When to use `self.foo` instead of `foo` in Ruby methods

Question

This is not specific for Rails - I am just using Rails as an example.

I have a model in Rails:

class Item < ActiveRecord::Base

  def hello
    p         


        

Answer 1

If you omit self Ruby will first look for local variables with that name, then for an instance method. It's not idiomatic to write self.. In any case, you have to write self.something = value on assignations.

Note that you cannot use self when calling private methods (no problem with protected methods):

class A
  def foo; self.bar; end

private

  def bar; "bar"; end
end

A.new.foo  
# private method `bar' called for # (NoMethodError)