After checking each time, it will remain vague, so write it down as a memorandum.

Overview

attr_reader

Define a method to read the instance variable name.

Source: https://docs.ruby-lang.org/ja/latest/method/Module/i/attr_reader.html

class Human
  #Defined here
  attr_reader :name

  def initialize(name)
    @name = name
  end
end

#Instantiate from here

human1 = Human.new(sato)
p human1.name
# => sato

attr_writer

Define a write method (name =) to the instance variable name.

Source: https://docs.ruby-lang.org/ja/latest/class/Module.html#I_ATTR_ACCESSOR


class Human
  #Defined here
  attr_writer :name

  def initialize(name)
    @name = name
  end
end

#Instantiate from here

human1 = Human.new(sato)

#attr_Readable thanks to render
p human1.name
# => sato

#attr_Can be changed thanks to writer
human1.name = 'kato'

#The value has changed
p human1.name
# => kato

attr_accessor

It has two functions, attr_reader and attr_writer.

[Ruby] Forget what attr_reader, attr_writer, attr_accessor are doing many times

Overview