If I have a directive that responds to the status of a particular attribute on the scope, and I want to change that attribute in my test and verify that it responds correctly, which is the best way of doing that change?
I've seen both these patterns:
scope.$apply(function() {
scope.myAttribute = true;
});
and
scope.myAttribute = true;
scope.$digest();
What is the difference between them, and which is better and why?
scope.$digest() will fire watchers on the current scope, and on all of its children, too. scope.$apply will evaluate passed function and run $rootScope.$digest().
The first one is faster, as it needs to evaluate watchers for current scope and its children. The second one is slower, as it needs to evaluate watchers for$rootScope and all it's child scopes.
When an error occurs in one of the watchers and you use scope.$digest, it's not handled via $exceptionHandler service, so you need to handle exception yourself. scope.$apply uses a try-catch block internally and passes all exceptions to $exceptionHandler.
As the documentation itself mentions $digest cycle is peformed any time you do $scope.$apply. As per developer guide on scope
After evaluating the expression, the $apply method performs a $digest. In the $digest phase the scope examines all of the $watch expressions and compares them with the previous value.
And as per the Scope API documentation
Usually you don't call $digest() directly in controllers or in directives. Instead a call to $apply() (typically from within a directives) will force a $digest().
So you should not explicitly call $digest, you calling $apply method would trigger a digest cycle.
