NSPredicate - 用于查找在特定日期范围内发生的事件

Question

这比刚才复杂一点

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"startDate >= %@ AND endDate <= %@", startDay,endDay];

我正在构建一个日历应用程序，我需要从我的核心数据存储中提取特定日期发生的事件。但是，活动的开始/结束日期可能与我尝试显示的日期不同，例如

我的日期范围（开始 = 2011-12-02 00:00:00 到结束 = 2011-12-02 23:59:59）

一个事件（开始 = 2011-12-01 23:00:00 到结束 = 2011-12-02 05:00:00）

如何编写谓词来确定该事件是否在该日期范围内。请记住，事件可能在日期范围之前和之后开始。

谢谢！

Answer 1

这是一种构建谓词以检索给定日期发生的非重复事件（重复事件需要额外处理）的方法：

- (NSPredicate *) predicateToRetrieveEventsForDate:(NSDate *)aDate {

    // start by retrieving day, weekday, month and year components for the given day
    NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDateComponents *todayComponents = [gregorian components:(NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit) fromDate:aDate];
    NSInteger theDay = [todayComponents day];
    NSInteger theMonth = [todayComponents month];
    NSInteger theYear = [todayComponents year];

    // now build a NSDate object for the input date using these components
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setDay:theDay]; 
    [components setMonth:theMonth]; 
    [components setYear:theYear];
    NSDate *thisDate = [gregorian dateFromComponents:components];
    [components release];

    // build a NSDate object for aDate next day
    NSDateComponents *offsetComponents = [[NSDateComponents alloc] init];
    [offsetComponents setDay:1];
    NSDate *nextDate = [gregorian dateByAddingComponents:offsetComponents toDate:thisDate options:0];
    [offsetComponents release];

    [gregorian release];


    // build the predicate 
    NSPredicate *predicate = [NSPredicate predicateWithFormat: @"startDate < %@ && endDate > %@", nextDate, thisDate];

        return predicate;

}

谓词几乎等于@Tony 提出的那个，除了它不检查相等性。这就是为什么。假设您有一个从 12 月 8 日 23:00 开始到 12 月 9 日 00:00 结束的事件。如果您检查结束日期为 >= 而不是 > 的事件，您的应用将在 12 月 8 日和 9 日都报告该事件，这显然是错误的。尝试将此类事件添加到 iCal 和 Google 日历中，您会看到该事件仅出现在 12 月 8 日。实际上，您不应假设给定的一天在 23:59:59 结束（尽管这当然是true)：您需要将午夜视为给定日期的最后一秒（关于事件的结束）。另外，请注意，这不会阻止从午夜开始的事件。

Answer 2

你想要的是：

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"startDate <= %@ AND endDate >= %@", endDay, startDay];

换句话说，您正在消除在范围结束之后开始或在开始之前结束的事件，即与范围有空交集的事件。

Answer 3

虽然建议的解决方案是正确的，但它也相当冗长。我在 Swift 3.0 中重新实现了它：

import Foundation

extension NSPredicate {

    static func filter(key: String, onDayRangeForDate date: Date, calendar: Calendar = Calendar(identifier: .gregorian)) -> NSPredicate {

        let dateComponents = calendar.dateComponents([.day, .month, .year], from: date)

        let startOfDay = calendar.date(from: dateComponents)!

        let offsetComponents = NSDateComponents()
        offsetComponents.day = 1
        let endOfDay = calendar.date(byAdding: offsetComponents as DateComponents, to: startOfDay)!

        return NSPredicate(format: "\(key) >= %@ && \(key) < %@",
            startOfDay as NSDate, endOfDay as NSDate)
    }
}

Answer 4

Massimo Camaro 给出了一个很好的答案。我冒昧地将它移植到 Swift 并稍作修改以支持不同的列名。

斯威夫特 2.0

func predicateToRetrieveEventsForDate(aDate:NSDate, predicateColumn:String) -> NSPredicate {
    
    // start by retrieving day, weekday, month and year components for the given day
    let gregorian = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)
    let todayComponents = gregorian?.components([.Day, .Month, .Year], fromDate: aDate)
    let theDay = todayComponents?.day
    let theMonth = todayComponents?.month
    let theYear = todayComponents?.year
    
    // now build a NSDate object for the input date using these components
    let components = NSDateComponents()
    components.day = theDay!
    components.month = theMonth!
    components.year = theYear!
    let thisDate = gregorian?.dateFromComponents(components)
    
    // build a NSDate object for aDate next day
    let offsetComponents = NSDateComponents()
    offsetComponents.day = 1
    let nextDate = gregorian?.dateByAddingComponents(offsetComponents, toDate: thisDate!, options: NSCalendarOptions(rawValue: 0))
    
    // build the predicate
    let predicate = NSPredicate(format: "\(predicateColumn) >= %@ && \(predicateColumn) < %@", thisDate!, nextDate!)
    
    return predicate
}