I read about bitwise operators today and they seem rather handy to me. I also noticed Apple uses them too, for example with UIViewAutoresizing .
In my app I need to keep track of the seven days of the week. Each day can be either enabled or disabled. I used to have seven BOOL 's, but now I'm trying to use a single integer for this:
enum {
DaysMonday = 1 << 0,
DaysTuesday = 1 << 1,
DaysWednesday = 1 << 2,
DaysThursday = 1 << 3,
DaysFriday = 1 << 4,
DaysSaturday = 1 << 5,
DaysSunday = 1 << 6
};
typedef NSUInteger Days;
My question is, how can I enable/disable those values now? I know I can check a variable days for a specific day like this:
if (days & DaysThursday) {
// thursday enabled
}
But how do I..
- enable thursday?
- disable thursday?
- toggle thursday?
- enable all?
- disable all?
Thank you.
Source: Tips4all, CCNA FINAL EXAM
I'm not too familiar with objective-c, but here are the basics when dealing with bitwise operators.
ReplyDeleteEnable Thursday
days = days | DaysThursday;
Disable Thursday
allDays = DaysMonday | DaysTuesday | ... | DaysSunday;
days = days & (allDays ^ DaysThursday);
// OR
days = days & ~DaysThursday;
Toggle Thursday
days = days ^ DaysThursday;
Enable All
allDays = DaysMonday | DaysTuesday | ... | DaysSunday;
days = days | allDays;
// OR
days = allDays;
Disable All
days = days ^ days;
// OR
days = 0;
days = DaysMonday | DaysWednesday | DaysFriday | DaysSaturday;
ReplyDeletedays = days | DaysThursday;
days = days & ~DaysSaturday;