What is initialised first - controller or partial/html? - javascript

Hi please explain reason for following three scenarios as I am unable to know why is this happening -
1)
<div ng-controller="myctrl">
<p>something for DOM manipulation</p>
</div>
2)in route I write
('someroute',{
templateUrl : "mytemplate",
controller : "myctrl"
});
mytemplate:
<div>
<p>something for dom manipulation</p>
</div>
3)
<div ng-include="mytemplate" ng-controller="myctrl"></div>
with template being same as above
The controllers in all the above scenarios are same, and in all of them I am just trying to select p tag of DOM by writing angular.element('p'). But this seems inconsistent. It works very well in 2nd scenario, it never works in 3rd scenario and I am not sure about 1st sccenario. Can someone explain which method is best for dom selection/manipulation, as I have to add a class to this 'p' tag on hover.
I am not understanding which gets initialized first- controller or partial?

Manipulating DOM inside controllers is discouraged. Quote from Best Practice - Dom Manipulations:
Dom Manipulations should not exist in controllers, services or anywhere else but in directives.
If you only need to style elements on hover, using the p:hover CSS selector would be enough without touching the DOM. ng-class and ng-mouseover can help you if you really want the class.
For more complex scenarios, you may want to write your own directive. You can check the article above for a guide to do that.
Load order from the first case: HTML first. Directives like ngController are loaded after parsing the HTML. Therefore the HTML already exists when the controller is loaded.
Load order for the second case: I'm not sure about it. You may check documentation for ngRoute or uiRouter depending on the router you are using.
Execution order for the third case: Controller first. The directive ngController have higher priority than the ngInclude directive. Therefore, the controller is loaded first.
Quote from ngController documentation :
This directive executes at priority level 500.
Quote from ngInclude documentation :
This directive executes at priority level 400.

Related

Angular.js: ngSwitch to show/hide rather than add/remove DOM elements

As I've recently found out, ngSwitch acts a bit like ngIf, in that it outright removes elements from the DOM rather than just hide them. Now in my application this strikes me as both needlessly expensive and potentially problematic down the line (if I need to access properties of my hidden DOM elements). At the same time I like the cleanliness of the ngSwitch syntax as opposed to a bunch of different ngShow directives (which would not allow me to include a 'default' behaviour either). Is there any way I can modify the way this directive works to have it merely hide elements, not remove them altogether? Thanks.
OK, I understood better your need and I have the same need before.
I advice you to use ngSwitch with custom directives like this :
<div ng-switch="mode">
<directive-a ng-switch-when="a"></directive-a>
<directive-b ng-switch-when="b">...</directive-b>
<directive-c ng-switch-default>...</directive-c>
</div>
and in the definitions of your directives directiveA, directiveB and directiveC you use the templateUrl wich will use the cache from the second call of the directive.
The second approach is to use ng-show on every directive but I prefer the ng-switch because it let the dom lighter.
I know this is a bit old but I faced the same issue today and I managed to cache segments views by not using ngSwitch but directly the [hidden] attributes with the segment condition this way :
<ion-segment [(ngModel)]="segmentName">
<ion-segment-button value="profile">
Profile
</ion-segment-button>
<ion-segment-button value="friends">
Friends
</ion-segment-button>
</ion-segment>
<page-profile [hidden]="segmentName != 'profile'" ></page-profile>
<page-friends [hidden]="segmentName != 'friends'" ></page-friends>
Just replace ngSwitchCase by the [hidden] conditional
No, there isn't any way to keep nodes hidden as ngShow and ngHide do if you use ngSwitch. Only the ngSwitchWhen node will be created if its condition is true, all others are commented.
The advantage of ngSwitch is that the dom will be lighter.

Custom Attribute Directive being matched to ng-attr-myCustomAttribute

I am using a third party lib with the following custom attribute directive:
angular.directive('snapDrawer', function () {
'use strict';
return {
restrict: 'AE',
...
So if the attribute "snap-drawer" is found in an HTML element the directive implementation has a match and fires, for example:
<div snap-drawer></div>
I am using Angular 1.3 which has an "AllOrNothing" approach to ng-attr where if the value conditional is undefined then the attribute does not render like so:
<div ng-attr-snap-drawer="{{data.addSnapDrawer}}"></div>
100% fact this works, the value of data.addSnapDrawer in my controller is undefined and the snap-drawer attr does not render in the DOM
I have verified that Angular 1.3 does this AllOrNothing approach with ng-attr here: What is the best way to conditionally apply attributes in Angular? (take a look at Mathew Foscarini's answer)
BUT what does render in the DOM is:
<div ng-attr-snap-drawer="{{data.addSnapDrawer}}" class="snap-drawer snap-drawer-left" style=""></div>
So, unbelievably, the angular.directive('snapDrawer') is matching to "ng-attr-snap-drawer". How can this be, I am really shocked that AngularJS, in all its glory, has a bug like this.
I cannot find anything online. I cannot set snap-drawer="false" I need it to not appear in the DOM, which I achieved by upgrading from Angular 1.2 to 1.3.
This is old, but I stumbled upon something very similar. https://github.com/angular/angular.js/issues/16441 - angular authors made it this way.
You need to devise a different way (depending on your usecase) to conditionally apply directives (e.g. use ng-switch and have two versions of the HTML; one with the directive and one without, or have a terminal directive with high priority that evaluates the expression during the linking phase, applies the necessary directive(s) and compiles the element).

