此函数有一个查询，该查询应该获取数据库中的前5个值。它使用lastPostKey在检索第一个5之后获得接下来的5个。
static func showEvent(pageSize: UInt, lastPostKey: String? = nil,completion: @escaping ([Event]) -> Void) {
//getting firebase root directory
var currentEvents = [Event]()
let eventsByLocationRef = Database.database().reference().child("eventsbylocation").child(User.current.location!)
//let ref = Database.database().reference().child("events")
var query = eventsByLocationRef.queryOrderedByKey().queryLimited(toFirst: pageSize)
由于某种原因，这个if语句中的查询在获取下一个5时会返回null。我个人看不出它有什么问题我甚至在使用正确的方法时使用它但是它返回null无论什么
if let lastPostKey = lastPostKey {
query = query.queryEnding(atValue: lastPostKey)
}
query.observeSingleEvent(of: .value, with: { (snapshot) in
print(snapshot)
print(snapshot.value)
guard let allObjects = snapshot.children.allObjects as? [DataSnapshot] else{
return
}
allObjects.forEach({ (snapshot) in
print(snapshot.value)
EventService.show(forEventKey: snapshot.value as! String, completion: { (event) in
currentEvents.append(.init(currentEventKey: snapshot.value as! String, dictionary: (event?.eventDictionary)!))
// print(currentEvents)
print(currentEvents.count)
completion(currentEvents)
})
})
})
}
如果其他人可以看一下并修复它，我会非常感激。下面是我的数据库中查询的图片。
"events" : {
"CCDS" : {
"attend:count" : 2,
"event:city" : "San Francisco",
"event:date" : {
"end:date" : "08/09/2017",
"end:time" : "7:00 PM",
"start:date" : "08/09/2017",
"start:time" : "5:00 PM"
},
"event:description" : "Happy hour is more joyful in the summer thanks to Center City District Sips, which offers discounted drinks and appetizers every Wednesday evening. Catch up with old friends and make a few new ones as Center City’s best bars and restaurants host the summer’s happiest hour every Wednesday from 5-7 p.m. Enjoy $5 cocktails, $4 wine, $3 beers and half-price appetizers at dozens and dozens of bars and restaurants.",
"event:imageURL" : "https://firebasestorage.googleapis.com/v0/b/eventful-3d558.appspot.com/o/event_flyers%2FCCDS-compressor.jpg?alt=media&token=bcce3968-1cca-4890-a3d0-d8064bd0d1da",
"event:name" : "center city district sips",
"event:promo" : "https://firebasestorage.googleapis.com/v0/b/eventful-3d558.appspot.com/o/event_promo_vid%2FMIA%2FBudweiser%20Made%20In%20America%20Festival%202013%20August%2031%20-%20September%201.mp4?alt=media&token=9b4b9d4f-2d6d-4762-a5fd-c72edb943ac4",
"event:state" : "PA",
"event:street:address" : "660 Chestnut St",
"event:zip" : 19130
},
"DD" : {
"attend:count" : 2,
"event:city" : "New York",
"event:date" : {
"end:date" : "08/26/2017",
"end:time" : "5:00 PM",
"start:date" : "08/26/2017",
"start:time" : "1:00 PM"
},
"event:description" : "Help us celebrate the hard work and creativity of the students and demo the iOS apps and games they've built in only 8 weeks! Developers, entrepreneurs, friends, and industry professionals are all welcome to attend",
"event:imageURL" : "https://firebasestorage.googleapis.com/v0/b/eventful-3d558.appspot.com/o/event_flyers%2Fmakeschooldemo-compressor.jpg?alt=media&token=1e75d18d-1949-48e8-a208-2ca88cde395b",
"event:name" : "demo day",
"event:promo" : "https://firebasestorage.googleapis.com/v0/b/eventful-3d558.appspot.com/o/event_promo_vid%2FDD%2FDemo%20Night%202017%20-%20Make%20School%20Product%20College.mp4?alt=media&token=d9adb4b1-5689-4b15-96b2-e18138701526",
"event:state" : "PA",
"event:street:address" : "394 Broadway",
"event:zip" : 10013
},
"MIA" : {
"attend:count" : 23,
"event:city" : "San Francisco",
"event:date" : {
"end:date" : "09/03/2017",
"end:time" : "7:00 PM",
"start:date" : "09/02/2017",
