Inheritance, Composition, and Mixins

• These are all forms of code organization and reuse
• Ways of DRYing up your code so you're not copy pasting
• Each form is good for different use cases of modeling real world stuff
• Each form has trade-offs

Inheritance

• hierarchy of types
• is-a relationship, is-a-type-of
• specialization, refinement, customization
• provides implicit behavior, overriding behavior, altering behavior
• super keyword
• interpreter searches up the class chain for an implementation of a method

Composition

• ownership
• has-a relationship
• dependency injection

Mixins

• accomplished through the use of modules or classes
• acts-like relationship or takes the role of or a concern
• adjective names vs. noun names typical of a class
• using a module vs. using a class
  • a class has an instance and models a real world thing
  • a class can only have one superclass, but mixin as many modules as it wants
  • include keyword
• duck typing

Conclusion

• Read POODIR!
• Read The Well Grounded Rubyist!