@distinctUnionOfObjects 可以在 Swift 中使用吗？

Posted 2023-03-15

【中文标题】@distinctUnionOfObjects 可以在 Swift 中使用吗？

【英文标题】：is @distinctUnionOfObjects usable in Swift?

【发布时间】：2016-10-12 08:39:16

【问题描述】：

我正在尝试从this 很好的例子开始快速制作日历。到目前为止，我设法展示了自定义 UICollectionViewLayout 的网格和所有补充视图。问题是当我尝试在日历中添加事件时。日期行和日历都在同一个NSMutableDictionary 中，它有一个使用此格式2016-10-12 表示日期（字符串）的键。目标c代码是

-(void)groupEventsBySection
   //toDeviceTimezoneDateString simply take a Date and make a string
_eventsBySection = [mEvents groupBy:@"StartDate.toDeviceTimezoneDateString"].mutableCopy;
     // after groupBy is performed _eventsBySection contains only those keys found in mEvents with inside an array of objects 
   // "2016-10-12" =     (
   // "<MSEvent: 0x60000004a680>",
   // "<MSEvent: 0x60000004a380>");
   // "2016-10-13" =     (
   // "<MSEvent: 0x600000049b10>");
   // "2016-10-17" =     (
   // "<MSEvent: 0x600000049fc0>");
   //    

NSDate* date = [NSDate today:@"device"]; // today's date
if(self.daysToShow == 1 && _eventsBySection.count == 1)
    date = [NSDate parse:_eventsBySection.allKeys.firstObject];

 //here it adds the remaining "daysToShow" if the key doesn't already exist in the MutableDictionary. 
for(int i = 0; i< self.daysToShow; i++)
    if(![_eventsBySection.allKeys containsObject:date.toDeviceTimezoneDateString])
        [_eventsBySection setObject:@[] forKey:date.toDeviceTimezoneDateString];
    
    date = [date addDay]; // this just add one day to date 
 

到目前为止，这很清楚。问题是当我尝试更改目标 c 中的 groupBy 函数时：

- (NSDictionary*)groupBy:(NSString*)keypath
return [self groupBy:keypath block:^NSString *(id object, NSString *key) 
    return key;
];


- (NSDictionary*)groupBy:(NSString*)keypath block:(NSString*(^)(id object, NSString* key))block
    NSMutableDictionary *result = [NSMutableDictionary new];
    NSString* finalKeypath = [NSString stringWithFormat:@"%@[e-mail]",keypath];
    NSArray *distinct = [self valueForKeyPath:finalKeypath];

    [distinct each:^(NSString* value) 
        NSPredicate *predicate  = [NSPredicate predicateWithFormat:@"%K = %@", keypath,value];
        NSArray *objects        = [self filteredArrayUsingPredicate:predicate];
        [result setObject:objects forKey:block(objects[0],value)];
    ];
        return result;


- (NSDictionary*)expand:(NSString*)keypath
    return [self expand:keypath unique:NO];

到目前为止，这是我在 swift 中所做的：

我有这个类，在原始代码中是MSEvent

class Event : NSObject 

var title:String?
var location:String?
var startTime:Date?
var endTime:Date?
var duration:Int?
var subtitle:String?

 init(startTime: Date, duration: Int, title: String, subtitle: String) 
    super.init()
    self.startTime = startTime
    self.duration = duration
    self.title = title
    self.subtitle = subtitle

我创建了一些假事件：

override func viewDidLoad() 
        let today = Date()
        let event1 = Event(startTime: today, duration: 60, title: "prova", subtitle: "HEllo")
        let event2 = Event(startTime: today, duration: 60, title: "prova", subtitle: "HEllo")
        let event3 = Event(startTime: today.dateByAddingDays(days: 1), duration: 60, title: "prova", subtitle: "HEllo")

        var array:[Event] = []
        array.append(event1)
        array.append(event2)
        array.append(event3)

        calendarView.setEvents(events: array)
 

func setEvents(events:[Event])

    mEvents = events as NSArray    
    print(mEvents)
    //this right now returns the 3 event objects I added:
    // (
    // "<myapp.Event: 0x60800032ba40>",
   //  "<myapp.Event: 0x60800032bae0>",
   //  "<myapp.Event: 0x60800032bcc0>"
   //  )
    self.forceReload(reloadEvent: true) //force reload eventually call the groupEventsBy days



func groupEventsByDays()
    // of course everything works without the next line of code 
    eventsBySection = mEvents.groupBy(keypath:  "startTime").mutableCopy() as! NSMutableDictionary
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd"
    var date = dateFormatter.date(from: "2016-10-01")
                  // right now daysToShow is equal to 30
            for _ in 0..<daysToShow

        eventsBySection.setObject([], forKey: self.setFormatDate(date: date!) as NSCopying)


        date = self.addDay(date: date!)

