angular link function iElement magic in angular-ui example - javascript

Angular provides the instance element of the current scope within a link function.
The iElement angular passes is capable of doing things beyond a standard HTML element. How does angular do this? Wrap it with jQuery first?
How does the link element in this angular-ui tinymce implementation get the tinymce method e.g. the method shown below on line 49:
elm.tinymce();
I get that the ui-tinymce attribute links to the directive named uiTinymce, and that tinymce is included in the main html, but i don't understand how elm get the method tinymce.
As a reference I've provided the relevant documentation on iElement from http://docs.angularjs.org/guide/directive below.
Linking function:
function link(scope, iElement, iAttrs, controller) { ... }
The link function is responsible for registering DOM listeners as well as updating the DOM. > It is executed after the template has been cloned. This is where most of the directive logic > will be put.
scope - Scope - The scope to be used by the directive for registering watches.
iElement - instance element - The element where the directive is to be used. It is safe to manipulate the children of the element only in postLink function since the children have already been linked.

From the angular.element page:
Note: All element references in Angular are always wrapped with jQuery
or jqLite; they are never raw DOM references.
So yes, the iElement argument is a jQueryLite, or full jQuery object, which has all of the relevant additional methods that jQuery/jQueryLite provide.
This includes any additional methods that are added via jQuery's plugin mechanisms, which have the effect of being able to call those methods directly on the jQuery object itself.
So the TinyMCE JS file would have code to add in a .tinymce() function to all jQuery objects, which is how the iElement object has it.
Does that make sense?

Related

In angularjs, when making a directive, is there a way to manipulate the DOM of the template using the link function?

Let's say I'm creating a dynamic directive in angularjs. I want to use the link function to manipulate the DOM of the template html based on the arguments.
So in vanilla javascript, I would do something like the following:
var template = ... //something here that sets the variable to the template
var newdiv = document.createElement("div");
template.appendChild(newdiv);
I found some answers where they treat the template like a string and just splice in the literal string "<div></div>".
However, I plan to do a lot of modification so treating it as a string will quickly get too confusing, and will be unmaintainable if I do it. If possible, I would like to treat it the same way I treat the page's DOM in regular js.
I am also open to having no template, and just dynamically generating the whole thing in the link function, if it's possible for me to somehow get the directive to return this
Compiled element can be modified in link function. No bindings or directives can be added to the element at this point without recompilation.
...
link: function (scope, element, attrs) {
// jqLite element that partly implements jQuery API
element.append(...);
// native element that is wrapped with jqLite
var nativeElement = element[0];
nativeElement.appendChild(...);
}

AngularJS: Dynamically add/remove wrapping directives to existing ones

So I need to be able to call a function of a directives controller, have it wrap an existing child directive in a new one while maintaining the now wrapped directive's state (both it's controller and all possible children) and otherwise modify the parent directive's template. This process also has to able to reversed.
Quick and super dirty fiddle to show the idea
So the DOM starts as:
<split>
<innerDirective></innerDirective>
</split>
When the split directive's controller's function is called, this should happen:
<split> // same outer parent
<split> // new directive
<innerDirective></innerDirective>// SAME innerDirective instance
</split>
<split>// new directive
<innerDirective></innerDirective> //New innderDirective instance
</split>
</split>
I originally used the .html function to set the split directives content, and used $compile service to reconstruct the DOM. This of course destroys the original innerDirective. Since it may be deep, it is not feasible to store it's data in the parent split and retrieve with a link function (although I tried).
I also tried using jquery's .wrap and .unwrap functions, which works, except the added tags aren't compiled as directives, so not really.
Is there a proper way to do this, or a way to compile just the outer tag added with the .wrap, and update the scope of the innerDirective to the new parent?
Thanks for any help and advice you may have!
Edit:
I have a controller along this lies, lets say set to control the split 'E' directive:
function SplitCtrl($scope, $compile){
//stuff
//First way, redefine html contents and recompile
this.split1 = function(){
//element has been linked to the directive's element
$scope.element.html('<split></split><split></split>');
$compile($scope.element.contents())($scope);
};
//Second way, jquery.wrap
this.split2 = function(){
$($scope.element).children('innerDirective').wrap('<split />');
// then I need to instantiate the new split
// without reinstantiating now wrapped directive.
// Adding second split is fine in this case, I can do that.
};
};
The template is:
<innderDirective></innerDirective>

What are the benefits of a directive template function in Angularjs?