Angular custom directive - two way binding which always sets attribute to true or false

I'm creating a custom Angular directive for a slide in menu which needs to watch a couple of attributes and one of those attributes needs to be two way bound to the main controller scope (sometimes). However, sometimes the attribute will not be added by the developer so it needs to be added automatically and set to the default (false). So, the directive can be used like this.
<slide-menu position="right" is-open="menuIsOpen"></slide-menu>
or like this:
<slide-menu></slide-menu>
When used the first way the main controller will be able to open and close the menu by changing the value of the boolean $scope.menuIsOpen.
When used without supplying the is-open attribute it should default to false and is obviously used internally and by a child toggle directive.
An additional complication is that whether the attribute is supplied by the developer or not it should exist in the DOM. so in the second example above the directive would set itself to false by default and add the attribute is-open="false" to the DOM?
The reason for requiring is-open="false/true" in the DOM at all times is that the menu is actually operated using CSS tansitions which use the following selector:
slide-menu[is-active="true"]{
// Slide the menu in using transforms/transitions
}
There is a jsfiddle here which shows how far I have got.
http://jsfiddle.net/jonhobbs/gEPvE/
Obviously it doesn't work, but it shows how I have tried to set a default and how I have tried to use # and & on the isolated scope for a one time binding (the menu position) and a 2 way bound expression for the is-open variable.
I'm clearly a long way from achieving what I need but any advice would really be appreciated.
Have a look at this fiddle http://jsfiddle.net/gEPvE/38/
I took the one you started and updated it to act like you specified.
You can make a two way binding value optional by adding a ? on the scope definition.
Like this
{
scope: {
'isOpen':'=?'
}
}
Now the is-open attribute is optional.
Then you can set the default value in the directive controller, like you had started to do.
Next, in order to synchronize the DOM attribute with the scope value you can use $watch.
$scope.$watch('isOpen', function(val) {
$element.attr('is-open', val);
});
Finally, I changed the second 'slideMenuToggle' directive to wrap/transclude its element in order to add an ng-click handler. This is mainly to avoid any nastiness with calling $scope.$apply yourself.
Let me know if that works for you.
EDIT
Answering your question in the comment, you can pass a value directly without having it be bound to the scope, you just need to wrap the value in quotes.
For example
<div ng-controller='ctrl'>
<hello world='imOnScope'></hello>
</div>
Assuming 'hello' is a directive with a scope of 'world': '=?' then angular will assign a reference to the parent scope's 'imOnScope' object to the directive's $scope.world member, allowing a two way binding scenario.
To just provide a value directly you may do something like this
<div ng-controller="ctrl">
<hello world="'directValue'"></hello>
</div>
In this scenario angular will just assign 'directValue' to the directive's $scope.world member.
You need to add ngTouch to your module.
var app = angular.module('app', ['ngTouch']);
And add this script:
http://ajax.googleapis.com/ajax/libs/angularjs/1.2.1/angular-touch.js
The reason for requiring is-open="false/true" in the DOM at all times
is that the menu is actually operated using CSS tansitions which use
the following selector
Forcing directive attributes to be appropriate for css selectors is terrible idea. As you correctly stated, they are for developers. So add a class to the element dynamically.
It seems that you're misusing &, it would be ok to set up a callback, but since you don't do this, in its current state you can end up with one-way # with confidence.
I guess it can be something like this (just added ngTouch and ng-controller for parent scope).
You could replace
$scope.watch('isOpen', function () {
$element.toggleClass('opened', $scope.isOpen);
});
with
$scope.watch('isOpen', function () {
$attrs.isOpen = !!$scope.isOpen;
});
and get the behaviour you're asking for, easy as that. Ok, it is boolean now, and it reflects the scope, and you can use [is-open=true] selector. But guess what will happen with your binding? Broken. Fortunately, you can do
$scope.watch('isOpen', function () {
$element.attr('is-open', !!$scope.isOpen);
});
instead. Voila, we tricked Angular because it doesn't look after jqlite. But what will will happen with the binding when the directive will be re-compiled for any reason? Again, isOpen's binding is non-existing 'true' or 'false' scope variable. Broken.

