Firebase Authentication in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Firebase Authentication module in Swift.

iOS Swift

import [1]

Drag options to blanks, or click blank then click option'

AFoundation

BFirebaseAuth

CUIKit

DSwiftUI

Attempts:

3 left

💡 Hint

Common Mistakes

Importing UIKit or Foundation instead of FirebaseAuth.

Forgetting to import any Firebase module.

You need to import FirebaseAuth to use Firebase Authentication features in your Swift app.

2fill in blank

medium

Complete the code to sign in a user with email and password using Firebase Authentication.

iOS Swift

Auth.auth().signIn(withEmail: email, password: password) { authResult, error in
  if let error = [1] {
    print("Error signing in: \(error.localizedDescription)")
  } else {
    print("User signed in successfully")
  }
}

Drag options to blanks, or click blank then click option'

Aerror

BauthResult

Cpassword

Demail

Attempts:

3 left

💡 Hint

Common Mistakes

Checking the wrong variable for errors.

Not handling the error case at all.

The error variable holds any error returned by the sign-in attempt. You check if it is not nil to handle sign-in failures.

3fill in blank

hard

Fix the error in the code to create a new user with email and password.

iOS Swift

Auth.auth().createUser(withEmail: email, password: password) { [1], error in
  if let error = error {
    print("Failed to create user: \(error.localizedDescription)")
  } else {
    print("User created successfully")
  }
}

Drag options to blanks, or click blank then click option'

Aresult

Buser

Cerror

DauthResult

Attempts:

3 left

💡 Hint

Common Mistakes

Using user or result instead of authResult.

Confusing the error parameter with the first parameter.

The first closure parameter is usually named authResult to hold the user creation result.

4fill in blank

hard

Fill both blanks to send a password reset email to the user.

iOS Swift

Auth.auth().[1](withEmail: email) { error in
  if let [2] = error {
    print("Failed to send reset email: \(error.localizedDescription)")
  } else {
    print("Password reset email sent")
  }
}

Drag options to blanks, or click blank then click option'

AsendPasswordReset

BresetPassword

Cerror

Dfailure

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong method name like resetPassword.

Using a different variable name than error.

The method to send a password reset email is sendPasswordReset. The error variable is named error to check for failures.

5fill in blank

hard

Fill all three blanks to check if a user is currently signed in and print their email.

iOS Swift

if let user = Auth.auth().[1] {
  let email = user.[2]
  print("Signed in user email: \(email)")
} else {
  print("No user is signed in")
}

// To sign out the user:
try? Auth.auth().[3]()

Drag options to blanks, or click blank then click option'

AcurrentUser

Bemail

CsignOut

DuserEmail

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method instead of property for current user.

Accessing a non-existent property like userEmail.

Forgetting to handle sign out with try/catch.

Auth.auth().currentUser returns the current user if signed in. The user's email is accessed via email. To sign out, use signOut().

Practice

1. What is the main purpose of Firebase Authentication in an iOS app?

easy

A. To send push notifications to users

B. To store large files in the cloud

C. To design the app's user interface

D. To let users sign up and log in easily

Solution

1. Step 1: Understand Firebase Authentication's role

   Firebase Authentication helps manage user sign-up and sign-in processes.

2. Step 2: Compare options with this role

   Only To let users sign up and log in easily matches this purpose; others relate to different Firebase features or app functions.

3. Final Answer:

   To let users sign up and log in easily -> Option D

4. Quick Check:

   Firebase Authentication = User sign-in [OK]

Hint: Firebase Auth is for user login/signup only [OK]

Common Mistakes:

• Confusing Authentication with storage or UI design
• Thinking it handles notifications
• Assuming it manages app layout

2. Which Swift code snippet correctly creates a new user with Firebase Authentication?

easy

A. Auth.signIn(withEmail: email, password: password)

B. Auth.auth().createUser(withEmail: email, password: password) { result, error in }

C. FirebaseAuth.createUser(email, password)

D. Auth.createUser(email: email, password: password)

Solution

1. Step 1: Recall correct Firebase method for user creation

   The method is Auth.auth().createUser(withEmail:password:completion:).

2. Step 2: Check each option's syntax

   Only Auth.auth().createUser(withEmail: email, password: password) { result, error in } uses the correct method and parameters; others are invalid or for sign-in.

3. Final Answer:

   Auth.auth().createUser(withEmail: email, password: password) { result, error in } -> Option B

4. Quick Check:

   Create user method = Auth.auth().createUser(withEmail: email, password: password) { result, error in } [OK]

Hint: Use Auth.auth().createUser for new users [OK]

Common Mistakes:

• Using signIn method instead of createUser
• Wrong method call without Auth.auth()
• Missing completion handler closure

3. What will be printed if the following Swift code runs and the user enters a wrong password?

Auth.auth().signIn(withEmail: email, password: wrongPassword) { authResult, error in
  if let error = error {
    print("Login failed: \(error.localizedDescription)")
  } else {
    print("Login successful")
  }
}

medium

A. Login failed: The password is invalid or the user does not have a password.

B. No output

C. Login successful

D. Crash due to missing error handling

Solution

1. Step 1: Understand signIn completion handler behavior

   If sign-in fails, error is non-nil and prints the error message.

2. Step 2: Analyze wrong password case

   Wrong password triggers error with message about invalid password.

3. Final Answer:

   Login failed: The password is invalid or the user does not have a password. -> Option A

4. Quick Check:

   Error message prints on wrong password [OK]

Hint: Errors print message; success prints success [OK]

Common Mistakes:

• Assuming success prints even on error
• Ignoring error optional unwrapping
• Expecting no output on failure

4. Identify the error in this Swift Firebase sign-in code:

Auth.auth().signIn(withEmail: email, password: password) { authResult, error in
  if error != nil {
    print("Error signing in")
  }
  print("User signed in")
}

medium

A. Missing else block causes "User signed in" to print even on error

B. Incorrect method name for signIn

C. No completion handler provided

D. Password parameter is missing

Solution

1. Step 1: Review control flow in completion handler

   Code prints "User signed in" regardless of error presence.

2. Step 2: Identify missing else block

   Without else, success message prints even if sign-in failed.

3. Final Answer:

   Missing else block causes "User signed in" to print even on error -> Option A

4. Quick Check:

   Print success only if no error [OK]

Hint: Use else to separate success from error prints [OK]

Common Mistakes:

• Printing success message unconditionally
• Not checking error properly
• Confusing method names

5. You want to create a Swift function that registers a user and shows an alert with success or error message. Which approach correctly handles this using Firebase Authentication?

hard

A. Call createUser, then immediately show success alert without waiting for completion

B. Call signIn instead of createUser for registration

C. Call createUser with completion handler, show alert inside handler based on error or success

D. Use createUser without email or password parameters

Solution

1. Step 1: Understand asynchronous nature of createUser

   createUser runs asynchronously; alerts must be shown after completion.

2. Step 2: Choose correct alert timing and method

   Showing alert inside completion handler ensures correct success or error message.

3. Step 3: Eliminate incorrect options

   Call createUser, then immediately show success alert without waiting for completion shows alert too early; C uses wrong method; D misses required parameters.

4. Final Answer:

   Call createUser with completion handler, show alert inside handler based on error or success -> Option C

5. Quick Check:

   Show alert after createUser completes [OK]

Hint: Show alerts only inside completion handlers [OK]

Common Mistakes:

• Showing alerts before async call finishes
• Using signIn for registration
• Omitting required parameters