What is the significance of '?ngModel' when creating an AngularJS directive?

Question

I\'m working my way through the new ng-book. The chapter on filters includes a section on defining parsers with the following code:

angular.module(\'myApp\')         


        

Answer 1

The Required can be explained as:

[?][^][directiveName].

It is used to specify which directive controller should be used("inherited from"). So for instance a directive needs to find the parent controller . There are a couple of symbols that can be used along with this attribute and they can also be combined:

^ = it indicates angular to seek up the DOM to find the directive.

? = it indicates angular that the directive is optional and angular will not throw an exception if not found.

So ?ngModel is saying that the ngModel needs be declared along with this directive.