Call an AngularJS function when an NFC tag is read?

Question

I've written a small demo application using Ionic and the phonegap-nfc which can read the unique ID from an NFC tag.

Now, I'm trying to create a list that shows previous read events. An event should be added to this list a tag is read.

I have a list which can have events added to it. The code looks like this:

<ion-view view-title="Usage History">
  <ion-content>
    <button class="button button-icon" ng-click="newTask()">
      <i class="icon ion-compose"></i>
    </button>
    <ion-list>
      <ion-item class="item-remove-animate item-avatar item-icon-right" ng-repeat="chat in chats" type="item-text-wrap" href="#/tab/tasks/{{task.id}}">
        <img ng-src="{{task.pic}}">
        <h2>{{task.name}}</h2>
        <p>{{task.lastText}}</p>
        <i class="icon ion-chevron-right icon-accessory"></i>

        <ion-option-button class="button-assertive" ng-click="remove(task)">
          Delete
        </ion-option-button>
      </ion-item>
    </ion-list>
    <script id="new-task.html" type="text/ng-template">

    <div class="modal">

    <!-- Modal header bar -->
    <ion-header-bar class="bar-secondary">
    <h1 class="title">New Task</h1>
    <button class="button button-clear button-positive" ng-click="closeNewTask()">Cancel</button>
    </ion-header-bar>

    <!-- Modal content area -->
    <ion-content>

    <form ng-submit="createTask(task)">
    <div class="list">
    <label class="item item-input">
    <input type="text" placeholder="What do you need to do?" ng-model="task.name">
    </label>
    </div>
    <div class="padding">
    <button type="submit" class="button button-block button-positive">Create Task</button>
    </div>
    </form>

    </ion-content>

    </div>

    </script>
  </ion-content>
</ion-view>

The controller looks like this:

.controller('TasksCtrl', function($scope, $ionicModal) {

  $scope.tasks= [];

  // Create and load the Modal
  $ionicModal.fromTemplateUrl('new-task.html', function(modal) {
    $scope.taskModal = modal;
  }, {
    scope: $scope,
    animation: 'slide-in-up'
  });

  // Called when the form is submitted
  $scope.createTask = function(task) {
    $scope.chats.push({
      name: task.name
    });
    $scope.taskModal.hide();
    task.name= "";
  };

  // Open our new task modal
  $scope.newTask = function() {
    $scope.taskModal.show();
  };

  // Close the new task modal
  $scope.closeNewTask = function() {
    $scope.taskModal.hide();
  };

  $scope.remove = function(task) {
    tasks.remove(task);
  };
})

All of this works fine. You have a button which opens up a modal where you can add a task. Pressing the button closes the modal and the task is now in the list.

However, I want to automatically create a task when a NFC tag is read. I'm a beginner using Angular, so I don't know how to replace the "ng-click" action with something else that corresponds to a NFC action with phonegap-nfc.

The controller for the NFC events looks like this:

.controller('MainController', function ($scope, nfcService) {

  $scope.tag = nfcService.tag;
  $scope.clear = function() {
    nfcService.clearTag();
  };
})

.factory('nfcService', function ($rootScope, $ionicPlatform) {
  var tag = {};
  $ionicPlatform.ready(function() {
    nfc.addTagDiscoveredListener(function (nfcEvent) {
      console.log(JSON.stringify(nfcEvent.tag, null, 4));
      $rootScope.$apply(function(){
        angular.copy(nfcEvent.tag, tag);
        // if necessary $state.go('some-route')
      });
    }, function () {
      console.log("Listening for tags.");
    }, function (reason) {
      alert("Error adding NFC Listener " + reason);
    });

    nfc.addMimeTypeListener('', function (nfcEvent) {
      console.log(JSON.stringify(nfcEvent.tag, null, 4));
      $rootScope.$apply(function(){
        angular.copy(nfcEvent.tag, tag);
        // if necessary $state.go('some-route')
      });
    });
  });
  return {
    tag: tag,
    clearTag: function () {
      angular.copy({}, this.tag);
    }
  };
});

How can I perform this?

Answer 1

Your nfcService is already listening for the tagDiscovered event so you just need to let the TaskCtrl know that something happened. To do that you have a couple of options

1. Use events / broadcast

a. In nfcService

$rootScope.$emit('tagFound', tag);

b. In TaskCtrl

$rootScope.$on('tagFound', function(tag) {
    newTask();
});

2. Register a callback function

a. Add function in nfcService

var cb = null;
this.registerListener = function (callback){
    this.cb = callback;
}
// inside addTagDiscoveredListener
...
cb.call(tag)

b. in taskCtrl

// inject service as nfcService
nfcService.registerListener(myCallback)

function myCallback(tag) { 
    newTask();
}

3. Go to a new state

   // in nfcService $state.go('/tasks/add');

I usually do option 2 but don't forget to unregister to unblock garbage collection. Services shouldn't care about states though so option 3 is not the best way imho