Firebase iOS - fetching data with boolean operator - swift

Question

I am trying to use firebase for iOS and I am in front of a problem.
I am using the following JSON tree :
{
"expressions" : {
"expr0" : {
"id" : 0,
"text" : "Text0"
},
"expr1" : {
"id" : 1,
"text" : "Text1"
},
"expr2" : {
"id" : 2,
"text" : "Text2"
},
"expr3" : {
"id" : 3,
"text" : "Text3"
}
},
"levels" : {
"level0" : {
"coverImage" : "lvl0",
"expressions" : {
"expr0" : true,
"expr2" : true
},
"id" : 0,
"title" : "Level0"
},
"level1" : {
"coverImage" : "lvl1",
"expressions" : {
"expr0" : true,
"expr1" : true,
"expr3" : true
},
"id" : 1,
"title" : "Level1"
},
"level2" : {
"coverImage" : "lvl2",
"expressions" : {
"expr1" : true,
"expr2" : true,
"expr3" : true
},
"id" : 2,
"title" : "Level2"
},
"level3" : {
"coverImage" : "lvl3",
"expressions" : {
"expr3" : true
},
"id" : 3,
"title" : "Level3"
}
}
}
I have two kind of objects, expressions and levels. Here are the data models of those 2 objects :
struct Level {
let id : Int
let coverImage : String
let title : String
let expressions : [Expression]
}
struct Expression {
let id : Int
let expression : String
}
I also have a DataService singleton to provide me Firebase Database References :
import UIKit
import FirebaseDatabase
class DataService {
private static let _instance = DataService()
static var instance: DataService {
return _instance
}
var mainRef: FIRDatabaseReference {
return FIRDatabase.database().reference()
}
var levelsRef: FIRDatabaseReference {
return mainRef.child("levels")
}
var expressionsRef: FIRDatabaseReference {
return mainRef.child("expressions")
}
}
I want to store on a Levels array the level with their corresponded expressions and display this array with a collectionView. Based on the JSON file, the final result must be :
levelsArr[Level(id: 0, coverImage: "lvl0", title: "Level0", expressions: [Expression(id: 0, expression: "Text0"), Expression(id: 2, expression: "Text2")]), Level(id: 1, coverImage: "lvl1", title: "Level1", expressions: [Expression(id: 0, expression: "Text0"), Expression(id: 1, expression: "Text1"), Expression(id: 3, expression: "Text3")]), Level(id: 2, coverImage: "lvl2", title: "Level2", expressions: [Expression(id: 1, expression: "Text1"), Expression(id: 3, expression: "Text3"), Expression(id: 2, expression: "Text2")]), Level(id: 3, coverImage: "lvl3", title: "Level3", expressions: [Expression(id: 3, expression: "Text3")])]
Here is the following function I have for the moment :
private var levelsArr = [Level]()
func fetchLevels() {
DataService.instance.levelsRef.observeSingleEvent(of: .value, with: { (snapshot) in
if let levels = snapshot.value as? Dictionary<String, AnyObject> {
for(_, valueLvl) in levels {
if let dictLvl = valueLvl as? Dictionary<String, AnyObject> {
if let id = dictLvl["id"] as? Int, let coverImage = dictLvl["coverImage"] as? String, let title = dictLvl["title"] as? String {
var expressionsArr = [Expression]()
if let expr = dictLvl["expressions"] as? Dictionary<String, AnyObject> {
for(keyLvlExp, _) in expr {
DataService.instance.expressionsRef.observeSingleEvent(of: .value, with: { (snapshot) in
print(snapshot)
if let expressions = snapshot.value as? Dictionary<String, AnyObject> {
for (keyExpr, valueExpr) in expressions {
if keyLvlExp == keyExpr {
if let dictExpr = valueExpr as? Dictionary<String, AnyObject> {
if let id = dictExpr["id"] as? Int, let text = dictExpr["text"] as? String{
let expression = Expression(id: id, expression: text)
expressionsArr.append(expression)
}
}
}
}
}
let level = Level(id: id, coverImage: coverImage, title: title, expressions: expressionsArr)
self.levelsArr.append(level)
print(level)
})
}
}
}
}
}
}
})
DispatchQueue.main.async{
self.collectionView?.reloadData()
}
}
The function fetchLevels() is called in the viewDidLoad().
The result of the print(snapshot) is :
Snap (expressions) {
expr0 = {
id = 0;
text = Text0;
};
expr1 = {
id = 1;
text = Text1;
};
expr2 = {
id = 2;
text = Text2;
};
expr3 = {
id = 3;
text = Text3;
};
}
Thank you.