Add method to an instanced object

Question

obj = SomeObject.new

def obj.new_method
  \"do some things\"
end

puts obj.new_method
> \"do some things\"

This works ok. However, I need to do

Answer 1

Use instance_eval:

obj = SomeObject.new

obj.instance_eval do
  def new_method
    puts 'do something new'
  end
end

obj.new_method 
> "do something new"