Wsrtjtyk

This question may also be applicable to Vue in general, but I am using Vuex for my project.

I have an array of objects in my store for which I would like to have a calculated property.

To simplify, assume my store is as follows:

const state = {

    numbers = [

        {num: 2, multiplier: 3},

        {num: 5, multiplier: 10},

        {num: 1, multiplier: 6}

    ]

};

Now, I want a calculated property on each object of the numbers array, such that the result is num * multiplier (eg. 2*3 = 6, 5*10 = 50)

One solution is to make a calculated property that returns the numbers array, plus the calculated field... eg:

const getterrs = {

    num_list(state){

        const list = state.numbers

        list.map(n=>{

            n.value=n.num*n.multiplier;

        );

        return list;

    }

}

That works, but it has a couple issues:

• The array returned cannot be bound with v-model on the non-computed
  fields




• The entire array will be recalculated whenever any element in the
  array is changed... I only want to recalculate the individual element
  that changed.

Is that possible with Vue/Vuex?

You could do any computing of your store data in the component it is being used in. I would have your getter simply return the numbers array:

const getters = {

    num_list(state){

        return state.numbers;

    }

}

Then in your component you can access numbers with the getter and use it how you want. So if you want to display the original array you could get it like this:

computed: {

        num_list() {

            return this.$store.getters.num_list

        }

    }

and display it in your template like this:

<p>Our first number is {{num_list[0].num}} and it's multiplier is {{num_list[0].num}}</p>

If you want to have the multiplication calculated as well you can have another computed property:

multiplied() {

    return this.num_list[0].num*this.num_list[0].multiplier

}

and echo it in the template with {{multiplied}}.

Now it would make things a bit more flexible if you had a data element in your component that could be used as the index, or if you had a method instead of a computed property so you could pass a parameter. (You shouldn't pass parameters to computed property as I understand it). So your method of multiplied would be this:

multipliedMethod(index) {

    return this.num_list[index].num*this.num_list[index].multiplier

}

Or if you want to show all the results you can iterate through your num_list with v-for and do any calculation on the fly:

<div v-for="(num, index) in num_list" :key="index">

  <p>{{num.num*num.multiplier}}</p>

</div>