iOS-一周第一天和最后一天

(NSString *)getMonthBeginAndEndWith:(NSString *)dateStr {

NSDateFormatter *format = [[NSDateFormatter alloc] init];
[format setDateFormat:@"yyyy-MM"];
NSDate *newDate = [format dateFromString:dateStr];
double interval = 0;
NSDate *beginDate = nil;
NSDate *endDate = nil;
NSCalendar *calendar = [NSCalendar currentCalendar];

[calendar setFirstWeekday:2]; //设定周一为周首日
BOOL ok = [calendar rangeOfUnit:NSMonthCalendarUnit
startDate:&beginDate
interval:&interval
forDate:newDate];
//分别修改为 NSDayCalendarUnit NSWeekCalendarUnit NSYearCalendarUnit
if (ok) {
endDate = [beginDate dateByAddingTimeInterval:interval - 1];
} else {
return @"";
}
NSDateFormatter *myDateFormatter = [[NSDateFormatter alloc] init];
[myDateFormatter setDateFormat:@"YYYY.MM.dd"];
NSString *beginString = [myDateFormatter stringFromDate:beginDate];
NSString *endString = [myDateFormatter stringFromDate:endDate];
NSString *s = [NSString stringWithFormat:@"%@-%@", beginString, endString];
return s;
}