I am having a problem while iterating through a dictionary. First check my database
And here is my code
ref.child("Events").observe(.value, with: { (snapshot) in
for child in snapshot.children{
let snap = child as! DataSnapshot
let valueSnap = snap.value as? [[String:Any]]
let nombreEventDansClub = valueSnap?.count
print(valueSnap)
for index in 0...nombreEventDansClub!-1
{
print(valueSnap![index]["name"])
//print(valueSnap![index]["end_time"])
if(valueSnap![index]["end_time"] as? String == nil)
{
//do Something
}
else{
let end_time_test = valueSnap![index]["end_time"] as? String
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZ"
dateFormatter.timeZone = TimeZone(abbreviation: "GMT+2:00")
let end_test = dateFormatter.date(from: end_time_test!)!
The recuperation is perfect but for example : if Event-0-(3) didn't exist the app would crash, I know the problem is that I calculate the number of events in a : Event-(something) and iterate according to this. I was wondering if there is a smarter way. Thanks in advance
You can parse the snapshot this way:-
ref.child("Events").observe(.value, with: { (snapshot) in
guard let values = snapshot as? [Any] else { return }
for value in values {
guard let childrens = value as? [Any] else { continue }
for children in childrens {
guard let dict = children as? [String: Any] else { continue }
for key in dict.allkeys {
// TO debug all keys and values
print(dict[key])
}
print(dict["description"] as? String)
print(dict["end_time"] as? String)
print(dict["id"] as? String)
// other keys
}
}
}
Force unwrapping may cause your app crash unexpectedly.
Related
I am trying to fill an array with data from Firebase. But after filling the array I can't call its' members from their index. I am filling the array by this function
func loadSounds(){
Firestore.firestore().collection("data").getDocuments{ (snapshot, error) in
if error == nil{
for document in snapshot!.documents{
let name = document.data()["name"] as? String ?? "error"
let sounds = document.data()["sounds"] as? [String : [String : Any]]
var soundsArray = [dataSound]()
if let sounds = sounds{
for sound in sounds {
let soundName = sound.value["name"] as? String ?? "error"
let soundImage = sound.value["image"] as? String ?? "error"
soundsArray.append(dataSound(name: soundName , image: soundImage ))
}
}
categoriesArray.append(Category(category: name , sounds: soundsArray))
}
print(categoriesArray[0].category)
} else {
print(error)
}
} }
When I try to access it from View, It gives index out of bounds error.
struct ContentView: View {
init(){
loadSounds()
}
var body: some View {
Text(categoriesArray[0].category)}}
If I try to access it via ForEach, it works, also when I try to print it from loadSounds function it works, but I need to access them from their index in View. Thanks for any help.
Never access items of an array by index in the rendering area of a SwiftUI View, in almost all cases the array is empty when the view is rendered the first time.
In your case use .first and handle the optional
var body: some View {
Text(categoriesArray.first?.category ?? "No value")}} // or empty string
I am trying to read nested data structures from Firebase Database, but I don't know how to manage the case when an object of type [String:AnyObject] could be nil.
When readFeesCleaner(callback_) is called, it throws an error.
func readFeesCleaner(callback: #escaping ((_ feesCleaner: FeesCleaner) -> Void)) {
dbRef.child("FeesCleaner").child(self.uidOfTextField!).observeSingleEvent(of: .value, with: { (snapshot: FIRDataSnapshot) in
guard !(snapshot.value is NSNull) else {
return
}
//throws error: signal SIGABRTCould not cast value of type '__NSDictionaryM' (0x1111152b0) to 'FIRDataSnapshot' (0x10ef16d18).
let feesCleanersReceived = FeesCleaner(snapshot: (snapshot.value)! as! FIRDataSnapshot)
callback(feesCleanersReceived)
}) { (error:Error) in
print(#line, "\(error.localizedDescription)")
}
}
struct FeesCleaner {
var outstandingFees: AnyObject!
var timeStampFeesSaved: [String:AnyObject]!
var backgroundCheck: AnyObject!
init(
outstandingFees: AnyObject? = nil, //value might not exist when reading
timeStampFeesSaved: [String:AnyObject]? = nil,// value might not exist when reading
backgroundCheck: AnyObject) {
self.outstandingFees = outstandingFees
self.timeStampFeesSaved = timeStampFeesSaved
self.backgroundCheck = backgroundCheck
}//end of init
//read data here
[full struct data here][1]
https://gist.github.com/bibscy/dc48f7107459379e045a50fdbbc35335
}//end of struct
There's a number of issues here. First:
how to manage the case when an object of type [String:AnyObject]
could be nil.
