AngularJs select directive with init value from another scope attribute

Question

I can't get the ng-init directive in my select picker with AngularJs. No option is selected even id productQuantity/unitName has a value.

Here how my JSON Object is formed:

inventoryLines: Array[1]
 0: Object
   permitedFormatUnits: Array[2]
     0: Object
       unitName: "Kilo"
     1: Object
       unitName: "Gramme
   productQuantity: Object
     formatUnit: Object
       unitName: "Gramme"
     quantity: 456

I need the permitedFormatUnits to be the choices that the user can make and the productQuantity/formatUnit to be the ng-init value and the ng-model value has well.

Here's my html where line represents an inventoryLines in a ng-repeat loop:

 <select class="selectpicker" name="unitFormat"
   ng-init="formatUnit = line.productQuantity.formatUnit.unitName"
   ng-model="line.productQuantity.formatUnit"
   ng-options="formatUnit as formatUnit.unitName for formatUnit in line.permitedFormatUnits">
 </select>

Thanks you very much for your help, hope I have been clear enough! :

Answer 1

Here is a working plunkr: http://plnkr.co/edit/TyWqjW2KQ0LEngWX9uVx

You need to use the track by to make it work (see the doc - https://docs.angularjs.org/api/ng/directive/select):

<select class="selectpicker" name="unitFormat"
        ng-init="formatUnit = line.productQuantity.formatUnit"
        ng-model="line.productQuantity.formatUnit"
        ng-options="formatUnit as formatUnit.unitName for formatUnit in line.permitedFormatUnits track by formatUnit.unitName">
</select>   

the js:

angular.module('myApp', [])
    .controller('myCtrl', function($scope) {
        $scope.line = {
            permitedFormatUnits: [{
                unitName: "Kilo"
            }, {
                unitName: "Gramme"
            }],
            productQuantity: {
                formatUnit: {
                    unitName: "Gramme",
                    quantity: 456
                }
            }

        }
    })