Angular component - associated calls

I've created a unique custom directive specifically for the widget attribute shown below:

<div widget></div>

Essentially, this directive generates template code and inserts the html inside the widget-tag. Here's a snippet of the directive in action:

skdApp.directive("widget", function() {
  return {
    restrict: 'A',
    template: customizedTemplate,
    link: function($scope, element, attributes) {
      /*
       * Implement event handlers and enhance user interface components here
       */
    }
  }

The customizedTemplate consists of basic HTML code which also utilizes other custom directives (such as the <seal> tag):

var customizedTemplate = '<div ng-controller="OfferCtrl">' +
                     '<div class="container">' +
                       <seal></seal>' +
                       '...'+
                     '</div>' +
                   '</div>';

Within my Controller, I initiate data retrieval to display within the <div widget>. I utilize an 'Offer' service that encapsulates all the logic for requesting server-side data using Offer.query().

skdApp.controller('OfferCtrl', function OfferCtrl ($scope, Offer) {
  var response = Offer.query({id: 1}, function (data) {
    $scope.offer = data;
  });
});

In the callback function, I bind the retrieved result to the scope. However, I encounter an issue where the directive itself initiates additional data requests based on the previously received data from Offer.query(). This implies that the ID returned by Offer.query() (referred to as MyID) is crucial for the seal directive to fetch more data.

Hence, I have concentrated most of my logic within the Offer.query() callback function. Yet, I'm pondering potential alternatives, like shifting this responsibility to the link function of the <seal> directive:

skdApp.directive("seal", function() {

  var sealMarkup = '<div>{{offer.data.foobar}}</div>';

  return {
    restrict: 'E',
    template: sealMarkup,
    link: function($scope, element, attrs) {

      $scope.$watch('offer.myId', function (newValue, oldValue) {

       if (typeof newValue !== "undefined") {

         /* Fetch supplementary data utilizing myID 
          * and assign the outcome to offer.data
          */    

       }

      });

    }
});

Is this angular-compatible approach optimal, or are there alternate methods (in terms of structure) within AngularJS that could be more efficient?

Answer №1

The ability to view offer.myId in the child directive is possible because both the parent (widget) and the child (seal) share the same scope. By default, a directive does not create a new scope.

To prevent scope clobbering, I suggest broadcasting a custom event to notify the child directive and using an isolated scope if necessary.

http://docs.angularjs.org/api/ng.$rootScope.Scope

Answer №2

Presenting this solution in a Reverse-Jeopardy style (a question posed as an answer), I've been contemplating a recently encountered problem. Initially, some behavioral traits of the solution seemed "incorrect" to me, but upon deeper examination, I realized that these traits might actually be beneficial in certain specific scenarios.

I must emphasize that this is not a one-size-fits-all solution for every instance of binding asynchronously returned data. Rather, it serves to illustrate that there are various possible approaches to tackling the questions raised by such scenarios. Sometimes, it may indeed be necessary to halt UI rendering until a service call completes, while in other situations, maintaining a responsive UI for unrelated tasks could be more suitable.

Consider, for instance, an order processing system where it may be crucial to prevent client interactions with view elements until a sales transaction outcome is known. In contrast, this approach would not be applicable to a web-based spreadsheet application involving server-side formula computations.

It's remarkable that both asynchronous and synchronous methods can coexist in addressing this requirement. Providing a promise object does not compel the client to utilize it any more than exposing return values in a scope forces a client to monitor them.

The following demonstrates handling this need synchronously, supplementing the previously explored asynchronous watch( ) method:

var servicesModule = servicesModule || angular.module('myModule', []);

servicesModule.factory('thingClient', 
    ['$http', '$q', function( $http, $q ) {
        return new ThingClient($http, $q);
    }]
);

function ThingClient($http, $q) {
    function callService(scopeObject) {
        var defer = $q.defer();
        var promise = defer.promise;
        $http({
            method: 'POST',
            url: 'http://at/some/url/',
            data: { x: 'y', y: 'z', z: 'x', one: 1, two: 2, three: 3},
            cache: false
        }, function(data) {
            scopeObject.data = data;
            defer.resolve(data);
        }, function() {
            scopeObject.data = null;
            defer.resolve(null)
        });

        return promise;
    }
}

client-service.js

function ConsumingController( $scope, thingClient ) {
    // Ensure to use an object (enabling prototypical inheritance and reference passing without altering the scope itself). Set the 'data' element as undefined to allow transitioning from undefined to null in case of failure.
    $scope.dto = { data: undefined };
    var promise = thingClient.callService(scope.dto);

    // Asynchronous strategy
    $scope.$watch('offer.myId', function (newValue, oldValue) {
        if( newValue == null ) {
            // Fail!
        } else {
            // Succeed!
        }
    }

    // Synchronous strategy
    if( promise.then( 
        function(data) { 
            if( data == null ) { 
                // Fail
            } else {
                // Succeed
            }
        }
    }
}

consuming-controller.js

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