How to solve Vue error: Unable to use props to pass data

How to solve Vue error: Unable to use props to pass data

Foreword:
In the development process of Vue, use props to transfer data between parent and child components Passing is very common. However, sometimes we may encounter a problem, that is, when using props to pass data, an error will occur. This article will focus on how to solve the error that props cannot be used to pass data in Vue.

Problem description:
In Vue development, when we use props in the parent component to pass data to the child component, if the passed data cannot be obtained in the child component, an error will occur. Condition. The error message usually looks like the following:

[Vue warn]: Failed prop type: The prop "xxx" is marked as required in "xxx", but its value is undefined.

Or it is similar to the following error message:

[Vue warn]: Invalid prop: type check failed for prop "xxx". Expected xxx, got undefined.

Problem analysis:
The reason for this problem is that the parent component is passing to the child component When data is generated, the following situations may exist:

1. The parent component does not declare and pass props correctly;
2. The props of the parent component do not correctly define the type and default value;
3. The child component failed to receive and use props correctly.

Solution:
We can adopt different solutions for different situations of the problem.

1. The parent component does not declare and pass props correctly:
   In Vue, when the parent component passes data to the child component, the props need to be explicitly declared in the child component to receive the passed data. If the parent component does not declare and pass props correctly, the child component will report an error when using props. We need to ensure that the data passed by the parent component to the child component has corresponding declarations in the props of the child component.

For example, we have a Parent component and a Child component, we want to pass the data in the Parent component to the Child component:

<!-- Parent.vue -->
<template>
  <Child :childData="data"></Child>
</template>

<script>
  import Child from './Child.vue';

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


<!-- Child.vue -->
<template>
  <div>{{ childData }}</div>
</template>

<script>
  export default {
    props: {
      childData: {
        type: String,
        default: ''
      }
    }
  }
</script>

2. The props of the parent component are not correct Define types and default values ​​locally:
   In Vue, we can declare types and default values ​​for props, which can improve the readability and robustness of the code. If the parent component's props do not have correctly defined types and default values, errors may occur when the child component obtains and uses the props. We need to ensure that the props types and default values ​​passed by the parent component to the child component are consistent with the requirements defined by the child component.

For example, we want to pass a number to the child component:

<!-- Parent.vue -->
<template>
  <Child :childNumber="10"></Child>
</template>

<script>
  import Child from './Child.vue';

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


<!-- Child.vue -->
<template>
  <div>{{ childNumber }}</div>
</template>

<script>
  export default {
    props: {
      childNumber: {
        type: Number,
        default: 0
      }
    }
  }
</script>

3. The child component fails to receive and use props correctly:
   Sometimes, we may Props will not be received and used correctly in child components, resulting in the failure to obtain the passed data. We need to ensure that child components receive and use props correctly, and use props inside the component instead of directly using the parent component's data.

For example, we need to process the data passed by the parent component before displaying it:

<!-- Parent.vue -->
<template>
  <Child :childData="data"></Child>
</template>

<script>
  import Child from './Child.vue';

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


<!-- Child.vue -->
<template>
  <div>{{ processedData }}</div>
</template>

<script>
  export default {
    props: {
      childData: {
        type: String,
        default: ''
      }
    },
    computed: {
      processedData() {
        // 处理数据后返回
        return this.childData.toUpperCase();
      }
    }
  }
</script>

Summary:
In Vue development, props is a common parent-child component The way to transfer data between them. When an error occurs that data cannot be passed using props, we need to carefully examine the cause of the problem and take appropriate solutions. This article introduces three common situations and corresponding solutions to solve this problem. I hope this article can help you solve the problem of being unable to use props to pass data in Vue.

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