# Fix中对于对象属性的监听,为什么要先定义属性才可以正常watch,如何解决?


先看如下代码示例,很明显按钮被点击后并不会输出phone的值,其实这和Vue2类似,是因为Fix在响应式处理的时候,遍历对象的每一个属性添加依赖的,并不能检测到新增的属性.

```javascript
const state = Fix.define({
    name: "小明",
    details: {
        age: 18,
        address: "北京",
    },
});

Fix.watch(state, "details.phone", phone => {
    console.log(phone);
});


const widget = BI.createWidget({
    type: "bi.button",
    text: "button",
    handler: () => {
        state.details.phone = "123456789";
    },
});
```

在日常实践中我们一般采用两种方式来处理这种情况

1. 修改整个对象的引用

```
const widget = BI.createWidget({
    type: "bi.button",
    text: "button",
    handler: () => {
        state.details = { ...state.details, phone: "123456789"};
    },
});
```

2. 使用Fix.set方法

类似vue的$set方法

```
const widget = BI.createWidget({
    type: "bi.button",
    text: "button",
    handler: () => {
        Fix.set(state.details, "phone", "123456789");
    },
});
```