# Ember.computed.sum
**URL:** https://discuss.emberjs.com/t/ember-computed-sum/9786
**Category:** Ember Data
**Created:** [February 15, 2016, 10:59pm UTC](https://discuss.emberjs.com/t/ember-computed-sum/9786 "2016-02-15T22:59:26Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@canop](https://discuss.emberjs.com/u/canop)
#### Post date: [February 15, 2016, 10:59pm UTC](https://discuss.emberjs.com/t/ember-computed-sum/9786/1 "2016-02-15T22:59:26Z")
Let’s have models:
Model: **basket**
```
export default DS.Model.extend({
fruits: DS.hasMany('fruit', { async: true }),
fruitCountArray: Ember.computed.mapBy('fruits', 'count'),
totalFruitCount: Ember.computed.sum('fruitCountArray')
});
```
Model: **Fruit**
```
export default DS.Model.extend({
name: DS.attr('string'),
count: DS.attr('number')
});
```
[Jsbin with working example](http://emberjs.jsbin.com/zukeci/edit?html,js,output). Can someone explain why `totalFruitCount` shows correct amount when page loads, but incorrect when value is updated by using given `{{input}}`. Is it because I’m missing something or it’s just how it works?
As far as I can tell, its something with incorrect type, after value modification `totalFruitCount` show appended array values of `fruitCountArray`. I can easily fix it by implementing my own computed property with **explicit parseInt** (doing exactly same as demo if parseInt isn’t used) such as:
```
totalFruitCount: Ember.computed('fruits,@each.count', function() {
let sum = 0;
this.get('fruits').forEach(fruit => {
sum += parseInt(fruit.get('hours'));
});
return sum;
})
```
But it feels wrong to me when there is already computed property just for this use-case. I’m using `Ember 2.3.0` and `Ember Data 2.3.0`.
---
### Author:  [@Sarath](https://discuss.emberjs.com/u/Sarath)
#### Post date: [February 16, 2016, 6:34am UTC](https://discuss.emberjs.com/t/ember-computed-sum/9786/2 "2016-02-16T06:34:41Z")
the problem is due to the array construction at
> [@canop](#):
>
> fruitCountArray: Ember.computed.mapBy(‘fruits’, ‘count’),
Find a suitable way to construct a numerical array or do it on your own