Vue2 响应式系统之分支切换

目录

• 场景
• observer(data)
• new Watcher(updateComponent)
• data.ok = false
• data.text = "hello, liang"
• 问题
• 去重
• 重置
• 测试
• 总结

import { observe } from "./reactive";
import Watcher from "./watcher";
const data = {
    text: "hello, world",
    ok: true,
};
observe(data);

const updateComponent = () => {
    console.log("收到", data.ok ? data.text : "not");
};

new Watcher(updateComponent); // updateComponent 执行一次函数，输出 hello, world

data.ok = false; // updateComponent 执行一次函数，输出 not

data.text = "hello, liang"; // updateComponent 会执行吗？

const updateComponent = () => {
    console.log("收到", data.ok ? data.text : "not");
};

/*************改动***************************/
let uid = 0;
/****************************************/
export default class Dep {
    static target; //当前在执行的函数
    subs; // 依赖的函数
  	id; // Dep 对象标识
    constructor() {
      /**************改动**************************/
        this.id = uid++;
      /****************************************/
        this.subs = []; // 保存所有需要执行的函数
    }

    addSub(sub) {
        this.subs.push(sub);
    }
    depend() {
        if (Dep.target) {
            // 委托给 Dep.target 去调用 addSub
            Dep.target.addDep(this);
        }
    }

    notify() {
        for (let i = 0, l = this.subs.length; i < l; i++) {
            this.subs[i].update();
        }
    }
}

Dep.target = null; // 静态变量，全局唯一

import Dep from "./dep";
export default class Watcher {
  constructor(Fn) {
    this.getter = Fn;
    /*************改动***************************/
    this.depIds = new Set(); // 拥有 has 函数可以判断是否存在某个 id
    /****************************************/
    this.get();
  }

  /**
     * Evaluate the getter, and re-collect dependencies.
     */
  get() {
    Dep.target = this; // 保存包装了当前正在执行的函数的 Watcher
    let value;
    try {
      value = this.getter.call();
    } catch (e) {
      throw e;
    } finally {
      this.cleanupDeps();
    }
    return value;
  }

  /**
     * Add a dependency to this directive.
     */
  addDep(dep) {
    /*************改动***************************/
    const id = dep.id;
    if (!this.depIds.has(id)) {
      dep.addSub(this);
    }
    /****************************************/

  }

  /**
     * Subscriber interface.
     * Will be called when a dependency changes.
     */
  update() {
    this.run();
  }

  /**
     * Scheduler job interface.
     * Will be called by the scheduler.
     */
  run() {
    this.get();
  }
}

import { remove } from "./util";
/*
export function remove(arr, item) {
    if (arr.length) {
        const index = arr.indexOf(item);
        if (index > -1) {
            return arr.splice(index, 1);
        }
    }
}
*/
let uid = 0;

export default class Dep {
    static target; //当前在执行的函数
    subs; // 依赖的函数
    id; // Dep 对象标识
    constructor() {
        this.id = uid++;
        this.subs = []; // 保存所有需要执行的函数
    }
		
    addSub(sub) {
        this.subs.push(sub);
    }
  /*************新增************************/
    removeSub(sub) {
        remove(this.subs, sub);
    }
  /****************************************/
    depend() {
        if (Dep.target) {
            // 委托给 Dep.target 去调用 addSub
            Dep.target.addDep(this);
        }
    }

    notify() {
        for (let i = 0, l = this.subs.length; i < l; i++) {
            this.subs[i].update();
        }
    }
}

Dep.target = null; // 静态变量，全局唯一

import Dep from "./dep";
export default class Watcher {
    constructor(Fn) {
        this.getter = Fn;
        this.depIds = new Set(); // 拥有 has 函数可以判断是否存在某个 id
      	/*************新增************************/
        this.deps = [];
        this.newDeps = []; // 记录新一次的依赖
        this.newDepIds = new Set();
      	/****************************************/
        this.get();
    }

    /**
     * Evaluate the getter, and re-collect dependencies.
     */
    get() {
        Dep.target = this; // 保存包装了当前正在执行的函数的 Watcher
        let value;
        try {
            value = this.getter.call();
        } catch (e) {
            throw e;
        } finally {
          	/*************新增************************/
            this.cleanupDeps();
          	/****************************************/
        }
        return value;
    }

    /**
     * Add a dependency to this directive.
     */
    addDep(dep) {
        const id = dep.id;
      /*************新增************************/
        // 新的依赖已经存在的话，同样不需要继续保存
        if (!this.newDepIds.has(id)) {
            this.newDepIds.add(id);
            this.newDeps.push(dep);
            if (!this.depIds.has(id)) {
                dep.addSub(this);
            }
        }
      /****************************************/
    }

    /**
     * Clean up for dependency collection.
     */
  	/*************新增************************/
    cleanupDeps() {
        let i = this.deps.length;
        // 比对新旧列表，找到旧列表里有，但新列表里没有，来移除相应 Watcher
        while (i--) {
            const dep = this.deps[i];
            if (!this.newDepIds.has(dep.id)) {
                dep.removeSub(this);
            }
        }

        // 新的列表赋值给旧的，新的列表清空
        let tmp = this.depIds;
        this.depIds = this.newDepIds;
        this.newDepIds = tmp;
        this.newDepIds.clear();
        tmp = this.deps;
        this.deps = this.newDeps;
        this.newDeps = tmp;
        this.newDeps.length = 0;
    }
  	/****************************************/
    /**
     * Subscriber interface.
     * Will be called when a dependency changes.
     */
    update() {
        this.run();
    }

    /**
     * Scheduler job interface.
     * Will be called by the scheduler.
     */
    run() {
        this.get();
    }
}

import { observe } from "./reactive";
import Watcher from "./watcher";
const data = {
    text: "hello, world",
    ok: true,
};
observe(data);

const updateComponent = () => {
    console.log("收到", data.ok ? data.text : "not");
};

new Watcher(updateComponent); // updateComponent 执行一次函数，输出 hello, world

data.ok = false; // updateComponent 执行一次函数，输出 not

data.text = "hello, liang"; // updateComponent 会执行吗？