我有一个带有NSDate 属性的核心数据模型。我想按天过滤数据库。我认为解决方案将涉及NSPredicate，但我不确定如何将它们放在一起。
我知道如何使用NSDateComponents 和NSCalendar 比较两个NSDates 的日期，但是如何使用NSPredicate 过滤它？
也许我需要在我的 NSManagedObject 子类上创建一个类别，该类别可以返回仅包含年、月和日的裸日期。然后我可以在NSPredicate 中进行比较。这是您的建议，还是有更简单的方法？
【问题讨论】：
标签： objective-c core-data nsdate nspredicate nsfetchedresultscontroller
给定一个 NSDate * startDate 和 endDate 以及一个 NSManagedObjectContext * moc：
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(date >= %@) AND (date <= %@)", startDate, endDate];
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
[request setEntity:[NSEntityDescription entityForName:@"EntityName" inManagedObjectContext:moc]];
[request setPredicate:predicate];
NSError *error = nil;
NSArray *results = [moc executeFetchRequest:request error:&error];
【讨论】：
==。如果您在白天搜索，请记住 NSDate 是日期和时间 - 您可能希望使用午夜到午夜的范围。
startDate 设置为 2012-09-17 0:00:00 并将 endDate 设置为 2012-09-18 0:00:00 和谓词开始日期
关于如何将 startDate 和 endDate 设置为上述答案的示例：
...
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components:(NSCalendarUnitYear | NSCalendarUnitMonth ) fromDate:[NSDate date]];
//create a date with these components
NSDate *startDate = [calendar dateFromComponents:components];
[components setMonth:1];
[components setDay:0]; //reset the other components
[components setYear:0]; //reset the other components
NSDate *endDate = [calendar dateByAddingComponents:components toDate:startDate options:0];
predicate = [NSPredicate predicateWithFormat:@"((date >= %@) AND (date < %@)) || (date = nil)",startDate,endDate];
...
我在这里搜索了一个月内的所有条目。值得一提的是，这个例子还展示了如何搜索“nil”日期元素。
【讨论】：
日期的 Swift 3.0 扩展：
extension Date{
func makeDayPredicate() -> NSPredicate {
let calendar = Calendar.current
var components = calendar.dateComponents([.year, .month, .day, .hour, .minute, .second], from: self)
components.hour = 00
components.minute = 00
components.second = 00
let startDate = calendar.date(from: components)
components.hour = 23
components.minute = 59
components.second = 59
let endDate = calendar.date(from: components)
return NSPredicate(format: "day >= %@ AND day =< %@", argumentArray: [startDate!, endDate!])
}
}
然后使用like：
let fetchReq = NSFetchRequest(entityName: "MyObject")
fetchReq.predicate = myDate.makeDayPredicate()
【讨论】：
在 Swift 中我得到了类似的东西：
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd"
let date = dateFormatter.dateFromString(predicate)
let calendar = NSCalendar(calendarIdentifier: NSGregorianCalendar)
let components = calendar!.components(
NSCalendarUnit.CalendarUnitYear |
NSCalendarUnit.CalendarUnitMonth |
NSCalendarUnit.CalendarUnitDay |
NSCalendarUnit.CalendarUnitHour |
NSCalendarUnit.CalendarUnitMinute |
NSCalendarUnit.CalendarUnitSecond, fromDate: date!)
components.hour = 00
components.minute = 00
components.second = 00
let startDate = calendar!.dateFromComponents(components)
components.hour = 23
components.minute = 59
components.second = 59
let endDate = calendar!.dateFromComponents(components)
predicate = NSPredicate(format: "day >= %@ AND day =< %@", argumentArray: [startDate!, endDate!])
我很难发现字符串插值"\(this notation)" 不适用于比较 NSPredicate 中的日期。
【讨论】：
我将答案从 Glauco Neves 移植到 Swift 2.0 并将其包装在一个函数中，该函数接收日期并返回对应日期的 NSPredicate：
func predicateForDayFromDate(date: NSDate) -> NSPredicate {
let calendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)
let components = calendar!.components([.Year, .Month, .Day, .Hour, .Minute, .Second], fromDate: date)
components.hour = 00
components.minute = 00
components.second = 00
let startDate = calendar!.dateFromComponents(components)
components.hour = 23
components.minute = 59
components.second = 59
let endDate = calendar!.dateFromComponents(components)
return NSPredicate(format: "day >= %@ AND day =< %@", argumentArray: [startDate!, endDate!])