Getting an Element in AngularJS

It seems that getting an element in AngularJS is a bad idea, i.e. doing something like:
$('.myElement')
in say, a controller is not an angular way of doing things.
Now my question is, how should I get something in angular?
Right now, what I'm doing (and is an accepted way of doing it) is by watching a variable, and my directive does something based on it.
scope.$watch('varToWatch', function (varToWatch) {
if(attrs.id == varToWatch)
{
//Run my Directive specific code
}
});
However, while this particular design works for most cases, watch is an expensive operation, and having lots of directives watching can really slow down your application.
TL:DR - What is an angular way of getting a directive based on a variable on the directive? (like the one above)?
If you want to get/set values you don't need to fetch the element using jQuery. Angular data binding is the way to do it.
directives is the way to go if you want to do animations or any kind of element attributes and DOM manipulation.
Your code is basically right; the directive should watch something in the $scope and perform it's logic when that thing changes. Yes, watch statements are expensive, and that is a problem once your number of watches start to approach ~2000.
Looking at your code though, I see one problem:
The variable $scope.varToWatch references an id in the template.
When this variable changes, you want something to happen to the element which has this id.
The problem here is in the first point: The controller should know nothing about the DOM, including the id of any element. You should find another way to handle this, for example:
<div my-directive="one"> ... </div>
<div my-directive="two"> ... </div>
<div my-directive="three"> ... </div>
...etc
And in your directive:
scope.$watch('varToWatch', function (varToWatch) {
if(attrs.myDirective == varToWatch)
{
// Run my Directive specific code
}
});
You are very vague as to what you're trying to achieve, but I'll try to answer in context of your last comment.
I have a lot of the same directives (therefore the code will run on all of them), but I need to get only one directive from the lot.
You talk a lot about getting the right element. The directive element is passed to the link function in the directive. If you are not using this element (or children of it) directly, but rather trying to search for the element you want somehow, you are most likely approaching the problem the wrong way.
There are several ways to solve this, I'm sure. If you're thinking about animations, there is already support for that in Angular, so please don't try reinvent the wheel yourself. For other logic, here are two suggestions:
Secondary directive
If the logic you want to apply to this directive is generic, i.e. it could be applied to other directives in your application, you could create a new directive which works together with directives. You can set prioritization in directive in order to control which directive is executed first.
<main-directive ... helper-directive="{{condition_for_applying_logic}}"></main-directive>
jsFiddle example
Expanding main directive
If the logic is tightly coupled to this directive, you can just create a new attribute, either dynamic or static, and bind to it in the directive. Instead of checking 'attrs.id == varToWatch', you check if $scope.apply-logic === 'true' and apply the logic then.
<main-directive ...></main-directive> <!-- Not applied here -->
<main-directive apply-logic="true" ...></main-directive> <!-- Applied here -->
<main-directive apply-logic="{{some.varOnScope}}"...></main-directive> <!-- Conditional -->
Please comment if something is unclear.

AngularJS : Apply a directive only if element is a textarea

I wrote an attribute restricted Angular directive (restrict:'a') that adds features to textarea. It makes no sense to apply it to any other type of element.
Adding a if (element.nodeName == 'TEXTAREA') { is really dirty and unreliable.
I tried to add require: textarea to it but it does not work and I get this error: Error: No controller: textarea
Question: Is there any cleaner way to properly apply this restriction?
EDIT: Additional constraint following the first answer.
I want to avoid using a template in this directive as I want to be able to use several directive of this type. Here is an example of what I'd like:
<textarea splittable shared mergeable></textarea>
When using your own directive (eg my-textarea) with restrict: 'E', replace: true, any additional attributes will get carried over to the root-element of the directive, even other attribute directives. So:
<my-textarea splittable class="foobar"></my-textarea>
could be rendered as:
<textarea splittable="" class="foobar"></textarea>
with splittable being executed.
demo: http://jsfiddle.net/LMq3M/
So I think using your own directive is realy the cleanest way to handle this.
In my opinion there is no need to add such controls as they just tend to add complex code when the real issue is human error.
Just document what the purpose and usage is for the directive.
The idea is you give your directive a unique name, like myDirective and you can use it in HTML as such.
<body>
<my-directive></my-directive>
</body>
The directive will replace the tag with the template you provided in the directive controller. Which could be in your case a simple textarea element with added properties.
I recommend watching this video to clearly grasp the concept of directives.
http://www.youtube.com/watch?v=xoIHkM4KpHM

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