Tests whether a given object is special marker object used for indicating the state of a selection in relation to a key.
- macOS 10.3+
Specify the object you want to check. This parameter can be
true if the object is one of the designated controller markers or
false if it is not.
This function helps you to create bindings between user interface elements and controller objects. The Application Kit predefines several special marker objects used as values for indicating selection state; currently these are
NSNot. These markers are typed as
id and only exist for the purpose of indicating a state; they are never archived and cannot be used as object values in controls. You use this function to test whether a given object value is a marker, in which case it is not directly assignable to the object that is bound. This check is important, especially since additional markers may be added in the future.
NSKey header file for further details.