Send for calling methods dynamically in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby code using send?

Consider the following Ruby code snippet:

class Calculator
  def add(a, b)
    a + b
  end
end

calc = Calculator.new
result = calc.send(:add, 5, 7)
puts result

What will be printed when this code runs?

Ruby

class Calculator
  def add(a, b)
    a + b
  end
end

calc = Calculator.new
result = calc.send(:add, 5, 7)
puts result

A nil

B 57

C Error: undefined method 'add'

D 12

💡 Hint

Remember that send calls the method named by the symbol with given arguments.

The send method calls add with arguments 5 and 7, so it returns 12.

❓ Predict Output

intermediate

What error does this code raise when using send with a private method?

Look at this Ruby code:

class Secret
  private
  def whisper
    "secret message"
  end
end

s = Secret.new
puts s.send(:whisper)

What will happen when this code runs?

Ruby

class Secret
  private
  def whisper
    "secret message"
  end
end

s = Secret.new
puts s.send(:whisper)

A secret message

B NoMethodError

C ArgumentError

D NameError

💡 Hint

Does send allow calling private methods?

send can call private methods, so it prints "secret message".

🔧 Debug

advanced

Why does this send call raise an error?

Examine this Ruby code:

class Person
  def greet(name)
    "Hello, #{name}!"
  end
end

p = Person.new
p.send(:greet)

Why does this code raise an error?

Ruby

class Person
  def greet(name)
    "Hello, #{name}!"
  end
end

p = Person.new
p.send(:greet)

A TypeError because send cannot call instance methods

B ArgumentError because greet expects 1 argument but none given

C SyntaxError due to missing parentheses

D NoMethodError because greet is private

💡 Hint

Check the method parameters and how send is called.

The method greet requires one argument, but send was called without any arguments, causing an ArgumentError.

🧠 Conceptual

advanced

Which option correctly uses send to call a method with a block?

Given this Ruby code:

class Repeater
  def repeat(times)
    result = []
    times.times { result << yield }
    result
  end
end

r = Repeater.new

Which send call correctly invokes repeat with argument 3 and a block that returns "hi"?

A r.send(:repeat, 3) { "hi" }

B r.send(:repeat) { 3; "hi" }

C r.send(:repeat, 3, &proc { "hi" })

D r.send(:repeat, 3, block: -> { "hi" })

💡 Hint

How do you pass a block to a method called by send?

You can pass a block directly after the send call, like in option A.

❓ Predict Output

expert

What is the output of this dynamic method call with method_missing?

Consider this Ruby code:

class Dynamic
  def method_missing(name, *args)
    "Called #{name} with #{args.join(", ")}"
  end
end

d = Dynamic.new
puts d.send(:hello, 1, 2, 3)

What will be printed?

Ruby

class Dynamic
  def method_missing(name, *args)
    "Called #{name} with #{args.join(", ")}"
  end
end

d = Dynamic.new
puts d.send(:hello, 1, 2, 3)

A NoMethodError

B ArgumentError

C Called hello with 1, 2, 3

D nil

💡 Hint

What happens when a method is missing and send is used?

The method_missing method catches calls to undefined methods, so it returns the formatted string.