ImageLoader

ImageLoader is a lightweight Swift SDK designed to load images asynchronously from a URL and cache them using NSCache. It also provides an extension to UIImageView in UIKit, making it easy to load and display images in your app with caching enabled.

Features

• Asynchronously loads images from a URL.
• Caches images using NSCache to minimize network usage.
• Provides a convenient UIImageView extension for seamless integration with UIKit.
• Automatically handles image loading cancellation, making it ideal for use in table or collection views.
• Provides error handling and allows setting a placeholder image in case of failure.

Installation

To add ImageLoader to your project: Add the repository URL to your project’s package dependencies.

Usage

Loading an Image into a UIImageView

Using ImageLoader, you can load an image from a URL and cache it with just a few lines of code. The library provides an extension for UIImageView to simplify the process.

let imageView = UIImageView()
let url = NSURL(string: "https://example.com/image.png")!

do {
    try imageView.loadImage(from: url, errorPlaceholderImage: UIImage(named: "placeholder"))
} catch {
    print("Failed to load image: \(error.localizedDescription)")
}

NOTE : You can also load a thumbnail of the loaded image into the image view as below. But it requires the minimum os target iOS 15.0.

do {
    try imageView.loadThumbnail(from: url, of: CGSize(width: 100, height: 160), errorPlaceholderImage: UIImage(named: "placeholder"))
} catch {
    print("Failed to load image thumbnail: \(error.localizedDescription)")
}

Cancelling Image Loading

In cases where the UIImageView is reused (e.g., in a table or collection view), you may want to cancel any ongoing image loading.

imageView.cancelLoading()

Error Handling

Errors during image loading (e.g., network issues) are captured in the custom CachedImageLoaderError enum:

• .errorLoading(Error): An error occurred during the download.
• .errorDecoding: The downloaded data could not be decoded as an image.
• .cancelled: The operation was manually cancelled.

Example of Usage in UITableViewCell

To effectively use this SDK with reusable views like UITableViewCell, you should cancel image loading before the cell is reused.

override func prepareForReuse() {
    super.prepareForReuse()
    imageView.cancelLoading()
}

UIImageLoader Singleton

The UIImageLoader.shared instance manages image loading and caching. By default, images are cached in memory using NSCache, making subsequent requests faster.

Custom Placeholder

If an error occurs during image loading, you can specify a custom placeholder image:

let placeholder = UIImage(named: "errorPlaceholder")
try? imageView.loadImage(from: url, errorPlaceholderImage: placeholder)

API Documentation

CachedImageLoader

Methods

• loadImage(from url: NSURL, completion: @escaping (Result<UIImage, Error>) -> Void) -> UUID?
  Loads an image from the provided URL and caches it if successful. Returns a UUID for the request which can be used to cancel the operation.

• cancelLoading(id: UUID)
  Cancels an ongoing image load operation associated with the provided UUID.

UIImageLoader

Methods

• load(from url: NSURL, for imageView: UIImageView, errorPlaceholderImage: UIImage? = nil)
  Loads an image from the URL and sets it in the provided UIImageView.

• cancel(for imageView: UIImageView)
  Cancels the image loading operation for the specified UIImageView.

• cancelAll()
  Cancels all ongoing image loading operations.

UIImageView Extension

Methods

• loadImage(from url: NSURL, errorPlaceholderImage: UIImage? = nil)
  Loads an image directly into the UIImageView using UIImageLoader.

• cancelLoading()
  Cancels the image loading operation for the UIImageView.