One way binding to an object in angular - javascript

I'd like to have a one-way (not one time) binding between an attribute on a directive, but i'm struggling with how to express this without attrs.$observe. The best I can come up with at the moment is to bind via &attr and invoke the variables I am binding to in my template e.g. {{attr()}}
app.controller('MainCtrl', function($scope) {
$scope.names = ['Original'];
setTimeout(function () {
$scope.names.push('Asynchronously updated name');
$scope.$apply();
}, 1000);
});
app.directive('helloComponent', function () {
return {
scope: {
'names': '&names'
},
template: '<li ng-repeat="name in names()">Hello {{name}}</li>'
}
});
<body ng-controller="MainCtrl">
<ul>
<hello-component names="names"/>
</ul>
</body>
Plunker
Is there a better way to do this that preserves the one-way binding without the need to invoke the bound properties?
Edit
I've updated the example code to clarify that I want to bind to an object, not just a string. So #attr (which works with a string attribute) is not a solution.

The "&" is actually the right thing to do. I have argued against this approach (with #JoeEnzminger, here and here) on the basis that it is semantically questionable. But overall Joe was right - this is the way to create a one-way binding to an actual object vs. "#" which binds to a string.
If you don't fancy an isolate scope, then you could get the same effect by using $parse:
var parsedName = $parse(attrs.name);
$scope.nameFn = function(){
return parsedName($scope);
}
and use it in the template as:
"<p>Hello {{nameFn()}}</p>"

I didn't see any mention of it in the other answers, but as of Angular 1.5, one-way bindings for objects are supported (see scope section in $compile docs for Angular 1.5.9):
< or <attr - set up a one-way (one-directional) binding between a local scope property and an expression passed via the attribute attr. The expression is evaluated in the context of the parent scope. If no attr name is specified then the attribute name is assumed to be the same as the local name. You can also make the binding optional by adding ?: <? or <?attr.
For example, given <my-component my-attr="parentModel"> and directive definition of scope: { localModel:'<myAttr' }, then the isolated scope property localModel will reflect the value of parentModel on the parent scope. Any changes to parentModel will be reflected in localModel, but changes in localModel will not reflect in parentModel. There are however two caveats:
one-way binding does not copy the value from the parent to the isolate scope, it simply sets the same value. That means if your bound value is an object, changes to its properties in the isolated scope will be reflected in the parent scope (because both reference the same object).
one-way binding watches changes to the identity of the parent value. That means the $watch on the parent value only fires if the reference to the value has changed. In most cases, this should not be of concern, but can be important to know if you one-way bind to an object, and then replace that object in the isolated scope. If you now change a property of the object in your parent scope, the change will not be propagated to the isolated scope, because the identity of the object on the parent scope has not changed. Instead you must assign a new object.
One-way binding is useful if you do not plan to propagate changes to your isolated scope bindings back to the parent. However, it does not make this completely impossible.
In the example below, one-way binding is used to propagate changes in an object in the scope of a controller to a directive.
Update
As pointed out by #Suamere, you can indeed change properties of a bound object with one-way-binding; however, if the whole object is changed from the local model, then the binding with the parent model will break, as the parent and local scope will be referring to different objects. Two-way binding takes care of this. The code snippet was updated to highlight the differences.
angular.module('App', [])
.directive('counter', function() {
return {
templateUrl: 'counter.html',
restrict: 'E',
scope: {
obj1: '<objOneWayBinding',
obj2: '=objTwoWayBinding'
},
link: function(scope) {
scope.increment1 = function() {
scope.obj1.counter++;
};
scope.increment2 = function() {
scope.obj2.counter++;
};
scope.reset1 = function() {
scope.obj1 = {
counter: 0,
id: Math.floor(Math.random()*10000),
descr: "One-way binding",
creator: "Directive"
};
};
scope.reset2 = function() {
scope.obj2 = {
counter: 0,
id: Math.floor(Math.random()*10000),
descr: "Two-way binding",
creator: "Directive"
};
};
}
};
})
.controller('MyCtrl', ['$scope', function($scope) {
$scope.increment = function() {
$scope.obj1FromController.counter++;
$scope.obj2FromController.counter++;
};
$scope.reset = function() {
$scope.obj1FromController = {
counter: 0,
id: Math.floor(Math.random()*10000),
descr: "One-way binding",
creator: "Parent"
};
$scope.obj2FromController = {
counter: 0,
id: Math.floor(Math.random()*10000),
descr: "Two-way binding",
creator: "Parent"
};
};
$scope.reset();
}])
;
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.5.6/angular.js"></script>
<div ng-app="App">
<script type="text/ng-template" id="counter.html">
<h3>In Directive</h3>
<pre>{{obj1 | json:0}}</pre>
<button ng-click="increment1()">
Increment obj1 from directive
</button>
<button ng-click="reset1()">
Replace obj1 from directive (breaks binding)
</button>
<pre>{{obj2 | json:0}}</pre>
<button ng-click="increment2()">
Increment obj2 from directive
</button>
<button ng-click="reset2()">
Replace obj2 from directive (maintains binding)
</button>
</script>
<div ng-controller="MyCtrl">
<counter obj-one-way-binding="obj1FromController"
obj-two-way-binding="obj2FromController">
</counter>
<h3>In Parent</h3>
<pre>{{obj1FromController | json:0}}</pre>
<pre>{{obj2FromController | json:0}}</pre>
<button ng-click="increment()">
Increment from parent
</button>
<button ng-click="reset()">
Replace from parent (maintains binding)
</button>
</div>
</div>

