is there a post render callback for Angular JS directive?

The question:

I ‘ve just gotten my directive to pull in a template to append to its element like this:

# CoffeeScript
.directive 'dashboardTable', ->
  controller: lineItemIndexCtrl
  templateUrl: "<%= asset_path('angular/templates/line_items/dashboard_rows.html') %>"
  (scope, element, attrs) ->
    element.parent('table#line_items').dataTable()
    console.log 'Just to make sure this is run'

# HTML
<table id="line_items">
    <tbody dashboard-table>
    </tbody>
</table>

I am also using a jQuery Plugin called DataTables. The general usage of it is like this: $(‘table#some_id’).dataTable(). You can pass in the JSON data into the dataTable() call to supply the table data OR you can have the data already on the page and it will do the rest.. I am doing the latter, having the rows already on the HTML page.

But the problem is that I have to call the dataTable() on the table#line_items AFTER DOM ready. My directive above calls the dataTable() method BEFORE the template is appended to the directive’s element. Is there a way that I can call functions AFTER the append?

Thank you for your help!

UPDATE 1 after Andy’s answer:

I want to make sure that the link method does only get called AFTER everything is on the page so I altered the directive for a little test:

# CoffeeScript
#angular.module(...)
.directive 'dashboardTable', ->
    {
      link: (scope,element,attrs) -> 
        console.log 'Just to make sure this gets run'
        element.find('#sayboo').html('boo')

      controller: lineItemIndexCtrl
      template: "<div id='sayboo'></div>"

    }

And I do indeed see “boo” in the div#sayboo.

Then I try my jquery datatable call

.directive 'dashboardTable',  ->
    {
      link: (scope,element,attrs) -> 
        console.log 'Just to make sure this gets run'
        element.parent('table').dataTable() # NEW LINE

      controller: lineItemIndexCtrl
      templateUrl: "<%= asset_path('angular/templates/line_items/dashboard_rows.html') %>"
    }

No luck there

Then I try adding a time out :

.directive 'dashboardTable', ($timeout) ->
    {
      link: (scope,element,attrs) -> 
        console.log 'Just to make sure this gets run'
        $timeout -> # NEW LINE
          element.parent('table').dataTable()
        ,5000
      controller: lineItemIndexCtrl
      templateUrl: "<%= asset_path('angular/templates/line_items/dashboard_rows.html') %>"
    }

And that works. So I wonder what goes wrong in the non-timer version of the code?

The Solutions:

Below are the methods you can try. The first solution is probably the best. Try others if the first one doesn’t work. Senior developers aren’t just copying/pasting – they read the methods carefully & apply them wisely to each case.

Method 1

If the second parameter, “delay” is not provided, the default behaviour is to execute the function after the DOM has completed rendering. So instead of setTimeout, use $timeout:

$timeout(function () {
    //DOM has finished rendering
});

Method 2

I had the same problem and I believe the answer really is no. See Miško’s comment and some discussion in the group.

Angular can track that all of the function calls it makes to manipulate the DOM are complete, but since those functions could trigger async logic that’s still updating the DOM after they return, Angular couldn’t be expected to know about it. Any callback Angular gives might work sometimes, but wouldn’t be safe to rely on.

We solved this heuristically with a setTimeout, as you did.

(Please keep in mind that not everyone agrees with me – you should read the comments on the links above and see what you think.)

Method 3

You can use the ‘link’ function, also known as postLink, which runs after the template is put in.

app.directive('myDirective', function() {
  return {
    link: function(scope, elm, attrs) { /*I run after template is put in */ },
    template: '<b>Hello</b>'
  }
});

Give this a read if you plan on making directives, it’s a big help: http://docs.angularjs.org/guide/directive

Method 4

Although my answer is not related to datatables it addresses the issue of DOM manipulation and e.g. jQuery plugin initialization for directives used on elements which have their contents updated in async manner.

Instead of implementing a timeout one could just add a watch that will listen to content changes (or even additional external triggers).

In my case I used this workaround for initializing a jQuery plugin once the ng-repeat was done which created my inner DOM – in another case I used it for just manipulating the DOM after the scope property was altered at controller. Here is how I did …

HTML:

<div my-directive my-directive-watch="!!myContent">{{myContent}}</div>

JS:

app.directive('myDirective', [ function(){
    return {
        restrict : 'A',
        scope : {
            myDirectiveWatch : '='
        },
        compile : function(){
            return {
                post : function(scope, element, attributes){

                    scope.$watch('myDirectiveWatch', function(newVal, oldVal){
                        if (newVal !== oldVal) {
                            // Do stuff ...
                        }
                    });

                }
            }
        }
    }
}]);

Note: Instead of just casting the myContent variable to bool at my-directive-watch attribute one could imagine any arbitrary expression there.

