My Data in Firebase looks like this:
I am retrieving the data with
var ref: DatabaseReference
ref = Database.database().reference()
ref.child("peopleReminders").child("-LBO0TMbOM0cwd5TMMiP").observe(.value) { snapshot in
for value in snapshot.children {
print(value)
}
}
This prints the following:
Snap (0) r04
Snap (1) r02
Snap (2) r01
This should be an array. What I need to do is get the values R04, R02, and R01 out of it.
You don't need a loop or enumeration to parse it into an array as Firebase supports both Array and Dictionary. You can directly cast the result into an array. Below piece of code will work:
ref.child("peopleReminders").child("-LBO0TMbOM0cwd5TMMiP").observeSingleEvent(of: DataEventType.value) { (snapshot) in
if snapshot.exists() {
let result: [String] = snapshot.value as? [String] ?? []
print(result)
}
}
Note: Always check snapshot existence it will be false if data doesn't exist for the requested reference. Use observeSingleEvent when you need to fetch the data for once if you use observe the call back will be call many times whenever there is a change in requested node so that delete, insert, update etc.
I replaced for value in snapshot.children with the following code.
let enumerator = snapshot.children
while let rest = enumerator.nextObject() as? DataSnapshot {
print(rest.value!)
}
The new output is now:
R04
R02
R01
Related
I am trying to get values from my database. However, I am unsuccessful. Here is what the DB looks like:
Here is what I tried to do, to read the values:
taskRef = Database.database().reference(withPath: "Tasks").child(titleOfTask)
taskRef?.observeSingleEvent(of: .childAdded, with: { (snapshot) in
if let taskDict = snapshot.value as? [String:Any] {
print("Printing ---------> ",taskDict["Description"] as Any)
}
})
but nothing happens. Ideally, I want to read both the description in a different variable and due date into a different variable.
Important Things to know:
"Tasks" is.. you can think of it as a table name.
Alpha, Bravo, Jalabi... etc are all "Task Names" or childs of "Tasks"
Description, Due Date are the values
You're attaching a listener to /Tasks/$titleOfTask in your JSON, say /Tasks/Alpha. That listener is asking to be called for the first child node of /Tasks/Alpha, so the snapshot in your code will point to /Tasks/Alpha/Description. When you then print taskDict["Description"], you are printing the value of /Tasks/Alpha/Description/Description, which does not exist.
The simplest fix is to listen for the .value event:
taskRef?.observeSingleEvent(of: .value, with: { (snapshot) in
if let taskDict = snapshot.value as? [String:Any] {
print("Printing ---------> ",taskDict["Description"] as Any)
}
})
Now the snapshot has all data from /Tasks/Alpha, and thus the taskDict["Description"] ends up being the value from /Tasks/Alpha/Description.
I have a piece of code inside my Swift built iOS app, to retrieve all the nodes from a Firebase Realtime database. When I execute the code below I've noticed that it does not return all the child nodes.
When I query the particular nodes which are not being returned individually, at first the code returns 'nil' and then on a second attempt retrieves the nodes. (without doing any code changes in the process). Following this process, the node starts to show up in the results with the retrieve all nodes function.
Example 1: First returns nil, then on a second attempt returns the node. Which I can see from the console and definitely exists on the database.
ref?.child("transactions").child(email).child("14526452327").observeSingleEvent(of: .value, with: { (snapshot) in
// Get user value
let value = snapshot.value as? NSDictionary
print(value)
print("!!****************!!")
// ...
}) { (error) in
print(error.localizedDescription)
}
The following is being used to retrieve all child values; at first this doesn't get all the nodes, however after running the code from Example 1 (twice) it starts to return the node in question.
ref?.child("transactions").child(email).observeSingleEvent(of: .value, with: { (snapshot) in
let childrenCount = snapshot.childrenCount
var counter : Int = 0
for trans in snapshot.children.allObjects as! [DataSnapshot]
{
counter = counter + 1
self.ref?.child("transactions").child(email).child(trans.key).observeSingleEvent(of: .value, with: { (snapshot2) in
I've also checked my Firebase query and data limits and I am nowhere near the threshold for the free account. Any help is greatly appreciated.
Try this:
func getData() {
// Making a reference
let transactionRef = Database.database().reference(withPath: "transactions")
transactionRef.observeSingleEvent(of: .value, with: { (snapshot) in
// Printing the child count
print("There are \(snapshot.childrenCount) children found")
// Checking if the reference has some values
if snapshot.childrenCount > 0 {
// Go through every child
for data in snapshot.children.allObjects as! [DataSnapshot] {
if let data = data.value as? [String: Any] {
// Retrieve the data per child
// Example
let name = data["name"] as? String
let age = data["age"] as? Int
// Print the values for each child or do whatever you want
print("Name: \(name)\nAge: \(age)")
}
}
}
})
}
I'm currently retrieving data from a firebase database, and storing the data in a dictionary. When I try to list the keys in the dictionary like this: snapDict?.keys the indexes of the elements aren't the same as how they are in the database.
Database.database().reference().child("\(UserData().mySchool!)/posts").observeSingleEvent(of: .value, with: { (snapshot) in
print(snapshot.childrenCount)
let snapDict = snapshot.value as? [String: Any]
print(snapshot.value!)
let names = snapDict?.keys
print(names!)
for id in names! {
self.searchNames(id: id)
self.tableView.reloadData()
}
})
This is what the elements that will be in the dictionary look like in the database:
So, you would think when they are put into the dictionary they would be printed as -LJRUC8n........-LOF6JUdm-onVuaq-zij?
snapDict?.keys
prints:
["-LOBSAv_l5_x1xnKwx3_", "-LJRUC8nPF3Vg-DDGiYQ", "-LOBLXpTs39yLZo6EnHl", "-LOF6JUdm-onVuaq-zij", "-LODhXPQi8G7MX1bSfeb", "-LJaUiEnGOcBjKsTWSCS", "-LOBLZzrLAlzkhoidnKf"]
I can't figure out the order/pattern here. Alphabetical? Any ideas why the order turns out this way?
