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Firebase v3 Query by Grandchild
(2 answers)
Closed 6 years ago.
I have a data structure like this:
groups
-KOrPKM2QUzuMnMlHfJu
name: "Testgroup 1"
members
0: 123456789
1: 987654321
-KOrPKM2QUzuMnMFGfXa
name: "Testgroup 2"
members
0: 123456789
The number of members is not defined.
How can I get every group where one of the members is 123456789?
This question is different from this because in the other one the key of the value to check is actually known.
The unique ID is generated when push is used, to retrieve the values under that node, you can use child_added.
firebase.database().ref('groups').on('child_added', snap => {
firebase.database().ref('groups/'+snap.key+'/members').on('child_added', childSnapshot => {
if(childSnapshot.val() == '123456789') {
console.log('123456789 found in ' + snap.val().name);
}
});
});
The above code adds a child_added listener to groups so the moment it finds an existing child under groups or when a new child is added, it will trigger child_added, now snap.key contains what you want, the unique generated ID, to compare the value stored in members, another child_added listener is set on members which returns all the value stored under 0, 1...
Now childSnapshot.val() contains the value you want to compare, a simple IF statement is enough and if a match is found, you just print the group name with snap.val().name;
I created NSObject class and called it FBNSArrayDB, inside it I created the firebase ID's in your case it will be:
var name: NSString?
var members: NSString?
var 0: NSString?
var 1: NSString?
then do this in your UIViewController
var fbarray = [FBNSArrayDB]()//at the top
inside func
let ref = FIRDatabase.database().reference().child(uid!)// I assume you are saving this under uid nod!
ref.child("groups").observeEventType(.ChildAdded, withBlock: { (snapshot) in
if let dictionary = snapshot.value as? [String: AnyObject]{
let xy = FBNSArrayDB()
xy.setValuesForKeysWithDictionary(dictionary)
guard let SomeV = xy.0
else {
print ("NA")
return
}
if SomeV == "123456789"
{
self.fbarray.append(xy) //this way you can use the array values outside the Func
print (xy.name)
print (xy.0)
print (xy.1)
print (snapshot.key) // if you want to get the AutoID
}
}
}, withCancelBlock: nil)
Related
I want to save new objects via a view controller in my app. However, I want these new objects to load when the app is logged into. I am using firebase to save data into a database, but how can I save an object and have it return when the app is logged into again? I am new-ish to programming, sorry for any potential confusion.
Here is where the goal information is read when the app has been logged into.
for i in 0 ... clientList.count - 1 {
screenHandle = ref?.child(organizationCode).child(clientList[i].name).observe(.value, with: { (snapshot) in
let clientStuffLoad = snapshot.value as! [String:Any]
if clientStuffLoad["Goal 1 Description"] != nil {
clientList[i].goal1 = clientStuffLoad["Goal 1"] as! String
} else {
clientList[i].goal1 = ""
}
This is essentially what I have regarding adding a new member to the class Client:
#IBAction func addingClientSaveButton(_ sender: Any) {
var client7 = Client(name: addingClientName.text!,
goal1: addingClientGoal1.text!, goal2:
addingClientGoal2.text!,
goal3: addingClientGoal3.text!,
isSelected: false, s: 1,
ind: 1, targetBehavior1 : addingClientTB1.text!,
targetBehavior2 : addingClientTB2.text!,
targetBehavior3 : addingClientTB3.text!,
targetBehavior1Info : addingClientTB1Info.text!,
targetBehavior2Info : addingClientTB2Info.text!,
targetBehavior3Info : addingClientTB3Info.text!)
but I would like the object name to read the client name input as opposed to client7
The second part to this is that I want a way to write this to the database, and be able to read it at log in so that I can use the properties of the class and add to it when adding a new client.
This is a super broad question because it covers a lot of different aspects of working with Firebase; writing, reading, handling DataSnapshots etc. Also, I don't know what your data represents so I picked something for me to cover some of the aspects of working with Firebase.
There's no error checking but it works as is. I've commented along the way.
