Image loading from URL in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a URL from a string.

iOS Swift

let url = URL(string: [1])

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

Ahttps://example.com/image.png

B"https://example.com/image.png"

CURL(string: "https://example.com/image.png")

DimageURL

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put quotes around the URL string.

Passing a variable name instead of a string.

The URL initializer requires a string literal with quotes. So the correct answer is a quoted string.

2fill in blank

medium

Complete the code to start a data task to download image data.

iOS Swift

URLSession.shared.dataTask(with: url!) { data, response, error in
    if let data = [1] {
        // Use data
    }
}.resume()

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

Adata

Burl

Cerror

Dresponse

Attempts:

3 left

💡 Hint

Common Mistakes

Checking 'response' or 'error' instead of 'data'.

Forgetting to unwrap the optional data.

The downloaded image data is in the 'data' variable, so we check if 'data' is not nil.

3fill in blank

hard

Fix the error in updating the UI image inside the data task.

iOS Swift

DispatchQueue.main.[1] {
    imageView.image = UIImage(data: data)
}

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

Aasync

Bsync

CasyncAfter

Dbackground

Attempts:

3 left

💡 Hint

Common Mistakes

Using sync which can cause deadlocks.

Updating UI on a background thread.

UI updates must happen on the main thread asynchronously, so use DispatchQueue.main.async.

4fill in blank

hard

Fill both blanks to safely unwrap the URL and start the data task.

iOS Swift

guard let url = [1](string: [2]) else { return }
URLSession.shared.dataTask(with: url).resume()

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

AURL

BurlString

CURL(string: urlString)

DURLSession

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the whole initializer in one blank.

Using wrong variable names.

We unwrap the URL by calling URL(string: urlString). The first blank is the type 'URL', the second is the string variable 'urlString'.

5fill in blank

hard

Fill all three blanks to create a UIImage from data and assign it to imageView on the main thread.

iOS Swift

if let data = data {
    DispatchQueue.main.[1] {
        imageView.image = [2](data: [3])
    }
}

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

Aasync

BUIImage

Cdata

Dsync

Attempts:

3 left

💡 Hint

Common Mistakes

Using sync instead of async.

Forgetting to unwrap data.

Not creating UIImage correctly.

We use DispatchQueue.main.async to update UI, create UIImage(data: data), and assign it to imageView.image.