vue源码—03依赖收集与追踪

男娘i 2022-02-03 23:39 106阅读 0赞

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// new KVUE({data:{...}})
    
    class KVue {
        constructor(options) {
            this.$options = options;
    
            // 数据响应化
            this.$data = options.data;
            this.observe(this.$data)
    
            //模拟一下watcher的创建
            new Watcher();
            this.$data.test;
            new Watcher();
            this.$data.foo.bar;
    
        }
        observe(value) {
            if (!value || typeof value !== 'object') {
                return
            }
    
            // 遍历该对象
            Object.keys(value).forEach(key => {
                // 定义响应化
                this.defineReactive(value, key, value[key])
            })
        }
    
        // 数据的响应化
        defineReactive(obj, key, val) {
            this.observe(val);//解决数据嵌套
    
            // 初始化dep
            const dep = new Dep();
    
            Object.defineProperty(obj, key, {
                get() {
                    Dep.target && dep.addDep(Dep.target)
                    return val;
                },
                set(newVal) {
                    if (newVal === val) {
                        return;
                    }
                    val = newVal;
                    dep.notify();
                    // console.log(`${key}属性更新了:${val}`);
                }
            })
        }
    }
    
    // Dep 用来管理watcher
    class Dep {
        constructor() {
            // 这里存放若干依赖（watcher）
            this.deps = [];
        }
    
        addDep(dep) {
            this.deps.push(dep)
        }
    
        notify() {
            this.deps.forEach(dep=>dep.update())
        }
    }
    
    // watcher
    class Watcher {
        constructor(){
            // 将当前watcher实例指定到Dep静态属性target
            Dep.target = this
        }
        update() {
            console.log('属性更新了')
        }
    }

html

<html>
    
    <head>
        <title>definedproperty</title>
    </head>
    
    <body>
        <script src="./kvue.js"></script>
        <script>
            const app = new KVue({
                data: {
                    test: "I am test",
                    foo: {
                        bar: "bar"
                    }
                }
            });
            app.$data.test = "hello, jjsun";
            app.$data.foo.bar = "oh my bar";
        </script>
    </body>
    
    </html>

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