I have below code to get data from my firebase database
db.collection("users").getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
print("starting name display")
for document in (querySnapshot?.documents)! {
let documentUserId = document.get("uid") as?String
let temp = document.data()["displayName"]
print(temp)
}
}
}
The print statement displays as optional("test name")
Why am i keep getting optional in my string. Same displays on the screen as well.
You need to un-wrap because it's an Optional. Means it could have a value or it could not have a value. So this is one method to handle it:
let temp = document.data()["displayName"] ?? ""
print(temp)
You could also use if let or guard let statements if you need to handle the cases where the value is actually empty.
Note: Take a look at the basics of swift. There is a separate section for Optionals.
Related
Still learning some swift and managed to advance and retrieving data from a firestore database. I have a Data Controller whose task is to offload all the data retrieving from firestore. It does the calls and gets data, but when returning the info from the first function I have implemented on it, it's empty.
Here's an example of the funcion:
func fetchUnidades(for foo: MyFirstEnum, and bar: MySecondEnum ) -> [MyClassType]{
let db = Firestore.firestore()
let colPath = "my/firebase/path"
let results = [MyClassType]()
let collection = db.collection(colPath)
collection.whereField("myField", isEqualTo: foo.rawValue).getDocuments() { querySnapshot, err in
if let err = err {
print("Error getting documents: \(err)")
} else {
for document in querySnapshot!.documents {
do {
print("\(document.documentID) => \(document.data())") // 1st print
let newMyClass = try document.data(as: MyClassType.self)
results.append(newMyClass)
print("here") // 2nd print - debug breakpoint
}catch (let error) {
print("\(error)")
}
}
}
}
print("DC - Recovered \(results.count) results")
return results
}
Assume MyFirstEnum, MySecondEnum and MyClassType are correct, because the database retrieves info. On the 1st print line, there's output for data retrieved, and on the 2nd print - debug breakpoint line, if I do a po results, it has one value, which is the one retrieved as you can see here:
unidades being the name on my code of results on this example.
But right after continuing with the execution, unidades, aka results is empty, the line:
print("DC - Recovered \(results.count) results")
prints DC - Recovered 0 results and the return also returns an empty array with zero values on it.
Any idea about why this might be happening? And how to solve the issue? Obviously the goal is to return the info...
That's because the result comes asynchronously. Your fetchUnidades returns results array before it's populated.
You need to add a completion closure in this case. Instead of returning results you call that completion closure and pass the results as its argument.
func fetchUnidades(for foo: MyFirstEnum, and bar: MySecondEnum, completion: (results: [MyClassType]?, error: Error?) -> Void) {
let db = Firestore.firestore()
let colPath = "my/firebase/path"
let collection = db.collection(colPath)
collection.whereField("myField", isEqualTo: foo.rawValue).getDocuments() { querySnapshot, err in
if let err = err {
print("Error getting documents: \(err)")
completion(nil, err)
} else {
let results = [MyClassType]()
for document in querySnapshot!.documents {
do {
print("\(document.documentID) => \(document.data())") // 1st print
let newMyClass = try document.data(as: MyClassType.self)
results.append(newMyClass)
print("here") // 2nd print - debug breakpoint
}catch (let error) {
print("\(error)")
}
}
completion(results, nil)
}
}
This is the first time I am using a Firestore Query and I'm struggling to parse the data. I normally use the same setup when I get documents (which works), but when I attach it to a query it does not work.
I am trying to query the database for the shop most visited, so I can later set it as favourite.
My Code:
func findFavouriteShop(completed: #escaping ([String]) -> Void)
{
// Variables
let dispatch = DispatchGroup()
var dummyDetails = [String]()
// References
let db = Firestore.firestore()
let userID = Auth.auth().currentUser?.uid
let groupCollectionRef = String("visits-" + userID! )
// Query the database for the document with the most counts
dispatch.enter()
db.collectionGroup(groupCollectionRef).order(by: "count", descending: true).limit(to: 1).getDocuments { (snapshot, error) in
if let err = error {
debugPrint("Error fetching documents: \(err)")
}
else {
print(snapshot)
guard let snap = snapshot else {return}
for document in snap.documents {
let data = document.data()
// Start Assignments
let shopName = data["shopName"] as? String
let count = data["count"] as? String
// Append the dummy array
dummyDetails.append(shopName!)
dummyDetails.append(count!)
}
dispatch.leave()
}
dispatch.notify(queue: .main, execute: {
print("USER number of documents appended: \(dummyDetails.count)")
completed(dummyDetails)}
)
}
Using Print statements it seems as if the guard statement kicks the function out. The processor does not reach the for-loop to do the assignments. When I print the snapshot it returns an empty array.