The keys in a dictionary are by definition unordered. So when you convert the snapshot to a dictionary, any information on the order of the nodes is lost.
On top of that, you don't specify an order before reading the data.
To fix both:
Database.database().reference()
.child("\(UserData().mySchool!)/posts")
.queryOrderedByKey()
.observeSingleEvent(of: .value, with: { (snapshot) in
print(snapshot.childrenCount)
for child in snapshot.children.allObjects as! [FIRDataSnapshot] {
print(child.value)
}
})
I have imported a simple json file and published on the realtime database called ("Quiz1"). I have then tried accessing it using the following code
var ref: FIRDatabaseReference!
ref = FIRDatabase.database().reference()
print(ref.child("Quiz1").description())
ref.childByAutoId().observeSingleEvent(of:.value, with: {snapshot in
for child in snapshot.children {
print(child)
}
}, withCancel: {error in print("WHAT")})
From what I can see in the documentation, this should trigger the first time the app is launched. But the code just skips over this part, I don't get any error. I have also changed the read/write permissions to make sure there are no authentication steps required at this point.
In order to get the reference to a table in your Firebase database you need to call:
let ref = FIRDatabase.database().reference().child("your table name")
Then from here you can make a listener and get the values from the table
ref(of: .value, with: { snapshot in
First if you want to reference to the node "Quiz1", you need to access it using the child method something like this:
ref.child("Quiz1") and saving that reference in a variable (refQuiz), for then you can make queries (observeSingleEvent) with that reference (refQuiz).
let ref = FIRDatabase.database().reference()
let refQuiz = ref.child("Quiz1")
refQuiz.observeSingleEvent(of: .value) { (snapshot: FIRDataSnapshot) in
for child in snapshot.children {
print(child)
}
}
childByAutoId() creates new child under the ref and newly created node don't have any child nodes.
There's no child nodes to observe on your code.
If you are going to get nodes under "Quiz" please try below:
refHandle = ref.child("Quiz").observe(FIRDataEventType.value, with: { (snapshot) in
let quizDict = snapshot.value as? [String : AnyObject] ?? [:]
// process quizDict
})
So this is my Firebase Structure:
I'm trying to get all books pictures (bookImage), add them to list and then use this list to fill a table or anythings else. (I'm using swift 3)
struct item {
let picture: String!}
var items = [item]()
func getLatestAddedItems(){
let databaseRef = FIRDatabase.database().reference()
databaseRef.child("Items").observe(.childAdded, with: {
FIRDataSnapshot in
let picture = (FIRDataSnapshot.value as? NSDictionary)?["bookImage"] as? String ?? ""
//self.items.insert(item(picture: picture), at: 0)
self.items.append(item(picture: picture))
print(self.items[0].picture)
print(self.items[1].picture) // error here
})}
I'm able to see the first print output but on the second one I'm getting fatal error: Index out of range even I have 3 books on my database.
Since your using .childAdded, it iterates through that closure for each object in the data tree, in this case, each book. When you try to print the second picture, its still in its first iteration. Meaning you only have retrieved the first book so far. That's why you can print the first book item but not the second one. If you moved the print statements outside of the closure, and then did the print statements after the closure iterated over all three books, you wouldn't get the error.
Don't change it to .value unless if every time a new one is subsequently added you want to get the entire list of books all over again. If its a large amount of books, it will be a lot of data to go through each time.
Summary: .childAdded gives you one book at a time, with a new snapshot for each one. .value gives you all the books in one snapshot, then you must iterate over them yourself in the closure. ex.
for snap in snapshot.children {
// now you can do something with each individual item
}
also I just noticed your using the FIRDataSnapshot type in your closure, that should be a variable which represents the snapshot you received, not the type itself. Change "FIRDataSnapshot in" to something like "snapshot in" snapshot is a representation of what information was given to you by the observe closure, in this case, an object with a type of FIRDataSnapshot.
Edit:
Your solution you mentioned below works fine, but I'll add an alternative that is cleaner and easier to use.
add an init method to your Book class that takes a FIRDataSnapshot as the init parameter, then init the object when you query Firebase:
struct Book {
let bookImageString: String
init?(snapshot: FIRDataSnapshot) {
guard let snap = snapshot.value as? [String : AnyObject], let urlString = snap["bookImage"] else { return nil }
bookImageString = imageString
{
{
then when you query firebase you can do this:
for snap in snapshot.children {
if let snap = snap as? FIRDataSnapshot, let book = Book(snapshot: snap) {
self.items.append(book)
{
}
doing it this way cleans up the code a little bit and leaves less chance of error in the code.
Also, since your using .value, make sure to empty the data source array at the beginning of the closer, or else you will get duplicates when new books are added.
items.removeAll()
Finally I'm posting the solution:
func getLatestAddedItems(){
let databaseRef = FIRDatabase.database().reference()
databaseRef.child("Items").observe(.value, with: {
snapshot in
//self.items.insert(item(picture: picture), at: 0)
for childSnap in snapshot.children.allObjects {
let snap = childSnap as! FIRDataSnapshot
print(snap.key)
let picture = (snap.value as? NSDictionary)?["bookImage"] as? String ?? ""
print(picture)
}
})
}