You've handled that with the prior statement, noting that you can also add
if snapshot.exists == false {return}
Second: You've got to handle optionals properly - if a var could be nil, you need code in place to handle that situation and not plow through it. If you force unwrap an optional you are essentially stating that for sure, it will never be nil, so basically, don't do that.
One fix could be to simply pass the snapshot as a DataSnapshot and then pull out the properties one at a time; if they exist, assign them, if not set to 0 or nil or some other placeholder.
Something like this inside the Firebase closure:
let feesCleanersReceived = FeesCleaner(withSnapshot: snapshot)
and then your struct like this: note we are leveraging the nil coalescing operator, ??
struct FeesCleanerStruct {
var outstandingFees: String?
var timeStampFeesSaved: String?
init(withSnapshot: DataSnapshot) {
let dict = withSnapshot.value as! [String: Any]
self.outstandingFees = dict["outstandingFees"] as? String ?? "0.0"
self.timeStampFeesSaved = dict["timeStampFeesSaved"] as? String ?? "0"
}
}
I have an old type of web service built on ASP.Net. With the following function, I was able to fetch some type of data from the asmx web service:
func getJsonData(sql: String, spparamnames: String, spParamValues: String, completeonClosure: #escaping (AnyObject?) -> ()) {
let url = URL(string:"http://www.example.com/MyWebService.asmx/GetDataTableAsJson")
var request = URLRequest(url: url!)
request.setValue("application/json; charset=utf-8", forHTTPHeaderField: "Content-Type") // the request is JSON
request.setValue("application/json; charset=utf-8", forHTTPHeaderField: "Accept") // the expected response is also JSON
request.httpMethod = "POST"
let dictionary = ["sql" : sql, "spparamnames" : spparamnames, "spparamvalues" : spParamValues] //Parameters are here seperated with comma
request.httpBody = try! JSONSerialization.data(withJSONObject: dictionary)
let task = URLSession.shared.dataTask(with: request) { data, response, error in
guard let data = data, error == nil else {
print(error.debugDescription) // some fundamental network error
return
}
do {
if response != nil {
let myJson = try JSONSerialization.jsonObject(with: data, options: JSONSerialization.ReadingOptions.mutableContainers) as! [String:AnyObject]
let isCorectJson = JSONSerialization.isValidJSONObject(myJson)
let charcount = (myJson["d"] as? String)?.characters.count
let cc = charcount ?? 0
if isCorectJson == true && cc > 0 {
completeonClosure(myJson as AnyObject?)
)
} else {
let str2 = "Connection Error"
completeonClosure(str2 as AnyObject?)
}
}
} catch let JsonError {
print(JsonError)
}
}
task.resume()
}
When I run a query with Swift, and cast the object type as NSDictionary, my output result is the following:
getJsonData(sql: "SELECT TOP 3 User_id, LoweredUserName FROM Users", spparamnames: "", spParamValues: "") {
returnJSON in
OperationQueue.main.addOperation {
let mystr = returnJSON as? NSDictionary
print(mystr!)
}
}
Result:
{
d = "[{\"User_id\":102,\"LoweredUserName\":\"abu alay\"},{\"User_id\":90,\"LoweredUserName\":\"ali es\"},{\"User_id\":95,\"LoweredUserName\":\"alper ay\"}]";
}
I think that the result is some kind of dictionary, I was not able to convert the result to an array, therefore I cannot iterate between the rows and use the result efficiently. What should I do in order to read the result like: print(returnJSON[0]["LoweredUserName"]) ? What is the meaning of the letter "d" at the beginning of the result? Many thanks in advance.
It looks like your response is an Array, try to cast to an array of dictionary objects.
if let myJson = try JSONSerialization.jsonObject(with: data, options: JSONSerialization.ReadingOptions.mutableContainers) as? [[String:AnyObject]] {
// parse each object here
}
This example code I ran in a playground seems to work fine:
let jsonString = "[{\"User_id\":102,\"LoweredUserName\":\"abu alay\"},{\"User_id\":90,\"LoweredUserName\":\"ali es\"},{\"User_id\":95,\"LoweredUserName\":\"alper ay\"}]"
let jsonData = jsonString.data(using: String.Encoding.utf8)
if let json = try? JSONSerialization.jsonObject(with: jsonData!, options: .mutableContainers) as? [[String:AnyObject]] {
print(json)
}
Output:
Optional([["User_id": 102, "LoweredUserName": abu alay], ["User_id": 90, "LoweredUserName": ali es], ["User_id": 95, "LoweredUserName": alper ay]])
If the text you have shown is the entire body of the result you got:
{
d = "[{\"User_id\":102,\"LoweredUserName\":\"abu alay\"},{\"User_id\":90,\"LoweredUserName\":\"ali es\"},{\"User_id\":95,\"LoweredUserName\":\"alper ay\"}]";
}
Then this is not properly formatted JSON. For it to be formatted properly the "d" would have to be shown in double quotes.