}
【讨论】：
添加到 Rafael 的答案（非常有用，谢谢！），移植到 Swift 3。
func predicateForDayFromDate(date: Date) -> NSPredicate {
let calendar = Calendar(identifier: Calendar.Identifier.gregorian)
var components = calendar.dateComponents([.year, .month, .day, .hour, .minute, .second], from: date)
components.hour = 00
components.minute = 00
components.second = 00
let startDate = calendar.date(from: components)
components.hour = 23
components.minute = 59
components.second = 59
let endDate = calendar.date(from: components)
return NSPredicate(format: "YOUR_DATE_FIELD >= %@ AND YOUR_DATE_FIELD =< %@", argumentArray: [startDate!, endDate!])
}
【讨论】：
我最近花了一些时间尝试解决同样的问题，并将以下内容添加到准备开始和结束日期的备选列表中（包括 iOS 8 及更高版本的更新方法）...
NSDate *dateDay = nil;
NSDate *dateDayStart = nil;
NSDate *dateDayNext = nil;
dateDay = <<USER_INPUT>>;
dateDayStart = [[NSCalendar currentCalendar] startOfDayForDate:dateDay];
// dateDayNext EITHER
dateDayNext = [dateDayStart dateByAddingTimeInterval:(24 * 60 * 60)];
// dateDayNext OR
NSDateComponents *dateComponentDay = nil;
dateComponentDay = [[NSDateComponents alloc] init];
[dateComponentDay setDay:1];
dateDayNext = [[NSCalendar currentCalendar] dateByAddingComponents:dateComponentDay
toDate:dateDayStart
options:NSCalendarMatchNextTime];
...以及核心数据NSFetchRequest 的NSPredicate（如上面其他答案中所示）...
[NSPredicate predicateWithFormat:@"(dateAttribute >= %@) AND (dateAttribute < %@)", dateDayStart, dateDayNext]]
【讨论】：
基于之前的答案，使用 Swift 5.x 的更新和替代方法
func predicateForDayUsingDate(_ date: Date) -> NSPredicate {
var calendar = Calendar.current
calendar.timeZone = NSTimeZone.local
// following creates exact midnight 12:00:00:000 AM of day
let startOfDay = calendar.startOfDay(for: date)
// following creates exact midnight 12:00:00:000 AM of next day
let endOfDay = calendar.date(byAdding: .day, value: 1, to: startOfDay)!
return NSPredicate(format: "day >= %@ AND day < %@", argumentArray: [startOfDay, endOfDay])
}
如果您希望将 endOfDay 的时间创建为晚上 11:59:59，则可以改为包含...
let endOfDayLessOneSecond = endOfDay.addingTimeInterval(TimeInterval(-1))
但是您可能会将 NSPredicate 更改为...
return NSPredicate(format: "day >= %@ AND day <= %@", argumentArray: [startOfDay, endOfDayLessOneSecond])
...具体说明从 day < %@ 到 day <= %@ 的更改。
【讨论】：
对我来说这是可行的。
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit ) fromDate:[NSDate date]];
//create a date with these components
NSDate *startDate = [calendar dateFromComponents:components];
[components setMonth:0];
[components setDay:0]; //reset the other components
[components setYear:0]; //reset the other components
NSDate *endDate = [calendar dateByAddingComponents:components toDate:startDate options:0];
startDate = [NSDate date];
endDate = [startDate dateByAddingTimeInterval:-(7 * 24 * 60 * 60)];//change here
NSString *startTimeStamp = [[NSNumber numberWithInt:floor([endDate timeIntervalSince1970])] stringValue];
NSString *endTimeStamp = [[NSNumber numberWithInt:floor([startDate timeIntervalSince1970])] stringValue];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"((paidDate1 >= %@) AND (paidDate1 < %@))",startTimeStamp,endTimeStamp];
NSLog(@"predicate is %@",predicate);
totalArr = [completeArray filteredArrayUsingPredicate:predicate];
[self filterAndPopulateDataBasedonIndex];
[self.tableviewObj reloadData];
NSLog(@"result is %@",totalArr);
我已经过滤了从当前日期到 7 天前的数组。我的意思是我从当前日期获得一周的数据。这应该有效。
注意：我将以毫秒为单位的日期转换为 1000，然后进行比较。如果您需要任何澄清，请告诉我。
【讨论】：
completeArray 中是否有dictionary 或dataModel 的数组我想申请DataModel。