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  • 扩展NSDate类(NSDateHelper)

    // NSDate+Helper.h
    
    #import <Foundation/Foundation.h>
    
    @interface NSDate (Helper)
    
    - (NSUInteger)daysAgo;
    - (NSUInteger)daysAgoAgainstMidnight;
    - (NSString *)stringDaysAgo;
    - (NSString *)stringDaysAgoAgainstMidnight:(BOOL)flag;
    - (NSUInteger)weekday;
    
    + (NSDate *)dateFromString:(NSString *)string;
    + (NSDate *)dateFromString:(NSString *)string withFormat:(NSString *)format;
    + (NSString *)stringFromDate:(NSDate *)date withFormat:(NSString *)string;
    + (NSString *)stringFromDate:(NSDate *)date;
    + (NSString *)stringForDisplayFromDate:(NSDate *)date;
    + (NSString *)stringForDisplayFromDate:(NSDate *)date prefixed:(BOOL)prefixed;
    + (NSString *)stringForDisplayFromDate:(NSDate *)date prefixed:(BOOL)prefixed alwaysDisplayTime:(BOOL)displayTime;
    
    - (NSString *)string;
    - (NSString *)stringWithFormat:(NSString *)format;
    - (NSString *)stringWithDateStyle:(NSDateFormatterStyle)dateStyle timeStyle:(NSDateFormatterStyle)timeStyle;
    
    - (NSDate *)beginningOfWeek;
    - (NSDate *)beginningOfDay;
    - (NSDate *)endOfWeek;
    
    + (NSString *)dateFormatString;
    + (NSString *)timeFormatString;
    + (NSString *)timestampFormatString;
    + (NSString *)dbFormatString;
    
    @end
    #import "NSDate+Helper.h"
    
    @implementation NSDate (Helper)
    
    /*
     * This guy can be a little unreliable and produce unexpected results,
     * you're better off using daysAgoAgainstMidnight
     */
    - (NSUInteger)daysAgo {
        NSCalendar *calendar = [NSCalendar currentCalendar];
        NSDateComponents *components = [calendar components:(NSDayCalendarUnit) 
                                                   fromDate:self
                                                     toDate:[NSDate date]
                                                    options:0];
        return [components day];
    }
    
    - (NSUInteger)daysAgoAgainstMidnight {
        // get a midnight version of ourself:
        NSDateFormatter *mdf = [[NSDateFormatter alloc] init];
        [mdf setDateFormat:@"yyyy-MM-dd"];
        NSDate *midnight = [mdf dateFromString:[mdf stringFromDate:self]];
        [mdf release];
    
        return (int)[midnight timeIntervalSinceNow] / (60*60*24) *-1;
    }
    
    - (NSString *)stringDaysAgo {
        return [self stringDaysAgoAgainstMidnight:YES];
    }
    
    - (NSString *)stringDaysAgoAgainstMidnight:(BOOL)flag {
        NSUInteger daysAgo = (flag) ? [self daysAgoAgainstMidnight] : [self daysAgo];
        NSString *text = nil;
        switch (daysAgo) {
            case 0:
                text = @"Today";
                break;
            case 1:
                text = @"Yesterday";
                break;
            default:
                text = [NSString stringWithFormat:@"%d days ago", daysAgo];
        }
        return text;
    }
    
    - (NSUInteger)weekday {
        NSCalendar *calendar = [NSCalendar currentCalendar];
        NSDateComponents *weekdayComponents = [calendar components:(NSWeekdayCalendarUnit) fromDate:self];
        return [weekdayComponents weekday];
    }
    
    + (NSDate *)dateFromString:(NSString *)string {
        return [NSDate dateFromString:string withFormat:[NSDate dbFormatString]];
    }
    
    + (NSDate *)dateFromString:(NSString *)string withFormat:(NSString *)format {
        NSDateFormatter *inputFormatter = [[NSDateFormatter alloc] init];
        [inputFormatter setDateFormat:format];
        NSDate *date = [inputFormatter dateFromString:string];
        [inputFormatter release];
        return date;
    }
    
    + (NSString *)stringFromDate:(NSDate *)date withFormat:(NSString *)format {
        return [date stringWithFormat:format];
    }
    
    + (NSString *)stringFromDate:(NSDate *)date {
        return [date string];
    }
    
    + (NSString *)stringForDisplayFromDate:(NSDate *)date prefixed:(BOOL)prefixed alwaysDisplayTime:(BOOL)displayTime {
        /* 
         * if the date is in today, display 12-hour time with meridian,
         * if it is within the last 7 days, display weekday name (Friday)
         * if within the calendar year, display as Jan 23
         * else display as Nov 11, 2008
         */
        NSCalendar *calendar = [NSCalendar currentCalendar];
        NSDateFormatter *displayFormatter = [[NSDateFormatter alloc] init];
        
