aurelia-store

aurelia-store

Aurelia single state store based on RxJS.

Various examples can be found in the samples repository.

THIS IS WORK IN PROGRESS, DO NOT USE YET FOR PRODUCTION

Install

Install the npm dependency via

npm install aurelia-store

or via the CLI

au install aurelia-store

Aurelia CLI Support

If your Aurelia CLI build is based on RequireJS or SystemJS you can setup the plugin using the following dependency declaration:

au import aurelia-store

alternatively you can manually add these dependencies to your vendor bundle:

...
"dependencies": [
  {
    "name": "aurelia-store",
    "path": "../node_modules/aurelia-store/dist/amd",
    "main": "aurelia-store"
  },
  {
    "name": "rxjs",
    "path": "../node_modules/rxjs",
    "main": false
  }
]

Configuration

In your main.ts you'll have to register the Store using a custom entity as your State type:

import {Aurelia} from 'aurelia-framework'
import {initialState} from './state';

export function configure(aurelia: Aurelia) {
  aurelia.use
    .standardConfiguration()
    .feature('resources');

  ...

  aurelia.use.plugin("aurelia-store", { initialState });  // <----- REGISTER THE PLUGIN

  aurelia.start().then(() => aurelia.setRoot());
}

The state itself can be a simple object like this:

// state.ts
export interface State {
  frameworks: string[];
}

export const initialState: State = {
  frameworks: ["Aurelia", "React", "Angular"]
};

Usage

Once the plugin is installed and configured you can use the Store by injecting it via constructor injection.

You register actions (reducers) with methods, which get the current state and have to return the modified next state.

An example VM and View can be seen below:

import { autoinject } from 'aurelia-dependency-injection';
import { State } from './state';
import { Store } from "aurelia-store";

// An action is a simple function which gets the current state and should return a modified clone of it.
// You should not modify and return the previous state, as the states act as snapshots of your app over time
// which enables cool features like time-travelling, Redux DevTools integration and so on ...
const demoAction = (state: State) => {
  const newState = Object.assign({}, state);
  newState.frameworks.push("PustekuchenJS");

  return newState;
}

@autoinject()
export class App {

  public state: State;

  constructor(private store: Store<State>) {
    this.store.registerAction("DemoAction", demoAction);
  }

  attached() {
    // this is the single point of data subscription, the state inside the component will be automatically updated
    // no need to take care of manually handling that. This will also update all subcomponents.
    // Since the state is an observable you can use all kinds of RxJS witchcraft to skip,filter,map streamed states.
    this.store.state.subscribe(
      (state: State) => this.state = state
    );
  }

  addAnotherFramework() {
    // you create a new state by dispatching your action using the stores method
    this.store.dispatch(demoAction);
  }
}

<template>
  <h1>Frameworks</h1>

  <ul>
    <li repeat.for="framework of state.frameworks">${framework}</li>
  </ul>

  <button click.delegate="addAnotherFramework()">Add one more</button>
</template>

Dispatching unregistered actions will result in an error

In order to remove a registered action, simply call store.unregisterAction

...
store.unregisterAction(demoAction);

Execution order

If multiple actions are dispatched, they will get queued and executed one after another in order to make sure that each dispatch starts with an up to date state.

Passing parameters to actions

You can provide parameters to your actions by adding them after the state parameter. When dispatching provide your values which will be spread to the actual reducer.

// additional parameter
const greetingAction = (state: State, greetingTarget: string) => {
  const newState = Object.assign({}, state);
  newState.target = greetingTarget;

  return newState;
}

...

// dispatching with the value for greetingTarget
this.store.dispatch(greetingAction, "zewa666");

Dispatchifying actions

Perhaps you don't want or can't obtain a reference to the store but still would like to dispatch your actions. In order to do so you can leverage the higher order function dispatchify like this:

import { dispatchify } from "aurelia-store";
import { yourAction } from "./where/ever";

dispatchify(yourAction)("PARAM1", "MYPARAM2", "AND_SO_ON");

Undo / Redo support

If you need to keep track of the history of states you can provide additional options to setup the store to work on a StateHistory vs State model.

export function configure(aurelia: Aurelia) {
  aurelia.use
    .standardConfiguration()
    .feature('resources');

  ...

  const initialState: State = {
    frameworks: ["Aurelia", "React", "Angular"]
  };

  aurelia.use.plugin("aurelia-store", { initialState, history: { undoable: true } });  // <----- REGISTER THE PLUGIN WITH HISTORY SUPPORT

  aurelia.start().then(() => aurelia.setRoot());
}

Now when you subscribe to new state changes instead of a simple State you'll get a StateHistory object returned:

import {StateHistory} from "aurelia-store";
...

constructor(private store: Store<StateHistory<State>>) {
  this.store.registerAction("DemoAction", demoAction);
}

attached() {
  this.store.state.subscribe(
    (state: StateHistory<State>) => this.state = state
  );
}

A state history is an interface defining all past and future states as arrays of these plus a currently present one.

