining the method.

The method 'greet' is added to the String class and called on the string "World".

2fill in blank

medium

Complete the code to reopen the Integer class and add a method that doubles the number.

Ruby

class Integer
  def [1]
    self * 2
  end
end

puts 5.double

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Amultiply

Btwice

Ctimes_two

Ddouble

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name that does not match the call.

Not returning the correct calculation.

The method 'double' is added to Integer and returns the number multiplied by 2.

3fill in blank

hard

Fix the error in reopening the Array class to add a method that returns the first element doubled.

Ruby

class Array
  def double_first
    [1] * 2
  end
end

puts [1, 2, 3].double_first

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Afirst()

Bself[0]

Cself.first

Dself[1]

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'self[1]' which accesses the second element.

Using 'first()' without 'self'.

Using 'self.first' correctly accesses the first element of the array.

4fill in blank

hard

Fill both blanks to reopen the Hash class and add a method that returns keys with values greater than 10.

Ruby

class Hash
  def keys_with_large_values
    select { |[1], [2]| [2] > 10 }.keys
  end
end

puts({a: 5, b: 15, c: 20}.keys_with_large_values)

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Akey

Bvalue

Ck

Dv

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'key' and 'value' which are valid but not the correct answer here.

Mixing up the order of key and value.

The block variables 'k' and 'v' represent key and value respectively in the Hash select method.

5fill in blank

hard

Fill all three blanks to reopen the Numeric class and add a method that returns the number squared if positive, else zero.

Ruby

class Numeric
  def positive_square
    if [1] > 0
      [2] [3] 2
    else
      0
    end
  end
end

puts 4.positive_square
puts (-3).positive_square

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Aself

C**

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*' instead of '**' for squaring.

Not using 'self' to refer to the number.

Check if 'self' is positive, then return 'self ** 2' (square). The '*' operator is incorrect for exponentiation.