Note: Isolating the scope like in the above example can only be done once per element – trying to do this with multiple directives on the same element will result in a $compile:multidir Error – see: https://docs.angularjs.org/error/$compile/multidir

Method 5

May be am late to answer this question. But still someone may get benefit out of my answer.

I had similar issue and in my case I can not change the directive since, it is a library and change a code of the library is not a good practice. So what I did was use a variable to wait for page load and use ng-if inside my html to wait render the particular element.

In my controller:

$scope.render=false;

//this will fire after load the the page

angular.element(document).ready(function() {
    $scope.render=true;
});

In my html (in my case html component is a canvas)

<canvas ng-if="render"> </canvas>

Method 6

I had the same issue, but using Angular + DataTable with a fnDrawCallback + row grouping + $compiled nested directives. I placed the $timeout in my fnDrawCallback function to fix pagination rendering.

Before example, based on row_grouping source:

var myDrawCallback = function myDrawCallbackFn(oSettings){
  var nTrs = $('table#result>tbody>tr');
  for(var i=0; i<nTrs.length; i++){
     //1. group rows per row_grouping example
     //2. $compile html templates to hook datatable into Angular lifecycle
  }
}

After example:

var myDrawCallback = function myDrawCallbackFn(oSettings){
  var nTrs = $('table#result>tbody>tr');
  $timeout(function requiredRenderTimeoutDelay(){
    for(var i=0; i<nTrs.length; i++){
       //1. group rows per row_grouping example
       //2. $compile html templates to hook datatable into Angular lifecycle
    }
  ,50); //end $timeout
}

Even a short timeout delay was enough to allow Angular to render my compiled Angular directives.

Method 7

None of the solutions worked for me accept from using a timeout. This is because I was using a template that was dynamically being created during the postLink.

Note however, there can be a timeout of ‘0’ as the timeout adds the function being called to the browser’s queue which will occur after the angular rendering engine as this is already in the queue.

Refer to this: http://blog.brunoscopelliti.com/run-a-directive-after-the-dom-has-finished-rendering

Method 8

Here is a directive to have actions programmed after a shallow render. By shallow I mean it will evaluate after that very element rendered and that will be unrelated to when its contents get rendered. So if you need some sub element doing a post render action, you should consider using it there:

define(['angular'], function (angular) {
  'use strict';
  return angular.module('app.common.after-render', [])
    .directive('afterRender', [ '$timeout', function($timeout) {
    var def = {
        restrict : 'A', 
        terminal : true,
        transclude : false,
        link : function(scope, element, attrs) {
            if (attrs) { scope.$eval(attrs.afterRender) }
            scope.$emit('onAfterRender')
        }
    };
    return def;
    }]);
});

then you can do:

<div after-render></div>

or with any useful expression like:

<div after-render="$emit='onAfterThisConcreteThingRendered'"></div>

Method 9

I got this working with the following directive:

app.directive('datatableSetup', function () {
    return { link: function (scope, elm, attrs) { elm.dataTable(); } }
});

And in the HTML:

<table class="table table-hover dataTable dataTable-columnfilter " datatable-setup="">

trouble shooting if the above doesnt work for you.

1) note that ‘datatableSetup’ is the equivalent of ‘datatable-setup’. Angular changes the format into camel case.

2) make sure that app is defined before the directive.
e.g. simple app definition and directive.

var app = angular.module('app', []);
app.directive('datatableSetup', function () {
    return { link: function (scope, elm, attrs) { elm.dataTable(); } }
});

Method 10

Following the fact that the load order cannot be anticipated, a simple solution can be used.

Let’s look at the directive-‘user of directive’ relationship.
Usually the user of the directive will supply some data to the directive or use some functionality ( functions ) the directive supplies.
The directive on the other hand expects some variables to be defined on its scope.

If we can make sure that all players have all their action requirements fulfilled before they attempt to execute those actions – everything should be well.

And now the directive:

app.directive('aDirective', function () {
    return {
        scope: {
            input: '=',
            control: '='
        },
        link: function (scope, element) {
            function functionThatNeedsInput(){
                //use scope.input here
            }
            if ( scope.input){ //We already have input 
                functionThatNeedsInput();
            } else {
                scope.control.init = functionThatNeedsInput;
            }
          }

        };
})

and now the user of the directive html

<a-directive control="control" input="input"></a-directive>

and somewhere in the controller of the component that uses the directive:

$scope.control = {};
...
$scope.input = 'some data could be async';
if ( $scope.control.functionThatNeedsInput){
    $scope.control.functionThatNeedsInput();
}

That’s about it. There is a lot of overhead but you can lose the $timeout.
We also assume that the component that uses the directive is instantiated before the directive because we depend on the control variable to exist when the directive is instantiated.


All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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