        NSDate *today = [NSDate date];
        NSDateComponents *offsetComponents = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) 
                                                         fromDate:today];
    
        NSDate *midnight = [calendar dateFromComponents:offsetComponents];
        NSString *displayString = nil;
    
        // comparing against midnight
        NSComparisonResult midnight_result = [date compare:midnight];
        if (midnight_result == 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 toDate:today options:0];
            [componentsToSubtract release];
            NSComparisonResult lastweek_result = [date compare:lastweek];
            if (lastweek_result == NSOrderedDescending) {
                if (displayTime) {
                    [displayFormatter setDateFormat:@"EEEE h:mm a"];
                } else {
                    [displayFormatter setDateFormat:@"EEEE"]; // Tuesday
                }
            } else {
                // check if same calendar year
                NSInteger thisYear = [offsetComponents year];
    
                NSDateComponents *dateComponents = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) 
                                                               fromDate:date];
                NSInteger thatYear = [dateComponents year];            
                if (thatYear >= thisYear) {
                    if (displayTime) {
                        [displayFormatter setDateFormat:@"MMM d h:mm a"];
                    }
                    else {
                        [displayFormatter setDateFormat:@"MMM d"];
                    }
                } else {
                    if (displayTime) {
                        [displayFormatter setDateFormat:@"MMM d, yyyy h:mm a"];
                    }
                    else {
                        [displayFormatter setDateFormat:@"MMM d, yyyy"];
                    }
                }
            }
            if (prefixed) {
                NSString *dateFormat = [displayFormatter dateFormat];
                NSString *prefix = @"'on' ";
                [displayFormatter setDateFormat:[prefix stringByAppendingString:dateFormat]];
            }
        }
    
        // use display formatter to return formatted date string
        displayString = [displayFormatter stringFromDate:date];
        
        [displayFormatter release];
        
        return displayString;
    }
    
    + (NSString *)stringForDisplayFromDate:(NSDate *)date prefixed:(BOOL)prefixed {
        return [[self class] stringForDisplayFromDate:date prefixed:prefixed alwaysDisplayTime:NO];
    }
    
    + (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]];
    }
    
    - (NSString *)stringWithDateStyle:(NSDateFormatterStyle)dateStyle timeStyle:(NSDateFormatterStyle)timeStyle {
        NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init];
        [outputFormatter setDateStyle:dateStyle];
        [outputFormatter setTimeStyle:timeStyle];
        NSString *outputString = [outputFormatter stringFromDate:self];
        [outputFormatter release];
        return outputString;
    }
    
    - (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:&beginningOfWeek
                               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];
    
        /*
         Create a date components to represent the number of days to subtract from the current date.
         The weekday value for Sunday in the Gregorian calendar is 1, so subtract 1 from the number of days to subtract from the date in question.  (If today's Sunday, subtract 0 days.)
         */
        NSDateComponents *componentsToSubtract = [[NSDateComponents alloc] init];
        [componentsToSubtract setDay: 0 - ([weekdayComponents weekday] - 1)];
        beginningOfWeek = nil;
        beginningOfWeek = [calendar dateByAddingComponents:componentsToSubtract toDate:self options:0];
        [componentsToSubtract release];
    
        //normalize to midnight, extract the year, month, and day components and create a new date from those components.
        NSDateComponents *components = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit)
                                                   fromDate:beginningOfWeek];
        return [calendar dateFromComponents:components];
    }
    
    - (NSDate *)beginningOfDay {
        NSCalendar *calendar = [NSCalendar currentCalendar];
        // Get the weekday component of the current date
        NSDateComponents *components = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) 
                                                   fromDate:self];
        return [calendar dateFromComponents:components];
    }
    
    - (NSDate *)endOfWeek {
        NSCalendar *calendar = [NSCalendar currentCalendar];
        // Get the weekday component of the current date
        NSDateComponents *weekdayComponents = [calendar components:NSWeekdayCalendarUnit fromDate:self];
        NSDateComponents *componentsToAdd = [[NSDateComponents alloc] init];
        // to get the end of week for a particular date, add (7 - weekday) days
        [componentsToAdd setDay:(7 - [weekdayComponents weekday])];
        NSDate *endOfWeek = [calendar dateByAddingComponents:componentsToAdd toDate:self options:0];
        [componentsToAdd release];
    
        return endOfWeek;
    }
    
    + (NSString *)dateFormatString {
        return @"yyyy-MM-dd";
    }
    
    + (NSString *)timeFormatString {
        return @"HH:mm:ss";
    }
    
    + (NSString *)timestampFormatString {
        return @"yyyy-MM-dd HH:mm:ss";
    }
    
    // preserving for compatibility
    + (NSString *)dbFormatString {    
        return [NSDate timestampFormatString];
    }
    
    @end
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  • 原文地址:https://www.cnblogs.com/hellocby/p/2582167.html
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