Download address from firebase in mapView - swift

Question

Trying to upload an address from firebase and post it on mapView. But for some reason the address doesn't want to unload. The address spelled out by the string in firebase example - Moscow, Street so-and-so, house 1. What could be the reason for not loading the data?
var allAddresses: String = ""
addressRef = Database.database().reference(withPath: "Address")
addressRef.observe(.value, with: { (snapshot) in
let value = snapshot.value as! NSDictionary
self.allAddresses = value["address"] as? String ?? ""
})
}
Firebase:
{
«Address» : {
«AddressOne» : {
"address" : "Москва, Пресненская набережная д.8, квартира 195, подъезд 94",
},
"AddressTwo» : {
"address" : "Москва, ул. Правды д.24 строение 3",
},
"AddressThree» : {
"address" : "Москва,ул.Электрозаводская д.21",
}
}
}

Answer 1

You're attaching a value observer to /Address, which means that you get a snapshot with all data at that location. Since there are multiple child addresses, your code will need to handle those.
The simplest way to do that is by listening for .childAdded instead of .value:
var allAddresses: String = ""
addressRef = Database.database().reference(withPath: "Address")
addressRef.observe(.childAdded, with: { (snapshot) in
let value = snapshot.value as! NSDictionary
self.allAddresses = value["address"] as? String ?? ""
})
Now your code gets triggered with each individual address.
You can also stick to observing .value and then loop over the results in the snapshot:
var allAddresses: String = ""
addressRef = Database.database().reference(withPath: "Address")
addressRef.observe(.value, with: { (snapshot) in
for address in snapshot.children.allObjects as [FIRDataSnapshot] {
let value = address.value as! NSDictionary
self.allAddresses = value["address"] as? String ?? ""
})
})

Answer 2

Use optional unwrapping and set breakpoints on some lines to see where your code doesn't do what you want :
var allAddresses: String = ""
addressRef.observe(.value, with: { (snapshot) in
if let value = snapshot.value as? [String:Any] {
if let address = value["address"] as? String {
self.allAddresses = address
} else {
print("no address in value")
}
} else {
print("no value from firebase")
}
})
}
You should also use swift types in swift, it's a good practice.