Ruby - attr_accessor

class Person
  attr_accessor :name

  def greeting
    "Hello #{@name}"
  end
end

person = Person.new
person.name = "Dennis"
person.greeting # => "Hello Dennis"

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1865down voteaccepted

Let's say you have a class Person. class Person end person = Person.new person.name # => no method error Obviously we never defined method name. Let's do that. class Person def name @name # simply returning an instance variable @name end end person = Person.new person.name # => nil person.name = "Dennis" # => no method error Aha, we can read the name, but that doesn't mean we can assign the name. Those are two different methods. The former is called reader and latter is called writer. We didn't create the writer yet so let's do that. class Person def name @name end def name=(str) @name = str end end person = Person.new person.name = 'Dennis' person.name # => "Dennis" Awesome. Now we can write and read instance variable @name using reader and writer methods. Except, this is done so frequently, why waste time writing these methods every time? We can do it easier. class Person attr_reader :name attr_writer :name end Even this can get repetitive. When you want both reader and writer just use accessor! class Person attr_accessor :name end person = Person.new person.name = "Dennis" person.name # => "Dennis" Works the same way! And guess what: the instance variable @name in our person object will be set just like when we did it manually, so you can use it in other methods. class Person attr_accessor :name def greeting "Hello #{@name}" end end person = Person.new person.name = "Dennis" person.greeting # => "Hello Dennis" That's it. In order to understand how attr_reader, attr_writer, and attr_accessor methods actually generate methods for you, read other answers, books, ruby docs. https://stackoverflow.com/questions/4370960/what-is-attr-accessor-in-ruby