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AngularJS: Function in controller called multiple times by template

I know this question has been asked in here before it seem that all the answers is either quotes from AngularJS doc or doesn't provide with a solution (not a solution I understand anyway) so I'll give it a try once more.
My experience with Angular is relatively new, started out some month ago, so please forgive my ignorance if this is basic knowledge.
Within a list of posts (iterate by using ng-repeat) I've a special "share to" button.
The link on the button (href) depends on three different factors: post_id, user_id, network.
I'm trying to do this, within my ng-repeat="post in posts"
<a href ng-href="{{genShareUrl(post.id,post.author_id,'fb')}}>Facebook</a>
The original function which perform the generation is in a factory, I just use genShareUrl as a middleman function between controller and factory.
When logging out from the genShareUrl function in the post controller, I see this function is called multiple times.
Actually, if I run it on full scale on all posts fetched from backend, my app just come to a halt. No error, just eternal loading (I figured that I might have inadvertently triggered some kind of eternally $digest loop I'm unfamiliar with or at least some exponentially call pattern).
I've tried to recreate the scenario with a simple example:
http://codepen.io/Mestika/pen/xVexRa
Here I can see, that the function first is called twice, then four times - which indicates to me that the digest cycle is triggered multiple time.
In such a case as described, how would I best go about generating some value in a link? Is this the best practice? If no, how or could you give me an example on how to refactor the code.

Angular uses dirty checking to achieve two-way binding, all two-way binding watchers would be evaluated in each digest cycle, that is the reason genShareUrl be called multiple times, to avoid this happened, you could use one-way binding in your template:
<a href ng-href="{{::genShareUrl(post.id,post.author_id,'fb')}}>Facebook</a>

I'd like suggest a best practice for your case:
Resolve start-up logic for a controller in an activate function.
So, you can add an activate function as follows:
activate();
function activate() {
angular.forEach($scope.json, function (p) {
p.btoa = $scope.func(p.id);
});
}
After that, you can update your template and use:
<div ng-repeat="person in json">
<a href ng-href="/user/{{person.btoa}}">{{person.firstName + ' ' + person.lastName}}</a>
</div>
In that way you'll avoid multiple calls to your function due to two-way data binding behavior.
Take a look following links:
Angular Styleguide
Your example updated: http://codepen.io/anon/pen/wGZBEX

Is there really no difference between AngularJS $scope and Controller as syntax?

I am learning angularJS and while learning found the controller as syntax much easier to read and a little easier for me coming from the OO world to understand. I have read several articles and SO answers that all seem to point to $scope and the 'controller as ' syntax being the same and that the 'controller as' syntax is just syntactical sugar.
However, I posted another question on SO here and the user that answered the question says that I have to still inject $scope to use the 'ui select' directives even though I am using the controller as syntax. Which is it? And if I don't have to use the $scope, what am I missing to get the 'controller as' syntax to work with ui-select?

Sorry this is long with no examples.
A controller in both forms Controller and Controller As are functions. The main difference from my understanding is Controller As when called is called using the new keyword which is why the 'this' syntax works. This is also why you can do the prototype inheritance with Controller As syntax while you can't do that with the normal Controller syntax. The other cool part about Controller As is the namespacing you can place the scope variables in which means in the HTML it is easy to reason which parts go to which controller. If you want I can give examples but that is the core difference from my understanding.

The controllerAs syntax exposes your controller to the template, so rather than binding a bunch of properties to $scope in your controller, you can make them properties of an instance of your controller. (Controllers are JavaScript "class" constructors.)
So if you have the following:
angular.module('myApp')
.controlller('MyController', function() {
var vm = this;
vm.foo = 'bar';
});
...you can access it in your template like this:
<div ng-controller="MyController as vm">
{{ vm.foo }}
</div>
Now, if you want to access scope variables in your controller -- or call a scope method such as $on -- you still need to inject $scope into your controller. Note the $ before scope, which indicates it is a service. This $scope service simply exposes the current scope.
All of that said, if you find yourself injecting $scope into your controller, you should question your approach. Better to create a custom directive and access scope via the link function, or access scope from the template.
Recommended reading: http://www.johnpapa.net/do-you-like-your-angular-controllers-with-or-without-sugar/

controller as is nice because you can nest ng-controllers and know which controller you're acting on
<div ng-controller="Ctrl1 as c1">
<--Using c1 here -->
<div ng-controller="Ctrl2 as c2">
<-- Using c2 here -->
</div>
<--Using c1 here -->
</div>

In AngularJS, how does $scope get passed to scope?