Firebase has no objects; just parent and child nodes. Everything can be thought of as key: value pairs like a dictionary. You cannot write an object or read an object. Only NSString, NSNumber, NSDictionary and the dreaded NSArray (or their Swift counterparts)
Let's start with a class - there's 100 ways to do this but I like classes to be responsible for their properties as well as accepting them and presenting them
class WineClass {
var wine_key = ""
var name = ""
var varietal = ""
//this is used when creating a new wine object before storing in firebase
init(withName: String, andVarietal: String) {
self.name = withName
self.varietal = andVarietal
}
//this is used when we are loading data from firebase to create the wineclass object
init(withSnapshot: DataSnapshot) {
let wineName = withSnapshot.childSnapshot(forPath: "wine_name").value as? String ?? "No Wine Name"
let wineDict = withSnapshot.value as! [String: Any]
let wineVarietal = wineDict["wine_varietal"] as? String ?? "No Wine Varietal"
self.wine_key = withSnapshot.key //when we read a wine, this will be it's reference in case we want to update or delete it
self.name = wineName
self.varietal = wineVarietal
}
//this is use to create a dictionary of key:value pairs to be written to firebase
func getWineDictForFirebase() -> [String: Any] {
let d = [
"wine_name": self.name,
"wine_varietal": self.varietal
]
return d
}
}
Then, we need a class var to store the WineClass's. This would be for example a dataSource for a tableView
var wineArray = [WineClass]() //a class var array to store my wines
Then I will give you two buttons, one that populates and writes some wine to Firebase and then a second that read them in and prints to console
func button0() {
self.writeWine(withName: "Scarecrow", andVarietal: "Red Blend")
self.writeWine(withName: "Ghost Horse", andVarietal: "Cabernet Sauvignon")
self.writeWine(withName: "Screaming Eagle", andVarietal: "Cabernet Sauvignon, Merlot, Cabernet Franc")
}
func button1() {
self.readWines()
}
And then the function that accepts some strings as properites for each wine and writes them to Firebase
func writeWine(withName: String, andVarietal: String) {
let newWine = WineClass(withName: withName, andVarietal: andVarietal) //create a new wine object
let wineListRef = self.ref.child("wine_list") //get a reference to my firebase wine_list
let thisWineRef = wineListRef.childByAutoId() //a new node for this wine
let d = newWine.getWineDictForFirebase() //get the wine properties as a dictionary
thisWineRef.setValue(d) //save it in firebase
}
and finally a function that reads in those wines, and prints their properties in console
func readWines() {
let wineRef = self.ref.child("wine_list")
wineRef.observeSingleEvent(of: .value, with: { snapshot in //we are reading in the entire wine node which will contain many child nodes
let allWines = snapshot.children.allObjects as! [DataSnapshot] //cast each child node as a DataSnapshot & store in array
for wineSnap in allWines { //iterate over each child node in the array
let wine = WineClass(withSnapshot: wineSnap) //create a new wine, ensuring we also keep track of it's key
self.wineArray.append(wine) //add to the array
}
for wine in self.wineArray {
print(wine.wine_key, wine.name, wine.varietal)
}
})
}
lastly, when button0 is clicked, our Firebase looks like this
wine_list
-LhbjhkEC8o9TUISCjdw
wine_name: "Scarecrow"
wine_varietal: "Red Blend"
-LhbjhkEC8o9TUISCjdx
wine_name: "Ghost Horse"
wine_varietal: "Cabernet Sauvignon"
-LhbjhkEC8o9TUISCjdy
wine_name: "Screaming Eagle"
wine_varietal: "Cabernet Sauvignon, Merlot, Cabernet Franc"
and then the output when button1 is clicked
-LhbjhkEC8o9TUISCjdw Scarecrow Red Blend
-LhbjhkEC8o9TUISCjdx Ghost Horse Cabernet Sauvignon
-LhbjhkEC8o9TUISCjdy Screaming Eagle Cabernet Sauvignon, Merlot, Cabernet Franc
Note that self.ref is a reference to the root node of my firebase yours will need to reference your firebase.
So I have managed to retrieve some data from Firebase and it looks like this when printed:
[Resturant.CustomerList(key: "-LQQlhEmNZb8Kaha9uCk", customerLastName:
“Kendrick”, customerFirstName: “Anna”, customerSeat: "100",
customerOrder: “Noodle”, Timestamp: 1541290545703.0)]
Question: How do I unwrap them so I can put individual value into other String variables?