Doing an attribute literally passes a string. So instead of doing this:
<hello-component name="name"/>
You can do this:
<hello-component name="{{name}}"/>

This may be essentially the same approach proposed by New Dev, but I solved a similar problem for myself by taking an object off of my isolate scope and creating a getter function for it which called scope.$parent.$eval(attrs.myObj).
In a simplified version that looks more like yours I changed:
app.directive('myDir', [function() {
return {
scope : {
id : '#',
otherScopeVar : '=',
names : '='
},
template : '<li ng-repeat="name in names">{{name}}</li>'
}
}]);
to
app.directive('myDir', [function() {
return {
scope : {
id : '#',
otherScopeVar : '='
},
template : '<li ng-repeat="name in getNames()">{{name}}</li>',
link : function(scope, elem, attrs) {
scope.getNames() {
return scope.$parent.$eval(attrs.myList);
};
}
}
}]);
That way whenever a digest runs your object is pulled as is from the parent scope. For me, the advantage to doing it this way was that I was able to change the directive from two-way to one-way binding (which took my performance from unusable to working fine) without changing the views that used the directive.
EDIT
On second thought I am not sure this is exactly one-way binding, because while updating the variable and running a digest will always use the updated object, there is no inherent way to run other logic when it changes, as one could with a $watch.

Related

How The Object Scope Get That update available and get it ready to be exposed on the view AngularJs

In AngularJS the data-binding work to expose immediate data to our View !!
this stuff's due of the object scope which is the glue between the Logic Code AND The View.
Also all we know that AngularJs support the tow-way-binding !!!
My Question Is :
How the $scope can know that there object binding was changed or not??
if there while condition inside scope for auto-change detect or what?
Check angular.js file, we will get the code for ngBindDirective:
var ngBindDirective = ['$compile', function($compile) {
return {
restrict: 'AC',
compile: function ngBindCompile(templateElement) {
$compile.$$addBindingClass(templateElement);
return function ngBindLink(scope, element, attr) {
$compile.$$addBindingInfo(element, attr.ngBind);
element = element[0];
scope.$watch(attr.ngBind, function ngBindWatchAction(value) {
element.textContent = isUndefined(value) ? '' : value;
});
};
}
};
}];
Note the last two line, it used watcher for attribute ngBind, for any change it apply to the element.

