karma

by cgarciae

cgarciae / karma

An MVC framework for Unity3D

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What is Karma?

MVC Framework for Unity3D

Karma is an MVC framework for Unity3D. Because of how Unity is structured, it actually turns out to be an MVCP architecture (Model/View/Controller/Presenter) where the Presenter is a MonoBehaviour that serves as an intermediary between the Controller and the View. You can read more about this in MODEL VIEW CONTROLLER PATTERN FOR UNITY3D USER INTERFACES.

Based on Zenject

It's built on top of Zenject which provides Dependency Injection (DI). DI is mainly used to route the app to the desired view, it also enables us to build composable and testable systems.

Inspired by AngularJS and ASP vNext

Some of the basic constructs and code layout is inspired by other MVC frameworks such as AngularJS and ASP vNext.

Note to Game Developers

Karma uses concepts like views and presenters instead of

scenes
. The problem with scenes is that they are too heavy weight, there is no good way to communicate between them, changing scenes is slow (especially if you are doing UI stuff), and they aren't composable. The "Karmic" way of doing a game would be to store each level/scene in a prefab, treat it as a MVC View, store all your characters/entities in separate prefabs, and get them instantiated onto the level's view through DI.
Simple Routing System

Karma has a built in routing system that enables you to create isolated views/scenes as prefabs and easily switch between them. Using an

http-like
flow, a presenter can
Request
the
router
to render another view.
As Stateless as possible

Karma aims to be as stateless as possible to try to give you the guarantee that if you entered a view once with certain

Request
parameters and reached a successful state, then you will always reach that same state if you pass the the same parameters. Unity3D doesn't provide by default a best practice changing from a view to another. A common way to do this is to have all possible views instantiated in the scene but only enable the current one, the problem is that you maintain state when reusing Game Objects and often end in bad states because of the many paths you need to account for. Karma keeps things simple and functional by just destroying the current view and instantiates a new next view when changing views.
Message Passing

In Karma state is mainly maintained through message passing, being as true as possible to Go's philosophy:

Don't communicate by sharing memory; share memory by communicating.

The added benefit of this is that views become configurable without depending on local storage or static variables, is in turn is very important to keep a system testable.

Pub/Sub System

All

Presenters
integrate a pub/sub system that enables the communication between entities on different branches and levels in the dependency hierarchy. It's a simple yet powerful message passing mechanism on channels by topic where any
Presenter
can subscribe and broadcast. By convention the top level application is used as the main channel.
Folder Structure + Conventions

As many MVC frameworks, Karma tries to keep the developers sane by establishing conventions. Among these conventions are the folder structure, concepts (presenters, controllers, services, etc), code organization, a configuration mechanism (dev, prod, test environments).

Parts

  • Views
    • Plain old prefabs
  • Presenters
    • Handle the presentation layer
    • Extend MonoBehaviour
    • Are tied to a Prefab
    • Get instantiated on Game Objects
    • Integrate a Pub/Sub mechanism
    • Are Transient
    • Are divided as:
      • Plain Presenter (Routable)
      • Elements (Reusable)
      • Layouts (Provide context)
  • Controllers
    • Handle the logic layer
    • Don't extend MonoBehaviour
    • Are Transient
    • Are 100% testable
    • Are usually coupled to a Presenter
  • Services
    • Handle Resources
    • Should be Stateless
    • Are Singleton
    • Usually handle communication with a server on a particular resource, local storage, specialized logic for e.g. handling certain user inputs, etc.
  • Applications
    • Handle general configuration
    • Are Presenters
    • Contain the current view
    • Can be nested to create subviews
  • Router
    • Belongs to a specific Application
    • Tells the application which view to render next
    • Can store request history
  • Middleware
    • Each application can configure its one pipeline
    • Each middleware can modify the
      Request
      and
      Response
    • Enables to e.g. create an authentication layer separate from the view itself
    • It's asynchronous so e.g. http requests can be made to the server to get extra information

Why Karma?

Unity3D doesn't give much structure

While good developers do follow certain conventions, new developers struggle to keep their project in order. Karma provides conventions for both code structure and folder organization so you can keep your project clean and productive.

Composable elements

Mainly thanks to Zenject, with Karma you can create composable elements that you can reuses through your application. Defining you all the components in your view/level directly in the hierarchy, with Karma you define each subcomponent in a separate prefab with their own presenter, and get them to you current view through DI. This way you avoid these common problems: * Finding components in hierarchy (you can stop abusing

GameObject.Find
) * Having to update prefabs that are also nested in other prefabs
Testable components

One of the major goals of Karma is testability. This is achieved through these mechanisms:

  1. Configurable transient views
  2. POCO
    Controllers
    and
    Services
    that are 100% mockable
  3. Dependency Injection

Getting Started

Sample Project

The easiest way to get started is to clone this repository and open it with Unity3D. It contains a sample project layout with an

Application
,
Presenter
,
Controller
and a
Service
. Just
git clone https://github.com/cgarciae/karma.git

and open the

karma
folder with Unity3D. Then open the scene
/Assets/App/App.unity
and hit play!
Integrating it with your project

The easiest way to integrate Karma with your own project is to clone this repo with

git clone https://github.com/cgarciae/karma.git

and then copy the folders

/Assets/App
and
/Assets/Lib
to your project.
Zenject Contexts

Karma was built to work without any other library-specific stuff, like Zenject Contexts - and by default this means that contexts are wiped. To use your Zenject context features, like installers, scene persistent objects, etc. you need to enable the

Use Zenject Context
checkbox, which you will find on your
Karma App
gameobject (using the Unity Editor).
Videos
Hello World

Hello World

Dependency Injection

Dependency Injection

Pub Sub

Pub Sub

Guides

Coming soon!

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