It looks like you may need to do some custom parsing on the result to get at the JSON contained in the "d" area.
I would like to download from firebase:
data issued from a group profile (Firebase realtime DB)
including...
data issued from the group admin profile (Firebase realtime DB)
a group profile image (Firebase Storage)
Then I can instantiate a group object with its data and its image
First approach, I used 3 nested closures that allowed me to get data, and then to get the image.
It did work, but it was quite long to get sequentially all that stuffs from firebase.
So I tried to use GCD in order to push my 2 latest Firebase queries (user data + group image) at the same time (rather than one after the other), and to wait for the last callback to start instantiating my group.
Is it a correct approach ?
If yes, I find some difficulties to implement it...
My issue : returnedUser and returnedGroupImage are always nil
Here is my bunch of code :
static func getGroup(_ groupID:String, completionBlock: #escaping (_ group: Group?) -> ()) {
dataRef.child("data").child("groups").child(groupID).observe(.value, with: { (snapshot) in
if let snapshotValue = snapshot.value {
guard let name = (snapshotValue as AnyObject).object(forKey: "name") as? String else
{
completionBlock(nil)
return
}
guard let adminID = (snapshotValue as AnyObject).object(forKey: "adminID") as? String else
{
completionBlock(nil)
return
}
let queue = DispatchQueue(label: "asyncQueue", attributes: .concurrent, target: .main)
let dispatch_group = DispatchGroup()
var returnedUser: User?
var returnedGroupImage: UIImage?
queue.async (group: dispatch_group) {
FireBaseHelper.getUser(adminID, completionBlock: { (user) in
if user != nil {
returnedUser = user
}
})
}
queue.async (group: dispatch_group) {
FireBaseHelper.getGroupImage(groupID, completionBlock: { (image) in
if image != nil {
returnedGroupImage = image
}
})
}
dispatch_group.notify(queue: DispatchQueue.main) {
// Single callback that is supposed to be executed after all tasks are complete.
if (returnedUser == nil) || (returnedGroupImage == nil) {
// always true !
return
}
let returnedGroup = Group(knownID: (snapshotValue as AnyObject).key, named: name, createdByUser: currentUser!)
returnedGroup.groupImage = returnedGroupImage
completionBlock(returnedGroup)
}
}
})
}
Thanks for your help !
I believe that the way you are using DispatchGroups are not correct.
let dispatch_group = DispatchGroup()
var returnedUser: User?
var returnedGroupImage: UIImage?
dispatch_group.enter()
FireBaseHelper.getUser(adminID, completionBlock: { (user) in
if user != nil {
returnedUser = user
}
dispatch_group.leave()
})
dispatch_group.enter()
FireBaseHelper.getGroupImage(groupID, completionBlock: { (image) in
if image != nil {
returnedGroupImage = image
}
dispatch_group.leave()
})
dispatch_group.notify(queue: DispatchQueue.main) {
// Single callback that is supposed to be executed after all tasks are complete.
if (returnedUser == nil) || (returnedGroupImage == nil) {
// always true !
return
}
let returnedGroup = Group(knownID: (snapshotValue as AnyObject).key, named: name, createdByUser: currentUser!)
returnedGroup.groupImage = returnedGroupImage
completionBlock(returnedGroup)
}
everyone. I have troubles with fetching a chunk of images from a child in my Firebase database. I am doing an iOS project and using swift 3 and XCode. Basically, after all, my "image" variable returns "nil" Please, help me if you can. Here is the code I am using:
let ref = FIRDatabase.database().reference().child("menu")
ref.observeSingleEvent(of: .value, with: { (snapshot) in
if let dictionary = snapshot.value as? [String: AnyObject] {
let image = dictionary["foodImageUrl"] as? String
print(image as Any) // this returns nil
and an example of a database structure
I need to fetch all the "foodImageUrl" from all children from the menu node
your snapshot.value is the list of sub items from menu, not the details info of each node, so you have to use forEach, and then inside each node, use dictionary["foodImageUrl"] as? String to get your image
try this
let ref = FIRDatabase.database().reference().child("menu")
ref.observeSingleEvent(of: .value, with: { (snapshot) in
for rest in snapshot.children.allObjects as! [FIRDataSnapshot] {
if let dictionary = rest.value as? [String: AnyObject]{
let image = dictionary["foodImageUrl"] as? String
print(image as Any)
}
}