CODEWITHSUNDEEP
javascriptvue.jsvuejs2
Giacomo Ciampoli
Giacomo Ciampoli

Reputation: 821

How to avoid v-if on an element which uses v-for

I have a literal object like so:

    export default {
        pizze:{
            type:"pizze",
            typeOne:{
                title: "Pizze Rosse",
                data:[
                    {id:1,type:"pizza",name:"Margherita",price:4,ingredients:["pomodoro","mozzarella"],quantity:0,inventory:100},
                    {id:2,type:"pizza",name:"Marinara",price:3.5,ingredients:["aglio","pomodoro"],quantity:0,inventory:100},
                    {id:3,type:"pizza",name:"Salsiccia e funghi",price:6,ingredients:["salsiccia","funghi","mozzarella","pomodoro"],quantity:0,inventory:100},
                    {id:4,type:"pizza",name:"Carciofi",price:4,ingredients:["mozzarella","carciofi","pomodoro"],quantity:0,inventory:100},  
                ]
            },
            typeTwo:{
                title:"Pizze Bianche",
                data:[
                    {id:5,type:"pizza",name:"Gorgonzola e noci",price:5.50,ingredients:["gorgonzola","noci","mozzarella"],quantity:0,inventory:100},
                    {id:6,type:"pizza",name:"Stracchino e rucola",price:4.50,ingredients:["stracchino","rucola","basilico"],quantity:0,inventory:100},
                    {id:7,type:"pizza",name:"Tartufo e salsiccia",price:8,ingredients:["tartufo","salsiccia","mozzarella"],quantity:0,inventory:100},
                    {id:8,type:"pizza",name:"Zucchine e Gamberi",price:5,ingredients:["zucchine","gamberi","pomodorini"],quantity:0,inventory:100},
                ]
    
            }
        },
        primiPiatti:{
            type:"primiPiatti",
            typeOne:{
                title: "Primi di carne",
                data:[
                    {id:12,type:"primiPiatti",name:"Lasagne alla Bolognese",price:9,quantity:0,inventory:100},
                    {id:13,type:"primiPiatti",name:"Spaghetti alla carbonara",price:14,quantity:0,inventory:100},
                    {id:14,type:"primiPiatti",name:"pennette all'amatriciana",price:10,quantity:0,inventory:100},
                    {id:15,type:"primiPiatti",name:"paccheri salsiccia e funghi",price:12,quantity:0,inventory:100},  
                ]
            },
            typeTwo:{
                title:"Primi di pesce",
                data:[
                    {id:16,type:"primiPiatti",name:"spaghetti allo scoglio",price:8.50,quantity:0,inventory:100},
                    {id:17,type:"primiPiatti",name:"zuppa di cozze",price:14.50,quantity:0,inventory:100},
                    {id:18,type:"primiPiatti",name:"pappardelle asparagi e gamberi",price:18,quantity:0,inventory:100},
                    {id:19,type:"primiPiatti",name:"lasagne al salmone",price:15,quantity:0,inventory:100},
                ]
    
            },
...

I was not aware that it was bad to use v-if inside a v-for loop and my first approach to display the code in the view was this:

<div class="menu__container">
          <div v-if="menuVoice!=='type'"class="menu__container--box" v-for="menuVoice in Object.keys(menuData)" :key="menuVoice">
              <div class="title">{{menuData[menuVoice].title}}</div>
              <item-record v-for="data in menuData[menuVoice].data" :key="data.id" :data="data"></item-record>
          </div>
        </div>

What I was trying to do is to avoid to display a div block related to the type property of the object MenuVoice. Since I need it for other purpose (retrieving the right object for instance). So I refactored the code in this way:

<div class="menu__container">
          <div :style="[menuVoice === 'type' ? {display:'none'} : {display:'block'}]" class="menu__container--box" v-for="menuVoice in Object.keys(menuData)" :key="menuVoice">
              <div class="title">{{menuData[menuVoice].title}}</div>
              <item-record v-for="data in menuData[menuVoice].data" :key="data.id" :data="data"></item-record>
          </div>
        </div>

I'm not sure it is ok because there is always an if statement there. The code works in both cases, but I'm wondering if there is a better way to do something like that.

I tried also moving the v-if down on a child div, like so:

<div class="menu__container">
          <div"class="menu__container--box" v-for="menuVoice in Object.keys(menuData)" :key="menuVoice">
            <div v-if="menuVoice !=='type'>
                <div class="title">{{menuData[menuVoice].title}}</div>
              <item-record v-for="data in menuData[menuVoice].data" :key="data.id" :data="data"></item-record>
            </div>  
          </div>
        </div>

but it doesn't works because I will still get with three divs with class '.menu__container--box'.

Upvotes: 3

Views: 112

Answers (2)

Emile Bergeron
Emile Bergeron

Reputation: 17430

The trick to avoid using v-if with v-for is to filter your dataset with a computed property.

Here I created a computed named menuList which filters menuData, returning a filtered shallow clone.

computed: {
  menuList() {
    return Object.keys(this.menuData)
      .filter(key => key !== 'type')
      .reduce((res, key) => (res[key] = this.menuData[key], res), {});
  }
}

So your template uses just the right list out of the box. v-for="(item, key) in menuList"

<div class="menu__container">
  <div class="menu__container--box" v-for="(item, key) in menuList" :key="key">
      <div class="title">{{item.title}}</div>
      <item-record v-for="data in item.data" 
                   :key="data.id" :data="data"></item-record>
  </div>
</div>

Templates logic should be kept to a minimum. Anything that's more than a reference to a value, or a simple assignment, should be moved into computed and methods.

Upvotes: 2

codejockie
codejockie

Reputation: 10892

You should have avoid doing this:

<div class="menu__container">
  <div v-if="menuVoice !== 'type'"class="menu__container--box" v-for="menuVoice in Object.keys(menuData)" :key="menuVoice">
    <div class="title">{{menuData[menuVoice].title}}</div>
    <item-record v-for="data in menuData[menuVoice].data" :key="data.id" :data="data"></item-record>
  </div>
</div>

You can use what you already did to avoid doing the code above:

<div class="menu__container">
  <div :style="[menuVoice === 'type' ? {display:'none'} : {display:'block'}]" class="menu__container--box" v-for="menuVoice in Object.keys(menuData)" :key="menuVoice">
    <div class="title">{{menuData[menuVoice].title}}</div>
    <item-record v-for="data in menuData[menuVoice].data" :key="data.id" :data="data"></item-record>
  </div>
</div>

Upvotes: 0

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