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I have understood the basics of decorators and mixins. Decorators add a new functionality to an object without changing other object instances of the same class, while a mixin is a kind of multiple inheritance used to inherit from multiple parent classes.
Does it mean that decorators should be used when you'd need to modify only a single object instance and use mixins when you'd need a whole new class of objects. Or, is there something more to it that I might be missing? What can be real life use cases for both?
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A decorator is a design pattern in Python that allows a user to add new functionality to an existing object without modifying its structure. Decorators are usually called before the definition of a function you want to decorate.
When to Use a Decorator in Python. You'll use a decorator when you need to change the behavior of a function without modifying the function itself. A few good examples are when you want to add logging, test performance, perform caching, verify permissions, and so on.
A mixin is a class that provides method implementations for reuse by multiple related child classes. However, the inheritance is not implying an is-a relationship. A mixin doesn't define a new type. Therefore, it is not intended for direction instantiation.
Mixins encourage code reuse and can be used to avoid the inheritance ambiguity that multiple inheritance can cause (the "diamond problem"), or to work around lack of support for multiple inheritance in a language. A mixin can also be viewed as an interface with implemented methods.
In my opinion, you need mixins when you have a few different classes that should have same functionality.
Good examples of using mixins are Django's class-based views. For example, you have a few different classes: FormView, TemplateView, ListView. All of them have one similar piece of functionality: they have to render templates. Every one of these classes has a mixin, which adds methods required for template rendering.
Another example is if you needed to add a class for an API that returns a JSON result. It could also be inherited from a base, View class. You simply skip template mixins, and define what you need (and probably write your own mixin for JSON encoding).
Additionally, you may override some of methods proposed in mixins which allow you to modify some parts of common code for your local case. It's all about OOP, buddy!
Long story short: mixins add new functionalities.
Decorators are used to modify existing functionalities. For example, if you need to log what is returned from a method in your class. The right choice here is a decorator (added to appropriate methods).
Hope it is helpful. If not, please ask questions. I will update my response.
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