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simple immutable state object with reflection
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| import * as deepMerge from 'deepmerge'; | |
| import * as deepFreeze from 'deep-freeze'; | |
| function sealed(constructor: Function) { | |
| Object.seal(constructor); | |
| Object.seal(constructor.prototype); | |
| } | |
| @sealed | |
| export class StateObject<T> { | |
| private state: T; | |
| constructor(state: T) { | |
| this.setState(state); | |
| return new Proxy(this, { | |
| get(instance, prop) { | |
| if (prop in instance) { | |
| if (prop in instance.state) { | |
| throw new Error(`Property collision ${prop}`); | |
| } | |
| return instance[prop]; | |
| } else { | |
| return instance.state[prop]; | |
| } | |
| }, | |
| }); | |
| } | |
| public setState(transition: (prevState: T) => T, callback?: (newState: T) => void); | |
| public setState(nextState: T, callback?: (newState: T) => void); | |
| public setState(args: T & ((prevState: T) => T), callback?: (newState: T) => void) { | |
| let nextState: T; | |
| if (typeof args === 'function') { | |
| nextState = args(this.state); | |
| } | |
| if (typeof args === 'object') { | |
| nextState = args; | |
| } | |
| this.state = deepMerge.all<T>([this.state, nextState]); | |
| deepFreeze(this.state); // make state immutable | |
| if (callback) { | |
| callback(this.state); | |
| } | |
| } | |
| } | |
| export class StateDependent<T> { | |
| protected readonly stateObject: StateObject<T>; | |
| constructor(stateObject: StateObject<T>) { | |
| this.stateObject = stateObject; | |
| return new Proxy(this, { | |
| get(instance, prop) { | |
| if (prop in instance) { | |
| return instance[prop]; | |
| } else { | |
| return instance.stateObject[prop]; | |
| } | |
| }, | |
| }); | |
| } | |
| protected setState(transition: (prevState: T) => T, callback?: (newState: T) => void); | |
| protected setState(nextState: T, callback?: (newState: T) => void); | |
| protected setState(args: T & ((prevState: T) => T), callback?: (newState: T) => void) { | |
| this.stateObject.setState(args, callback); | |
| }; | |
| } | |
| interface Header { | |
| readonly headerCode?: number; | |
| } | |
| interface Body { | |
| readonly bodyLength?: number; | |
| } | |
| export class Collector extends StateDependent<Header & Body> implements Header, Body { | |
| // RUNTIME VARIABLES | |
| public readonly headerCode: number; | |
| public readonly bodyLength: number; | |
| // PROXIES | |
| private readonly header: StateDependent<Header>; | |
| private readonly body: StateDependent<Body>; | |
| constructor() { | |
| super(new StateObject<Header & Body>({ | |
| bodyLength: 0, | |
| headerCode: 0, | |
| })); | |
| this.header = new StateDependent(this.stateObject); | |
| this.body = new StateDependent(this.stateObject); | |
| } | |
| change() { | |
| this.setState({ | |
| headerCode: 100, | |
| bodyLength: 200, | |
| }); | |
| } | |
| } | |
| const o = new Collector(); | |
| o.change(); | |
| console.log(o, o.bodyLength); |
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