NSPredicate 与 NSDate 按 day/month 过滤但不是年份

Question

我需要创建一个谓词，它需要使用 NSDate 对象属性 creationDate 过滤对象列表。我想获取具有相同日期和月份但不同年份的对象列表。实际上，我想要过去发生在今天（如 day/month）的对象。我怎样才能创建这个谓词？例如：今天是 2016 年 7 月 27 日，我想要创建日期为 7 月 27 日的所有对象。

Answer 1

首先，从日期中提取日和月...

NSDateComponents *components = [[NSCalendar currentCalendar] components:NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear fromDate:date];
NSInteger day = [components day];
NSInteger month = [components month];

接下来，（一种方式）构建谓词...

[NSPredicate predicateWithBlock:^BOOL(id object, NSDictionary * bindings) {
    // object must be cast to the type of object in the list
    MyObject *myObject = (MyObject *)object;
    NSDate *creationDate = myObject.creationDate;

    // do whatever you want here, but this block must return a BOOL
}];

将这些想法放在一起...

- (NSPredicate *)predicateMatchingYearAndMonthInDate:(NSDate *)date {
    NSDateComponents *components = [[NSCalendar currentCalendar] components:NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear fromDate:date];
    NSInteger day = [components day];
    NSInteger month = [components month];

    return [NSPredicate predicateWithBlock:^BOOL(id object, NSDictionary * bindings) {
        MyObject *myObject = (MyObject *)object;
        NSDate *creationDate = myObject.creationDate;
        NSDateComponents *creationComponents = [[NSCalendar currentCalendar] components:NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear fromDate:creationDate];
        NSInteger creationDay = [creationComponents day];
        NSInteger creationMonth = [creationComponents month];
        return day == creationDay && month == creationMonth;
    }];
}

就是这样。使用数组中要匹配的 NSDate 谁的日期和月份构建谓词，然后运行数组中的谓词 (filteredArrayUsingPredicate:).

NSDate *today = [NSDate date];
NSPredicate *predicate = [self predicateMatchingYearAndMonthInDate:today];
NSArray *objectsCreatedToday = [myArray filteredArrayUsingPredicate:predicate];

Answer 2

这里是 Swift 版本：

import Photos

func predicateMatchingYearAndMonth(in date: Date?) -> NSPredicate? {
    var components: DateComponents? = nil
    if let date = date {
        components = Calendar.current.dateComponents([.day, .month, .year], from: date)
    }
    let day = components?.day
    let month = components?.month

    return NSPredicate { (date:Any?, [String : Any]?) -> Bool in
        var creationDate:Date?
        var creationComponents: DateComponents? = nil

        if let date = date as? PHAsset {
            creationDate = date.creationDate
        }
        if let creationDate = creationDate {
            creationComponents = Calendar.current.dateComponents([.day, .month, .year], from: creationDate)
        }
        let creationDay: Int? = creationComponents?.day
        let creationMonth: Int? = creationComponents?.month
        return day == creationDay && month == creationMonth
    }
}

NSPredicate 与 NSDate 按 day/month 过滤但不是年份

NSPredicate with NSDate filtering by day/month but not year

objective-c

nsdate

nspredicate

ios

swift