Understanding one-way binding with angular 1.5

There is one thing I don't understand with one-way bindings demonstrated by the code and demo below:
var example = {
bindings: {
obj: '<',
prim: '<'
},
template: `
<div class="section">
<h4>
Isolate Component
</h4>
<p>Object: {{ $ctrl.obj }}</p>
<p>Primitive: {{ $ctrl.prim }}</p>
<a href="" ng-click="$ctrl.updateValues();">
Change Isolate Values
</a>
</div>
`,
controller: function () {
this.updateValues = function () {
this.prim = 10;
this.obj = {
john: {
age: 35,
location: 'Unknown'
}
};
};
}
};
function ParentController() {
this.somePrimitive = 99;
this.someObject = {
todd: {
age: 25,
location: 'England, UK'
}
};
this.updateValues = function () {
this.somePrimitive = 33;
this.someObject = {
jilles: {
age: 20,
location: 'Netherlands'
}
};
};
}
angular
.module('app', [])
.component('example', example)
.controller('ParentController', ParentController);
DEMO
The thing I don't understand is how the primitive value changes (or doesn't change) if you modify it in the isolated scope. As far as I understand if you one-way bind a primitive, the binding will break if you change that value within the isolated scope. With break I mean that an update by the parent will not propagate anymore into the isolated scope.
However, in the demo it doesn't exactly work like that.
HOW TO REPRODUCE: Go to the DEMO and first click the Change isolate values button. This will change the primitive in the isolated scope. Next click the Change Parent Values button. As you can see the primitive within the isolated scope is still updated. Based on this, I guess the binding doesn't break if you update a primitive inside the isolated scope, right?! But now things get weird. If you repeat this, you'll notice that this time the binding doesn't work anymore.
Can someone explain why the primitive value did change the first time but didn't the second time ?
UPDATE: Found the solution. The binding works perfect, because the value of the parent doesn't change anymore, its always 10. Here is an updated example which shows that it still works

Why is my angular directive not getting Parent controller scope inside isolated scope?

I've followed Angular docs precisely to get a directive working with an isolated scope containing a couple of vars from the parent Controller's scope object.
app.controller('MainCtrl', function($scope) {
$scope.name = 'Parent Name';
$scope.pokie = {
whyIs: "thisUndefined?"
};
});
app.directive('parseObject', function() {
var preLink = function($scope, el, att, controller) {
console.log('[link] :: ', $scope);
};
var postLink = function($scope, el, att, controller) {
console.log('[PostLink] :: ', $scope);
console.log('[$Parent] :: ', $scope.$parent.name);
};
return {
restrict: 'E',
scope: {
myPokie: '=pokie',
name: '=name'
},
template: [
'<div>',
'<h1>Directive does not get parent scope</h1>',
'<h1>{{ myPokie }}</h1>',
'<h2>{{ name }}</h2>',
'</div>'
].join(''),
compile: function() {
return {
pre: preLink,
post: postLink
}
}
}
});
http://plnkr.co/edit/FpQtt9?p=preview
Can anyone tell me what is wrong with my code? Why does the directive's Isolate scope return undefined values for 'myPokie' and 'name'?
I've seen other people saying you have to use $scope.watch for this.. but angular's directive docs don't say anything about that.. And I really don't want to use $scope.watch for something so trivial which should work out of the box.
As you declared isolated scope in your directive, that means you are going to provide those value to your directive using attribute.
scope: {
myPokie: '=pokie',
name: '=name'
}
This means your directive scope will not be prototypically inherited from the parent scope. pokie attribute provide the value for myPokie & name attribute will provide value of name for your directive, = indicating a two way binding if your myPokie value change in directive, the same referencing value will change in the parent controller. The same is true for the name attribute.
Your directive element markup should be:
<parse-object pokie="pokie" name="name"></parse-object>
Working Plunkr
You're using isolated scope but you're not passing the variables. The problem is in your HTML:
Change your HTML from:
<parse-object></parse-object>
To:
<parse-object pokie="pokie" name="name"></parse-object>
Isolated scope takes its parameters from the DOM element. So if you have inside the scope declaration:
myPokie: '=pokie',
That means that myPokie variable should be taken from the pokie attribute that's on the scope. Your name: "=name" can be changed to name: "=" since it is exactly the same name.
Plunker