I am sure I have used the wrong notation, but I'm just not sure where.
There's a lot to comment on, such as your choice of collection groups over collections (maybe that's what you need), why you limit the results to one document but feel the need to query a collection, the naming of your collections (seems odd), the query to get multiple shops but creating a function that only returns a single shop, using a string for a count property that should probably be an integer, and using a string array to return multiple components of a single shop instead of using a custom type.
That said, I think this should get you in the right direction. I've created a custom type to show you how I'd start this process but there's a lot more work to be done to get this where you need it to be. But this is a good starting point. Also, there was no need for a dispatch group since you weren't doing any additional async work in the document parsing.
class Shop {
let name: String // constant
var count: Int // variable
init(name: String, count: Int) {
self.name = name
self.count = count
}
}
func findFavouriteShops(completion: #escaping (_ shops: [Shop]?) -> Void) {
guard let userID = Auth.auth().currentUser?.uid else {
completion(nil)
return
}
var temp = [Shop]()
Firestore.firestore().collection("visits-\(userID)").order(by: "count", descending: true).limit(to: 1).getDocuments { (snapshot, error) in
guard let snapshot = snapshot else {
if let error = error {
print(error)
}
completion(nil)
return
}
for doc in snapshot.documents {
if let name = doc.get("shopName") as? String,
let count = doc.get("count") as? String {
let shop = Shop(name: name, count: count)
temp.append(Shop)
}
}
completion(temp)
}
}
You can return a Result type in this completion handler but for this example I opted for an optional array of Shop types (just to demonstrate flexibility). If the method returns nil then there was an error, otherwise there are either shops in the array or there aren't. I also don't know if you're looking for a single shop or multiple shops because in some of your code it appeared you wanted one and in other parts of your code it appeared you wanted multiple.
findFavouriteShops { (shops) in
if let shops = shops {
if shops.isEmpty {
print("no error but no shops found")
} else {
print("shops found")
}
} else {
print("error")
}
}
I am looking to add all my "usernames" into a dictionary. I am having some trouble doing this. I am sure it's very obvious, but I am very new to coding.
I am stuck at, right now and can't seem to find a clear answer anywhere:
func fetchUser() {
let db = Firestore.firestore()
let usernameSearch = db.collection("users")
usernameSearch.getDocuments { (snapshot, error) in
if error != nil {
print("Error obtaining usernames")
} else {
for field in snapshot!.documents {
let field = field.get("username")
print(field!)
}
}
}
}
I would really appreciate it if somebody could help me out. I am sure it's very obvious, or I'm just doing it totally wrong.
First, get into the habit of safely unwrapping over force unwrapping. And choose more accurate names for your objects (i.e. usersCollection over usernameSearch). However, in this case, there's no need to instantiate individual properties for the database and the collection since they're not being used anywhere else but here (so be efficient and omit them).
var usersDictionary = [String: [String]]()
func fetchUser() {
Firestore.firestore().collection("users").getDocuments { (snapshot, error) in
if let snapshot = snapshot { // unwrap the snapshot safely
var usernames = [String]()
for doc in snapshot.documents {
if let username = doc.get("username") as? String {
usernames.append(username)
}
}
usersDictionary["usernames"] = usernames
} else {
if let error = error {
print(error)
}
}
}
}
Or if you actually meant an array of users:
var usersArray = [String]()
func fetchUser() {
Firestore.firestore().collection("users").getDocuments { (snapshot, error) in
if let snapshot = snapshot { // don't force unwrap with !
for doc in snapshot.documents {
if let username = doc.get("username") as? String {
usersArray.append(username)
}
}
} else {
if let error = error {
print(error)
}
}
}
}
I'm assuming that what you're looking for is an Array, not a Dictionary. I'll also assume that you are indeed getting the correct value that you'd expect out of field.get("username"), e.g. a string such as "Bob." Therefore, what you are trying to do is map the list of document objects to a list of strings.
If you scroll to the Topics section of the Array documentation from Apple, you can find some of the operations they provide for arrays such as snapshot!.documents.
One of those operations is actually map, and its description is:
Returns an array containing the results of mapping the given closure over the sequence’s elements.
https://developer.apple.com/documentation/swift/array/3017522-map
In other words, you provide a transformation to perform for each instance of a document belonging to the snapshot!.documents Array and get back a new Array containing the resultant values of that transformation.
