Vue custom component implements two-way binding

Scenario:

The interaction methods between parent and child components that we commonly use are:
The parent component flows data into the child component through props;
The child component sends the updated array to the parent component via $emit;

Today, we implement interaction in another way, referring to the v-model of the input box to implement two-way data binding of custom components.
That is, when the value of the parent component changes, the value of the child component changes accordingly; conversely, when the value of the child component changes, the value of the parent component changes accordingly

Subcomponent definition:

Since the props attribute value cannot be modified directly, we define valueData here, receive the value in real time by listening, and modify valueData through the click method.
Note that the model syntax sugar prop is the received props attribute value, which should be kept consistent. event is the name of the event passed earlier.

The code is as follows:

<template>
  <div>
    <div>{{ `Subcomponent value: ${value}` }}</div>
    <div @click="click">Click here to modify the value</div>
  </div>
</template>

<script>
export default {
  name: "",
  model: {
    prop: "value",
    event: "change"
  },
  props: {
    value: Number
  },
  components: {},
  data() {
    return {
      valueData: ""
    };
  },
  watch:
    value(newValue, oldValue) {
      this.valueData = newValue;
      console.log(`Subcomponent value: ${newValue}`);
    }
  },
  created() {
  },
  mounted() {
  },
  methods: {
    click() {
      this.valueData++;
      this.$emit("change", this.valueData);
    }
  }
};
</script>
<style lang='less' scoped>
</style>

Parent component definition:

The parent component binds the text value through v-model. The name is not necessarily value, it can be any other string that conforms to the naming convention, here it is text.
After the child component updates the data through the change event, the v-mode binding value changes accordingly.
Or when the parent component modifies the text value, the value of the child component changes accordingly.

The code is as follows:

<template>
  <div>
    <div>{{ `Parent component value: ${text}` }}</div>
    <div @click="click">Click here to modify the value</div>


    <span>-----------------------------------------------------------</span>

    <test-children v-model="text"></test-children>

  </div>
</template>

<script>
import TestChildren from "@/views/TestChildren";

export default {
  name: "",
  components: { TestChildren },
  data() {
    return {
      text: 1
    };
  },
  created() {
  },
  mounted() {
  },
  watch:
    text(newValue, oldValue) {
      console.log(`parent component value: ${newValue}`);
    }
  },
  methods: {
    click() {
      this.text--;

    }
  }
};
</script>
<style lang='less' scoped>
</style>

result:

Directly copy the code to your own project for testing. Whether the value is changed by the parent component or the child component. The values ​​of the two components bound by v-mode are always consistent.

Q&A:

A classmate asked, isn't this the same as flowing data downward through props and then passing data upward through $emit? It can also achieve the effect of two-way binding like mine. In fact, if we don’t use v-model, we will inevitably write the following code in the parent component:

<test-children @change="changeText"></test-children>

Then modify the text value by defining the changeText method.

Imagine that when our page is more complex and the number of referenced components is larger, we need to define more than ten or twenty methods like this in the page. The number of readable lines is greatly reduced, increasing maintenance costs.

Extensions:

After vue2.3, the sync method is provided, which can also realize two-way binding

Writing in the parent component:

<test-children :value.sync="text"></test-children>

The following model definition is not needed in the subcomponent, just delete it.

model: {
prop: "value",
event: "change"
},

Passing data to the parent component uses the following method:

this.$emit("update:value", this.valueData);

The above is the full content of this article. I hope it will be helpful for everyone’s study. I also hope that everyone will support 123WORDPRESS.COM.