How to Use Firebase Firestore in an iOS App

import Foundation

public struct TaskModelDetails {
    var taskDetails: String

    init(taskDetails: String){
        self.taskDetails = taskDetails
    }
}

class TaskModel {
    var task: TaskModelDetails
    
    init(task: TaskModelDetails) {
        self.task = TaskModelDetails(taskDetails: task.taskDetails)
    }
}

Reading Tasks From the Collection

We will be displaying our tasks in a simple table view.

First, let’s create a ToDoListViewController.swift class. Then, add ToDoListViewController in Main.storyboard and connect it to ToDoListViewController.swift. Add a UITableView to ToDoListViewController in the storyboard and implement delegates. 

Now we’ll create ListService.swift to hold the code to retrieve task data. Start by importing FirebaseFirestore. Then create a Firestore instance withFirestore.firestore(). ListService.swift should look as follows:

import Foundation
import FirebaseFirestore

class ListService {
    let db = Firestore.firestore()
}

Next, we’ll add the completeList method in the ListService class. We’ll get all the data and documents from the tasks collection by using the getDocuments() method from Firebase. This will return either data or an error.

func completeList(completion: @escaping (Bool, [TaskModel]) -> ()){
    db.collection("tasks").getDocuments() { (querySnapshot, err) in
    }
}

In this code, querySnapshot contains the returned data. It will be nil if there is no collection with the name tasks. 

Here is the rest of the completeList function: it retrieves the task data and calls the completion callback with any retrieved data.

func completeList(completion: @escaping (Bool, [TaskModel]) -> ()){
    var tasks = [TaskModel]()
    db.collection("tasks").getDocuments() { (querySnapshot, err) in
        if let err = err {
            print("Error getting documents: (err)")
            completion(false, tasks)
        } else {
            for document in querySnapshot!.documents {
                print("(document.documentID) => (document.data())")
            }
            completion(true, tasks)
        }
    }
}

Let’s try it out! Use the code below to call completeList from ToDoListViewController. 

import Foundation
import UIKit

class ToDoListViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, UIGestureRecognizerDelegate{
    let taskService = ListService()
    override func viewDidLoad() {
        super.viewDidLoad()
        getAllTasks()
    }

    func getAllTasks() {
        taskService.completeList(completion: { (status, tasks) in
            print(status)
        })
    }
}

There should be no errors, but querySnapshot will be nil since we do not have any documents in our collection yet. In the next section, we’ll add some data and then try calling the completeList method again.

Adding Tasks to the Collection

Let’s create an addToList method in ListService().

func addToList(taskDescription: String, completion: @escaping (Bool) -> ()) {
    completion(false)
}

We’ll use the passed-in task description to create a taskData instance and add it to the tasks collection. To do this, we will use the addDocument method from Firestore Firebase. 

  func addToList(taskDescription: String, completion: @escaping (Bool) -> ()) {
        var ref: DocumentReference? = nil

        ref = db.collection("tasks").addDocument(data: [
            "task_details": taskDescription,
            "task_id" : "",
            ]) { err in
                if let err = err {
                    print("Error adding document: (err)")
                    completion(false)
                } else {
                    print("Document added with ID: (ref!.documentID)")
                    completion(true)
                }
        }
    }

If there is no error, we’ll print the document id and return true in our completion block. task_id will be the document id. For now, we’ll just send the empty string, but eventually we’ll update the task_id with the correct document id.

Let’s add some test data by calling addToList from ViewController. After running the below code, go back to the console and you’ll see that an entry was added. Now, running getAllTasks() should return true and a tasks count of 1.

import Foundation
import UIKit

class ToDoListViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, UIGestureRecognizerDelegate{
    
    let taskService = ListService()
    override func viewDidLoad() {
        super.viewDidLoad()
        addTask(taskText: "Buy Grocery")
        getAllTasks()
    }

    func addTask(taskText: String) {
        taskService.addToList(taskDescription: text, completion: { (status) in
            if status {
                print("Status", status)
            }
        })
    }
    
     func getAllTasks() {
        taskService.completeList(completion: { (status, tasks) in
            print(tasks.count)
        })
    }
}

Of course, in a real app, you’d want to create a user interface for adding tasks!

Deleting a Task Document in Firestore

Finally, let’s see how we can delete a document in Firestore. Go back to the Firebase Firestore console and make a note of the document id value for “Buy Groceries“. We will be deleting the document based on the document id.

Now, add a deleteFromList method to our ListService as shown below.

func deleteFromList(taskId: String, completion: @escaping (Bool) -> ()){
    db.collection("tasks").document(taskId).delete() { err in
        if let err = err {
            print("Error removing document: (err)")
            completion(false)
        } else {
            completion(true)
        }
    }
}

Let’s call deleteFromList from ToDoListViewController. We’ll pass it the document id of “Buy Groceries”, which we copied from the Firebase console. 

import Foundation
import UIKit

class ToDoListViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, UIGestureRecognizerDelegate{
    let taskService = ListService()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        deleteTask(taskId: "ddiqw8bcnalkfhcavr")
    }

    func deleteTask(taskId: String) {
        taskService.deletFromList(taskId: taskId, completion: { (status) in
            print(status)
        })
    }
}

Running the above code, you should see status as true. If we go to the Firebase Firestore console, we should see that the “Buy Groceries” task has been deleted.

Conclusion

With that, you’ve learned how to create, read and delete data from a Firebase Firestore database. In this tutorial, we built an app to manage tasks using Xcode and Firebase. Hopefully, this has given you some new skills which you’ll be able to put into practice in your upcoming projects. 

To make this app more functional, you could implement table view delegate methods to display the tasks in your database, a UITextField to add new tasks, and a swipe gesture to delete tasks. Try it out!

If you have any questions, let me know in the comments below.