// aurelia-store -> history.ts
export interface StateHistory<T> {
  past: T[];
  present: T;
  future: T[];
}

Now keep in mind that every action will receive a StateHistory<T> as input and should return a new StateHistory<T>. You can use the nextStateHistory helper function to easily push your new state and create a proper StateHistory representation, which will simply move the currently present state to the past, place your provided one as present and remove the future states.

import { nextStateHistory } from "aurelia-store";

const greetingAction = (currentState: StateHistory<State>, greetingTarget: string) => {
  return nextStateHistory(currentState, { target: greetingTarget });
}

Which is the same as returing a handcrafted object like the following:

const greetingAction = (currentState: StateHistory<State>, greetingTarget: string) => {
  return Object.assign(
    {},
    currentState,
    { 
      past: [...currentState.past, currentState.present],
      present: { target: greetingTarget },
      future: [] 
    }
  );
}

Navigating through history

In order to do state time-travelling you can import the pre-registered action jump and pass it either a positive number for traveling into the future or a negative for travelling to past states.

import { jump } from "aurelia-store";

...
// Go back one step in time
store.dispatch(jump, -1);

// Move forward one step to future
store.dispatch(jump, 1);

Limiting the number of history items

Having too many items could result in a memory hit. Thus you can specify the limit for when the histories past and future start to overflow. That means your past and future arrays can hold only a max of the provided limit and new entries start to kick out respectively the first or last item of your history stacks.

...
// REGISTER THE PLUGIN WITH HISTORY SUPPORT AND OVERFLOW LIMIT OF 10
aurelia.use.plugin("aurelia-store", { initialState, history: { undoable: true, limit: 10 } });

Async actions

You may also register actions which resolve the newly created state with a promise. Same applies for history enhanced Stores. Just make sure the all past/present/future states by themselves are synchronous values.

Middleware

A middleware is similar to an action, with the difference that it may return void as well. Middlewares can be executed before the dispatched action, thus potentially manipulating the current state which will be passed to the action, or afterwards, thus modifying the returned value from the action. Either way the middleware reducer can be sync as well as async.

You register a middleware by it as the first parameter to store.registerMiddleware and the placement before or after as second.

const customLogMiddleware = (currentState) => console.log(currentState);
// In TypeScript you can use the exported MiddlewarePlacement string enum
store.registerMiddleware(customLogMiddleware, MiddlewarePlacement.After);

// in JavaScript just provide the string "before" or "after"
store.registerMiddleware(customLogMiddleware, "after");

In order to remove a registered middleware, simply call store.unregisterMiddleware

...
store.unregisterMiddleware(customLogMiddleware);

Additionally a middleware placed after the action might accept a second argument which reflects the current unmodified state, this means the one before any other middlewares or the result of the dispatched action. This can be useful to determine the state diff that happened in the middleware chain or to reset the next state at certain conditions.

...
const decreaseBefore = (currentState: TestState, originalState: TestState) => {
  const newState = Object.assign({}, currentState);
  newState.counter = originalState.counter;

  return newState;
}

Propagating errors

By default errors thrown by middlewares will be thrown in order to guarantee continues states. If you would like to stop state propagation you need to pass in the propagateError option:

aurelia.use.plugin("aurelia-store", { initialState, propagateError: true });

LocalStorage Middleware

Out of the box aurelia-store provides an localStorageMiddleware which stores your most recent emitted state in the window.localStorage. In order to make use of it all you need to do is to register it as usual:

import { localStorageMiddleware } from "aurelia-store";

...

store.registerMiddleware(localStorageMiddleware, MiddlewarePlacement.After);

Now in order to rehydrate the stored state all you need to do is to dispatch the provided rehydrateFromLocalStorage action:

import { rehydrateFromLocalStorage } from "aurelia-store";

...

store.registerAction("Rehydrate", rehydrateFromLocalStorage);
store.dispatch(rehydrateFromLocalStorage);

Performance measurement

In order to get insights in total run durations to effectively calculate and dispatch the next state you can pass in additional options in the plugin configuration section:

...
// typescript options (PerformanceMeasurement.All | PerformanceMeasurement.StartEnd)
aurelia.use.plugin("aurelia-store", { initialState, measurePerformance: PerformanceMeasurement.All });

// javascript options ("all" | "startEnd")
aurelia.use.plugin("aurelia-store", { initialState, measurePerformance: "all" });

You can choose between startEnd - which gets you a single measure with the duration - or all, which will provide you, besides the total duration, all single marks after every middleware and the actual dispatching.

Custom LogLevels

For various features, the plugin does create log statements if turned on. E.g the dispatch info of the currently dispatched action will log on an info level by default. Combining multiple of those features, might create an overflow of your console window. As such you can define the log level to be used per feature in the plugin init options. In the following example we'd like to have the logLevel for the dispatchAction info set to debug instead of the default info level:

// Available features
export interface LogDefinitions {
  performanceLog?: LogLevel;
  dispatchedActions?: LogLevel;
  devToolsStatus?: LogLevel;
}

// Available log levels

// Setup TypeScript
import { LogLevel } from "aurelia-store";
...
aurelia.use.plugin("aurelia-store", { initialState, history: {
  logDispatchedActions: true,
  logDefinitions: {
    dispatchedActions: LogLevel.debug
  }
}});

// Setup JavaScript
...
aurelia.use.plugin("aurelia-store", { initialState, history: {
  logDispatchedActions: true,
  logDefinitions: {
    dispatchedActions: "debug"
  }
}});

Acknowledgement

Thanks goes to Dwayne Charrington for his Aurelia-TypeScript starter package https://github.com/Vheissu/aurelia-typescript-plugin

Further info

If you want to learn more about state containers in Aurelia take a look at this article from Pragmatic Coder