is #distinctUnionOfObjects usable in Swift? - swift

Question

I am trying to make a calendar in swift starting from this great example. So far I managed to show the grid and all the supplementary views customizing UICollectionViewLayout. The problem is when I am trying to add the events in the calendar. Both the day row and the calendar are in the same NSMutableDictionary which has a key that represent the date (String) using this format 2016-10-12. The objective c code is
-(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
}
}
it's quite clear so far. The problem is when I try to change the groupBy function which in objective c is:
- (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:#"%#.#distinctUnionOfObjects.self",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];
}
So far this is what I have done in swift:
I have this class which in the original code is 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
}
I create some fake events:
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!)
}
}
here is the problem. This is my extension.
extension 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)
})
}
}
it crashes with the error this class is not key value coding-compliant for the key startTitle.distinctUnionOfObjects.self.'
I have tried to use map like this
let startDate = array.map ({ $0.startTime })
I managed to get all the date (no distinct though) but I have no idea how to achieve the same result shown in the above code using swift.

Answer 1

I finally managed to do what the above objective c code does with #distinctUnionOfObjects.sel. I am not really sure this is an elegant way of doing it though. All comments or better answers are welcome.
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
}