In this case I will use a more specific operation; compactMap. We have to try and cast the returned value from Any to String. If that does not succeed, it will return nil, and we'll want to filter that out. I expect it to be an unlikely case due to the type requirements made by the Firebase Console, but it's good to be aware of it. Here is the example:
func fetchUsernames(from usernameCollection: String, completion: #escaping ([String]) -> Void) {
let db = Firestore.firestore()
let collection = db.collection(usernameCollection)
collection.getDocuments { snapshot, error in
guard error != nil,
let usernames = snapshot?.documents.compactMap { $0.get("username") as? String }
else { return print("Error obtaining usernames") }
completion(usernames)
}
}
The key line here being let usernames = snapshot?.documents.compactMap { $0.get("username") }. We are passing the map function a closure. This closure is passed an argument itself; each value from the snapshot?.documents array. You may refer to this passed in value with $0.
I am trying to read the value of a Firestore document. I have tried doing it two different ways, but each fails.
In the first one, an error is thrown on the return line: Unexpected non-void return value in void function. I found out why this happened, and so, I implemented the second way.
import UIKit
import Firestore
func readAvailableLists(forUser user: String) -> [String] {
let db = Firestore.firestore()
db.collection("userslist").document(user).getDocument { (document, err) in
if let document = document, document.exists {
return UserInformationDocument(dictionary: document.data()!)?.lists!
} else {
print("Document does not exist")
}
}
}
In the second method, I assign the UserInformationDocument(dictionary: document.data()!)?.lists! to a variable and return that variable at the end of the function (see code below). However, when I do this, it the function returns an empty array. What surprises me is that the print return the correct value, but after long after the function has executed the return statement. Is it because it is an async demand? And if so, how should I fix this?
import UIKit
import Firestore
func readAvailableLists(forUser user: String) -> [String] {
let db = Firestore.firestore()
var firestoreUserDocument: [String] = []
db.collection("userslist").document(user).getDocument { (document, err) in
if let document = document, document.exists {
firestoreUserDocument = (UserInformationDocument(dictionary: document.data()!)?.lists!)!
print((UserInformationDocument(dictionary: document.data()!)?.lists!)!)
} else {
print("Document does not exist")
}
}
return firestoreUserDocument
}
The Firebase call is an asynchronous function. It takes extra time to execute because it's talking to a server (as you've noted) - as a result, the completion block (the block that defines document and err in your example) happens at a different time, outside of the rest of the body of the function. This means you can't return a value from inside it, but you can pass another closure through to it, to execute later. This is called a completion block.
func readAvailableLists(forUser user: String, completion: #escaping ([String]?, Error?) -> Void) -> [String] {
let db = Firestore.firestore()
db.collection("userslist").document(user).getDocument { (document, err) in
if let document = document, document.exists {
// We got a document from Firebase. It'd be better to
// handle the initialization gracefully and report an Error
// instead of force unwrapping with !
let strings = (UserInformationDocument(dictionary: document.data()!)?.lists!)!
completion(strings, nil)
} else if let error = error {
// Firebase error ie no internet
completion(nil, error)
}
else {
// No error but no document found either
completion(nil, nil)
}
}
}
You could then call this function elsewhere in your code as so:
readAvailableLists(forUser: "MyUser", completion: { strings, error in
if let strings = strings {
// do stuff with your strings
}
else if let error = error {
// you got an error
}
})
I am still new in swift development, my problem is, I have Firestore structure as below:
the problem is to display the list of title from firestore into a uipicker, I need to get data into an array like below:
[firsProgramme, secondProgramme, thirdProgramme]
I managed to display all the "title" from firestore in the string, not in the array
below is the code:
func getprogram() {
let db = Firestore.firestore()
db.collection("Programme").getDocuments()
{
(querySnapshot, err) in
if let err = err
{
print("Error getting documents: \(err)");
}
else
{
for document in querySnapshot!.documents {
let data = document.data()
let program = data["title"] as? String ?? ""
// let agencyId = document.documentID
print(program)
//print("\(document.documentID) => \(document.data())");
}
}
}
}
result print(program) return as below :
firstprogramme
secondprogramme
thirdprogramme
the other part for UIPicker is already being managed well.
Thanks in advance.
In you class create an array variable to hold information about your programs:
var programsArray: [String] = []
When reading data from Firebase, instead of print(program) use programsArray.append(program). Call UIPickerView reload function after you have all data.
DispatchQueue.main.async {
self.your_picker_view.reloadAllComponents()
}
And of course, use this array inside your pickerview datasource methods.