问题
As far as I know that basically scope is an instance of a controller.
Every time I declare a controller scope will be available for that controller.
But then why directive has scope in link function ?
I didn't declare any controller for the directive.
Then why link function has scope ? Any Idea ?
回答1:
From the doc:
scope: The scope to be used by the directive for registering watches.
You may also be interested to see the differences between $scope and scope.
All directives have a scope associated with them. They use this scope for accessing data/methods inside the template and link function. By default, unless explicitly set, directives don’t create their own scope. Therefore, directives use their parent scope ( usually a controller ) as their own.
However, AngularJS allows us to change the default scope of directives by passing a configuration object known as directive definition object. A directive definition object –– let’s call it as DDO –– is a simple JavaScript object used for configuring the directive’s behaviour,template..etc. Check out AngularJS docs about DDO.
So, we can use scope inside linking function to work with parent scope, child scope or isolated scope.
You may visit this for detailed information about scope inside directive.
You can share the data between controller and linking function.
Sometimes we would like to access that same data in both controller and link functions in Angular directive. Usually we add this data to the scope object. This has certain problems, for example exposing it to any child scope. Add the shared properties to the controller instance itself and access in the link function.
You may also be interested in what is need of link function?
回答2:
A directive is Angular's way of defining 'components': you specify how its markup looks and how it behaves before, during and after being rendered. The link functions allow you to hook up events to the DOM element before or after it gets 'linked' (see also: pre-link and post-link methods). When these events are fired you might want to change some of the variables within the scope, and that's why you have access to it within the link functions.
来源：https://stackoverflow.com/questions/34038699/why-directive-has-scope