一文教会你用redux实现computed计算属性

import { Store } from 'redux';

const collector = [];

class ObjectDeps {
  protected readonly deps: string[];
  protected readonly name: string;
  protected readonly store: Store;
  protected snapshot: any;

  constructor(store: Store, name: string, deps: string[] = []) {
    this.store = store;
    this.name = name;
    this.deps = deps;
    collector.push(this);
  }
  
  proxy(currentState) {
    if (state === null || typeof state != 'object') return state;
    
    const proxyData = Array.isArray(state) : [] : {};
    const currentDeps = this.deps.slice();
    const keys = Object.keys(currentState);
    
    for (let i = keys.length; i-- > 0; ) {
      const key = keys[i]!;

      Object.defineProperty(proxyData, key, {
        enumerable: true,
        get: () => {
          if (visited) {
            return new ObjectDeps(
              this.store, 
              this.name, 
              currentDeps.slice(),
            ).proxy(currentState)[key];
          }

          visited = true;
          this.deps.push(key);
          return this.proxy((this.snapshot = currentState[key]));
        },
      });
    }
  }
}

// 假设user里的对象为：{ firstName: 'lady', lastName: 'gaga' }
const userState = store.getState()['user'];

function computedFullName() {
  const proxy = new ObjectDeps(store, 'user').proxy(userState);
  return proxy.firstName + '-' + proxy.lastName;
}

const fullname = computedFullName();

console.log(collector); // [ ObjectDeps, ObjectDeps ]

class ObjectDeps {
  protected snapshot: any;

  proxy() {...}
  
  isDirty() {
    return this.snapshot !== this.getSnapshot();
  }
  
  protected getSnapshot() {
    const deps = this.deps;
    let snapshot = this.store.getState();

    for (let i = 0; i < deps.length; ++i) {
      if (snapshot == null || typeof snapshot !== 'object') {
        break;
      }
      snapshot = snapshot[deps[i]!];
    }

    return snapshot;
  }
}

import { defineModel, useComputed } from 'foca';

export const userModel = defineModel('user', {
  initialState: {
    firstName: 'lady',
    lastName: 'gaga',
  },
  computed: {
    // 清爽
    fullName() {
      return this.state.firstName + '-' + this.state.lastName;
    },
  },
});

// App.tsx
const App: FC = () => {
  const fullName = useComputed(userModel.fullName);
  
  return <div>{fullName}</div>;
};