Objective-C Bitmask Enumeration Essentials
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Objective-C Bitmask Enumeration Essentials
1–9 of 9 posts
Re: Objective-C Bitmask Enumeration Essentials
#2>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
NSEventMask mask = NSEventMaskEndGesture;
BOOL end = mask & NSEventMaskEndGesture;
if (!end) NSLog(@"Oops");Re: Objective-C Bitmask Enumeration Essentials
#3>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 NSEventMask mask = NSEventMaskEndGesture; BOOL end = mask & NSEventMaskEndGesture; if…
Is this the correct approach?
BOOL end = mask & NSEventMaskEndGesture ? YES : NO;Re: Objective-C Bitmask Enumeration Essentials
#4>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 NSEventMask mask = NSEventMaskEndGesture; BOOL end = mask & NSEventMaskEndGesture; if…
Is this the correct approach? BOOL end = mask & NSEventMaskEndGesture ? YES : NO;
or just != 0
Re: Objective-C Bitmask Enumeration Essentials
#5This is just plain old C (which, yes, Objective-C is a superset of).
Re: Objective-C Bitmask Enumeration Essentials
#6>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 NSEventMask mask = NSEventMaskEndGesture; BOOL end = mask & NSEventMaskEndGesture; if…
Is this the correct approach? BOOL end = mask & NSEventMaskEndGesture ? YES : NO;
(mask & NSEventMaskEndGesture) == NSEventMaskEndGesture is the most correct, as it handles the case where NSEventMaskEndGesture has multiple bits set.
Re: Objective-C Bitmask Enumeration Essentials
#7Isn't this applicable to any kind of bitmask, and not just Obj-C?
I suppose that Cocoa uses bitmasks fairly often, but this article could have been titled "Working With Bitmasks in C" and it would have been just as accurate.
Re: Objective-C Bitmask Enumeration Essentials
#8>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 NSEventMask mask = NSEventMaskEndGesture; BOOL end = mask & NSEventMaskEndGesture; if…
Is this the correct approach? BOOL end = mask & NSEventMaskEndGesture ? YES : NO;
I think, not!!
BOOL end = !! (mask & NSEventMaskEndGesture);
Also works for pointers:
BOOL hasError = !! errorObj;