I tried many ways but I get errors such cannot subscript a value of type [CustomerList] with an index of type String if I do something like let custName = self.list["Name"] as? String
ps. CustomerList is a struct
pps. The print out of list is what is shown
As you have a list of CustomerList objects i.e, [CustomerList] so you should first get a single object from this list. Lets say we want the very first object from this list to access its properties then we can do it as below,
if let firstCustomer = self.list.first {
let firstName = firstCustomer.customerFirstName
let lastName = firstCustomer.customerLastName
}
If you want to access an object at a specific index then you can do as below,
let index = 0
let customer = self.list[index]
let firstName = customer.customerFirstName
let lastName = customer.customerLastName
To find a particular customer, you can filter that as below,
let johny = self.list.filter{ $0.customerFirstName == "Jonhny"}.first {
print(johny.customerLastName)
}
To get a custom list created from the customers list, you can use map as below,
let lastNamesArray = self.list.map({ $0.customerLastName })
class Employee{
var id:Int
var name:String
var salary:Int
init(){
self.id=0
self.name=""
self.salary=0
}
func getInfo(){
self.name=readLine()!
self.id=Int(readLine()!)!
self.salary=Int(readLine()!)!
}
}
var count=0
var flag="y"
var empData:[Employee]=[]
repeat{
count+=1
empData[count]=Employee()
empData[count].getInfo()
flag=readLine()!
}while(flag=="y") `
I have a class Employee with properties id , nam and salary. The function getInfo() is used to get information from user. I want to read data until the flag!="y" . I am getting index out of range error.
What is the right way of inputting data? Can we index the objects ?
You need to append to your array to make it increase in size. Replace
empData[count]=Employee()
with
empData.append(Employee())
to avoid index out of range error
Update
To make your code a little less horrible I would do
repeat {
var employee = Employee()
employee.getInfo()
empData.append(employee)
flag=readLine()!
}while( flag == "y" )
The subscript operator cannot be used to add elements to an array index which doesn't exist yet. You either need to initialize the array with an element count if you know at the time of initialization how many elements your array will have or use the append operator to add new elements to the array after the last index.
You don't even need the count variable, as you can simply access empData.last safely after calling append and adding a new Employee to the Array.
var flag="y"
var empData:[Employee]=[]
repeat {
empData.append(Employee())
empData.last!.getInfo()
flag=readLine()!
} while(flag=="y")
I would advise you to seriously reconsider your implementation as it is really unsafe at the moment. You are not validating user input in any way, hence your getInfo function can easily cause runtime errors if the user input is not in the expected form. Moreover, creating an empty initializer for Employee doesn't make sense, you could simply create a failable initializer, where you read the input and if the input is not of the correct form, make the initializer return nil.
class Employee{
let id:Int
let name:String
let salary:Int
init?(){
guard let name = readLine() else { return nil }
self.name = name
guard let idString = readLine(), let id = Int(idString) else { return nil }
self.id = id
guard let salaryString = readLine(), let salary = Int(salaryString) else { return nil}
self.salary = salary
}
}
var flag="y"
var empData:[Employee]=[]
repeat {
if let employee = Employee() {
empData.append(employee)
} else {
// Display error message to the user
}
flag=readLine() ?? ""
} while(flag=="y")
This is my first question and I'm still learning Swift/Xcode/Firebase, so I appreciate your patience. I've been stalking StackOverflow and have found a lot of answers to help with various things, but nothing that makes sense for the problem I've been struggling with for 2 days.