I'm a bit confused with the use of $scope in controllers and of scope in directives. Please verify if my understanding is correct (and also provide some alternative ways how to do this).
Let's say I have an html:
<div ng-controller="app1_Ctrl">
.
.
.
<input type="text" ng-model="value"/>
<input type="checkbox" />
<button ng-click="submit()"></button>
</div>
And my main.js
(function() {
angular.module('mainApp', ['app1']);
})();
And my app1 looks like this (based on official AngularJS documentation here)
(function() {
var app = angular.module('app1', []);
app.controller('app1_Ctrl', ["$scope", function($scope) {
.
.
.
}]);
app.directive('app1_Dir1', [function() {
function link(scope, element, attr) {
scope.$watch(attr.someAttrOfCheckBox, function() {
// some logic here
});
function submit() {
// some logic here
}
}
return link;
}]);
})();
How does $scope.value passed in scope in directive so that I can do some manipulations there? Will ng-click fire the function submit() in the directive link? Is it correct to use scope.$watch to listen for an action (ticked or unticked of course) in checkbox element?
Many thanks to those who can explain.

By default, directive scope is controller $scope; but it means the directive is directly dependent on your controller and you need a different controller for each instance of the directive you want to use. It is usually considered a best practice to isolate your directive scope and specifically define the variables you wish to pass it from your controller.
For this, you will need to add a scope statement to your directive :
scope {
label :'#',
context : '=',
function : '&'
}
and update your view :
<my-directive label="labelFromController" context="ctxtFromController" function="myFunction()" ></my-directive>
The symbols denote the kind of thing you wish to pass through : # is for one-way binding (as a string in your directive), = is for two-way binding of an object (which enables the directive to update something in your controller), and & is for passing a function.
There are a lot of additional options and subtleties that are best explained by the Angular doc https://docs.angularjs.org/guide/directive. There are also some nice tutorials out there (e.g. http://www.sitepoint.com/practical-guide-angularjs-directives/)
Your submit() function is not attached to anything, so you won't be able to call if from your viewer. You need to define it as scope.submit = function() ... in your link function if you wish to access it.
You can use $watch for this kind of thing, but there are usually other more elegant ways to achieve this by leveraging the fact that angular already "watches" the variables it is aware of and monitors any changes he can (this can be an issue when some external service changes data for exemple, because angular cannot listen to events it is not made aware of). Here, you can probably simply associate the ng-model directive to your input checkbox to store its true/fale (checked/unchecked) value, and the ng-change or ng-click directives to act on it. The optimal solution will mostly depend on the exact nature of your business logic.
Some additional thoughts :
The HTML insides of your directive should be packaged in an inline template field, or in a separate HTML file referenced by the templateUrl field in your directive.
In your HTML code above, your directive is not referenced anywhere. It should be an element, attribute or class (and your directive definition should reflect the way it can be called, with the restrict field). Maybe you have omitted the line containing the directive HTML, but as it stands, your directive doesn't do anything.
To my knowledge, you don't need to return link. Think of it as the "body" of your directive, where you define the variables and functions you will call in the HTML.
Your directive doesn't actually need HTML code and the above thoughts might be irrelevant if you are going in a different direction, but encapsulating some kind of view behaviour that you want to reuse is probably the most common use of directives.

AngularJs "controller as" syntax - clarification?

I read about the new syntax from angularJS regarding controller as xxx
The syntax InvoiceController as invoice tells Angular to instantiate
the controller and save it in the variable invoice in the current
scope.
Visualization :
Ok , so I wont have the parameter $scope in my controller and the code will be much cleaner in the controller.
But
I will have to specify another alias in the view
So Until now I could do :
<input type="number" ng-model="qty" />
....controller('InvoiceController', function($scope) {
// do something with $scope.qty <--notice
And now I can do :
<input type="number" ng-model="invoic.qty" /> <-- notice
....controller('InvoiceController', function() {
// do something with this.qty <--notice
Question
What is the goal of doing it ? removing from one place and add to another place ?
I will be glad to see what am I missing.

