Vue.js using unique id in my objects array to grab the index of my object?

Question

Vue.component('post', {
  template: "#my-component",
  props: ['posty'],
  methods: {
  	testFunc: function(index){
  		 this.$parent.parentMethod(index);
  	}
  }
});

var vm = new Vue({
  el: "#app",
  data: {
    posts: [{	uuid: '88f86fe9d',
				title: "hello",
				votes: '15'
			},
			{	
				uuid: '88f8ff69d',
				title: "hello",
				votes: '15'
			},
			{	
				uuid: '88fwf869d',
				title: "hello",
				votes: '10'
			}]
  },

  methods: {
  	parentMethod: function(index){
  		this.posts.splice(index, 1)
  	}
  }
});

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JS Bin</title>
</head>
<body>

  
<div id="app">
  <div class="container-fluid">
    <ul class="list-group">
      <post v-for="posty in posts" :posty="posty" track-by="uuid"></post>
    </ul>
  </div>
</div>  
  
<template id="my-component">
	<div v-if="posty.votes === '15'">
	  <button v-on:click="testFunc(uuid)">{{posty.title}}</button>
	</div>
	<div v-else>
	  <button v-on:click="testFunc(uuid)">No</button>
	</div>
</template>
  
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/1.0.16/vue.js"></script>
  
</body>
</html>

I think I am missing something really important here but I believe using track-by="uuid" will allow me to grab the index of that respective object so I can do an array operation on that object. My example does not return the index of the object.

1) what does track by id really do in Vue.js ?

2) How to I get a return for my objects index? track-by="$index" does not work for objects array but only a simple array. I need a solution that gives me the index from track-by="uuid"

Dan Mindru · Accepted Answer · 2016-11-13 13:00:12Z

1

'track-by' is only used to hint Vue so that it can track each node’s identity, and thus reuse and reorder existing elements.

It's not something you can access in a method, it's used by Vue internals only.

Therefore, you have to refer to each object's uuid on the click events, like so:

 <button v-on:click="testFunc(posty.uuid)">{{posty.title}}</button>

However, I think what you are looking for is the following:

<ul class="list-group">
  <li v-for="(item, index) in items">
    {{ testMethod(index) }}
  </li>
</ul>

v-for also supports an optional second argument for the index of the current item. That's the 'Vue way' to pass an item's index in a v-for loop.

answered Nov 13, 2016 at 13:00

Dan Mindru

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