Bringing array values ​containing map in firestore using Swift

Question

I'm developing an app for my school project and I stuck in an issue and I'm not able to handle it. I’m trying to get midTerm, finalTerm and lectureGradeId values from my Firebase Cloud Firestore. Except that values, I'm able to get every value from Firestore.

To make it clear, I'm putting my codes and my Firestore structure below:

Students.swift

import Foundation
import FirebaseFirestore

struct Grades: Codable, Hashable {
var lectureGradeId: String
var midTerm: String
var endTerm: String
}

struct Students: Identifiable, Codable {
var id: String
var email: String
var studentName: String
var studentSurname: String
var studentTerm: String
var studentBirthday: String
var studentClass: Int
var studentDept: String
var studentFaculty: String
var studentIsActive: Bool
var studentIsGraduated: Bool
var studentLectures: [String]?
var studentGrades: [Grades]?
}

StudentsViewModel.swift

import Foundation
import Firebase

class StudentsViewModel: ObservableObject {
@Published var students = [Students]()

private var db = Firestore.firestore()

func fetchData() {
    db.collection("Students").whereField("id", isEqualTo: "20704029").addSnapshotListener { querySnapshot, error in
        guard let documents = querySnapshot?.documents else {
            print("No documents")
            return
        }
        
        self.students = documents.map { (queryDocumentSnapshot) -> Students in
            let data = queryDocumentSnapshot.data()
            
            let id = data["id"] as? String ?? ""
            let email = data["email"] as? String ?? ""
            let studentName = data["studentName"] as? String ?? ""
            let studentSurname = data["studentSurname"] as? String ?? ""
            let studentTerm = data["studentTerm"] as? String ?? ""
            let studentBirthday = data["studentBirthday"] as? String ?? ""
            let studentClass = data["studentClass"] as? Int ?? 0
            let studentDept = data["studentDept"] as? String ?? ""
            let studentFaculty = data["studentFaculty"] as? String ?? ""
            let studentIsActive = data["studentIsActive"] as? Bool ?? true
            let studentIsGraduated = data["studentIsGraduated"] as? Bool ?? false
            let studentLectures = data["studentLectures"] as? Array ?? [""]
            
            let student = Students(id: id, email: email, studentName: studentName, studentSurname: studentSurname, studentTerm: studentTerm, studentBirthday: studentBirthday, studentClass: studentClass, studentDept: studentDept, studentFaculty: studentFaculty, studentIsActive: studentIsActive, studentIsGraduated: studentIsGraduated, studentLectures: studentLectures)
            //print(student)
            return student
        }
    }
}
}

GradesPage.swift

import SwiftUI

struct GradesPage: View {

@ObservedObject private var viewModel = StudentsViewModel()

var body: some View {
    NavigationView {
        List(viewModel.students) { student in
            VStack(alignment: .leading) {
                Text("Student Name: ") + Text(" ") + Text(student.studentName) + Text(" ") + Text(student.studentSurname)
                //I want to add the grades to see in here but don't know how to handle it
            }
        }
    }.onAppear {
        self.viewModel.fetchData()
    }
}
}

Firestore Structure:

Solutions that I tried:

Peter Friese Documentation

Firestore Official Documentation

Thanks in advance, all helps are welcome!

Answer 1

Note, you should be using @StateObject private var viewModel = StudentsViewModel(). Also note, there is no finalTerm in your code and NavigationView is deprecated, use NavigationStack

To display studentGrades in your GradesPage View, simply use a ForEach, such as:

struct GradesPage: View {
    @StateObject private var viewModel = StudentsViewModel()
    
    var body: some View {
        NavigationStack {  // <--- here
            List(viewModel.students) { student in
                VStack(alignment: .leading) {
                    Text("Student Name: ") + Text(" ") + Text(student.studentName) + Text(" ") + Text(student.studentSurname)

                    ForEach(student.studentGrades ?? []) { grade in  // <--- here
                       Text(grade.lectureGradeId)
                       Text(grade.midTerm)
                       Text(grade.endTerm)
                    }
                }
            }
        }
        .onAppear {
            self.viewModel.fetchData()
        }
    }
}

struct Grades: Identifiable, Codable, Hashable {  //<--- here
    let id = UUID()
    var lectureGradeId: String
    var midTerm: String
    var endTerm: String
    
    enum CodingKeys: String, CodingKey {
        case lectureGradeId, midTerm, endTerm
    }
}

struct Students: Identifiable, Codable {
    var id: String
    var email: String
    var studentName: String
    var studentSurname: String
    var studentTerm: String
    var studentBirthday: String
    var studentClass: Int
    var studentDept: String
    var studentFaculty: String
    var studentIsActive: Bool
    var studentIsGraduated: Bool
    var studentLectures: [String]?
    var studentGrades: [Grades]?
}


class StudentsViewModel: ObservableObject {
    @Published var students = [Students]()

    private var db = Firestore.firestore()
    
    func fetchData() {
        db.collection("Students").whereField("id", isEqualTo: "20704029").addSnapshotListener { querySnapshot, error in
            guard let documents = querySnapshot?.documents else {
                print("No documents")
                return
            }
            
            self.students = documents.map { (queryDocumentSnapshot) -> Students in
                let data = queryDocumentSnapshot.data()
                
                let id = data["id"] as? String ?? ""
                let email = data["email"] as? String ?? ""
                let studentName = data["studentName"] as? String ?? ""
                let studentSurname = data["studentSurname"] as? String ?? ""
                let studentTerm = data["studentTerm"] as? String ?? ""
                let studentBirthday = data["studentBirthday"] as? String ?? ""
                let studentClass = data["studentClass"] as? Int ?? 0
                let studentDept = data["studentDept"] as? String ?? ""
                let studentFaculty = data["studentFaculty"] as? String ?? ""
                let studentIsActive = data["studentIsActive"] as? Bool ?? true
                let studentIsGraduated = data["studentIsGraduated"] as? Bool ?? false
                let studentLectures = data["studentLectures"] as? Array ?? [""]
                
                // <--- something like this, adjust as needed, don't remember how it works
                let studentGrades = data["studentGrades"] as? [Grades] ?? []

                let student = Students(id: id, email: email, studentName: studentName, studentSurname: studentSurname, studentTerm: studentTerm, studentBirthday: studentBirthday, studentClass: studentClass, studentDept: studentDept, studentFaculty: studentFaculty, studentIsActive: studentIsActive, studentIsGraduated: studentIsGraduated, studentLectures: studentLectures,
                    studentGrades: studentGrades   //<--- here
                )

                //print(student)
                return student
            }
        }
    }
}

Note, you could try mapping the results of the firebase query directly into your codable Students struct, see for example: https://firebase.google.com/docs/firestore/solutions/swift-codable-data-mapping and https://firebase.google.com/docs/firestore/query-data/get-data

For example, from: https://firebase.google.com/docs/firestore/solutions/swift-codable-data-mapping

func fetchData() {
    let docRef = db.collection("Students").whereField("id", isEqualTo: "20704029")
    docRef.getDocument(as: Students.self) { result in
        switch result {
        case .success(let students):
            self.students = students
        case .failure(let error):
            print("Error decoding document: \(error)")
            // todo deal with errors
        }
    }
}