According to the documentation a template can be a function which takes two parameters, an element and attributes and returns a string value representing the template. It replaces the current element with the contents of the HTML. The replacement process migrates all of the attributes and classes from the old element to the new one.
The compile function deals with transforming the template DOM. It takes three parameters, an element, attributes and transclude function. The transclude parameter has been deprecated. It returns a link function.
It appears that a template and a compile functions are very similar and can achieve the same goal. The template function defines a template and compile function modifies the template DOM. However, it can be done in the template function itself. I can't see why modify the template DOM outside the template function. And vice-versa if the DOM can be modified in the compile function then what's the need for a template function?
The compilation function can be used to change the DOM before the resulting template function is bound to the scope.
Consider the following example:
<div my-directive></div>
You can use the compile function to change the template DOM like this:
app.directive('myDirective', function(){
return {
// Compile function acts on template DOM
// This happens before it is bound to the scope, so that is why no scope
// is injected
compile: function(tElem, tAttrs){
// This will change the markup before it is passed to the link function
// and the "another-directive" directive will also be processed by Angular
tElem.append('<div another-directive></div>');
// Link function acts on instance, not on template and is passed the scope
// to generate a dynamic view
return function(scope, iElem, iAttrs){
// When trying to add the same markup here, Angular will no longer
// process the "another-directive" directive since the compilation is
// already done and we're merely linking with the scope here
iElem.append('<div another-directive></div>');
}
}
}
});
So you can use the compile function to change the template DOM to whatever you like if your directive requires it.
In most cases tElem and iElem will be the same DOM element, but sometimes it can be different if a directive clones the template to stamp out multiple copies (cf. ngRepeat).
Behind the scenes, Angular uses a 2-way rendering process (compile + link) to stamp out copies of a compiled piece of DOM, to prevent Angular from having to process (= parse directives) the same DOM over and over again for each instance in case the directive stamps out multiple clones resulting in much better performance.
Hope that helps!
ADDED AFTER COMMENT:
The difference between a template and compile function:
Template function
{
template: function(tElem, tAttrs){
// Generate string content that will be used by the template
// function to replace the innerHTML with or replace the
// complete markup with in case of 'replace:true'
return 'string to use as template';
}
}
Compile function
{
compile: function(tElem, tAttrs){
// Manipulate DOM of the element yourself
// and return linking function
return linkFn(){};
}
}
The template function is called before the compile function is called.
Although they can perform almost identical stuff and share the same 'signature', the key difference is that the return value of the template function will replace the content of the directive (or the complete directive markup if replace: true), while a compile function is expected to change the DOM programmatically and return a link function (or object with pre and post link function).
In that sense you can think of the template function as some kind of convenience function for not having to use the compile function if you simply need to replace the content with a string value.
Hope that helps!
One of the best uses of the template function is to conditionally generate a template. This allows you to automate the creation of a template based on an attribute or any other condition.
I have seen some very large templates that use ng-if to hide sections of the template. But instead of placing everything into the template and using ng-if, which can cause excessive binding, you can remove sections of the DOM from the output of the template function that will never be used.
Let's say you have a directive that will include either sub-directive item-first or item-second. And the sub-directive will not ever change for the life of the outer directive. You can adjust the output of the template, prior to the compile function being called.
<my-item data-type="first"></my-item>
<my-item data-type="second"></my-item>
And the template string for these would be:
<div>
<item-first></item-first>
</div>
and
<div>
<item-second></item-second>
</div>
I agree that this is an extreme simplification, But I have some very complicated directives and the outer directive needs to display one of, about, 20 different inner directives based on a type. Instead of using transclude, I can set the type on the outer directive and have the template function generate the correct template with the correct inner directive.
That correctly formatted template string is then passed on to the compile function, etc.

Detect "hooked" DOM elements

So I have a set of jQuery plugins, really basic stuff, but I split the code into plugins because I don't like having a huge jQuery(document).ready() function where I store the entire application logic.
Each plugin has a "destructor", which is basically a function that I defined in the plugin prototype object. This function unbinds events used by the plugin, removes DOM elements that were added by the plugin etc.
Plugins are initialized like this:
$('.element').plugin();
Is there any way I can get all the elements that have my plugins attached to them, from another plugin which is supposed to replace the body HTML, so I can call the destructor function?
I was thinking to store each plugin instance inside a global array, then I can access that array from any plugin. But maybe there is a better way that doesn't use the global state?
I don't think there is a ready made method for it... but as a hack you can add a class to the target elements in your plugin and then use that class to get all elements with the widget initialized lke
$.fn.plugin = function(){
this.addClass('my-plugin-class');
}
then to initialize
$(element).plugin()
to get all elements with the plugin
$('.my-plugin-class')....
But if it is a jQuery UI widget then you can use the selector $(':ui-widgetname'), see this answer
Arun P Johny wrote the rigth idea -- just delete 'footprint' of your job by marking the affected DOM elements with some specific class name.
I want just add an idea. Plugins are the methods of the library and nothing more. If you need the destroyer for constructor -- just make another plugin for it:
$.fn.overture = function (){...};// construct
$.fn.crescendo = function (){...};// more construct
$.fn.quietFarewell = function (){...};// destructor for everything above
$(...).overture().crescendo().quietFarewell();

What does this.$('.selector') do in jQuery?

I see this in someone's code: this.$('.selector') and am curious what that does. "this" is a Backbone view. So what does prefixing "this." onto a jQuery selector, in the given context, do?
From the doc:
$ (jQuery or Zepto)view.$(selector)
If jQuery or Zepto is included on
the page, each view has a $ function that runs queries scoped within
the view's element. If you use this scoped jQuery function, you don't
have to use model ids as part of your query to pull out specific
elements in a list, and can rely much more on HTML class attributes.
It's equivalent to running: view.$el.find(selector)
ui.Chapter = Backbone.View.extend({
serialize : function() {
return {
title: this.$(".title").text(),
start: this.$(".start-page").text(),
end: this.$(".end-page").text()
};
}
});
In short, it's used to access some elements of View with a familiar syntax.
It is basically limiting the search for elements with a class of selector to the element your View is based off of.
It's basically changing the scope of the search from document to this, which is obviously some element.

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