Class: WhyClasses::Rules::InheritanceForMixins

Inherits:
WhyClasses::Rule show all
Defined in:
lib/why_classes/rules/inheritance_for_mixins.rb

Overview

Thomas criticises inheriting from a fat base class purely to inject behaviour (e.g. < ActiveRecord::Base pulls in hundreds of methods) rather than to specialise. Advice-only: safe rewriting needs whole-program knowledge of which inherited methods are actually used.

Constant Summary

Constants inherited from WhyClasses::Rule

WhyClasses::Rule::H

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from WhyClasses::Rule

autocorrectable?, #call, inherited, #initialize, rule_name

Constructor Details

This class inherits a constructor from WhyClasses::Rule

Class Method Details

.description ⇒ Object 



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# File 'lib/why_classes/rules/inheritance_for_mixins.rb', line 12

def self.description
  "Inheriting a fat base class to inject methods -> include only the mixins you use."
end

Instance Method Details

#on_class(node) ⇒ Object 



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# File 'lib/why_classes/rules/inheritance_for_mixins.rb', line 16

def on_class(node)
  return unless rails?

  s = shape(node)
  return if s.name.nil?
  return unless s.superclass?

  mixins = configuration.mixin_suggestions_for(s.superclass)
  return if mixins.nil?

  add_offense(
    node,
    message: "#{s.name} < #{s.superclass} inherits a large surface just to gain behaviour.",
    suggestion: "If you only need part of it, include the specific mixins instead:\n" \
                "    class #{s.name}\n" +
                mixins.map { |m| "      include #{m}" }.join("\n") +
                "\n    end\n  Inherit only when you are genuinely specialising #{s.superclass}."
  )
end