VUEJS: Model not changing in for loop - vue.js

Question

The V-model:"question.answer" is the same for each loop.
The content of rating_questions is:
rating_question = [
{
"id":1,
"question":"How did you like this?",
"amount_of_stars":8,
"answer":0
},
{
"id":2,
"question":"Second question?",
"amount_of_stars":3,
"answer":0
}]
When I select an answer for the first question, the answer is saved in rating_question[0].answer but if I select an answer for the second question, it is also saved in rating_question[0].answer and not in rating_questions[1].answer as I would expect.
<template>
<div class="ratings">
<div class="rating" v-for="(question, index) in rating_questions">
<div class="question">
{{ question.question }}
</div>
<div class="answer">
<div class="rating-stars">
<span v-for="i in question.amount_of_stars">
<input :id="i" name="rating" v-model="question.answer" type="radio" :value="i" class="radio-btn hide" />
<label :for="i" >☆</label>
</span>
{{ rating_questions[index]['answer'] }}
{{index}}
<div class="clear"></div>
</div>
</div>
</div>
<span class="input-group-btn">
<button class="btn btn-primary btn-sm" id="btn-chat" #click="sendRating">
Send
</button>
</span>
</div>
</template>
<script>
export default {
props: ['user', 'event', 'rating_questions'],
methods: {
sendRating() {
this.$emit('ratingsent', {
rating_questions: this.rating_questions
});
}
}
}
</script>

Answer 1

Your problem is not in Vue usage but how you use <input> and <label> HTML elements...
<input> id and <label> for attributes are assigned with simple number
1..question.amount_of_stars...which means first combo for every question will have id = 1, second 2 etc. Moreover you are using same name for every combo!
Now if you click on the label (star) in second question, browser just switch active combo on 1st question.
Try this:
<input :id="`rating-${question.id}-${i}`" :name="`rating-${question.id}`" v-model="question.answer" type="radio" :value="i" class="radio-btn hide" />
<label :for="`rating-${question.id}-${i}`" >☆</label>
Now:
every combo in the group (single question) will have same name (OK!)
every combo (and it's corresponding label) will have different id (OK!)
Also it's usually better to use :key together with v-for
new Vue({
data() {
return {
rating_questions: [
{
"id":1,
"question":"How did you like this?",
"amount_of_stars":8,
"answer":0
},
{
"id":2,
"question":"Second question?",
"amount_of_stars":3,
"answer":0
}]
}
}
}).$mount("#app")
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
<div class="ratings">
<div class="rating" v-for="(question, index) in rating_questions" :key="question.id">
<div class="question">
{{ question.question }}
</div>
<div class="answer">
<div class="rating-stars">
<span v-for="i in question.amount_of_stars">
<input :id="`rating-${question.id}-${i}`" :name="`rating-${question.id}`" v-model="question.answer" type="radio" :value="i" class="radio-btn hide" />
<label :for="`rating-${question.id}-${i}`" >☆</label>
</span>
{{ question.answer }}
<div class="clear"></div>
</div>
</div>
</div>
</div>
</div>

Answer 2

The error was in my input id's...
Each new question had the same id's.
<template>
<div class="ratings">
<div class="rating" v-for="(question, index) in rating_questions">
<div class="question">
{{ question.question }}
</div>
<div class="answer">
<div class="rating-stars">
<span v-for="i in question.amount_of_stars">
<input :id="'rating' + index + i" name="rating" v-model="question.answer" type="radio" :value="i" class="radio-btn hide" />
<label :for="'rating' + index + i" >☆</label>
</span>
<div class="clear"></div>
</div>
</div>
</div>
<span class="input-group-btn">
<button class="btn btn-primary btn-sm" id="btn-chat" #click="sendRating">
Send
</button>
</span>
</div>
</template>
<script>
export default {
props: ['user', 'event', 'rating_questions'],
methods: {
sendRating() {
this.$emit('ratingsent', {
rating_questions: this.rating_questions
});
}
}
}
</script>

Answer 3

There is very trivial fix of this problem.
See you are modifying the props. In vuejs, props are not supposed to be updated. I hope you might have encountered some error in the console (not sure though, as sometimes in my case also it doesn't appear)
Please use this SFC file
<template>
<div class="ratings">
<!-- using the data variable rather than props -->
<div class="rating" v-for="(question, index) in questions" :key="index">
<div class="question">
{{ question.question }}
</div>
<div class="answer">
<div class="rating-stars">
<span v-for="i in question.amount_of_stars" :key="i">
<input
:id="i"
name="rating"
v-model="question.answer"
type="radio"
:value="i"
class="radio-btn hide"
/>
<label :for="i">☆</label>
</span>
{{ questions[index]["answer"] }}
{{ index }}
<div class="clear"></div>
</div>
</div>
</div>
<span class="input-group-btn">
<button class="btn btn-primary btn-sm" id="btn-chat" #click="sendRating">
Send
</button>
</span>
</div>
</template>
<script>
export default {
props: ["user", "event", "rating_questions"],
data() {
return {
questions: this.rating_questions, // because you can not change props in vuejs
};
},
methods: {
sendRating() {
this.$emit("ratingsent", {
rating_questions: this.questions,
});
},
},
};
</script>