There are several things about it.
Some people don't like the $scope syntax (don't ask me why). They say that they could just use this. That was one of the goals.
Making it clear where a property comes from is really useful too.
You can nest controllers and when reading the html it is pretty clear where every property comes.
You can also avoid some of the dot rule problems.
For example, having two controllers, both with the same name 'name', You can do this:
<body ng-controller="ParentCtrl">
<input ng-model="name" /> {{name}}
<div ng-controller="ChildCtrl">
<input ng-model="name" /> {{name}} - {{$parent.name}}
</div>
</body>
You can modify both parent and child, no problem about that. But you need to use $parent to see the parent's name, because you shadowed it in your child controller. In massive html code $parent could be problematic, you don't know where that name comes from.
With controller as you can do:
<body ng-controller="ParentCtrl as parent">
<input ng-model="parent.name" /> {{parent.name}}
<div ng-controller="ChildCtrl as child">
<input ng-model="child.name" /> {{child.name}} - {{parent.name}}
</div>
</body>
Same example, but it is much much clearer to read.
$scope plunker
controller as plunker

The main advantage with controller as syntax I see is that you can work with controllers as classes, not just some $scope-decorating functions, and take advantage of inheritence. I often run into a situation when there's a functionality which is very similar to a number of controllers, and the most obvious thing to do is to create a BaseController class and inherit from it.
Even though there's is $scope inheritence, which partially solves this problem, some folks prefer to write code in a more OOP manner, which in my opinion, makes the code easier to reason about and test.
Here's a fiddle to demonstrate: http://jsfiddle.net/HB7LU/5796/

I believe one particular advantage is clear when you have nested scopes. It will now be completely clear exactly what scope a property reference comes from.

Source
Difference between Creating a controller using the $scope object and Using the “controller as” syntax and vm
Creating a controller using the $scope object
Usually we create a controller using the $scope object as shown in the listing below:
myApp.controller("AddController", function ($scope) {
$scope.number1;
$scope.number2;
$scope.result;
$scope.add = function () {
$scope.result = $scope.number1 + $scope.number2;
}
});
Above we are creating the AddController with three variables and one behaviour, using the $scope object controller and view, which talk to each other. The $scope object is used to pass data and behaviour to the view. It glues the view and controller together.
Essentially the $scope object performs the following tasks:
Pass data from the controller to the view
Pass behaviour from the controller to the view
Glues the controller and view together
The $scope object gets modified when a view changes and a view gets modified when the properties of the $scope object change
We attach properties to a $scope object to pass data and behaviour to the view. Before using the $scope object in the controller, we need to pass it in the controller function as dependencies.
Using the “controller as” syntax and vm
We can rewrite the above controller using the controller as syntax and the vm variable as shown in the listing below:
myApp.controller("AddVMController", function () {
var vm = this;
vm.number1 = undefined;
vm.number2=undefined;
vm.result =undefined;
vm.add = function () {
vm.result = vm.number1 + vm.number2;
}
});
Essentially we are assigning this to a variable vm and then attaching a property and behaviour to that. On the view we can access the AddVmController using controller as syntax. This is shown in the listing below:
<div ng-controller="AddVMController as vm">
<input ng-model="vm.number1" type="number" />
<input ng-model="vm.number2" type="number" />
<button class="btn btn-default" ng-click="vm.add()">Add</button>
<h3>{{vm.result}}</h3>
</div>
Ofcourse we can use another name than “vm” in the controller as syntax. Under the hood, AngularJS creates the $scope object and attaches the properties and behaviour. However by using the controller as syntax, the code is very clean at the controller and only the alias name is visible on the view.
Here are some steps to use the controller as syntax:
Create a controller without $scope object.
Assign this to a local variable. I preferred variable name as vm, you can choose any name of your choice.
Attach data and behaviour to the vm variable.
On the view, give an alias to the controller using the controller as syntax.
You can give any name to the alias. I prefer to use vm unless I’m not working with nested controllers.
In creating the controller, there are no direct advantages or disadvantages of using the $scope object approach or the controller as syntax. It is purely a matter of choice, however, using the controller as syntax makes the controller’s JavaScript code more readable and prevents any issues related to this context.
Nested controllers in $scope object approach
We have two controllers as shown in the listing below:
myApp.controller("ParentController", function ($scope) {
$scope.name = "DJ";
$scope.age = 32;
});
myApp.controller("ChildController", function ($scope) {
$scope.age = 22;
$scope.country = "India";
});
The property “age” is inside both controllers, and on the view these two controllers can be nested as shown in the listing below:
<div ng-controller="ParentController">
<h2>Name :{{name}} </h2>
<h3>Age:{{age}}</h3>
<div ng-controller="ChildController">
<h2>Parent Name :{{name}} </h2>
<h3>Parent Age:{{$parent.age}}</h3>
<h3>Child Age:{{age}}</h3>
<h3>Country:{{country}}</h3>
</div>
</div>
As you see, to access the age property of the parent controller we are using the $parent.age. Context separation is not very clear here. But using the controller as syntax, we can work with nested controllers in a more elegant way. Let’s say we have controllers as shown in the listing below:
myApp.controller("ParentVMController", function () {
var vm = this;
vm.name = "DJ";
vm.age = 32;
});
myApp.controller("ChildVMController", function () {
var vm = this;
vm.age = 22;
vm.country = "India";
});
On the view these two controllers can be nested as shown in the listing below:
<div ng-controller="ParentVMController as parent">
<h2>Name :{{parent.name}} </h2>
<h3>Age:{{parent.age}}</h3>
<div ng-controller="ChildVMController as child">
<h2>Parent Name :{{parent.name}} </h2>
<h3>Parent Age:{{parent.age}}</h3>
<h3>Child Age:{{child.age}}</h3>
<h3>Country:{{child.country}}</h3>
</div>
</div>
In the controller as syntax, we have more readable code and the parent property can be accessed using the alias name of the parent controller instead of using the $parent syntax.
I will conclude this post by saying that it’s purely your choice whether you want to use the controller as syntax or the $scope object. There is no huge advantage or disadvantage to either, simply that the controller as syntax you have control on the context is a bit easier to work with, given the clear separation in the nested controllers on the view.

