Evaluates an access control for a given operation.
- iOS 9.0+
- macOS 10.11+
The access control to be evaluated.
The operation for the access control to be evaluated. For possible values, see
The app-provided reason for requesting authentication, which displays in the authentication dialog presented to the user.
A block that is executed when access control evaluation finishes. This block is evaluated on a private queue internal to the framework in an unspecified threading context.
trueif policy evaluation succeeded, otherwise
nilif policy evaluation succeeded, an error object that should be presented to the user otherwise. See
LAErrorfor possible error codes
This method asynchronously evaluates an access control. Evaluating an access control may involve prompting the user for various kinds of interaction or authentication. The actual behavior is dependent on the access control and device type. It can also be affected by installed configuration profiles.
The localized string you present to the user should provide a clear reason for why you are requesting they authenticate themselves, and what action you will be taking based on that authentication. This string should be provided in the user’s current language and should be short and clear. It should not contain the app name, because that appears elsewhere in the authentication dialog. In macOS this appears in the dialog title, and in iOS this appears in the dialog subtitle.
You should not assume that a previous successful evaluation of an access control necessarily leads to a subsequent successful evaluation. Access control evaluation can fail for various reasons, including cancelation by the user or the system.