Unable to pass/update ngModel from controller to directive

I'm using ui-select plugin and I'm passing ng-model from my controller to a custom directive called richSelect but the ng-model doesn't seemed to get updated on select of any item.
<richselect ng-model="dataModel"></richselect>
Custom directive
app.directive('richselect', ['$compile', function ($compile) {
return {
restrict: 'AE',
scope: {
ngModel: '=' /* Model associated with the object */
},
link: function (scope, element, attrs, ngModel) {
scope.options = [
{
'Value' : 'value1',
'Desc' : 'Value One'
},
{
'Value' : 'value2',
'Desc' : 'Value Two'
}
]
scope.getRichSelectTemplate = function () {
return '<ui-select multiple ng-model="ngModel" theme="bootstrap" ng-disabled="disabled">' +
'{{ngModel}} <ui-select-match placeholder="Select">{{$select.selected.Desc}}</ui-select-match>' +
'<ui-select-choices repeat="option in options | filter: $select.search">' +
'<span ng-bind-html="option.Desc | highlight: $select.search"></span>' +
'</ui-select-choices>' +
'</ui-select>';
}
var linkFn = $compile(scope.getRichSelectTemplate())(scope);
element.append(linkFn);
}
}
}]);
Plnkr : http://plnkr.co/edit/Im8gpxEwnU7sgrKgqZXY?p=preview
Here, try this. I wasn't exactly sure what format or output you were trying to get, but this gets the selected options passed to the View.
EDIT - I got rid of the plunker that used to be here.
You have to use the ngModel.$setViewValue in order to change the value of ng-model in the directive in the view. Additionally, to get the value of the ui-select, you need to have ng-model pointed at the options.selected
Then it was just a matter of adding an ng-click that pointed to a function that updated the view with ngModel.$setViewValue(scope.options.selected.
Also, I believe you need to `require: 'ngModel' in your directive so you can access the ngModelController.
app.directive('richselect', ['$compile', function ($compile) {
return {
restrict: 'AE',
require: 'ngModel',
scope: {
blah: '=' /* Model associated with the object */
},
link: function (scope, element, attrs, ngModel) {
scope.changer = function() {
ngModel.$setViewValue(scope.options.selected)
console.log(scope.options.selected)
}
scope.options = [
{
'Value' : 'value1',
'Desc' : 'Value One'
},
{
'Value' : 'value2',
'Desc' : 'Value Two'
}
]
scope.getRichSelectTemplate = function () {
return '<ui-select multiple ng-model="options.selected" theme="bootstrap" ng-click="changer()" ng-disabled="disabled">' +
'{{options.selected}} <ui-select-match placeholder="Select">{{$select.selected.Desc}}</ui-select-match>' +
'<ui-select-choices repeat="option in options | filter: $select.search">' +
'<span ng-bind-html="option.Desc | highlight: $select.search"></span>' +
'</ui-select-choices>' +
'</ui-select>';
}
var linkFn = $compile(scope.getRichSelectTemplate())(scope);
element.append(linkFn);
}
}
}]);
EDIT:
After a lot of digging and tinkering, per the comment below - getting two-way binding working has proved somewhat elusive. I found it was quite easy to do using the standard ui-select directive, as seen here (modified example code from ui-select), because we can easily get access to the scope of the directive:
Standard Directive Demo
I also came across a similar wrapper as the one in the OP, but after playing with it,that one seemed to have the same issue - it's easy to get stuff out, but if you need to push data into the directive it doesn't want to go.
Interestingly, in my solution above, I can see that the `scope.options.selected' object actually contains the data, it just never gets down the the scope of the ui-select directive, and thus never allows us to push data in.
After encountering a similar issue with a different wrapper directive in a project I am working on, I figured out how to push data down through the different scopes.
My solution was to modify the ui-select script itself, adding an internal $watch function that checked for a variable in it's $parent scope. Since the ui-select directive uses scope: true, it creates a child scope (which, if I am not mistaken, the parent would be the directive in this OP).
Down at the bottom of the link function of the uiSelect directive I added the following watch function:
scope.$watch(function() {
return scope.$parent.myVar;
}, function(newVal) {
$select.selected = newVal;
})
In the link function of our directve here, I added this $watch function:
scope.$watch(function() {
return ngModel.$viewValue;
}, function(newVal) {
scope.myVar = newVal;
})
So what happens here is that if the $viewValue changes (i.e., we assign some data from a http service, etc. to the dataModel binding, the $watch function will catch it and assign it to scope.myVar. The $watch function inside the ui-select script watches scope.$parent.myVar for changes (We are telling it to watch a variable on the scope of it's parent). If it sees any changes it pushes them to $select.selected - THIS is where ui-select keeps whatever values that have been selected by clicking an item in the dropdown. We simply override that and insert whatever values we want.
Plunker - Two-way binding
First of all dataModel is a string. Since you defined multiple the model would be an array.
What's more important is that the uiSelectdirective creates a new scope. That means that ng-model="ngModel" does no longer point to dataModel. You effectively destroy the binding.
In your controller make dataModel an object:
$scope.dataModel = {};
In your directive let the selected values be bound to a property:
return '<ui-select multiple ng-model="ngModel.selection"
Now the the selected values will be bound to dataModel.selection.
If you don't use the ngModelController you shouldn't use ng-model with your directive.

