How To Watch A Variable In A Service
$scope acts as a built-in object in AngularJs.
It consists of awarding data and methods. The $scope is acts as a link betwixt a controller and view (HTML).
$scope is used to transfer the data.
$watch:
Scope in AngularJs object has $watch event which comes into moving-picture show when the model belongings gets inverse or altered.
When a data binding is created from some point of programme in the view to a variable on the $scope object, a watch is created internally in AngularJs.
The digest gets called multiple times, when nosotros $sentinel() a function.
Every time when nosotros bind the UI, We insert $watch in $watch listing.
User: <input blazon="text" ng-model="user" /> Countersign: <input type="password" ng-model="laissez passer" />
Example:
<!DOCTYPE html>
< html >
< head >
< championship >
AngularJs $spotter() Role with GFG
</ championship >
< script src =
</ script >
< script type = "text/javascript" >
var app = athwart.module("watchApp", []);
app.controller("watchCtrl", function ($scope) {
$scope.count = -i;
$scope.$lookout man(
"txtval", function (newval, oldval) {
$scope.count = $telescopic.count + 1;
});
});
</ script >
</ head >
< body >
< div ng-app = "watchApp"
ng-controller = "watchCtrl" >
Enter Text:< input type = "text"
ng-model = "txtval" />
< br />
< br />
< span style = "color: Light-green;" >
$watch() Function Fired: {{count}}</ span >
</ div >
</ trunk >
</ html >
$watch in AngularJs is a service.
Information technology is used to keep the track of the changes on specific properties inside a given scope. It is similar to an upshot listener. eastward changes are made in the value of specified variables.
When we register a watch we pass 2 functions equally parameters to the $watch() office.These functions are:
- A value part
- A listener function
Example:
$scope.$lookout(part() {}, //value function function() {} //listener function ); A watcher can change in responses on:
- Timeouts
- UI
- Circuitous asynchronous computations performed by web workers
- Ajax calls
Methods Used: $telescopic.$watchGroup
$watchGroup() is a shortcut to prepare watchers with the same callback, passing an array of watchExpressions.
$telescopic.$watchGroup(['obj.a', 'obj.b.bb[4]', 'letters[8]'], function(newValues, oldValues, scope) {
//…
});
$scope.$watchCollection is a shortcut to watch arrays or objects. In arrays, the listener is called when any of the elements are replaced, deleted, or added.
The $watch keeps rails of the variable. This role takes two arguments:
-
new value
$scope.$picket('expression', role (newvalue, oldvalue) { //expression parameter
//Code
}); -
old value
$scope.$watch(function () {}, function (newvalue, oldvalue) { //Part Parameter
// Code
});
Example:
<!DOCTYPE html>
< html >
< head >
< script src =
</ script >
</ caput >
< torso ng-app = "myNgApp" >
< div ng-controller = "myController" >
Message: < input type = "text"
ng-model = "message" />
< br />
New Message: {{newMessage}} < br />
One-time Message: {{oldMessage}}
</ div >
< script >
var ngApp = angular.module('myNgApp', []);
ngApp.controller('myController', role ($telescopic) {
$scope.message = "GeeksForGeeks!";
$telescopic.$watch(
'message', office (newValue, oldValue) {
$scope.newMessage = newValue;
$scope.oldMessage = oldValue;
});
});
</ script >
</ body >
</ html >
Others:
$digest()
We telephone call the the $digest() function when AngularJS thinks information technology is necessary.
For example, after a push button click handler is executed, or after an AJAX call returns.
$apply():
The $scope.$apply() function takes a part every bit parameter which it is executed, and after that $scope.$digest() is called internally. That makes it helpful to all the watches are checked
$scope.$utilise(function() { $telescopic.data.myVar = "value"; }); Example of $Watch:
< div class = "container" information-ng-app = "app" >
< div grade = "well" data-ng-controller = "FooCtrl" >
< p >< strong >Controller1</ strong ></ p >
< div class = "row" >
< div course = "col-sm-6" >
< p >< a href = ""
ng-click =
"setItems([ { name: 'I am single item' } ])" >
Send item one </ a ></ p >
< p >< a href = ""
ng-click=
"setItems([ { proper name: 'Detail one of 2' },
{ name: 'Item 2 of 2' } ])">
Ship particular two </ a ></ p >
< p >< a href = ""
ng-click=
"setItems([ { proper name: 'Detail one of 3' },
{ name: 'Detail 2 of three' },
{ proper noun: 'Item 3 of three' } ])">
Send detail three </ a ></ p >
</ div >
< div class = "col-sm-vi" >
< p >< a href = ""
ng-click = "setName('Sheldon')" >
Send name: Geeks</ a ></ p >
< p >< a href = ""
ng-click = "setName('Leonard')" >
Ship name: For</ a ></ p >
< p >< a href = ""
ng-click = "setName('Penny')" >
Send name: Geeks</ a ></ p >
</ div >
</ div >
</ div >
< div class = "well"
data-ng-controller = "BarCtrl" >
< p >< strong >Controller2</ strong ></ p >
< p ng-if = "name" >Name is: {{ name }}</ p >
< div ng-repeat = "item in items" >
{{ item.name }}</ div >
</ div >
</ div >
var app = angular.module( 'app' , []);
app.factory( 'PostmanService' , part () {
var Postman = {};
Postman.fix = function (key, val) {
Postman[primal] = val;
};
Postman.become = function (key) {
return Postman[primal];
};
Postman.watch = function ($telescopic, cardinal, onChange) {
render $scope.$spotter(
office () {
render Postman.get(fundamental);
},
function (newValue, oldValue) {
if (newValue !== oldValue) {
$scope[cardinal] = newValue;
if (athwart.isFunction(onChange)) {
onChange(newValue, oldValue);
}
}
}
);
};
return Postman;
});
app.controller( 'FooCtrl' , [ '$scope' ,
'PostmanService' ,
part ($scope, PostmanService) {
$scope.setItems = part (items) {
PostmanService.ready( 'items' , items);
};
$scope.setName = role (proper name) {
PostmanService.set( 'proper name' , name);
};
}]);
app.controller( 'BarCtrl' , [ '$scope' ,
'PostmanService' ,
function ($scope, PostmanService) {
$scope.items = [];
$scope.proper noun = '' ;
PostmanService.watch($scope, 'items' );
PostmanService.watch(
$scope, 'name' , function (newVal, oldVal) {
alarm( 'Hullo, ' + newVal + '!' );
});
}]);
CSS:
.well {
margin-top : 10px ;
margin-bottom : 10px ;
}
p:terminal-child {
margin-bottom : 0 ;
}
How To Watch A Variable In A Service,
Source: https://www.geeksforgeeks.org/how-to-watch-service-variables/
Posted by: fosterretion1985.blogspot.com
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