首先,我检查了这些对我没有帮助的答案: Swift JSON error, Could not cast value of type '__NSArrayM' (0x507b58) to 'NSDictionary' (0x507d74)
从 Firebase (3.x) 检索数据时,出现错误:
Could not cast value of type '__NSArrayM' (0x10ca9fc30) to 'NSDictionary' (0x10caa0108).
使用这段代码和树:
树:
检索函数:
func retrievePlanes() {
print("Retrieve Planes")
ref = FIRDatabase.database().reference(withPath: "results")
ref.observe(.value, with: { snapshot in
var newItems: [Planes] = []
for item in snapshot.children {
let planesItem = Planes(snapshot: item as! FIRDataSnapshot)
newItems.append(planesItem)
}
self.planes = newItems
self.tableView.reloadData()
})
}
Planes.swift - 管理数据
import Foundation
import Firebase
import FirebaseDatabase
struct Planes {
let key: String!
let name: String!
let code:String!
let flightRange: Int?
let typicalSeats: Int?
let maxSeats: Int?
let wingSpan: String!
let takeoffLength: Int?
let rateClimb: Int?
let maxCruiseAltitude: Int?
let cruiseSpeed: String!
let landingLength: Int?
let engines: String!
let votes: Int?
let data: String!
let imagePlane:String!
let imageTakenFrom: String!
let ref: FIRDatabaseReference?
init(name: String, code: String, flightRange: Int, typicalSeats: Int, maxSeats: Int, wingSpan: String, takeoffLength: Int, rateClimb: Int, maxCruiseAltitude: Int, cruiseSpeed: String, landingLength: Int, engines: String, votes: Int, data: String, imagePlane: String, imageTakenFrom: String, key: String = "") {
self.key = key
self.name = name
self.code = code
self.flightRange = flightRange
self.typicalSeats = typicalSeats
self.maxSeats = maxSeats
self.wingSpan = wingSpan
self.takeoffLength = takeoffLength
self.rateClimb = rateClimb
self.maxCruiseAltitude = maxCruiseAltitude
self.cruiseSpeed = cruiseSpeed
self.landingLength = landingLength
self.engines = engines
self.votes = votes
self.data = data
self.imagePlane = imagePlane
self.imageTakenFrom = imageTakenFrom
self.ref = nil
}
init(snapshot: FIRDataSnapshot) {
ref = snapshot.ref
key = snapshot.key
let snapshotValue = snapshot.value as! [String:AnyObject]
name = snapshotValue["name"] as! String
code = snapshotValue["code"] as! String
flightRange = snapshotValue["intFlightRange"] as? Int
typicalSeats = snapshotValue["intTypicalSeats"] as? Int
maxSeats = snapshotValue["intMaxSeats"] as? Int
wingSpan = snapshotValue["wingSpan"] as! String
takeoffLength = snapshotValue["intTakeoffLength"] as? Int
rateClimb = snapshotValue["intRateClimb"] as? Int
maxCruiseAltitude = snapshotValue["intMaxCruiseAltitude"] as? Int
cruiseSpeed = snapshotValue["cruiseSpeed"] as! String
landingLength = snapshotValue["intLandingLength"] as? Int
engines = snapshotValue["engines"] as! String
votes = snapshotValue["votes"] as? Int
data = snapshotValue["data"] as! String
imagePlane = snapshotValue["planeImage"] as! String
imageTakenFrom = snapshotValue["imageTakenFrom"] as! String
}
就行了:让snapshotValue = snapshot.value as! [字符串:AnyObject]
我想这是由于下面的 Int
而无法在 [String:AnyObject]
下检索快照值。
(在另一种情况下,当我只有 String
时它可以工作)。
我还知道 Firebase 将 JSON 树“转换”为这些对象 [link] :
NSString
NSNumber
NSArray
NSDictionnary
但我无法弄清楚必须在 snapshot.value 行中更改什么才能使其正常工作。
感谢您的帮助。
编辑:我刚刚发送了故障排除请求。将发布更新。 编辑 2:查看 Jay 的回答。就我而言,这棵树是错误的。
最佳答案
我使用了您的代码并将其缩小了一点以进行测试,它可以正常工作。 (注意 OS X 和 Swift 3 上的 Firebase 2.x,但代码相似)
Firebase 结构:
"what-am" : {
"results" : [ {
"code" : "738/B738",
"data" : "Boeing",
"engines" : "Rolls"
}, {
"code" : "727/B727",
"data" : "Boeing",
"engines" : "Pratt"
} ]
}
这是平面结构
struct Planes {
var code:String!
var data: String!
var engines: String!
init(code: String, data: String, engines: String ) {
self.code = code
self.data = data
self.engines = engines
}
init(snapshot: FDataSnapshot) {
let snapshotValue = snapshot.value as! [String:AnyObject]
code = snapshotValue["code"] as! String
data = snapshotValue["data"] as! String
engines = snapshotValue["engines"] as! String
}
}
然后是在两个平面中读取、填充和数组然后打印数组的代码。
let ref = self.myRootRef.child(byAppendingPath: "what-am/results")!
ref.observe(.value, with: { snapshot in
if ( snapshot!.value is NSNull ) {
print("not found")
} else {
var newItems: [Planes] = []
for item in (snapshot?.children)! {
let planesItem = Planes(snapshot: item as! FDataSnapshot)
newItems.append(planesItem)
}
self.planes = newItems
print(self.planes)
}
})
最后是输出
[Swift_Firebase_Test.Planes(code: 738/B738, data: Boeing, engines: Rolls),
Swift_Firebase_Test.Planes(code: 727/B727, data: Boeing, engines: Pratt)]
当我从 Planes 结构中删除时,键和名称为零。
你问的线路
let snapshotValue = snapshot.value as! [String:AnyObject]
有效,因为快照包含一系列键值对,因此 String:AnyObject 有效。
这一行由于 Swift 3 而改变
for item in (snapshot?.children)!
但除此之外,代码有效。
尝试此操作以确保您正在读取正确的节点。这将读取上述结构并打印出每种引擎类型。 (测试和工作)
let ref = self.myRootRef.child(byAppendingPath: "what-am/results")!
ref.observe(.value, with: { snapshot in
if ( snapshot!.value is NSNull ) {
print("not found")
} else {
for child in (snapshot?.children)! {
let snap = child as! FDataSnapshot
let dict = snap.value as! [String: String]
let engines = dict["engines"]
print(engines!)
}
}
})
关于ios - Firebase 检索数据 - 无法转换值(value),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/39934730/