Angularjs - sharing data between controllers

Question

There are two controllers. one controller will write data into an object & the other controller needs to read it. Can i have one global variable in my app.js file, that can be used in both the controllers. i am confused, why does one need to use service to share data between controllers? app.js::::::

var msg = 'message init'
app.controller('readController', function($scope){
      $scope.msg = msg
      console.log(msg)
});
app.controller('writeController', function(){
      msg = 'message is written'
});

Doesn't the change made in write controller get reflected into the read controller? in that case, the console must have 'message is written'.

Answer 1

You can read and write data from/to $rootScope. For simple data I do not think you'll need a service. Keep in mind however that this may not be a good design.

app.controller('readController', function($scope, $rootScope){
  $scope.myMsg = $rootScope.msg;
  console.log($scope.myMsg);
});

app.controller('writeController', function($rootScope){
  $rootScope.msg = 'message is written';
});

Answer 2

I will not advice to write global variable and then share data between controller. Instead of that, you can share data with service and factory that's more simple.