Event Communication in Angular: $on and $broadcast

In Angular, event communication is crucial for coordinating interactions between different parts of an application. $on and $broadcast are core Angular mechanisms that enable the effective broadcasting and handling of events across components.

Understanding $on and $broadcast

• $broadcast: Emitted by a scope to notify all its descendants (child scopes) and the scope's parent chain of a specific event.
• $on: Registered by a scope to listen for specific events broadcast from the current scope, its parent scopes, or its children scopes.

Implementing Event Communication in Your Example

In your case, you want a click event in the footer controller to trigger an event that can be handled by the code scanner controller. To achieve this:

1. Broadcaster (footerController):

• Use $rootScope to broadcast the event, as it encompasses all scopes in the application.
• Define a function like the following in the footerController:

$scope.startScanner = function() {
    $rootScope.$broadcast('scanner-started');
}

2. Receiver (codeScannerController):

• Use $on to listen for the broadcast event in the codeScannerController:

$scope.$on('scanner-started', function(event, args) {
    // Your logic here
});

Additional Capabilities:

• You can pass arguments when broadcasting events using $broadcast('event-name', { any: {} }).
• Accordingly, you can receive these arguments in the receiver's event handler.

Reference Documentation:

For more detailed information, refer to the official Angular documentation on scopes: https://docs.angularjs.org/api/ng/type/$rootScope.Scope