vue3 day4

我心飞翔发布于 1周前分类：vue

watchEffie

watch套路是：既要指明监视的属性，也要指明监视的回调
watchEffie的套路是：不用指明监视哪个属性，监视的回调中用到哪个，就监视哪个属性
watchEffie有点像computed
- 但是computed注重计算出来的值（回调函数的返回值），所以必须写返回值
- 而watchEffie更加注重的是过程（回调函数的函数体），所以不用写返回值

<template>
 <h1>求和结果是{{ sum }}</h1>
 <button @click="sum++">计算+1</button>
 <br>
 <h3>msg为{{ msg }}</h3>
 <button @click="msg+='!'">修改msg</button>

 <br>
 <h2>姓名:{{ person.name }}</h2>
 <h2>年龄:{{ person.age }}</h2>
 <h2>薪资:{{ person.job.j1.salary }}</h2>


 <button @click="person.age++">增加年龄</button>
 <button @click="person.name+='~'">增加姓名</button>
 <button @click="person.job.j1.salary++">涨薪</button>
 <button @click="person.job.j1.aaa[0] = 10 ">测试监听reactive中的数组</button>
</template>

<script>
import {reactive, ref, watchEffect} from "vue";

export default {
 name: "Demo",

 setup() {
   let sum = ref(0);
   let msg = ref("我是msg");
   let person = reactive({
     name: '花花',
     age: 20,
     job: {
       j1: {
         salary: 100,
         aaa: [1, 2, 3, 4]
      }
    }
  })

   //只要回调函数中用到的数据发生变化,就会自动执行回调
   //自带immediate:true
   watchEffect(() => {
     console.log(person.age)
     console.log(person.job.j1.salary)
     console.log("修改了")
  })


   return {
     sum, msg, person
  }
}
}
</script>

<style scoped>

</style>

生命周期

vue2的生命周期图

vue3的生命周期图‍

总结

vue3中依然可以使用v2的配置方式来定义生命周期钩子,但是有两个生命周期更改了名字

beforeDestroy改名为beforeUnmount
destroyed改名为unmounted

vue3也提供了composition api的形式的生命周期钩子,与vue2中钩子对应关系如下

beforeCreate=> setup()
created=> setup()
beforeMount => onBeforeMount
mounted => onMounted
beforeUpdate=>onBeforeUpdate
updated=> onUpdated
beforeUnmount=> onBeforeUnmount
unmounted=> onUnmounted

回顾vue2方式的生命周期写法

demo.vue

<template>

  <demo v-if="isShow">
  </demo>

  <button @click="isShow=!isShow">显示影藏</button>


</template>

<script>


import Demo from "@/components/Demo";
import {ref} from "vue";

export default {
  name: 'App',
  components: {Demo},
  setup(){

    let isShow = ref(true);
    return{
      isShow
    }
  }
}
</script>

<style>
#app {
  font-family: Avenir, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-align: center;
  color: #2c3e50;
  margin-top: 60px;
}
</style>

app.vue

<template>
  <h1>标题</h1>
  <h2>{{age}}</h2>
  <button @click="age++">更改数据</button>
</template>

<script>

import {ref} from "vue";

export default {
  name: "Demo",

  beforeCreate() {
    console.log('---beforeCreate---')
  },
  created() {
    console.log('---created---')
  },
  beforeUpdate() {
    console.log('---beforeUpdate---')
  },
  updated() {
    console.log('---updated---')

  },
  beforeMount() {
    console.log('---beforeMount---')

  },
  mounted() {
    console.log('---mounted---')

  },
  beforeUnmount() {
    console.log('---beforeUnmount---')

  },
  unmounted() {
    console.log('---unmounted---')

  },

  setup() {
    return {
      age:ref(10)
    }
  }
}
</script>

<style scoped>

</style>

使用vue3写法写生命周期

注意点 setup会最先执行
vue3写法执行会优先vue2

<template>
  <h1>标题</h1>
  <h2>{{ age }}</h2>
  <button @click="age++">更改数据</button>
</template>

<script>

import {onBeforeMount, onBeforeUnmount, onBeforeUpdate, onMounted, onUnmounted, onUpdated, ref} from "vue";

export default {
  name: "Demo",

  beforeCreate() {
    console.log('---beforeCreate---')
  },
  created() {
    console.log('---created---')
  },
  beforeUpdate() {
    console.log('---beforeUpdate---')
  },
  updated() {
    console.log('---updated---')

  },
  beforeMount() {
    console.log('---beforeMount---')

  },
  mounted() {
    console.log('---mounted---')

  },
  beforeUnmount() {
    console.log('---beforeUnmount---')

  },
  unmounted() {
    console.log('---unmounted---')

  },

  setup() {
    console.log("---setup---")

    onBeforeUpdate(() => {
      console.log("---onBeforeUpdate---")

    })

    onUpdated(() => {
      console.log("---onUpdated---")

    })

    onBeforeMount(() => {
      console.log("---onBeforeMount---")

