angularjs - ng-init does not initialize my selected model -

i have select option list of titles i.e. mr, mrs, dr etc. api, code looks in front end:

<select class="form-control" name="titleselect" id="titleselect" ng-options="option.value option in titledata.availableoptions track option.key" ng-model="adult[$index].selectedtitle" ng-init="adult[$index].selectedtitle = titledata.availableoptions[0]"></select> 

and in controller:

var getpassengertitle = passengerdetailsandcarddetailsservice.getpassengertitle(); 

passengerdetailsandcarddetailsservice service, api data i.e. title data. furthermore service returns promise.

this set title data:

    getpassengertitle.then(function(result){                         $scope.availabletitles = angular.fromjson(result.titlelist);         $scope.templistoftitles = [];          for(var key in $scope.availabletitles){                          $scope.templistoftitles.push({key : key, value : $scope.availabletitles[key]});         };                $scope.titledata = {                 availableoptions: $scope.templistoftitles,         };      }); 

when try ng-init first option (that mr.) not work in blank option shown. when tried statically defining titledata in object works, please me?

update:

i failed mention title data inside ng-repeat support input multiple people/passengers in case. therefore i'm using adult[$index] creates ng-model each person/passenger.

i not sure if required behavior want, if want initialise title on selecting option can either use value ng-model or use event handler ng-change. here example jsbin handles change , assigns new value ng-model. let me know if looking for