Using send and eval

Ruby provides powerful methods like send and eval to dynamically execute code.

These methods allow calling methods dynamically and evaluating Ruby expressions at runtime.

What is the send Method?

send allows calling methods dynamically by name.

It can invoke private and public methods.

class Person
  def greet
    'Hello!'
  end
end

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

Using send with Arguments

send can pass arguments to methods dynamically.

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

p = Person.new
puts p.send(:greet, 'Alice')

Calling Private Methods with send

send can bypass method visibility rules and call private methods.

class Person
  private
  def secret
    'This is a secret!'
  end
end

p = Person.new
puts p.send(:secret)

What is the eval Method?

eval executes a string as Ruby code at runtime.

code = "5 + 10"
puts eval(code) # Outputs: 15

Executing Dynamic Code with eval

eval can dynamically define variables and execute expressions.

eval("x = 100")
puts x

Defining Methods with eval

Use eval to define methods dynamically.

eval("def dynamic_method; 'Hello from eval'; end")
puts dynamic_method

Security Risks of send and eval

Using send and eval improperly can introduce security risks:

• eval can execute untrusted code, leading to security vulnerabilities.
• send can call private or sensitive methods.
• Use them cautiously to avoid unintended behavior.

Congratulations!

You have learned how to use send and eval for dynamic method execution.

This concludes the Metaprogramming in Ruby section.