In Vue, while templates cannot be assigned keys and cannot be replaced with a div element, it is important to utilize the v-for directive without a wrapper div element, especially when dealing with nested v-for loops

Question

In Vue, while templates cannot be assigned keys and cannot be replaced with a div element, it is important to utilize the v-for directive without a wrapper div element, especially when dealing with nested v-for loops

My JSON data looks like this:

{
   "data":{
      "1":{
         "color":"red",
         "size":"big"
      },
      "2":{
         "color":"red",
         "size":"big"
      },
      "3":{
         "color":"red",
         "size":"big"
      },
      "4":{
         "color":"red",
         "size":"big"
      },
      "5":{
         "color":"red",
         "size":"big"
      }
   }
}

I am using the following vue code to display it:

<template>
...

<template v-for="(obj, pos) in this.breakdown" :key="pos">
    <table class="table-auto" >
        <thead>
            <tr>
                <th class="px-4 py-2">Property</th>
                <th class="px-4 py-2">Value</th>
            </tr>
        </thead>

        <tbody>
            <template v-for = "(obj2, pos2) in obj" :key="pos2">
                <tr>
                    <td class="border px-4 py-2">
                        {{pos2}}
                    </td>
                    <td class="border px-4 py-2">
                        {{obj2}}
                    </td>
                </tr>
            </template>
        </tbody>
    </table>
</template>
...
</template>

I encountered an error that says

'<template>' cannot be keyed. Place the key on real elements

. Changing template to span or div resolves the error, but ruins the styling. I've heard that only the template tag can achieve the desired results without a wrapper element. Now, I'm unsure of how to adjust the v-for loops to eliminate the error.

javascript vue.js vuejs2 vue-component

Answer 1

Answer №1

Consider putting the v-for directive inside a template tag and using key on the tr element.

<template v-for="(i, j) in list" >   
            <tr :key="'1tr-'+j"> 
               <td..../>
            </tr>
            <tr :key="'2tr-'+j"> 
               <td..../>
            </tr>
 </template>

I have personally tested this method and it is working well for me. Hopefully, it will work for you too.

Answer 2

Consider putting the v-for directive inside a template tag and using key on the tr element.

<template v-for="(i, j) in list" >   
            <tr :key="'1tr-'+j"> 
               <td..../>
            </tr>
            <tr :key="'2tr-'+j"> 
               <td..../>
            </tr>
 </template>

I have personally tested this method and it is working well for me. Hopefully, it will work for you too.

Answer 3

Answer №2

For my particular scenario, I am tasked with rendering a sidebar menu that can consist of single elements or submenus. To achieve this, I attempted the following approach:

export interface DashboardRoute {
  icon: string
  label: string
  children?: string[]
}

const dashboardRoutes: DashboardRoute[] = [
  {
    label: 'Visão geral',
    icon: 'dashboard',
  },
  {
    label: 'Pessoas',
    icon: 'user',
  },
  {
    label: 'Categorias',
    icon: 'tags',
    children: [
      'Todas as categorias',
      'Alimentação',
      'Refeição',
    ],
  },
]

export default dashboardRoutes

<a-menu v-for="{ icon, label, children } in dashboardRoutes" :key="label" mode="inline">
  <a-sub-menu v-if="children">
     <span slot="title"
       ><a-icon :type="icon" /><span>{{ label }}</span></span
     >
    <a-menu-item v-for="child in children" :key="child">
      {{ child }}
    </a-menu-item>
  </a-sub-menu>
  <a-menu-item v-else>
    <a-icon :type="icon" />
    <span class="nav-text">{{ label }}</span>
  </a-menu-item>
</a-menu>

However, upon implementation, it was evident that multiple a-menu elements were being generated instead of a single one, which is inaccurate for our needs.

As a result, I made a naive attempt at an alternative solution:

<a-menu mode="inline">
  <template v-for="{ icon, label, children } in dashboardRoutes" :key="label">
     <a-sub-menu v-if="children">
       <span slot="title"
         ><a-icon :type="icon" /><span>{{ label }}</span></span
       >
       <a-menu-item v-for="child in children" :key="child">
         {{ child }}
       </a-menu-item>
     </a-sub-menu>
     <a-menu-item v-else>
       <a-icon :type="icon" />
       <span class="nav-text">{{ label }}</span>
     </a-menu-item>
  </template>
</a-menu>

This led to an error during execution, prompting me to conduct further research. I stumbled upon an issue that offered a potential solution.

The resolution requires moving the key property from the template tag to the first child element, or alternatively, any sibling elements if present (as per my specific case).

