@airma/react-state v18.4.3

@airma/react-state

Simple reducer-like state-management with method action dispatch mode for react components.

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Code first

Create reducer-like function:

export function counting(state:number){
    return {
        // reproduced state for render
        count: `mount: ${state}`,
        // action method
        increase:()=>count + 1,
        // action method
        decrease:()=>count - 1,
        // action method, define parameters freely.
        add(...additions: number[]){
            return additions.reduce((result, current)=>{
                return result + current;
            }, count);
        }
    };
}

Use reducer-like function:

import {counting} from './model';
import {useModel} from '@airma/react-state';

......
// give it an initialState can make it fly.
const {count, increase, decrease, add} = useModel(counting, 0); // initialState `0`
// call method `increase\decrease\add` can change `count` and make component rerender
......

The reducer-like function has a simple name model. Use API model can make it more simple.

Local state management

import {model} from '@airma/react-state';

// api model returns a wrap function for your model function.
// it keeps a same type of parameters and return data with the wrapped function.
const counting = model(function counting(state:number){
    return {
        count: `mount: ${state}`,
        increase:()=>count + 1,
        decrease:()=>count - 1,
        add(...additions: number[]){
            return additions.reduce((result, current)=>{
                return result + current;
            }, count);
        }
    };
});
......
// you can get useModel from the model wrapped function.
const {count, increase, decrease, add} = counting.useModel(0);
......

Though, the basic function about model is enhancing React.useReducer to manage a local state, it also supports store usage with or without React.Context to manage a global state.

React.Context state management

import {memo} from 'react';
import {model} from '@airma/react-state';

const countingStore = model(function counting(state:number){
    return {
        count: `mount: ${state}`,
        increase:()=>count + 1,
        decrease:()=>count - 1,
        add(...additions: number[]){
            return additions.reduce((result, current)=>{
                return result + current;
            }, count);
        }
    };
}).createStore(0);
......
const Increase = memo(()=>{
    // use store.useSelector can share state changes from store,
    // when the selected result is changed it rerender component. 
    const increase = countingStore.useSelector(i => i.increase);
    return <button onClick={increase}>+</button>;
});
const Count = memo(()=>{
    // use store.useModel can share state changes from store.
    const {count} = countingStore.useModel();
    return <span>{count}</span>;
});
const Decrease = memo(()=>{
    const decrease = countingStore.useSelector(i => i.decrease);
    return <button onClick={decrease}>-</button>;
});
// provide store to component for a React.Context usage.
const Component = countingStore.provideTo(function Comp() {
    return (
        <div>
            <Increase/>
            <Count/>
            <Decrease/>
        </div>
    );
});
......

Using model(xxx).createStore().asGlobal() can build a global store.

Global state management

import {model} from '@airma/react-state';

const countingStore = model(function counting(state:number){
    return {
        count: `mount: ${state}`,
        increase:()=>count + 1,
        decrease:()=>count - 1,
        add(...additions: number[]){
            return additions.reduce((result, current)=>{
                return result + current;
            }, count);
        }
    };
}).createStore(0).asGlobal();
// `createStore(0).static()` is same with `createStore(0).asGlobal()`.
......
const Increase = memo(()=>{
    const increase = countingStore.useSelector(i => i.increase);
    return <button onClick={increase}>+</button>;
});
const Count = memo(()=>{
    const {count} = countingStore.useModel();
    return <span>{count}</span>;
});
const Decrease = memo(()=>{
    const decrease = countingStore.useSelector(i => i.decrease);
    return <button onClick={decrease}>-</button>;
});
// use global store without provider.
const Component = function Comp() {
    return (
        <div>
            <Increase/>
            <Count/>
            <Decrease/>
        </div>
    );
};

The useSelector API is helpful for reducing render frequency, only when the selected result is changed, it make its owner component rerender.

A high performance usage about useSignal

In @airma/react-state@18.4.0, a more simple and higher performance API useSignal is provided.

import {model} from '@airma/react-state';

const counting = model(function countingModel(state:number){
    return {
        count: `mount: ${state}`,
        increase:()=>count + 1,
        decrease:()=>count - 1,
        add(...additions: number[]){
            return additions.reduce((result, current)=>{
                return result + current;
            }, count);
        }
    };
}).createStore().static();
// Give initialized state later in component render time.
......
const Increase = memo(()=>{
    // API `useSignal` returns a signal function,
    // which can be called to get the newest instance from store.
    // Only the render usage fields of this instance change makes component rerender.
    // Here, only the action method `increase` from instance is required, and as the action method is stable with no change, that makes component never rerender.
    const signal = counting.useSignal();
    return <button onClick={signal().increase}>+</button>;
});

const Count = memo(()=>{
    const signal = counting.useSignal();
    return <span>{signal().count}</span>;
});

const Decrease = memo(()=>{
    const signal = counting.useSignal();
    return <button onClick={signal().decrease}>-</button>;
});

const Component = function Comp({defaultCount}:{defaultCount:number}) {
    // API `useSignal` can initialize store state in render too.
    // The difference with `useModel` is that `useSignal` only rerenders component when the render usage fields of instance changes.
    counting.useSignal(defaultCount);
    return (
        <div>
            <Increase/>
            <Count/>
            <Decrease/>
        </div>
    );
};

The useSignal API is even better than API useSelector, it computes out when to rerender component by the fields getting from instance automatically. And by using the signal function, it always provides a newest instance in usage point, so it can avoid stale data and zombie-children problems more effectively.

Why support context store?

In @airma/react-state, store is dynamic, every provider copies a working instance for a context usage.

That means:

1. The store data can be destroyed with its provider component unmount.

2. Components with same store provider can be used together in one parent component without state change effect to each other.

   How to subscribe a grand parent provider store?

   The store provider system in @airma/react-state is designed with a tree structure. The nearest provider finds store one-by-one from itself to its root parent provider, and links the nearest matched provider store to the subscriber useModel/useSelector.

   Does the state change of store leads a whole provider component rerender?

   No, only the hooks subscribing this store may rerender their owners. Every store change is notified to its subscriber like useModel and useSelector, and then the subscriber rerenders its owner by useState.

   Why not async action methods

   Async action often makes the problem about stale data and zombie-children. So, a special tool to resolve this problem is necessary, you can try @airma/react-effect with it.

There are more examples, concepts and APIs in the documents of @airma/react-state.

Browser Support

chrome: '>=91',
edge: '>=91',
firefox: '=>90',
safari: '>=15'