Deep linking in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to handle a URL in the AppDelegate method.

iOS Swift

func application(_ app: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey : Any] = [:]) -> Bool {
    return [1]
}

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

Atrue

Bfalse

Cnil

Durl.isFileURL

Attempts:

3 left

💡 Hint

Common Mistakes

Returning false causes the system to think the URL was not handled.

Returning nil is invalid because the method expects a Bool.

Returning true indicates the app successfully handled the URL.

2fill in blank

medium

Complete the code to extract the host from the incoming URL.

iOS Swift

func application(_ app: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey : Any] = [:]) -> Bool {
    guard let host = url.[1] else { return false }
    print("Host: \(host)")
    return true
}

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

Apath

Bhost

Cscheme

Dquery

Attempts:

3 left

💡 Hint

Common Mistakes

Using url.path returns the path after the host, not the host itself.

Using url.scheme returns the protocol like 'https'.

The host property gives the domain or host part of the URL.

3fill in blank

hard

Fix the error in the code to correctly parse query parameters from the URL.

iOS Swift

func application(_ app: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey : Any] = [:]) -> Bool {
    let components = URLComponents(url: url, resolvingAgainstBaseURL: false)
    if let queryItems = components?.[1] {
        for item in queryItems {
            print("\(item.name): \(item.value ?? "")")
        }
    }
    return true
}

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

Aparameters

BqueryParameters

CqueryItems

Dquery

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'query' or 'parameters' causes a compile error because those properties do not exist.

Forgetting to unwrap optional components.

URLComponents has a property named queryItems which is an array of URLQueryItem.

4fill in blank

hard

Fill both blanks to create a URL scheme check and handle it.

iOS Swift

func application(_ app: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey : Any] = [:]) -> Bool {
    if url.[1] == "myapp" {
        // Handle the URL
        print("Custom scheme detected")
        return [2]
    }
    return false
}

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

Ascheme

Bhost

Ctrue

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Checking host instead of scheme for the URL type.

Returning false even after handling the URL.

The scheme property gives the URL scheme like 'myapp'. Returning true means the URL was handled.

5fill in blank

hard

Fill all three blanks to safely unwrap the URL, check the scheme, and extract the path.

iOS Swift

func application(_ app: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey : Any] = [:]) -> Bool {
    guard url.[1] == "myapp" else { return false }
    let path = url.[2] ?? ""
    print("Path: \(path)")
    return [3]
}

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

Ascheme

Bpath

Ctrue

Dhost

Attempts:

3 left

💡 Hint

Common Mistakes

Not unwrapping the optional URL before use.

Checking host instead of scheme.

Returning false even after handling the URL.

First check the scheme, then get the path property, and return true to confirm handling.

Practice

1. What is the main purpose of deep linking in an iOS app?

easy

A. To increase app storage capacity

B. To improve app startup speed

C. To open a specific screen or content inside the app from a link

D. To change the app's icon dynamically

Solution

1. Step 1: Understand deep linking concept

   Deep linking allows users to open a specific part of an app directly from a link, not just launch the app.

2. Step 2: Compare options

   Options A, B, and D are unrelated to deep linking's purpose.

3. Final Answer:

   To open a specific screen or content inside the app from a link -> Option C

4. Quick Check:

   Deep linking = open specific app content [OK]

Hint: Deep linking = direct app content access from links [OK]

Common Mistakes:

• Confusing deep linking with app performance improvements
• Thinking deep linking changes app appearance
• Mixing deep linking with app storage features

2. Which method in AppDelegate handles opening your app via a custom URL scheme?

easy

A. application(_:didFinishLaunchingWithOptions:)

B. application(_:open:options:)

C. applicationDidBecomeActive(_:)

D. applicationWillTerminate(_:)

Solution

1. Step 1: Identify URL handling method

   The method application(_:open:options:) is called when the app is opened via a URL scheme.

2. Step 2: Exclude other lifecycle methods

   Other methods handle app launch, active state, or termination, not URL opening.

3. Final Answer:

   application(_:open:options:) -> Option B

4. Quick Check:

   Custom URL open method = application(_:open:options:) [OK]

Hint: URL open handling uses application(_:open:options:) [OK]

Common Mistakes:

• Choosing didFinishLaunchingWithOptions for URL handling
• Confusing app lifecycle methods with URL handling
• Ignoring the options parameter in the method

3. Given this code snippet in AppDelegate, what will happen when the app opens with URL scheme myapp://profile?id=123?

func application(_ app: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey : Any] = [:]) -> Bool {
  if url.scheme == "myapp" && url.host == "profile" {
    print("Open profile with id: \(url.query ?? "none")")
    return true
  }
  return false
}

medium

A. Returns false without printing anything

B. Prints 'Open profile with id: none' and returns false

C. Crashes because url.query is nil

D. Prints 'Open profile with id: id=123' and returns true

Solution

1. Step 1: Check URL scheme and host

   The URL scheme is "myapp" and host is "profile", so the if condition is true.

2. Step 2: Evaluate url.query value

   The query part is "id=123", so url.query is "id=123" and prints correctly.

3. Final Answer:

   Prints 'Open profile with id: id=123' and returns true -> Option D

4. Quick Check:

   URL matches scheme and host, query printed [OK]

Hint: Check url.scheme and url.host before using url.query [OK]

Common Mistakes:

• Assuming url.query is nil and causes crash
• Ignoring url.host check
• Returning false despite matching URL

4. Identify the error in this AppDelegate method for handling deep links:

func application(_ app: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey : Any]) -> Bool {
  if url.scheme = "myapp" {
    // handle URL
    return true
  }
  return false
}

medium

A. Using single equals (=) instead of double equals (==) in the if condition

B. Missing return statement inside the if block

C. Incorrect method signature missing default value for options

D. URL scheme comparison should use url.host instead

Solution

1. Step 1: Check the if condition syntax

   The condition uses single equals (=) which is assignment, not comparison.

2. Step 2: Understand correct comparison operator

   In Swift, equality check uses double equals (==), so this is a syntax error.

3. Final Answer:

   Using single equals (=) instead of double equals (==) in the if condition -> Option A

4. Quick Check:

   Comparison needs '==' not '=' [OK]

Hint: Use '==' for comparison, '=' is assignment [OK]

Common Mistakes:

• Confusing assignment (=) with equality (==)
• Ignoring method signature correctness
• Mixing url.scheme and url.host in condition

5. You want to support universal links in your iOS app. Which of the following is NOT required for universal links to work correctly?

hard

A. Implementing application(_:open:options:) to handle the link

B. Hosting an apple-app-site-association file on your website

C. Adding associated domains capability in your app's entitlements

D. Configuring your website's HTTPS server with a valid certificate

Solution

1. Step 1: Understand universal links requirements

   Universal links require a hosted apple-app-site-association file, entitlements setup, and HTTPS with valid certificate.

2. Step 2: Identify handling method difference

   Universal links use NSUserActivity, not application(_:open:options:), which is for custom URL schemes.

3. Final Answer:

   Implementing application(_:open:options:) to handle the link -> Option A

4. Quick Check:

   Universal links use NSUserActivity, not open URL method [OK]

Hint: Universal links use NSUserActivity, not open URL method [OK]

Common Mistakes:

• Thinking application(_:open:options:) handles universal links
• Ignoring HTTPS requirement for universal links
• Skipping apple-app-site-association file setup