Angular callback scope.apply

Usually the socket.io's on method is like this:

socket.on('/msg', function(data){});

But in Angular that callback has to be wrapped inside its $rootScope.$apply() method otherwise anything that happens in the callback (like changing $scope properties) doesn't update in Angular.

Here's a simple way to do that:

function socketFactory($rootScope) {
    return {
        emit: socket.emit.bind(socket),
        on: function(msg, callback) {
            socket.on(msg, function() {
                var args = arguments;
                $rootScope.$apply(function(){
                    callback.apply(socket, arguments)
                });
            });
        },
    };
};

I was able to shorten this a little bit:

on: function(msg, callback) {
    socket.on(msg, function() {
        $rootScope.$apply(callback.apply(socket, arguments));
    });
},

I'm not sure if it'll go any further but I tried:

on: function(msg, callback) {
    socket.on(msg, $rootScope.$apply.apply(null, callback));
},

which threw an error:

Uncaught TypeError: Cannot read property 'apply' of undefined socket.io.js:1194

I'm guessing $apply.apply doesn't work.