Introduction to the method of implementing one-way data flow in the Vue documentation

Vue is a popular JavaScript framework that uses a one-way data flow model to control data transmission and communication between components. Within the Vue framework, data can only be passed from parent components to child components, and child components cannot directly modify parent component data. This pattern makes the code more maintainable, reliable, and easily reusable.

This article will introduce the method of implementing one-way data flow in the Vue document.

1. Prop delivery

Prop is one of the main methods to implement one-way data flow in the Vue framework. In Vue, we can use Props to pass data from parent component to child component. The Prop attribute received by the child component is read-only. It cannot directly modify the data of the parent component and can only communicate with the parent component through the emit event.

Use the v-bind directive in the parent component to pass data to the child component:

<template>
  <child-component :title="title"></child-component>
</template>

<script>
import ChildComponent from './ChildComponent.vue'

export default {
  components: {
    ChildComponent
  },
  data() {
    return {
      title: 'Hello, Vue!'
    }
  }
}
</script>

The props option in the child component receives data from the parent component:

<template>
  <h1>{{ title }}</h1>
</template>

<script>
export default {
  props: {
    title: String
  }
}
</script>

Above In the code, the title attribute is defined as String type, which means that validation and type conversion are handled by Vue. The passed title cannot be modified in the subcomponent, and can only be used for calculation operations or display.

2. Custom events

In the Vue framework, parent components and child components communicate by using custom events. The child component can use the $emit method provided by Vue to trigger a custom event and pass the data to the parent component. The parent component can listen to the event emitted by the child component through the v-on directive to receive data.

Trigger custom events in child components:

<template>
  <button @click="increment">{{ counter }}</button>
</template>

<script>
export default {
  data() {
    return {
      counter: 0
    }
  },
  methods: {
    increment() {
      this.counter++
      this.$emit('increment', this.counter)
    }
  }
}
</script>

Listen to custom events in parent components:

<template>
  <child-component @increment="onIncrement"></child-component>
</template>

<script>
import ChildComponent from './ChildComponent.vue'

export default {
  components: {
    ChildComponent
  },
  methods: {
    onIncrement(counter) {
      console.log(`Counter is ${ counter }`)
    }
  }
}
</script>

In the above code, the child component defines an increment Method, in which the $emit method is used to trigger a custom event of increment, and the counter value is passed to the parent component as a parameter. The parent component listens to the increment event bound to the child component through the v-on directive, and defines an onIncrement method to receive the data passed by the child component.

3. $attrs and $listeners

Sometimes, we will use native events inside the child component in the parent component, such as click and change events. To make these events work properly, Vue provides special attributes: $attrs and $listeners. $attrs allows the child component to pass all attributes that have not been defined by props to the parent component, while $listeners can pass all events bound by the child component (including native events and custom events) to the parent component.

Define a component with native events in the child component:

<template>
  <input type="text" @input="$emit('change', $event.target.value)">
</template>

<script>
export default {}
</script>

Use the child component in the parent component and bind the native event:

<template>
  <child-component v-on="$listeners"></child-component>
</template>

<script>
import ChildComponent from './ChildComponent.vue'

export default {
  components: {
    ChildComponent
  }
}
</script>

In the above code , the parent component uses the v-on directive to pass $listeners to the child component, so that the child component can pass bound native events and custom events to the parent component.

Summary

The one-way data flow pattern in the Vue framework makes communication between components clearer and more reliable. Data transfer and communication between components can be achieved using methods such as Prop, custom events, and $attrs/$listeners. Mastering these skills can help you better use the Vue framework to develop applications that meet user needs.

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