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why does Ruby throw warnings for private attributes

Take the example class:

# in ./example.rb
class Example
  private
    attr_accessor :name
end

When I run it in verbose mode, Ruby throws warnings at me:

$ ruby -W2 ./example.rb
example.rb:3: warning: private attribute?

Why is this not recommended?

Solution

  • Because it doesn't make much sense to define a getter/setter that is not visible from the outside in most cases. We generally use attr_accessor only to expose an instance variable outside of the class. However, the private keyword defeats this purpose by making the generated getter/setter methods invisible to the outside world.

    The only reason you would want to use a private setter/getter is when there is some additional logic involved. In this case, however, you would have to define those methods manually with def, anyway.