I find the main advantage is a more intuitive api since the methods/properties are associated with the controller instance directly and not the scope object. Basically, with the old approach, the controller becomes just a decorate for building up the scope object.
Here are some more info on this: http://www.syntaxsuccess.com/viewarticle/551798f20c5f3f3c0ffcc9ff

From what I've read, $scope will be removed in Angular 2.0, or at least how we view the use of $scope. It might be good to start using controller as as the release of 2.0 nears.
Video link here for more discussion on it.

How to dynamically inject controller in AngularJS

How to set ng-controller as an expression from the $scope?
According to the documentation:
ngController – {expression} – Name of a globally accessible
constructor function or an expression that on the current scope
evaluates to a constructor function.
But how to evaluate scope expression as a controller for controllers that have been registered with module .controller?
For example:
Layout:
<div ng-controller="myExpr"></div>
JavaScript (define controller):
app.controller('myCtrl', ['$scope', '$timeout', function () { ... }];
JavaScript (parent scope):
$scope.myExpr = ...;
What should be in myExpr to use myCtrl as a controller via expression?
I've tried $controller('myCtrl')... not working...
P.S. If controller has been defined via globally accessible function.. it's possible to provide it as myExpr. But what to do if it has been defined so?

The expressions that ng-controller accept are a bit wierd. So you can do this by writing your controller slightly differently (but read below as for why you probably don't want to).
function myCtrl($scope) {
$scope.value = 'Stuff';
}
This is a controller and will work like normal for this case. Like in this example: http://jsbin.com/ubevel/2/edit
So why not do it?
First of all this is not a good way to define things from a testing perspective. Secondly, this allows you to set the controller dynamically on load but it won't allow you to change things after that. If you change the value of myExpr after the page has loaded the controller will not change.
So what to do?
I would highly suggest looking at using a service instead. Swap out your actions by supplying your outer controller with a service that you then change in the same manner you are now trying to change the inner controller. So something like: http://jsbin.com/ubevel/5/edit
This service can be swapped out on the fly, changing it will change the actions that are available in the scope.
You could also use an include, but this would result in duplicate html. I personalty am fine with this since I am against reusing html for two different types objects (sooner or later you want to change one but not the other and it becomes a mess). But a lot of people would object to that.
An extra note: There are probably nicer ways to do it with controllers, I probably haven't looked at all angles, but I just don't think controllers are the right tool for this case.