"start:time" : "12:00 PM"
},
"event:description" : "Budweiser Made in America Festival is an annual music festival held in Philadelphia and formerly simultaneously held in Los Angeles.Sponsored by Anheuser–Busch and produced by Live Nation, the event features several stages that continuously host live music from a wide range of genres including hip hop, rock, pop, R&B, and EDM.",
"event:imageURL" : "https://firebasestorage.googleapis.com/v0/b/eventful-3d558.appspot.com/o/event_flyers%2FMadeInAmerica-compressor.jpg?alt=media&token=1ac6e794-6a1f-4f8a-bdb0-afc91f8ba6ae",
"event:name" : "made in america",
"event:promo" : "https://firebasestorage.googleapis.com/v0/b/eventful-3d558.appspot.com/o/event_promo_vid%2FMIA%2FBudweiser%20Made%20In%20America%20Festival%202013%20August%2031%20-%20September%201.mp4?alt=media&token=9b4b9d4f-2d6d-4762-a5fd-c72edb943ac4",
"event:state" : "PA",
"event:street:address" : "Ben Franklin Parkway",
"event:zip" : 19130
},
"MIA2" : {
"attend:count" : 2,
"event:city" : "Philadelphia",
"event:date" : {
"end:date" : "09/03/2017",
"end:time" : "7:00 PM",
"start:date" : "09/02/2017",
"start:time" : "12:00 PM"
},
"event:description" : "Budweiser Made in America Festival is an annual music festival held in Philadelphia and formerly simultaneously held in Los Angeles. Sponsored by Anheuser–Busch and produced by Live Nation, the event features several stages that continuously host live music from a wide range of genres including hip hop, rock, pop, R&B, and EDM. This is different regardless of the same name in database",
"event:imageURL" : "https://firebasestorage.googleapis.com/v0/b/eventful-3d558.appspot.com/o/event_flyers%2Fmadeinamerica2.jpg?alt=media&token=bd5eb5e4-4e22-4412-a34b-2dc6c9ae561e",
"event:name" : "made in america",
"event:promo" : "https://firebasestorage.googleapis.com/v0/b/eventful-3d558.appspot.com/o/event_promo_vid%2FMIA%2FBudweiser%20Made%20In%20America%20Festival%202013%20August%2031%20-%20September%201.mp4?alt=media&token=9b4b9d4f-2d6d-4762-a5fd-c72edb943ac4",
"event:state" : "PA",
"event:street:address" : "Ben Franklin Parkway",
"event:zip" : 19130
},
"MIA3" : {
"attend:count" : 8,
"event:city" : "Philadelphia",
"event:date" : {
"end:date" : "09/03/2017",
"end:time" : "7:00 PM",
"start:date" : "09/02/2017",
"start:time" : "12:00 PM"
},
"event:description" : "Budweiser Made in America Festival is an annual music festival held in Philadelphia and formerly simultaneously held in Los Angeles. Sponsored by Anheuser–Busch and produced by Live Nation, the event features several stages that continuously host live music from a wide range of genres including hip hop, rock, pop, R&B, and EDM.",
"event:imageURL" : "https://firebasestorage.googleapis.com/v0/b/eventful-3d558.appspot.com/o/event_flyers%2Fmadeinamerica3-compressor.jpg?alt=media&token=9166e2fb-ac9d-46d5-b06f-60cffc337b15",
"event:name" : "made in america",
"event:promo" : "https://firebasestorage.googleapis.com/v0/b/eventful-3d558.appspot.com/o/event_promo_vid%2FMIA%2FBudweiser%20Made%20In%20America%20Festival%202013%20August%2031%20-%20September%201.mp4?alt=media&token=9b4b9d4f-2d6d-4762-a5fd-c72edb943ac4",
"event:state" : "PA",
"event:street:address" : "Ben Franklin Parkway",
"event:zip" : 19130
}
},
"eventsbylocation" : {
"37%2e7,-122%2e4" : {
"event0" : "MIA",
"event1" : "CCDS",
"event2" : "MIA2",
"event3" : "MIA3",
"event4" : "CCDS",
"event5" : "MIA",
"event6" : "MIA2",
"event7" : "MIA3",
"event8" : "CCDS",
"event9" : "MIA"
},
"40%2e7,-74%2e0" : {
"event" : "DD"
}
},