Therefore, the updated and correct approach would be:

<a-menu mode="inline">
  <template v-for="{ icon, label, children } in dashboardRoutes">
     <a-sub-menu v-if="children" :key="label"> <!-- key should be placed here! -->
       <span slot="title"
         ><a-icon :type="icon" /><span>{{ label }}</span></span
       >
       <a-menu-item v-for="child in children" :key="child"> 
         {{ child }}
       </a-menu-item>
     </a-sub-menu>
     <a-menu-item v-else :key="label"> <!-- key should be placed here! -->
       <a-icon :type="icon" />
       <span class="nav-text">{{ label }}</span>
     </a-menu-item>
  </template>
</a-menu>

Answer 4

For my particular scenario, I am tasked with rendering a sidebar menu that can consist of single elements or submenus. To achieve this, I attempted the following approach:

export interface DashboardRoute {
  icon: string
  label: string
  children?: string[]
}

const dashboardRoutes: DashboardRoute[] = [
  {
    label: 'Visão geral',
    icon: 'dashboard',
  },
  {
    label: 'Pessoas',
    icon: 'user',
  },
  {
    label: 'Categorias',
    icon: 'tags',
    children: [
      'Todas as categorias',
      'Alimentação',
      'Refeição',
    ],
  },
]

export default dashboardRoutes

<a-menu v-for="{ icon, label, children } in dashboardRoutes" :key="label" mode="inline">
  <a-sub-menu v-if="children">
     <span slot="title"
       ><a-icon :type="icon" /><span>{{ label }}</span></span
     >
    <a-menu-item v-for="child in children" :key="child">
      {{ child }}
    </a-menu-item>
  </a-sub-menu>
  <a-menu-item v-else>
    <a-icon :type="icon" />
    <span class="nav-text">{{ label }}</span>
  </a-menu-item>
</a-menu>

However, upon implementation, it was evident that multiple a-menu elements were being generated instead of a single one, which is inaccurate for our needs.

As a result, I made a naive attempt at an alternative solution:

<a-menu mode="inline">
  <template v-for="{ icon, label, children } in dashboardRoutes" :key="label">
     <a-sub-menu v-if="children">
       <span slot="title"
         ><a-icon :type="icon" /><span>{{ label }}</span></span
       >
       <a-menu-item v-for="child in children" :key="child">
         {{ child }}
       </a-menu-item>
     </a-sub-menu>
     <a-menu-item v-else>
       <a-icon :type="icon" />
       <span class="nav-text">{{ label }}</span>
     </a-menu-item>
  </template>
</a-menu>

This led to an error during execution, prompting me to conduct further research. I stumbled upon an issue that offered a potential solution.

The resolution requires moving the key property from the template tag to the first child element, or alternatively, any sibling elements if present (as per my specific case).

Therefore, the updated and correct approach would be:

<a-menu mode="inline">
  <template v-for="{ icon, label, children } in dashboardRoutes">
     <a-sub-menu v-if="children" :key="label"> <!-- key should be placed here! -->
       <span slot="title"
         ><a-icon :type="icon" /><span>{{ label }}</span></span
       >
       <a-menu-item v-for="child in children" :key="child"> 
         {{ child }}
       </a-menu-item>
     </a-sub-menu>
     <a-menu-item v-else :key="label"> <!-- key should be placed here! -->
       <a-icon :type="icon" />
       <span class="nav-text">{{ label }}</span>
     </a-menu-item>
  </template>
</a-menu>

Answer 5

Answer №3

When using Vue, it is important to note that binding attributes on the template element is not supported. If you find yourself needing to use :key and cannot utilize the "div" element, consider using "span" instead.

    <span v-for="(obj, pos) in this.breakdown " :key="pos">
       <td>{{pos}}</td>
       <td>{{obj}}</td>
    </span>

Answer 6

When using Vue, it is important to note that binding attributes on the template element is not supported. If you find yourself needing to use :key and cannot utilize the "div" element, consider using "span" instead.

    <span v-for="(obj, pos) in this.breakdown " :key="pos">
       <td>{{pos}}</td>
       <td>{{obj}}</td>
    </span>

Answer 7

Answer №4

Consider placing the v-for directive directly inside the table element:

<table class="table-auto" v-for="(item, index) in this.items" :key="index">

Answer 8

Consider placing the v-for directive directly inside the table element:

<table class="table-auto" v-for="(item, index) in this.items" :key="index">

In Vue, while templates cannot be assigned keys and cannot be replaced with a div element, it is important to utilize the v-for directive without a wrapper div element, especially when dealing with nested v-for loops

Answer №1

Answer №2

Answer №3

Answer №4

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