如何使用Swift 5从Firebase中保存快照中的数据？

Question

I am trying to save the data that I get from a snapshot into different variables.

I have a class called QuotesModel and it has the QuoteID and the Quote as string variables. I am trying to save off the snapshot of a quote to the Quote variable in that class.

class QuotesModel:NSObject {
    var QuoteID:String = ""
    var quote:String = ""
}



var rootref: DatabaseReference?
var QuotesArr = [QuotesModel]()

override func viewDidLoad() {
    rootref = Database.database().reference()
    let ref = rootref!.child("HelloWorld")
    super.viewDidLoad()

ref.observe(.childAdded, with: {(snapshot) in
    print(snapshot)
    guard let dictionary = snapshot.value as? [String : AnyObject] 
    else {
            return
     }
        let Obj = QuotesModel()
        Obj.QuoteID = snapshot.key
        Obj.quote = (dictionary["Test1"] as? String)!
        self.QuotesArr.append(Obj)
    }, withCancel: nil)
}

Answer 1

Let's clean this up and make is Swifty as well.

First define your class and array. We are going to add logic to the class to 'break down' the snapshot into it's components and add some error checking in case the quote is nil.

class QuoteModel {
    var quoteID = ""
    var quote = ""

    init(withSnapshot: DataSnapshot) {
        self.quoteId = withSnapshot.key
        self.quote = withSnapshot.value as? String ?? "No Quote"
    }
}

then a reference to our root database and an array. Note that it's generally best practice to refer to class vars with 'self.' and also lower case is typically used for vars, upper case for class definitions.

var rootref: DatabaseReference?
var quotesArr = [QuoteModel]()

And then the code to iterate over all quotes and populate the array

func iterateOverAllQuotes() {
    self.rootref = Database.database().reference()
    let ref = self.rootref!.child("HelloWorld")
    super.viewDidLoad()

    ref.observe(.childAdded, with: { snapshot in
        let aQuote = QuoteModel(withSnapshot: snapshot)
        self.quotesArr.append(aQuote)
    })
}