README
Viewless, Action Driven Architecture
Getting
You can install this module using npm
with:
npm install vada
User's Guide
Routing
To create routes (or more specifically, RouteId
instances), just
declare them as follows:
export const main = new vada.RouteId<{}>("main");
export const search = new vada.RouteId<{term: string}>("search");
Background
While both migrating existing applications and creating new ones,
incorporating redux
and react
into my applications has pushed me
toward an approach that takes a hard line in the separation of view
from application logic.
My main motivation was around making testing as easy as possible. My
goal was to create applications where the view was completely external
to the application (hence the term "viewless"). Following this
approach, the flow of the application is entirely described via a
redux
store and actions dispatched against that store (hence the
term "action driven").
Another motivation behind this module, which is probably not of much interest to the larger Javascript development community, was to provide type constraints around many of these patterns. So if you use TypeScript, you can benefit from my efforts to include as many type constraints as possible. But the module should still be useful for ordinary Javascript developers as well.
This repository implements several patterns that I found useful in trying to achieve these goals. There are three main pieces of functionality that this library provides...
Routing
The first challenge I ran into was how to provide routing without
involving a view. Libraries like
UI-router and
react-router
are widely
used and well engineered approaches to routing. However, they both
integrate with the view to provide their functionality. So I wanted
to create an alternative approach. There are several viewless routing
tools and I've chosen to build my approach on top of
crossroads. But the
contribution of this library is to connect crossroads
with a set of
actions that can be used to manipulate application state contained in
a redux
store so that the entire collection of routes associated
with an application can be completely external to the view.
My initial goal with this approach was to migrate code from angular
to react
by externalizing all the routing specific code from any
particular view framework. But just as important, this view agnostic
approach means that applications can be written independent of a
particular view framework. This means that the same application code
could be used across desktop, web and mobile applications. In other
words, by keeping as much logic as possible out of the view, it makes
it easier to reuse application code between web and mobile versions.
It should be noted that if you are working with TypeScript, these implementations also provide some type constraints that help to ensure that route parameters can be statically checked at compile time.
Reactors
In trying to improve application testing, I wanted to see how far I
could push logic out of my view. My goal was to be able to go back to
doing testing with simple tools like mocha
instead of having to
build up tests that used tools like PhantomJS, etc. to actually
traverse my UI. I find the UI design is too fluid to build testing
on. But the underlying application structure can be relatively
invariant.
The obstacle here is that it is so common and relatively convenient to embed logic in a view. But I think this is actually unwise for many reasons. Not only does it mix view and application logic in such a way that the view must become part of the testing. It also makes it difficult to modularize the application.
So I wanted to get the application logic out of my view. But the
question was...where to put it? What form should this logic take and
how can I incorporate it into applications? I was inspired by
this article
on Actors. But I found the implementation to be problematic. So I
came up with a similar approach that I called reactors
. The re
prefix applies on several levels. First, this pattern provides a way
to react to changes in the application state unilaterally. Second,
the functionality itself is not associated with the redux
store, but
rather with the reducer. Finally, I find that it really helps keep
the actions simple and reusable while providing a way to extend the
application with additional functionality.
Operations
I think redux
is a great way to incorporate state monads into
Javascript applications. I think @gaeron has done a great job of
keeping the API clean, simple and composable. What I've tried to do
with the concept of operations is to build on those basic abstractions
the ability to create both actions and reducers in a way that is more
natural to me. In a typical redux
application you'll find both a
reducers.js
file and actions.js
file. One defines the identities
of the actions and other provides the effect of the actions.
I find it a bit confusing to keep these two things segregated. So I created a reducer implementation that allows me to combine the actions and effects into what I call an operation. This allows me to define everything in one place. I've also incorporated a scheme for generating unique action names so as to avoid action naming conflicts. Finally, if you are working with TypeScript, of providing some nice type constraints for type checking action payloads.
Additional Functionality
This module represents the core functionality for creating an
application where logic is decoupled from the view. As such, to
connect a vada
application to a particular view, some additional
functionality is required. The following modules build upon the
functionality defined by vada
.
vada-react
- Functionality to help syncronizereact
based applications tovada
application state.vada-browser
- This module is for browser based application and it ties the browser's currentwindow.location
to routes defined usingvada
.
TODO
More tests, more docs, more feedback.