iphone开发常用代码段(3)

*/

NSDate *today = [NSDate date];

NSCalendar *calendar = [NSCalendar currentCalendar]; NSDateComponents *offsetComponents =

[calendar components:(NSYearCalendarUnit | NSMonthCalenda rUnit |NSDayCalendarUnit)

fromDate:today];

NSDate *midnight =

[calendar dateFromComponents:offsetComponents]; NSDateFormatter *displayFormatter =

[[NSDateFormatter alloc] init];

NSString *displayString = nil;

// comparing against midnight

iphone开发常用代码段

if ([date compare:midnight] == NSOrderedDescending) {

if (prefixed) {

[displayFormatter setDateFormat:@"'at' h:mm a"]; // at 11:30 am

} else {

[displayFormatter setDateFormat:@"h:mm a"]; // 11:30 am }

} else {

// check if date is within last 7 days

NSDateComponents *componentsToSubtract = [[NSDateComponents alloc] init]; [componentsToSubtract setDay:-7];

NSDate *lastweek =

[calendar dateByAddingComponents:componentsToSubtract to Date:today options:0];

[componentsToSubtract release];

if ([date compare:lastweek] == NSOrderedDescending) { [displayFormatter setDateFormat:@"EEEE"]; // Tuesday

} else {

// check if same calendar year

NSInteger thisYear = [offsetComponents year];

NSDateComponents *dateComponents =

[calendar components:(NSYearCalendarUnit | NSMonthCalenda rUnit |NSDayCalendarUnit)

fromDate:date];

NSInteger thatYear = [dateComponents year];

if (thatYear >= thisYear) {

[displayFormatter setDateFormat:@"MMM d"];

} else {

[displayFormatter setDateFormat:@"MMM d, yyyy"];

}

}

iphone开发常用代码段

if (prefixed) {

NSString *dateFormat = [displayFormatter dateFormat]; NSString *prefix = @"'on' ";

[displayFormatter setDateFormat:[prefix stringByAppendingStri ng:dateFormat]];

}

}

// use display formatter to return formatted date string displayString = [displayFormatter stringFromDate:date]; [displayFormatter release];

return displayString;

}

+ (NSString *)stringForDisplayFromDate:(NSDate *)date { return [self stringForDisplayFromDate:date prefixed:NO];

}

- (NSString *)stringWithFormat:(NSString *)format { NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init];

[outputFormatter setDateFormat:format];

NSString *timestamp_str =

[outputFormatter stringFromDate:self];

[outputFormatter release];

return timestamp_str;

}

- (NSString *)string {

return [self stringWithFormat:[NSDate dbFormatString]];

}

iphone开发常用代码段

-

(NSString *)stringWithDateStyle:(NSDateFormatterStyle)dateS tyle timeStyle:(NSDateFormatterStyle)timeStyle { NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init];

[outputFormatter setDateStyle:dateStyle]; [outputFormatter setTimeStyle:timeStyle];

NSString *outputString =

[outputFormatter stringFromDate:self];

[outputFormatter release];

return outputString;

}

//返回周日的的开始时间

- (NSDate *)beginningOfWeek {

// largely borrowed from "Date and Time Programming Guide for Cocoa"

// we'll use the default calendar and hope for the best

NSCalendar *calendar = [NSCalendar currentCalendar]; NSDate *beginningOfWeek = nil;

BOOL ok =

[calendar rangeOfUnit:NSWeekCalendarUnit startDate:&beginni ngOfWeek

interval:NULL forDate:self];

if (ok) {

return beginningOfWeek;

}

// couldn't calc via range, so try to grab Sunday, assuming gregorian style

// Get the weekday component of the current date NSDateComponents *weekdayComponents =

[calendar components:NSWeekdayCalendarUnit fromDate:self] ;