retrieve array elements from firebase in swift

Question

I am completely new to swift and firebase, and I am having difficulties in retrieving array-elements from firebase database

So this is my firebase database

I can retrieve the other elements like this:

database reference

class ViewController: UIViewController {

var ref: FIRDatabaseReference?
let fileName : String = "jsonFile"

method

    func parseFirebaseResponse() { 
    ref?.child("Vandreture").child(fileName).observe(.value, with: 
    { (snapshot) in
            let dict = snapshot.value as? [String: AnyObject]
            let navn = dict!["navn"] as? String
            print(navn as Any)

            let type = dict!["type"] as? String
            print(type as Any)

            let Længde = dict!["length"] as? String
            print(Længde as Any)

            let link = dict!["link"] as? String
            print(link as Any)

        })

}

the console shows the result

But I have searched for a way to retrieve longitude/latitude pairs, The first pair should be latitude 109.987 longitude 102.987 - but so far without luck - help would really be appreciated :)

stackoverflow.com/a/45143371/7715250 check my answer there, should give the right direction — J. Doe
– J. Doe, Commented Aug 2, 2017 at 16:57

Victor Apeland · Accepted Answer · 2017-08-02 17:50:09Z

1

I think you should restructure your database to something like this:

Vandreture {
   jsonFile {
       length: "16.2"
       link: "www.second.com"
       navn: "Kagerup rundt"
       positions {
           -KqXukxnw3mL38oPeI4y {
               x: "102.987"
               y: "109.987"
           }
           -KqXukxnw3mL38oPeI5- {
               x: "108.234"
               y: "99.098"
           }
       }
   }
}

Then getting your coordinates would be far easier!

answered Aug 2, 2017 at 17:50

Victor Apeland

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Comments

Twitter khuong291 · Accepted Answer · 2017-08-02 18:18:26Z

0

Get your "position" as a dictionary (aka [String: AnyObject]).

Then get array of latitude and longitude. Then map of each element from latitude and longitude into a tuple or something like that.

guard let position = dict!["position"] as? [String: AnyObject], 
let latitudeArray =  position["latitude"] as? [String], 
let longitudeArray =  position["longitude"] as? [String] else { return }
print(latitudeArray)
print(longitudeArray)

edited Aug 2, 2017 at 18:18

answered Aug 2, 2017 at 17:07

Twitter khuong291

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2 Comments

Martin Utzon Over a year ago

When I add your code to my method, run the program and check the debugger, the "position" has 2 key/value pairs which are "longitude" and "latitude", but latitudeArray and longitudeArray do not contain any elements so they don't print anything to the console

Twitter khuong291 Over a year ago

sorry, this should be let longitudeArray = position["longitude"] instead of let longitudeArray = position["latitude"] :D

Martin Utzon · Accepted Answer · 2017-08-03 21:14:44Z

thanks Victor Apeland - now I changed the structure of the database. I was not able to do it exactly as you suggested!! I concatenated the lon/lat as a string (not the best - i know - I'm a newbie to swift, and firebase is not well documented) to retrieve the individual elements from my long/lat, I used this method, and I was particular interested in the first reading, so I made a list, populated it, and got the first element, parsing it to a new method

func responsePosition() {
    var positions = [String]()
    ref?.child("Vandreture").child(fileName).child("position").observe(.value, with: { (snapshot) in

    for snap in snapshot.children {
        let userSnap = snap as! FIRDataSnapshot
        let uid = userSnap.key //the uid of each user
        let userDict = userSnap.value as! String
        positions.append(userDict)

    }
      let  pos : String = positions[0]
        self.formatPositions(pos : pos)
    })
}

In my firebase lon-lat was divided by a space, so I split the string and cast to double.

func formatPositions(pos : String) {
let lotLangDivided = pos.components(separatedBy: " ")
let longitude = Double(lotLangDivided[0])
let latitude = Double(lotLangDivided[1]) 
}

now I got the result i wanted - thanks for the help Victor and Khuong :)

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