如何根据给定的NSDate生成方便的日期范围？

Question

我创建可可的报告生成器，我需要制作方便的日期范围，如“今天”，“本周”，“这个月”，“今年”，等等。

是否有好办法做到这一点？这里是我的骨架迄今：

@interface DateRange : NSObject 
{ 
    NSDate startDate; 
    NSDate endDate; 
} 

@property (nonatomic, retain) NSDate * startDate; 
@property (nonatomic, retain) NSDate * endDate; 

+ (DateRange *)rangeForDayContainingDate:(NSDate *)date; 
+ (DateRange *)rangeForWeekContainingDate:(NSDate *)date; 
+ (DateRange *)rangeForMonthContainingDate:(NSDate *)date; 
+ (DateRange *)rangeForYearContainingDate:(NSDate *)date; 

@end 

一些示例用例将如下所示：

DateRange * thisWeek = [DateRange rangeForWeekContainingDate:[NSDate date]]; 
DateRange * thisYear = [DateRange rangeForYearContainingDate:[NSDate date]]; 

从本质上讲，我想返回DateRange对象包含一周的开始和结束日期，月或目标日期周围的一年。例如（在伪代码）：

NSDate * today = [August 25, 2009]; 
DateRange * thisWeek = [DateRange rangeForWeekContainingDate:today]; 
assert(thisWeek.startDate == [August 23, 3009]); 
assert(thisWeek.endDate == [August 29, 3009]); 

更新：

我能得到这个工作，感谢answer provided by Kendall Helmstetter Geln。这里是一个星期的范围完整的方法：

+ (DateRange *)rangeForWeekContainingDate:(NSDate *)date 
{ 
    DateRange * range = [[self alloc] init]; 

    // start of the week 
    NSDate * firstDay; 
    [[self calendar] rangeOfUnit:NSWeekCalendarUnit 
         startDate:&firstDay 
         interval:0 
         forDate:date]; 
    [range setStartDate:firstDay]; 

    // end of the week 
    NSDateComponents * oneWeek = [[NSDateComponents alloc] init]; 
    [oneWeek setWeek:1]; 
    [range setEndDate:[[self calendar] dateByAddingComponents:oneWeek 
                 toDate:firstDay 
                 options:0]]; 
    [oneWeek release]; 

    return [range autorelease]; 
} 

Answer 1

好，因为一个时间间隔为秒，只是做数学题，找出多少秒一天：

60秒*60分钟* 24小时= 1天。

然后在您的rangeForDayContainingDate方法中，您可以提取日期组件，获取当前日期，基于时间和分钟设置为0:00的日期创建新日期，并创建结束日期，将时间间隔添加为计算的以上。

Answer 2

为了完整起见，这里是我的最终解决方案（与感谢肯德尔黑尔姆施泰特Geln和jbrennan）：

+ (NSCalendar *)calendar 
{ 
    NSCalendar * gregorian = [[NSCalendar alloc] 
           initWithCalendarIdentifier:NSGregorianCalendar]; 
    return [gregorian autorelease]; 
} 

//////////////////////////////////////////////////////////////// 

+ (NSDateComponents *)singleComponentOfUnit:(NSCalendarUnit)unit 
{ 
    NSDateComponents * component = [[NSDateComponents alloc] init]; 

    switch (unit) 
    { 
     case NSDayCalendarUnit: [component setDay:1]; break; 
     case NSWeekCalendarUnit: [component setWeek:1]; break; 
     case NSMonthCalendarUnit: [component setMonth:1]; break; 
     case NSYearCalendarUnit: [component setYear:1]; break; 
    } 

    return [component autorelease]; 
} 

//////////////////////////////////////////////////////////////// 

+ (WM_DateRange *)rangeForUnit:(NSCalendarUnit)unit 
       surroundingDate:(NSDate *)date 
{ 
    WM_DateRange * range = [[self alloc] init]; 

    // start of the period 
    NSDate * firstDay; 
    [[self calendar] rangeOfUnit:unit 
         startDate:&firstDay 
         interval:0 
         forDate:date]; 
    [range setStartDate:firstDay]; 

    // end of the period 
    [range setEndDate:[[self calendar] 
     dateByAddingComponents:[self singleComponentOfUnit:unit] 
         toDate:firstDay 
         options:0]]; 

    return [range autorelease]; 
} 

//////////////////////////////////////////////////////////////// 

+ (WM_DateRange *)rangeForDayContainingDate:(NSDate *)date 
{ return [self rangeForUnit:NSDayCalendarUnit surroundingDate:date]; } 

+ (WM_DateRange *)rangeForWeekContainingDate:(NSDate *)date 
{ return [self rangeForUnit:NSWeekCalendarUnit surroundingDate:date]; } 

+ (WM_DateRange *)rangeForMonthContainingDate:(NSDate *)date 
{ return [self rangeForUnit:NSMonthCalendarUnit surroundingDate:date]; } 

+ (WM_DateRange *)rangeForYearContainingDate:(NSDate *)date 
{ return [self rangeForUnit:NSYearCalendarUnit surroundingDate:date]; } 

//////////////////////////////////////////////////////////////// 

- (void)dealloc 
{ 
    [endDate release]; 
    [startDate release]; 
    [super dealloc]; 
}