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

It is idiomatic to prefer to omit self. when invoking methods; it is generally never needed.

You must use self.foo = xxx when calling a setter method, instead of foo = xxx, so that Ruby realizes that you are not trying create a new local variable.

• Similarly, in the unlikely event that you have an existing local variable do_something with the same name as a method, you must use self.do_something to invoke the method, as just do_something will end up reading the variable.

You cannot use self.foo(...) to call a private method; you must instead call just foo(...).