Vue not updating ARRAY properly using unshift

Question

PLEASE HELP ME!!!!!

When my application starts i run an ajax to get all my feeds. These are objects that I then store in my vue variable which is an array.

    props:['id'],
    data(){
        return {
            feedData: []
        } 
    },
    created(){
        axios.get('/feeds/'+this.id).then(response =>{
            this.feedData = response.data.data;
        });
    }

After that when the user types and sends a new post i store the new post in the database and then emit an event to capture the new post from the database. The function for this is in my methods.

    methods: {
        captureFeed: function (feedId) {
            const vm = this;
            axios.get('/feeds/'+this.id+'/'+feedId).then(response =>{
                vm.feedData.unshift(response.data);
                console.log(response.data);
            });
        }
    },

The weird thing is that when i successfully get the new feed i just created and try to add it to the array of feeds using unshift for some reason the very first post of the array is duplicated and i never get to see the new post until i refresh the page. When i check the console log, i can see that i got the new feed. The funny thing is that when i use

vm.feedData.push(response.data);

it works just fine, but the post is at the very bottom which is not what i want!

i have images to show:

first post:

picture of the first post

second post:

picture of the second post

<template> <div class = "col-xs-12 col-md-5 mt-m pr-sm pl-sm"> <timeline-headline></timeline-headline> <div class="panel panel-default"> <div class="panel-body"> <feed-constructor :timeline-id = "id" @newFeedSent = "captureFeed"></feed-constructor> <feed v-for = "feed in feedData" :feedContent="feed"></feed> </div> </div> </div> </template> — Julian Tabona
– Julian Tabona, Commented Sep 20, 2017 at 20:50
Try using a key in on the feed that you are looping over. :key="feed.id" where feed.id is some unique value for each feed. — Bert
– Bert, Commented Sep 20, 2017 at 20:54
hmm.. i did something like this where i used the feed id. <feed v-for = "feed in feedData" :id="'feed-'+feed.id" :feedContent="feed"></feed> not sure how to use the dynamic key or dynamic feed id to fix this, trying to figure it out — Julian Tabona
– Julian Tabona, Commented Sep 20, 2017 at 21:07

tony19 · Accepted Answer · 2022-07-15 23:52:56Z

2

The main issue here is that when you are looping over a component, you are required to use a key.

In 2.2.0+, when using v-for with a component, a key is now required.

That being the case, your template should look like this:

<feed v-for="feed in feedData" :key="feed.id" :feedContent="feed"></feed>

where feed.id is a unique value in each feed object. This is because of Vue's DOM update strategy. Using a key helps Vue identify which components need to be created/destroyed.

edited Jul 15, 2022 at 23:52

tony19

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answered Sep 20, 2017 at 21:38

Bert

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Comments

Lucas Katayama · Accepted Answer · 2017-09-20 21:32:58Z

1

Are you using the key param in your template? Like this?

 :key="<An ID>"

For instance:

<div  v-for="(item, index) in array" :key="item.id">
  {{index}} - {{item.name}}
</div>

answered Sep 20, 2017 at 21:32

Lucas Katayama

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1 Comment

Julian Tabona Over a year ago

Thank you @Lucas, your right the :key="<An ID>" helps solve this issue, had no idea, going to research and learn more on this

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