I am writing a program that will save a date picked on a previous viewcontroller and a set of user-entered floats from text fields to a Firebase database, and append each data set as a separate entry instead of overwriting the previous data. Using the first block of code below, I've got this problem solved except I can't find a way to do it without using AutoID. This leaves me with a setup like this in Firebase, but with multiple categories and "optionSelected" sections in each category:
program-name
Category 1
optionSelected
L1cggMnqFqaJf1a7UOv
Date: "21-12-2017"
Variable 1 Float: "12345"
Variable 2 Float: "26.51"
L1ciVpLq1yXm5khimQC
Date: "30-12-2017"
Variable 1 Float: "23456"
Variable 2 Float: "35.88"
Code used to save:
func newWithNewVars() {
let myDatabase = Database.database().reference().child("Category 1").child(optionSelected)
let variable1 = textField1.text
let variable2 = textField2.text
let variable1Float = (textField1.text! as NSString).floatValue
let variable2Float = (textField2.text! as NSString).floatValue
let writeArray = ["Date": textPassedOverDate, "Variable 1 Float": variable1Float, "Variable 2 Float": variable2Float]
myDatabase.childByAutoId().setValue(gasArray) {
(error, reference) in
if error != nil {
print(error!)
}
else {
print("Message saved successfully!")
}
}
}
The problem comes with recalling data. Since the AutoID is unique, I can't figure out how to access the data deeper inside for calculations. Specifically, I want to be able to make a new entry, press the save data button, and have it find the most recent entry in the "optionSelected" section so it can do calculations like subtract the older variable 1 from the new variable 1 and such.
Given the above description, layout, and code used above, what code structure would allow me to find the most recent date and access the data inside the AutoID sections for a specific category and "optionSelected"?
Thank you for your help.
The issue you're having is that you're trying to dig deeper but can't as you don't have a hold of that id. You'll want to use the .childAdded in your reference observation when you want to get inside of a list in your JSON tree when you don't have a hold of that id to get inside - this will be called as many times as there are values inside of Category 1 tree:
let reference = Database.database().reference()
reference.child("Category 1").child("optionSelected").observe(.childAdded, with: { (snapshot) in
let uniqueKey = snapshot.key // IF YOU WANT ACCESS TO THAT UNIQUE ID
print(uniqueKey)
guard let dictionary = snapshot.value as? [String: AnyObject] else { return }
let date = dictionary["date"] as? String
let variableOne = dictionary["Variable 1 Float"] as? Float
let variableOne = dictionary["Variable 2 Float"] as? Float
}, withCancel: nil)
You may also want to avoid using spaces in your database keys to avoid any problems in the near future. I'd stick with the common lowercased underscore practice e.g. "category_1" or "variable_2_float"
I'm trying to show a tableview similar to contacts with my list of users.
I declare a global variable of friends that will store the first character of a name and a list of users whose first name start with that
var friends = [Character: [User]]()
In my fetch method, I do this
for friend in newFriends {
let letter = friend.firstName?[(friend.firstName?.startIndex)!]
print(letter)
self.friends[letter!]?.append(friend)
}
After this, I should have my friends array with the first letter of the name and the users that fall in it; however, my friends dictionary is empty.
How do I fix this?
Edit: I'm following this tutorial and he doesnt exactly the same.. Swift: How to make alphabetically section headers in table view with a mutable data source
Rather than using Character as the key, use String. You need to be sure to init the [User] array for every new First Initial key you insert into groupedNames. I keep an array of groupedLetters to make it easier to get a section count
var groupedNames = [String: [User]]()
var groupedLetters = Array<String>()
func filterNames() {
groupedNames.removeAll()
groupedLetters.removeAll()
for friend in newFriends {
let index = friend.firstName.index(friend.firstName.startIndex, offsetBy: 0)
let firstLetter = String(friend.firstName[index]).uppercased()
if groupedNames[firstLetter] != nil {
//array already exists, just append
groupedNames[firstLetter]?.append(friend)
} else {
//no array for that letter key - init array and store the letter in the groupedLetters array
groupedNames[firstLetter] = [friend]
groupedLetters.append(firstLetter)
}
}
}
Creating a Dictionary structure with Characters as keys & values as Array of User will be more succinct.
The error occurs because you are declaring an empty dictionary, that means you have to add a key / empty array pair if there is no entry for that character.
Consider also to consolidate the question / exclamation marks
class User {
let firstName : String
init(firstName : String) {
self.firstName = firstName
}
}
var friends = [Character: [User]]()
let newFriends = [User(firstName:"foo"), User(firstName:"bar"), User(firstName:"baz")]
for friend in newFriends {
let letter = friend.firstName[friend.firstName.startIndex]
if friends[letter] == nil {
friends[letter] = [User]()
}
friends[letter]!.append(friend)
}