Vue error: Unable to use v-for correctly for list rendering, how to solve it?

Vue error: Unable to use v-for correctly for list rendering, how to solve it?

When developing with Vue, the v-for instruction is a very commonly used instruction, which can loop through the rendering list. However, sometimes we may encounter some problems when using v-for for list rendering, resulting in errors and the failure to render the list correctly. Next, I will introduce some common error situations and solutions.

1. Error: Repeated key in v-for

When using v-for loop to render the list, we need to add a unique key value to each loop item so that Vue can correctly Track changes in each item. If we do not set a key value for each loop item, or the set key values ​​are repeated, an error will be reported.

Sample code:

<ul>
  <li v-for="item in items">{{ item }}</li>
</ul>

In the above code, we did not set the key value for the li element in v-for, this will resulting in an error. In order to solve this problem, we can add a unique key value to the li element.

Solution:

<ul>
  <li v-for="(item, index) in items" :key="index">{{ item }}</li>
</ul>

In the above code, we set a unique key value for the li element, and the loop index index is used here As the key value, it ensures that each loop item has a unique identity.

2. Error: v-bind:key cannot use Object reference type as key value

When using v-for to render an object array, we can use a certain attribute of the object as the key value . However, if we use an object as the key value of the entire v-for, an error will be reported.

Sample code:

<div v-for="item in items" :key="item">
  {{ item.name }}
</div>

In the above code, we use the entire object item as the key value, which is the wrong way to write it.

Solution:

<div v-for="item in items" :key="item.id">
  {{ item.name }}
</div>

In the above code, we use a certain attribute id of the object as the key value to ensure that each object has a unique identity.

3. Error: v-for and v-if cannot be used on the same element at the same time

Vue official documentation clearly states that v-for and v-if cannot be used on the same element at the same time. If we need to perform conditional judgment while looping through the rendering list, an error will be reported.

Sample code:

<ul>
  <li v-for="item in items" v-if="item.visible">{{ item.name }}</li>
</ul>

In the above code, we use v-for and v-if at the same time in li# On the ## element, this is the wrong way to write it.

<ul>
  <template v-for="item in items">
    <li v-if="item.visible">{{ item.name }}</li>
  </template>
</ul>

This article introduces several common error situations and solutions, hoping to help everyone solve the problems encountered when using Vue for development. When using v-for for list rendering, be sure to set a unique key value for each loop item to avoid key duplication problems. In addition, please note that

and v-if cannot be used on the same element at the same time, and need to be wrapped with the <template></template> element. If you have other questions, it is recommended to consult the Vue official documentation or ask the community for help. I wish you all success in Vue development!

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