How to Lazyload controller and template in one request using angular-ui-router

Ronald Brinkerink

I'm trying to lazy-load components. The component is an html fragment with an embedded script tag that contains the controller.

<script>
    ... controller code .....
</script>
<div>
    ... template ....
</div>

The fragment is generated in ONE html request so I cannot use templateUrl AND componentURL in the state definition.

I have tried to use the templateProvider to get the component, than extract the script code for the function and register it using a reference to the controllerProvider.

I'm sure there must be a better way to do this than the ugly solution I have come up with. I make a global reference to the controllerpovider, then I read the component thru the templateProvide using a getComponent service. Next I extract the script and evaluate it, which also registers the controller.

See the plunker for the way I'm trying to solve this.

.factory('getComponent', function($http, $q) {
  return function (params) {
    var d = $q.defer();
    // optional parameters
    $http.get('myComponent.html').then(function (html) {
            // the component contains a script tag and the rest of the template.
            // the script tags contain the controller code.
            // first i extract the two parts
            var parser = new window.DOMParser();
            var doc = parser.parseFromString(html.data, 'text/html');
            var script = doc.querySelector('script');
            // Here is my problem. I now need to instantiate and register the controller. 
            // It is now done using an eval which of cours is not the way to go
            eval(script.textContent);
            // return the htm which contains the template
            var html = doc.querySelector('body').innerHTML;
            d.resolve(html);
    });
    return d.promise;
  };
})

Maybe it could be done using a templateProvider AND a controllerProvider but I'm not sure how to resolve both with one http request. Any help / ideas would be greatly appreciated.

Chris T

Here's a working plunkr

You do not have access to $controllerProvider at runtime, so you cannot register a named controller.
- UI-Router doesn't require named/registered controller functions. { controller: function() {} } is perfectly valid in a state definition
- However, if you need the controller to be registered, you could use a tool like ocLazyLoad to register it.
UI-Router links the controller to the template, so there's no need for ng-controllersprinkled in the html.

Here's how I hacked this together. getController factory now keeps a cache of "promises for components". I retained your eval and template parsing to split the response into the two pieces. I resolved the promise with an object containing the ctrl/template.

component factory

  .factory('getComponent', function($http, $q) {
      var components = {};
      return function (name, params) {
        if (components[name]) 
          return components[name];

        return components[name] = $http.get(name + '.html').then(extractComponent);

        function extractComponent(html) {
          var parser = new window.DOMParser();
          var doc = parser.parseFromString(html.data, 'text/html');
          var script = doc.querySelector('script');
          // returns a function from the <script> tag
          var ctrl = eval(script.textContent);
          // return the htm which contains the template
          var tpl = doc.querySelector('body').innerHTML;
          // resolve the promise with this "component"
          return {ctrl: ctrl, tpl: tpl};
        }
      };
  })

myComponent.html

<script>
  var controller = function($scope) {
    $scope.sayHi = function() {
      alert(' Hi from My controller')
    }
  };
  // This statement is assigned to a variable after the eval()
  controller;
</script>

// No ng-controller
<div>
  Lazyloaded template with controller in one pass.
  <button ng-click="sayHi()">Click me to see that the controller actually works.</button>
</div>

In the state definition:

I created a resolve called 'component'. That resolve asks the getComponent factory to fetch the component called 'myComponent' (hint: 'myComponent' could be a route parameter)
When it's ready, the resolve is exposed to the UI-Router state subtree.
The state is activated
The view is initialized
- The controller provider and template provider inject the resolved component, and return the controller/template to UI-Router.

Smell test

I should mention that fetching a controller and template in a single html file and manually parsing smells wrong to me.

Some variations you could pursue:

Improve the getComponent factory; Split the component into html/js and fetch each separately. Use $q.all to wait for both fetches.
Use ocLazyLoad to register the controller globally with $controllerProvider
Fetch and store the template in the $templateCache.

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edited at2021-03-30

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