How to Use send Method in Ruby: Syntax and Examples

In Ruby, send lets you call a method on an object by its name as a symbol or string, even if the method is private. You use it like object.send(:method_name, args) to invoke the method dynamically.

Syntax

The send method calls another method on an object using the method's name as a symbol or string. You can also pass arguments to the method being called.

• object: The instance you want to call a method on.
• send: The Ruby method that invokes another method dynamically.
• method_name: The name of the method to call, given as a symbol or string.
• args: Optional arguments to pass to the method.

ruby

object.send(:method_name, arg1, arg2)

Example

This example shows how to use send to call a public method and a private method dynamically on an object.

ruby

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

  private

  def secret
    "This is a secret message."
  end
end

person = Person.new
puts person.send(:greet, "Alice")
puts person.send(:secret)

Output

Hello, Alice!
This is a secret message.

Common Pitfalls

Common mistakes when using send include:

• Using send with user input without validation can cause security risks by calling unintended methods.
• Trying to call methods that do not exist will raise a NoMethodError.
• For safer calls that respect method visibility, use public_send instead of send.

ruby

class Example
  def hello
    "Hi!"
  end
end

obj = Example.new

# Wrong: calling a non-existent method
# obj.send(:bye) # Raises NoMethodError

# Safer: use public_send to avoid calling private methods
obj.public_send(:hello) # Works
# obj.public_send(:private_method) # Raises NoMethodError if private

Quick Reference

Method	Description
send(:method_name, *args)	Calls any method, including private ones, with arguments.
public_send(:method_name, *args)	Calls only public methods, respecting visibility.
respond_to?(:method_name)	Checks if the object has the method before calling.

Key Takeaways

Use send to call methods dynamically by name, including private methods.

Always validate method names if they come from user input to avoid security risks.

Use public_send to call only public methods safely.

Calling a non-existent method with send raises a NoMethodError.

Check if an object responds to a method with respond_to? before using send.