$on and $broadcast in angular

Title: Understanding $on and $broadcast in Angular: Solving the Mystery

🔍📢🆕😮💡🔧🔌🌟

Have you ever found yourself in a situation where you needed to communicate between controllers or different views in your Angular application? 🤔 You might have heard about the $on and $broadcast methods but had difficulty understanding how to use them effectively. Fear not, fellow Angular enthusiasts! In this blog post, we will unravel the mystery behind $on and $broadcast, provide you with practical examples, and guide you through easy solutions to achieve seamless communication across your application. Let's dive in! 🏊‍♂️💦

Understanding the problem 🧩

Consider a scenario where you have two controllers, footerController and codeScannerController, each associated with different views. The goal is to trigger an event in the codeScannerController when a specific action occurs in the footerController. In the given code snippet, we can see the attempt to achieve this using the ng-click directive and the startScanner() function.

angular.module('myApp').controller('footerController', ["$scope", function($scope) {}]);

angular.module('myApp').controller('codeScannerController', ["$scope", function($scope) {
  console.log("start");
  $scope.startScanner = function(){
    // ...
  }
}]);
<li class="button" ng-click="startScanner()">3</li>

However, the desired event is not being captured, and you are left puzzled. 🤨 So how do we bridge the gap and make the magic happen? Let's explore the solutions!

Solution 1: Using $rootScope and $broadcast 🌐📢

One way to achieve communication between controllers is by utilizing Angular's $rootScope and the $broadcast method. 💡

1. Inject $rootScope into the footerController and use the $broadcast method to emit the desired event.

angular.module('myApp').controller('footerController', ["$scope", "$rootScope", function($scope, $rootScope) {
  // ...
  $scope.startScanner = function() {
    // ...
    $rootScope.$broadcast('scannerStarted', data); // Emitting the event
  }
}]);

1. Inject $scope and $rootScope into the codeScannerController and listen for the event using the $on method.

angular.module('myApp').controller('codeScannerController', ["$scope", "$rootScope", function($scope, $rootScope) {
  // ...
  $scope.$on('scannerStarted', function(event, data) { // Listening for the event
    console.log("Scanner started!", data);
    // Perform necessary actions upon event triggered
  });
}]);

By broadcasting the event from the footerController and listening for it in the codeScannerController, you can now trigger the desired functionality when the startScanner function is executed. 😎🚀

Solution 2: Using $emit for Parent-Child Communication 👪📢

If you're dealing with a parent-child relationship between controllers or views, using $emit can be a viable alternative. Unlike $broadcast, $emit sends the event upwards to the parents until it is captured or reaches the $rootScope.

1. Modify the footerController to use $rootScope.$emit instead of $rootScope.$broadcast.

angular.module('myApp').controller('footerController', ["$scope", "$rootScope", function($scope, $rootScope) {
  // ...
  $scope.startScanner = function() {
    // ...
    $rootScope.$emit('scannerStarted', data); // Emitting the event upwards
  }
}]);

1. Update the codeScannerController to listen for the event using $rootScope.$on.

angular.module('myApp').controller('codeScannerController', ["$scope", "$rootScope", function($scope, $rootScope) {
  // ...
  $rootScope.$on('scannerStarted', function(event, data) { // Listening at the $rootScope level
    console.log("Scanner started!", data);
    // Perform necessary actions upon event triggered
  });
}]);

By utilizing $rootScope.$emit and $rootScope.$on, you can accomplish seamless communication between parent and child controllers or views within your Angular application. 🌟🔁

Wrapping Up and Taking Action 🎁💪📝

Communication between controllers or different views is a common challenge in Angular development, but with the power of $on and $broadcast (or $emit), you can conquer this challenge and streamline your application's functionality. Whether it's broadcasting events to communicate broadly or emitting events for parent-child relationships, these methods will assist you in unleashing the full potential of your Angular application. 🚀✨

So go ahead, give $on and $broadcast (or $emit) a try in your next Angular project! 💡🔧 If you have any additional tips or tricks, feel free to share them in the comments below. Let's level up our Angular game together! 🙌😄

Remember, effective communication leads to successful collaborations. Happy coding! 💻🔥

💌🔗💬 Do you have more questions or need further clarification? Reach out to us on Twitter or leave a comment below! Let's keep the conversation going. 💬🙋‍♀️🙋‍♂️