    

这就是问题所在。这是我的扩展。 扩展 NSArray

    func groupBy(keypath:NSString)->NSDictionary

        return self.groupBy(keypath: keypath, block:  (object, key) -> NSString in
            return key
        )
    

    func groupBy(keypath:NSString,block:@escaping ((_ object: Any, _ key:NSString )-> NSString))-> NSDictionary

        let result:NSMutableDictionary = NSMutableDictionary()

        let finalKeypath = String.localizedStringWithFormat("%@.distinctUnionOfObjects.self", keypath)
        let distinct:NSArray = self.value(forKey: finalKeypath) as! NSArray

        (distinct as AnyObject).each(operation:  (value) in
            let predicate = NSPredicate(format: "%K = %@", keypath,value as! CVarArg)
            let objects = self.filtered(using: predicate)
            result.setObject(objects, forKey: (block(objects[0], value as! NSString)))

            )

        return result;
    

    func each(operation:@escaping ((_ object: AnyObject)-> Void))

        self.enumerateObjects( (object, idx, stop) in
            operation(object as AnyObject)
        )

    

它因错误this class is not key value coding-compliant for the key startTitle.distinctUnionOfObjects.self.' 而崩溃 我试过像这样使用map

       let startDate = array.map ( $0.startTime )

我设法获得了所有日期（虽然没有不同），但我不知道如何使用 swift 实现上述代码中显示的相同结果。

【问题讨论】：

它应该可以工作，但是self 你在哪里查询 NSObject 的子类，并且 startTitle 是一个对 Objective-C 运行时可见的属性？ （即它是否属于与 Objective-C 兼容的类型 - 我根据其名称推测 String？）

啊，没关系，它在一个 NSArray 扩展中，所以self 确实是。但是，关于startTitle 的问题仍然存在。

【参考方案1】：

我终于设法用@distinctUnionOfObjects.sel 完成了上述目标c 代码所做的事情。不过，我不确定这是一种优雅的方式。欢迎所有 cmets 或更好的答案。

extension Collection 
    func find( predicate: (Self.Iterator.Element) throws -> Bool) rethrows -> Self.Iterator.Element? 
        return try index(where: predicate).map(self[$0])
    


override func viewDidLoad() 
    super.viewDidLoad()

let event1 = Event(startTime: today!, duration: 60, title: "prova", subtitle: "HEllo")
let event2 = Event(startTime: (today?.dateByAddingDays(days: 5))!, duration: 60, title: "prova", subtitle: "HEllo")
let event3 = Event(startTime: (today?.dateByAddingDays(days: 1))!, duration: 60, title: "prova", subtitle: "HEllo")
let event4 = Event(startTime: todayLater!, duration: 60, title: "prova", subtitle: "HEllo")

var array:[Event] = []
array.append(event1)
array.append(event2)
array.append(event3)
array.append(event4)

 // I create an array with all the date/startTime
let startTime = array.map ( $0.startTime )

let dict:NSMutableDictionary = [:]

   for date in startTime 
             //find the objects for that date
            let object =  array.find(predicate: $0.startTime?.toDeviceDateString() == date?.toDeviceDateString())
           //check if that key/date exist in the dictionary 
        if var val:[Event] = dict[(date?.setFormatDate())!] as! [Event]? 
               //if it does I simply add the object to the array 
            val.append(object!)
            dict.setObject(val, forKey: date?.setFormatDate() as! NSCopying)

         else 
            print("key is not present in dict")
            //otherwise I add a new array with that object inside for the date/key
            dict.setObject([object], forKey: date?.setFormatDate() as! NSCopying)
        


    

  calendarView.setEvents(events: dict)
 

func setEvents(events:NSMutableDictionary) 
//slots events hold the events objects
slotEvents = events
self.forceReload(reloadEvent: true)




 func groupEventsByDays()


let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd"
var date = dateFormatter.date(from: "2016-10-01")

for _ in 0..<daysToShow

    if let val:[Event] = slotEvents[(date?.setFormatDate())!] as! [Event]? 

        eventsBySection.setObject(val, forKey: date?.setFormatDate() as! NSCopying)

    else

        eventsBySection.setObject([], forKey: date?.setFormatDate() as! NSCopying)

    

    date = self.addDay(date: date!)


 print("after\(eventsBySection)")
  //Which print 
  //
 //"2016-10-01" =     (
 // );
//"2016-10-02" =     (
 // );
 // "2016-10-03" =     (
 //     "Optional(<myapp.Event: 0x6000001242e0>)",
 //     "<myapp.Event: 0x6000001242e0>"
//  );
//  "2016-10-04" =     (
//      "Optional(<myapp.Event: 0x600000124600>)"
//  );
//  "2016-10-05" =     (
//   );
//   "2016-10-06" =     (
//   );
//   "2016-10-07" =     (
//   );
//   "2016-10-08" =     (
//       "Optional(<myapp.Event: 0x600000124240>)"
//   );
//  "2016-10-09" =     (
 //   );
  //.... and so on up to 30 days