AngularJS checkbox dynamic ng-true-value expression

Question

I\'m trying to build a calculator for daycare prices in Angular.

Every location in the company franchise has separate prices for every day. So my thinking was to bui

Answer 1

Expression in the ng-true-value will be evaluated only once, so it won't be dynamic.

One alternative approach is to calculate the values in ng-change callback instead.

Please see my fork http://plnkr.co/edit/9zYS3OZ0sSkXX9rHwcgv?p=preview for the full example.

In html:

<input type="checkbox" ng-model="selectedDays.monday" ng-change="calculatePrice()" /> Mon
<input type="checkbox" ng-model="selectedDays.tuesday" ng-change="calculatePrice()" /> Tue            <br />
<input type="checkbox" ng-model="selectedDays.wednesday" ng-change="calculatePrice()" /> Wed
<input type="checkbox" ng-model="selectedDays.thursday" ng-change="calculatePrice()" /> Thu            <br />
<input type="checkbox" ng-model="selectedDays.friday" ng-change="calculatePrice()" /> Fri

and in controller:

$scope.calculatePrice = function(){
  $scope.formData.location.day = {};

  angular.forEach($scope.selectedDays, function (selected, day) {
    if (selected) {
      $scope.formData.location.day[day.slice(0, 3)] = $scope.data.bso[$scope.formData.location.ID].prices[day];
    }
  });
}

$scope.selectedDays = {};

Answer 2

It seems ng-true-value does not accept non-constant expressions. From the docs(v1.3.0):

Some attributes used in conjunction with ngModel (such as ngTrueValue or ngFalseValue) will only accept constant expressions.

Examples using constant expressions include:

<input type="checkbox" ng-model="..." ng-true-value="'truthyValue'">
<input type="checkbox" ng-model="..." ng-false-value="0">

Examples of non-constant expressions include:

<input type="checkbox" ng-model="..." ng-true-value="someValue">
<input type="checkbox" ng-model="..." ng-false-value="{foo: someScopeValue}">

An ideal workaround probably would be calling a Controller method on ng-click or ng-change inside which you can analyse all the checkboxes for truthy or non-truthy values.

Answer 3

Another approach is to delay the creation of the checkbox until the value is ready (on scope or whatever).

In my case I was loading a value via http that wasn't on the scope when the checkbox was created. So I just wrapped it in an ng-if.

          <div class="checkbox" ng-if="viewData.conditionId != undefined">
            <label>
              <input type="checkbox" ng-true-value="{{'\''+ viewData.conditionId + '\''}}" ng-false-value="undefined" ng-model="model.conditionId" required />
              I agree
            </label>
          </div>

Which worked perfectly for my scenario. Yours is a bit different but the same principal should apply - delay creation of the checkbox until you know the value being bound is there.

And yes the stupid quotation marks seem to be necessary.