    })


    onMounted(() => {
      console.log("---onMounted---")

    })

    onBeforeUnmount(() => {
      console.log("---onBeforeUnmount---")

    })

    onUnmounted(() => {
      console.log("---onUnmounted---")

    })


    return {
      age: ref(10)
    }
  }
}
</script>

<style scoped>

</style>

hook

需求,获取鼠标的点击位置

基础代码实现

<template>
  <h2>测试hook</h2>
  <p>鼠标点击的坐标是 x:{{ point.x }} ,y:{{ point.y }}</p>
</template>

<script>

import {onMounted, onUnmounted, reactive, ref} from "vue";

export default {
  name: "Demo",

  setup() {

    let point = reactive({
      x: 0,
      y: 0
    })

    const clickFun = event => {
      point.x = event.pageX
      point.y = event.pageY
    };

    onMounted(()=>{
      window.addEventListener("click",clickFun )

    })

    onUnmounted(()=>{
      window.removeEventListener("click",clickFun )

    })
    return {
      age: ref(10),
      point
    }
  }
}
</script>

<style scoped>

</style>

hook代码实现

usePoint.js

import {onMounted, onUnmounted, reactive} from "vue";

export default function () {

    let point = reactive({
        x: 0,
        y: 0
    })

    const clickFun = event => {
        point.x = event.pageX
        point.y = event.pageY
    };

    onMounted(() => {
        window.addEventListener("click", clickFun)

    })

    onUnmounted(() => {
        window.removeEventListener("click", clickFun)

    })

    return point
}

使用hook

<template>
  <h2>测试hook</h2>
  <p>鼠标点击的坐标是 x:{{ point.x }} ,y:{{ point.y }}</p>
</template>

<script>

import {ref} from "vue";
import usePoint from '../hooks/UserPoint'

export default {
  name: "Demo",

  setup() {

    const point = usePoint()
    return {
      age: ref(10),
      point
    }
  }
}
</script>

<style scoped>

</style>

自定义hook函数

什么是hook? 本质是一个函数,把setup函数中使用到的composition api 进行了封装
类似于vue2中的mixin
自定义hook的优势,复用代码,让setup中的逻辑更清晰易懂

toRef

先看下原始代码

<template>
  <h2>测试toRef</h2>
  <h1>姓名{{ person.name }}</h1>
  <h2>年龄{{ person.age }}</h2>
  <h3>薪水{{ person.job.j1.salary }}</h3>

  <button @click="person.age++">年龄增长</button>
  <button @click="person.name+='~'">姓名修改</button>
  <button @click="person.job.j1.salary++">涨薪</button>

</template>

<script>


import {reactive} from "vue";

export default {
  name: "Demo",

  setup() {

    let person = reactive({
      name: '花花',
      age: 20,
      job: {
        j1: {
          salary: 300
        }
      }
  })

  return {
    person
  }
}
}
</script>

<style scoped>

</style>

存在的问题: 在模板中反复使用了person.来取值

使用toRef简化操作

<template>
  <h2>测试toRef</h2>
  <h1>姓名{{ name }}</h1>
  <h2>年龄{{ age }}</h2>
  <h3>薪水{{ salary }}</h3>

  <button @click="age++">年龄增长</button>
  <button @click="name+='~'">姓名修改</button>
  <button @click="salary++">涨薪</button>

</template>

<script>


import {reactive, toRef} from "vue";

export default {
  name: "Demo",

  setup() {

    let person = reactive({
      name: '花花',
      age: 20,
      job: {
        j1: {
          salary: 300
        }
      }
    })

    return {
      name: toRef(person, 'name'),
      age: toRef(person, 'age'),
      salary: toRef(person.job.j1,'salary')
    }
  }
}
</script>

<style scoped>

</style>

注意,这里不能使用Ref,因为Ref会生成新对象,不会修改原有的person

使用ToRefs简化ToRef

<template>
  <h2>测试toRef</h2>
  <h1>姓名{{ name }}</h1>
  <h2>年龄{{ age }}</h2>
  <h3>薪水{{ job.j1.salary }}</h3>

  <button @click="age++">年龄增长</button>
  <button @click="name+='~'">姓名修改</button>
  <button @click="job.j1.salary++">涨薪</button>

</template>

<script>


import {reactive, toRefs} from "vue";

export default {
  name: "Demo",

  setup() {

    let person = reactive({
      name: '花花',
      age: 20,
      job: {
        j1: {
          salary: 300
        }
      }
    })

    //这里对toRefs之后的对象进行了解构
    return {
      person,
      ...toRefs(person)
    }
  }
}
</script>

<style scoped>

</style>

总结

作用：创建一个ref对象，其value值指向另一个对象中的某个属性
语法const name = toRef(person,'name')
应用": 要将响应式数据中的某一个属性给外部使用
扩展: toRef和toRefs功能一致,但是可以批量创建多个ref对象,语法:toRefs(person)

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