Retrieving DOM element after updating the model in Angular

Recently delving into Angular development. I've come across an issue where I'm attempting to retrieve a DOM element after the model has been updated, only to find it returning null. Below is the snippet of my HTML code.

<div ng-repeat="file in files">
 <span id="file{{file.id}}">{{file.name}}</span>
 <canvas id="canvas{{file.id}}" />
</div>

Shown here is the relevant controller code:

angular.module('mycontrollers',[])
 .controller('FileController',function(FileService) {
       $scope.files = {};
    FileService.updateFiles()
        .then(
        function(data) {
            $scope.files = data.files;
            updateCanvas($scope.files);
        },function(err) {
            console.log("error occured");
        };
 };
function updateCanvas(files) {
    files.forEach(function(file){
    var canvas = document.getElementById('canvas'+file.id);
    ... 
    do something with canvas
    ...
    }
}

The critical problem arises when the canvas appears as null due to document.getElementById failing to locate the desired element. The server response functions correctly (thus the exclusion of FileService code). Data within data.files remains appropriate.

Seeking insight on how to access the element post-model update.

Answer №1

The reason for this is that the model has been updated, but the DOM has not caught up yet.

To address this issue, you can use a timeout when calling your updateCanvas function. This will ensure that the function runs after the DOM has been fully updated:

.controller('FileController',function(FileService, $timeout) {
    ....
    $timeout(function() { updateCanvas($scope.files) });

Answer №2

I suggest utilizing directives for DOM manipulation rather than directly manipulating the DOM using IDs.

Here is a working example:

http://jsfiddle.net/jigardafda/1ou63cgf/2/

HTML

<div ng-app="app">
    <div ng-controller="tcrtl">
        <div ng-repeat="file in files">
            <span>{{file.name}}</span>
            <my-canvas conf="file"></my-canvas>
        </div>
    </div>
</div>

JS

var app = angular.module('app', []);
app
    .service('FileService', function($q){
        // Mock service 
        var files = [
            {
                name: "ONE",
                id: 'one'
            },
            {
                name: "TWO",
                id: 'two'
            }
        ]

        this.updateFiles = function(){
            var deferred = $q.defer();
            deferred.resolve({
                files: files
            });
            return deferred.promise;
        };

    })
    .directive('myCanvas', function(){
        return {
            restrict: 'E',
            template: "<canvas id='{{conf.id}}' />",
            scope: {
                conf: '='
            },
            controller: function(){
                // Perform actions 
            },
            link: function(scope, ele, attr){
                var c = ele[0].querySelector("canvas");
                var ctx = c.getContext("2d");
                ctx.fillStyle = "#FF0000";
                ctx.fillRect(0,0,150,75);
            }
        }
    })
    .controller('tcrtl',function($scope, FileService) {
        $scope.files = {};
        FileService.updateFiles().then(
            function(data) {
                $scope.files = data.files;
            },function(err) {
                console.log("error occurred");
            });
    });

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