gem install rails

bundle install

bundle exec rake db:migrate

rails s

Dynamic Dispatch

example 1

class Dog
  def bark
    puts "Woof, woof!"
  end
  def greet(greeting)
    puts greeting
  end
end

so:

dog = Dog.new
dog.bark # => Woof, woof!
dog.send("bark") # => Woof, woof!
dog.send(:bark) # => Woof, woof!

method_name = :bark
dog.send method_name # => Woof, woof!

dog.send(:greet, "hello") # => hello

example 2

irb

props = { name: "John", age: 15 }
=> {:name=>"John", :age=>15}

class Person
  attr_accessor :name, :age
end
=> nil

person = Person.new
=> #<Person:0x007f8d1c24b908>

props.each { |key, value| person.send("#{key}=", value)}
=> {:name=>"John", :age=>15}

person
=> #<Person:0x007f8d1c24b908 @name="John", @age=15>

Dynamic Methods

class Whatever
  define_method :make_it_up do
    puts "Whatever..."
  end
end

whatever = Whatever.new
whatever.make_it_up # => Whatever...