What does `send()` do in Ruby, and how is it used?

General Discussions
1

What does send() do in Ruby, and how is it used?

Can someone explain what the following snippet does?

obj.send("#{method_name}")

How does Ruby send work, and in what scenarios is it useful?

2

send() in Ruby is used to call a method dynamically by its name as a string or symbol. Instead of calling a method directly like obj.some_method, you can use obj.send(:some_method), which is particularly useful when the method name is stored in a variable.

For example:

class Greeting
  def hello
    "Hello, world!"
  end
end

g = Greeting.new
puts g.send(:hello)  # Outputs "Hello, world!"

This is the same as calling g.hello, but send lets you choose the method dynamically.

3

Using send() with Arguments : Another important use case for send() is when a method takes arguments. You can pass arguments after the method name:

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

math = MathOperations.new
puts math.send(:add, 2, 3)  # Outputs 5

This can be helpful when you don’t know beforehand which method needs to be called, such as when dynamically invoking methods in metaprogramming or when processing user input.

4

Both explanations are spot on! However, one thing to keep in mind is that send() can also invoke private methods, which isn’t always desirable:

class Secret
  private
  
  def hidden_message
    "This is private!"
  end
end

s = Secret.new
puts s.send(:hidden_message)  # Works, but bypasses privacy!

If you want to ensure only public methods are called, use public_send() instead:

s.public_send(:hidden_message) # Will raise an error since it's private

This makes the code safer and prevents accidentally calling internal methods.