vue3的computed.ts

 vue3的computed.ts

import { effect } from './effect';
class ComputedRefImpl {
    public _dirty = true;
    public _value;
    public effect;
    constructor(getter, public setter) {   //ts中默认不会挂在this上
        this.effect = effect(() => {   //计算属性 默认会产生一个effect

        }, {
            lazy: true,    //默认不执行
            scheduler: () => {
                if (!this._dirty) {
                    this._dirty = true;
                    trigger(this, TriggerOrTypes.SET, 'value');
                }
            }
        });

    }
    get value() {   //计算属性也要收集依赖
        if (this._dirty) {
            this._value = this.effect();   //会将用户的返回值   返回
            this._dirty = false;
        }
        track(this, TrackOpTypes.GET, 'value');
        return this._value;
    }
    set value(newValue) {
        this.setter(newValue);
    }
}

// vue2和vue3 的computed原理是不一样的
export function computed(getterOrOptions) {
    let setter;
    let getter;
    if (Function(getterOrOptions)) {
        getter = getterOrOptions;
        setter = () => {
            console.warn('computed value must be readonly ')
        }
    } else {
        getter = getterOrOptions.get;
        setter = getterOrOptions.set;
    }

    return new ComputedRefImpl(getter, setter);
}

// 缓存就靠dirty来的.
// 调试collectionHandlers ref 的api和computed