Retrieve data from "getDocument" query inside another "getDocument" query - ios

Question

I have a problem in my code retrieving data from Firestore.
I have 2 classes in my code: Exercise and Tag.
And I have 2 collections in my FirestoreDatabase: exercises and tags
I need to fecth all the "exercise" documents from the "exercises" collection. Every "exercise" document has a field called "tags" that is an array of strings. Each string of the array contains the "id" that refers to the document that "tag" has on "tags" collection. So, querying this id in "tags" collection, enables me to get the correct "tag" document and access all its data. And this is exactly what I want to do in my code.
I need to fecth all the exercises into a Exercise object and for that I have to use a getDocument query inside another getDocument query in order to get "Tags" of the exercise from "tags" collection
This are my classes Tag and Exercise:
class Tag {
var id: String?
var type: String?
var description: String?
init(id: String, type: String, description: String) {
self.id = id
self.type = type
self.description = description
}
}
class Exercise {
let id: String?
let group: String?
let tags: [Tag]
let title : String!
init(id: String, group: String, tags: [Tag], title: String){
self.id = id
self.group = group
self.tags = tags
self.title = title
}
}
And this is the code where I fetch my "exercises" from Firestore database:
func fetchExercises(completion: #escaping ([Exercise]) -> ()) {
let exercisesRef = Firestore.firestore().collection("exercises")
exercisesRef.getDocuments() { (querySnapshot, err) in
var exercisesArray = [Exercise]()
if let err = err {
print("Error getting documents: \(err)")
} else {
for document in querySnapshot!.documents {
//print("\(document.documentID) => \(document.data())")
let myData = document.data()
let exercise_ID = document.documentID
let exercise_group = myData["Group"] as! String
let tagsArray = myData["Tags"] as! [String]
var exercise_tags: [Tag] = [Tag]()
for tag in tagsArray {
let tagID: String = tag
fetchTagfromID(tagID: tagID) { (tag: Tag) in
exercise_tags.append(tag)
}
}
let exercise_title = myData["Title"] as! String
exercisesArray.append(Exercise(id: exercise_ID,
group: exercise_group,
tags: exercise_tags,
title: exercise_title,
))
}
DispatchQueue.main.async{
print("EXERCISE FETCH HAS FINIS")
completion(exercisesArray)
}
}
}
}
func fetchTagfromID(tagID: String, completion: #escaping (Tag) -> ()) {
let tagRef = Firestore.firestore().collection("tags").document(tagID)
tagRef.getDocument() { (document, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
let myData = document?.data()
let tagDescription: String = myData!["description"] as! String
let tagType: String = myData!["type"] as! String
let tag: Tag = Tag(id: tagID, type: tagType, description:
tagDescription)
DispatchQueue.main.async{
print("TAGS FETCH HAS FINISHED")
completion(tag)
}
}
}
}
My problems come with the timing (queues) code is executed.
I need to fill "exercise_tags" first (secondary getDocument query) and then continue and finish fetchExercise (main getDocument query) but Firestore do not allow (or do not know how) to do that. Code finishes first the main getDocument query (fetChExercises) and then get back to finish secondary getDocument Query (fetchTagfromID).
In summary I need that in runtime I get this log:
TAGS FETCH HAS FINISHED
EXERCISES FETCH HAS FINISHED
and now I am getting the opposite.
Do you know guys how to solve this problem? Maybe changing dispatch queing...
I now how to solve the problem doing this in two steps but elegant solution is doing everything in one step. This is, fetchExercises.
Thank you!

Answer 1

So what you need to do is get all tags for one Exercise then fetch another Exercise. and after all fetch call completion handler to update UI. I made some change in code you can check it.
var exercisesArray = [Exercise]()
var listFromFetchExercise = []() //it will contain all object of array
querySnapshot!.documents. set DataType according to that.
var completion_exercises_Listner: () -> ()
func fetchExercises(completion: #escaping ([Exercise]) -> ()) {
let exercisesRef = Firestore.firestore().collection("exercises")
exercisesRef.getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
listFromFetchExercise = querySnapshot!.documents
fetchAllExercise()
DispatchQueue.main.async{
print("EXERCISE FETCH HAS FINIS")
completion(exercisesArray)
}
}
}
}
func fetchAllExercise(completion: #escaping ([Exercise]) -> ()){
fetchExercise()
completion_exercises_Listner = {
completion(exercisesArray);
}
}
func fetchExercise(index:Int = 0) {
let document = listFromFetchExercise[index]
let myData = document.data()
let exercise_ID = document.documentID
let exercise_group = myData["Group"] as! String
let tagsArray = myData["Tags"] as! [String]
var exercise_tags: [Tag] = [Tag]()
fetchTagsFromIDS(tagsArray) { (tag: [Tag]) in
exercise_tags.append(contentsOf: tag)
let exercise_title = myData["Title"] as! String
exercisesArray.append(Exercise(id: exercise_ID,
group: exercise_group,
tags: exercise_tags,
title: exercise_title,
DispatchQueue.main.async{
exercisesArray.append(tag)
if (index + 1) < exercisesArray.count {
fetchExercise(index+1,)
}else{
//Done
completion_exercises_Listner()
}
}
))
}
var listofTags = [String]()
var resultofTags = [Tag]()
func fetchTagsFromIDS(tagIDS:[String],completion: #escaping (_ tags:[
String]) -> ()){
listofTags = tagIDS;
fetchTagfromID() //Start With first tag
completionListner = {
completion(resultofTags);
}
}
var completionListner: () -> ()
func fetchTagfromID(index:Int = 0) {
let tagRef = Firestore.firestore().collection("tags").document(tagID)
tagRef.getDocument() { (document, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
let myData = document?.data()
let tagDescription: String = myData!["description"] as! String
let tagType: String = myData!["type"] as! String
let tag: Tag = Tag(id: tagID, type: tagType, description:
tagDescription)
DispatchQueue.main.async{
print("TAGS FETCH HAS FINISHED")
resultofTags.append(tag)
if (index + 1) < listofTags.count {
fetchTagfromID(index+1,)
}else{
//Done
completionListner()
}
//completion(tag)
}
}
} }