Parse data JSON from Firebase Swift - ios

Question

I try to parse and assign data, which I am becoming from Firebase
The structure in Firebase looks like this:
I try to fetch data from database and assign it to instance of class Meal:
ref = Database.database().reference()
databaseHandle = ref.child("Meal").observe(.value, with: { (snapshot) in
var downloadedName : String!
var downloadedPhoto : String!
var downloadedRating : Int!
var downloadedSteps : Array <String>!
var downloadedIngredients : [Dictionary <String, String>]!
print(snapshot.value)
if let dict = snapshot.value as? Dictionary<String, Any>{
print("VALUES!!!")
for key in dict.keys {
if let values = dict[key] as? Dictionary<String, Any> {
print(values)
if let name = values["name"] as? String{
downloadedName = name
}
if let photo = values["photo"] as? String{
downloadedPhoto = photo
}
if let rating = values["rating"] as? Int{
downloadedRating = rating
}
if let steps = values["steps"] as? Array<String>{
downloadedSteps = steps
}
if let ingredients = values["ingredients"] as? [Dictionary <String, String>]{
downloadedIngredients = ingredients
}
let meal = Meal(name: downloadedName, photo: UIImage(named: downloadedPhoto), rating: downloadedRating, steps: downloadedSteps, ingredients: downloadedIngredients)
self.meals.append(meal!);
}
}
The Meal class itself looks like this:
class Meal {
var name: String
var photo: UIImage?
var rating: Int
var steps: Array<String>
var ingredients: [Dictionary<String, String>]}
I get the first print - the whole data, so the connection with DB is OK, but as i try to assign it - nothing happens, no errors, no data (the second print with message VALUES!!! is not shown at all, what am I doing wrong?
Here is also what I get by first print
Optional(<__NSArrayM 0x600002fdaa60>(
{
ingredients = (
{
amount = 100;
ingredient = milk;
measurement = ml;
},
{
amount = 120;
ingredient = milk;
measurement = ml;
}
);
name = "Caprese Salad";
photo = meal1;
rating = 4;
steps = (
test1,
test11
);
},
{
ingredients = (
{
amount = 100;
ingredient = milk;
measurement = ml;
},
{
amount = 120;
ingredient = milk;
measurement = ml;
}
);
name = "Chicken and Potatoes";
photo = meal2;
rating = 3;
steps = (
test2,
test22
);
},
{
ingredients = (
{
amount = 100;
ingredient = milk;
measurement = ml;
},
{
amount = 120;
ingredient = milk;
measurement = ml;
}
);
name = "Pasta with Meatballs";
photo = meal3;
rating = 2;
steps = (
test3,
test33
);
}
)
)
So, I assume, I retrieve the data in the false way at some point, how could i fix it?

Answer 1

You have:
print(snapshot.value)
if let dict = snapshot.value as? Dictionary<String, Any>{
print("VALUES!!!")
....
}
You say that print(snapshot.value) is called but not print("VALUES!!!").
Well, that means that snapshot.value or it isn't a Dictionary which keys are String objects and values are of type Any.
Now, let's see the output of snapshot.value:
Optional(<__NSArrayM 0x600002fdaa60> ...
NSArrayM => NSMutableArray, so snapshot.value is an Array, not a Dictionary. Of course then the as? Dictionary will fail!
So you need to treat it as an Array.
Quickly written:
if let array = snapshot.value as? [[String: Any]] {
for aValue in array {
let name = aValue["name"] as? String ?? "unnamed"
let photoName = aValue["photo"] as? String ?? "noPhoto"
let rating = aValue["rating"] as? Int ?? 0
let steps = aValue["steps"] as? [String] ?? []
let ingredients = aValue["ingredients"] as? [[String: String]] ?? [:]
let meal = Meal(name: name, photo: UIImage(named: photoName), rating: rating, steps: steps, ingredients: ingredients)
self.meals.append(meal)
}
}
What could also been wrong with your approach:
var downloadedName : String!
loop {
if let name = values["name"] as? String {
downloadedName = name
}
let meal = Meal(name: downloadedName, ...)
}
Well, if for the second value you didn't have a name (either because it's not a String or because the value doesn't exist), you downloadedName would have the value of the first one, but the rest of the values of the second one.
I used the approach:
let name = aValue["name"] as? String ?? "unnamed"
Meaning, that if it's nil, it gets a default value.
But you could decide to accept only valid one, by a guard let or if let potentially on all the subvalues.
For instance:
if let name = aValue["name"] as? String,
let let photoName = aValue["photo"] as? String,
... {
let meal = Meal(name: name, photo: UIImage(named: photoName)
self.meals.append(meal)
}
And since your Meal.init() seems to return an optional, you could add it also in the if let and avoid the force unwrap of meal.