rxjs-state

RxState is a light-weight reactive state management service especially useful for component state in SPAs.

Description

RxState is a light-weight reactive state management service which is especially useful to organize component state.

Angular version here

install

npm install --save rxjs-state

Setup

As the RxState class is just a plain vanilla Javascript Class

import { RxState } from 'rxjs-state';

interface MyState {
  foo: string;
  bar: number;
  loo: {
    boo: string;
    baz: number;
  };
}

const state = new RxState<MyState>();

API

setState

Add new slices to the state by providing an object

const state = new RxState<{ foo: string; bar: number }>();
state.setState({ foo: 'boo' });
// new state => { foo: 'boo' }

state.setState({ bar: 2 });
// new state => { foo: 'boo', bar: 2 }

Add new Slices to the state by providing a projection function

const state = new RxState<{ bar: number }>();

state.setState({ bar: 1 });
state.setState(currentState => ({ bar: currentState.bar + 2 }));
// new state => {bar: 3}

connect

Connect is one of the really cool thingy of this service. It helps to write the output of an Observable to the state and
handles subscription as well as unsubscription.

Connect to a single property

To understand that lets take a look at a normal implementation first:

const state = new RxState<{ bar: number }>();

const newBar$ = range(1, 5);
const subscription = newBar$.subscribe(bar => state.setState({ bar }));
subscription.unsubscribe();

Now lets compare that example with the connect usage:

state.connect('bar', newBar$);
// the property bar will get values 1, 2, 3, 4, 5

Connect multiple properties

const state = new RxState<{ foo: string; bar: number }>();

const slice$ = of({
  bar: 5,
  foo: 'foo'
});
state.connect(slice$);
// new state => { foo: 'foo', bar: 5}

select

Selecting state and extend the selection behavior with RxJS operators. Other state management libs provide selector functions like react. The downside is they are not compossable. RxState provides state selection fully reactive.

State is lazy!

State is lazy! If nothing is set yet, nothing will emit. This comes in especially handy for lazy view rendering!

const state = new RxState<{ foo: string; bar: number }>();

const bar$ = state.select();
bar$.subscribe(console.log);
// Never emits

Selecting the full state

const state = new RxState<{ foo: string; bar: number }>();

const bar$ = state.select();
bar$.subscribe(console.log);
// Does not emit
state.setState({ foo: 'boo' });
// emits { foo: 'boo'} for all old ane new subscriber

Access a single property

const state = new RxState<{ bar: number }>();
state.setState({ bar: 3 });

const bar$ = state.select('bar');
bar$.subscribe(console.log); // 3

Access a nested property

const state = new RxState<{ loo: { boo: number } }>();
state.setState({ loo: { boo: 42 } });

const boo$ = state.select('loo', 'boo');
boo$.subscribe(console.log); // '42'

Access by providing rxjs operators

const state = new RxState<{ loo: { bar: string } }>();
state.setState({ bar: 'boo' });

const customProp$ = state.select(map(state => state?.loo?.bar));
customProp$.subscribe(console.log); // 'boo'

const customProp$ = state.select(map(state => ({ customProp: state.bar })));
customProp$.subscribe(console.log); // { customProp: 'boo' }

hold

Managing side effects is core of every application. The hold method takes care of handling them.

It helps to handles subscription as well as unsubscription od side-effects

Hold a local observable side-effect

To understand that lets take a look at a normal implementation first:

const sideEffect$ = btnClick$.pipe(
  tap(clickEvent => this.store.dispatch(loadAction()))
);
const subscription = sideEffect$.subscribe();
subscription.unsubscribe();

If you would hold to achieve the same thing it would look like this:

state.hold(sideEffect$);

Connect an observable trigger and provide an project function

import { fromEvent } from 'rxjs/observable';
state.hold(btnClick$, clickEvent => console.log(clickEvent));