AngularJS: Modifying the template in a Directive with scoped attribute dependencies

As I delve into customizing a template within a directive and incorporating references to attributes in the parent scope, I find myself navigating through the Angular framework as a newcomer. My journey has led me to leaning on Customizing the template within a Directive, yet I hit a roadblock when attempting to pass a reference to a parent-scoped variable as an attribute to the directive; it remains unresolved, perhaps due to its undefined state at the time the compile function is invoked.

The blueprint of my directive appears as follows:

app.directive('sectionHeader', function() {
  return {
    restrict: 'EC',
    replace: true,
    transclude: true,
    scope: {sectionName:'@sectionName', imageUrl:'@imageUrl'},
    compile: function(element, attrs) {
      var imageHtml = attrs.hasOwnProperty('imageUrl') ? '<div style="float: left; padding-right: 5px;"><img class="float_left" src="' + attrs.imageUrl + '" alt=""/></div>' : '';
      var htmlText =
        '<div>' + imageHtml + '<h1 class="float-left">' + attrs.sectionName + '</h1>' +
        '<div class="clear"></div>' +
        '<div class="modal_hr"></div></div>';
      element.replaceWith(htmlText);
    },
  };
});

Meanwhile, the directive usage scenario unfolds like this:

 <div class="section-header" section-name="{{currentFeatureName}}"></div>

The hitch lies in the fact that the {{currentFeatureName}} variable from my controller seemingly lacks definition during the compilation process triggered by the directive.

In brainstorming potential workarounds, one idea involved establishing an observer function within the compile phase that monitors changes to the sectionName attribute, updating the h1 element's content accordingly. However, this approach struck me as somewhat cumbersome, prompting me to inquire if there exists a more streamlined or elegant alternative.

Answer №1

Make sure to explore the $observe feature found in the Directive documentation.

However, it seems like there might be a simpler way to achieve what you were attempting. Take a look at this:

var app = angular.module('plunker', []);
app.controller('AppController',
    [
      '$scope',
      function($scope) {
        $scope.currentFeatureName = 'Current Feature Name';
        $scope.imageUrl = "https://lh3.googleusercontent.com/GYSBZh5RpCFwTU6db0JlHfOr_f-RWvSQwP505d0ZjWfqoovT3SYxIUPOCbUZNhLeN9EDRK3b2g=s128-h128-e365";
      }
    ]
  );

app.directive('sectionHeader', function() {
  return {
    restrict: 'EC',
    replace: true,
    transclude: true,
    scope: {
      sectionName:'@',
      imageUrl:'@'
    },
    template: '<div><div style="float: left; padding-right: 5px;" ng-show="imageUrl"><img class="float_left" ng-src="{{imageUrl}}" alt=""/></div><h1 class="float-left">{{sectionName}}</h1><div class="clear"></div><div class="modal_hr"></div></div>'
  };
});

HTML:

<div ng-controller="AppController">
  <div class="section-header" section-name="{{currentFeatureName}}" image-url="{{imageUrl}}"></div>
</div>

Check it out on Plunker.

Answer №2

It's clear why this isn't working as expected. Interpolated attributes remain unresolved during the compile and link functions because a digest cycle hasn't occurred yet to evaluate them to their actual values. For further information, you can refer to this resource. Your suggestion of using

attrs.$observe( 'sectionName', function ( val ) { ... });
is on point.

However, it seems like there may not be a need for a dynamic template in your case. If your template looked like this:

<div>
  <div style="float: left; padding-right: 5px;" ng-show="{{imageUrl}}">
    <img class="float_left" ng-src="{{imageUrl}}" alt="" />
  </div>
  <h1 class="float-left">{{sectionName}}</h1>
  <div class="clear"></div>
  <div class="modal_hr"></div>
</div>

Then neither a compile nor a link function would require any additional logic. This approach could simplify your code structure as well.

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