Angularjs Dynamic Text Fields and multiply two field - angularjs

Question

Hi I have a Json Like this
[
{
"id": 1,
"name": "Furniture & Fixture",
"choices": [
{
"req_goods": "",
"qty": "10",
"rate": "",
"total": ""
}
]
},
{
"id": 2,
"name": "Miscellaneous Property",
"choices": [
{
"req_goods": "",
"qty": "",
"rate": "",
"total": ""
}
]
},
{
"id": 3,
"name": "Office Equipment",
"choices": [
{
"req_goods": "",
"qty": "",
"rate": "",
"total": ""
}
]
}
]
here choices are my dynamic fields user can add as much choices as they want, my add/remove js is like this
$scope.addNewChoice = function(id){
$scope.capital_budgets[id].choices.push({});
};
$scope.removeChoice = function(parent_id,id) {
$scope.capital_budgets[parent_id].choices.splice(id,1);
};
my html
<div ng-repeat="cb in capital_budgets">
<div><b><% $index+1 %> <% cb.name %></b></div>
<div ng-repeat="choice in cb.choices">
<input type="text" ng-model="choice.req_goods">
<input type="text" ng-model="choice.qty">
<input type="text" ng-model="choice.rate">
<input type="text" ng-model="choice.total">
<button type="button" ng-hide="$first" ng-click="removeChoice($parent.$index,$index)">-</button>
</div>
<button type="button" ng-click="addNewChoice($index)">+</button>
</div>
Now I want to calculate the total(qty*rate) of each added choices whenever they put qty and rate and put it in total field please help

Answer 1

One way to accomplish this would be to create a method in your controller to do the calculation and then just call it on a change of qty or rate.
controller:
$scope.updateTotal = function(choice) {
if(!choice.qty || !choice.rate) {
choice.total = 0;
} else {
choice.total = choice.qty * choice.rate;
}
};
html:
<input type="text" ng-model="choice.qty" ng-change="updateTotal(choice)">
<input type="text" ng-model="choice.rate" ng-change="updateTotal(choice)">