AngularJS: Indicate the scope of a directive

I am building a directive that can be use in different controllers, and I would like to be able of bind the directive to a particular property of my $scope.
I would like to do something like this:
<div ng-app="myapp">
<div ng-controller="myController">
<my-directive-wrapper ng-model="mymodel">
<my-directive-inner ng-repeat="item in items" />
</my-directive-wrapper>
</div>
</div>
With this model:
$scope.mymodel = {
name : "Transclude test",
items : [
{ title : "test1" },
{ title : "test2" },
{ title : "test3" }
]
};
So the directive myDirectiveWrapper gets $scope.mymodel as scope, and nothing else. Then I may put the directive twice, pointing to a different property each.
I have a demo project with the problem here: http://jsfiddle.net/vtortola/P8JMm/3/
And the same demo working normally (without limiting the scope) here: http://jsfiddle.net/vtortola/P8JMm
The question is, how to indicate in the use of my directive that I want to use a particular property of my $scope as scope of my directive. It should be possible to bind the directive to arbitrary properties in the same $scope.
Cheers.
So the basic answer to this question is - you can do what you want to do, but it is a bit more complicated than you might think. To understand what is happening here you need to know about scopes in angular. A scope is essentially an object that contains the data accessible to the view. There are (at least) three ways scopes operate in angular:
Isolated - In this case angular basically creates a brand new scope for the directive. None of the properties are copied over.
Extended - In this case you would start with the root scope but make a shallow copy of it. Objects that are changed will be changed in the root scope but primitives will not be.
Shared - In this case you share share some or even all of the data with the root scope.
Based on your question above, what you what to do here is to extend the parent scope - copying an object to a property with a specific name in the newly created child scope. The way to get this behavior is to manually create a new child scope before the transclude. The two key lines of code to do this are:
// create a "new" scope
var childScope = scope.$new();
// extend using the model binding provided
angular.extend(childScope, scope[iAttr.myModel]);
In the context of your directive this looks like:
.directive('myDirectiveWrapper', ['$compile', function ($compile) {
return {
transclude: true,
restrict: 'E',
compile: function (element, attrs, transclude) {
var contents = element.contents().remove();
var compiledContents;
return function(scope, iElement, iAttr) {
var childScope = scope.$new();
angular.extend(childScope, scope[iAttr.myModel]);
if (!compiledContents) {
compiledContents = $compile(contents, transclude);
}
compiledContents(childScope, function(clone, childScope) {
iElement.append(clone);
});
};
},
template: "<div><h3>{{ name }}</h6><a class='back'>Back</a><div ng-transclude class='list'></div><a class='next'>Next</a>"
}
}])
Now you can specify any variable that you want as the "model" for the child scope and you can then access that directly in the contents of your transcluded code!
SEE THE FIDDLE: http://jsfiddle.net/P8JMm/7/
EDIT: Just for fun, I created a more complicated use case for this directive: http://jsfiddle.net/P8JMm/9/
Note - angular site also has some really good resources to understand scope better. See here.
If you want two way binding to work it's going to be a lot easier to just create a variable on your directive scope rather than apply mymodel directly onto the directive scope.
HTML
<div ng-app="myapp">
<div ng-controller="myController">
<my-directive-wrapper model="mymodel">
<my-directive-inner ng-repeat="item in mymodel.items" />
</my-directive-wrapper>
</div>
</div>
Directive
.directive("myDirectiveWrapper", function(){
return {
scope: {
model: '='
},
restrict: 'E',
transclude: true,
link: function(scope, element, attrs, controller) {
},
template: "<div><h3>{{ model.name }}</h6><a class='back'>Back</a><div ng-transclude class='list'></div><a class='next'>Next</a>"
}
})
http://jsfiddle.net/kQ4TV/
If you don't care about two way binding I suppose you could do something like this but I wouldn't recommend it:
.directive("myDirectiveWrapper", function(){
return {
scope: {
model: '='
},
restrict: 'E',
transclude: true,
link: function(scope, element, attrs, controller) {
angular.extend(scope, scope.model);
},
template: "<div><h3>{{ name }}</h6><a class='back'>Back</a><div ng-transclude class='list'></div><a class='next'>Next</a>"
}
})
http://jsfiddle.net/vWftR/
Here is an example of when that second approach can cause problems. Notice that when you enter something into the input field it will change the directive's name but not the name in the outer scope: http://jsfiddle.net/r5JeJ/

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