>Use the bitwise AND operator & to check for a selected bitmask enumeration value.
You should take care if you store result of this in a BOOL (or pass it to a method or function that takes a BOOL). BOOL is only char big and plenty of common Cocoa bitmasks don't have any bits set in that range. For example NSEventMaskEndGesture is (1<<20).
NSEventMask mask = NSEventMaskEndGesture;
BOOL end = mask & NSEventMaskEndGesture;
if (!end) NSLog(@"Oops");
You should take care if you store result of this in a BOOL (or pass it to a method or function that takes a BOOL). BOOL is only char big and plenty of common Cocoa bitmasks don't have any bits set in that range. For example NSEventMaskEndGesture is (1<<20).