DownloadKit

Example

To run the example project, clone the repo, and run pod install from the Example directory first.

OR run pod try DownloadKit

Requirements

• iOS 10.0+
• Xcode 10.0+
• Swift 4.2+

Installation

DownloadKit is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod 'DownloadKit'

Usage

Shared Instance

A shared instance of DownloadKit can be utilised out of the box for managing download requests.

import DownloadKit

let downloader = DownloadKit.shared

The shared instance comes with a default in-memory cache size of 150 MBs.

Download Image

Images can be downloaded from a given URL, the library will parse the downloaded data as a UIImage object and return it via the completion block. If the parsing fails then a nil will be returned.

let url = URL(string: "https://httpbin.org/image/jpeg")

DownloadKit.shared.requestImage(from: url, completion: { (image, error) in
        guard error == nil else {
            print("Error Downloading:", error!)
            return
        }
        if let image = image {
            print("Downloaded Image:", image)
        }
})

Download JSON

JSON objects can be downloaded from a given URL, the library parses the returned data into the provided data model. The provided data model must conform to the Codable protocol. For example the following JSON object has to be downloaded:

{
    "userId": 1,
    "id": 1,
    "title": "JSON Example",
    "body": "This is how you download a JSON file."
}

Create a data model for the above JSON object, which conforms to the Codable protocol:

struct Post: Codable {
    let userId: Int
    let id: Int
    let title: String
    let body: String
}

Finally, call requestJSON(from:model:completion), passing it your JSON data model.

let url = URL(string: "https://jsonplaceholder.typicode.com/posts")

DownloadKit.shared.requestImage(from: url, model: [posts].self, completion: { (posts, error) in
        guard error == nil else {
            print("Error Downloading:", error!)
            return
        }
        if let posts = posts {
            print("Downloaded JSON:", posts)
        }
})

Download Raw Data

The library also allows downloading any other files from a given URL. The downloaded data is returned as a Data object, you may parse this data or store it as per your needs.

let url = URL(string: "https://httpbin.org/image/jpeg")

DownloadKit.shared.request(from: url, completion: { (data, error) in
        guard error == nil else {
            print("Error Downloading:", error!)
            return
        }
        if let data = data {
            print("Downloaded Data:", data)
        }
})

Cancel Request

Any download requests can be cancelled by calling cancelRequest(reference:). Whenever a request is made a RequestReference object is returned, which can be utilised to cancel the request.

let url = URL(string: "https://httpbin.org/image/jpeg")

let ref = DownloadKit.shared.request(from: url, completion: { (data, error) in
        guard error == nil else {
            print("Error Downloading:", error!)
            return
        }
        if let data = data {
            print("Downloaded Data:", data)
        }
})

DownloadKit.shared.cancelRequest(reference: ref)

Upon cancellation of a request the completion block for the request will be passed a DownloadKitError, indicating that the request was cancelled by the user.

Caching

The library comes with built in in-memory caching. This is achieved by using URLCache under the hood, which is configured to cache downloaded data into the memory. Hence, multiple requests to the same end-point will result in cached results being returned for subsequent requests. This is done to ensure efficiency.

Configuring Cache Size

The cache size can be configured as needed. However, ensure that you are making an informed decision regarding the cache size that your implementation requires. It is recommended that you change the cache size on app launch for the shared instance of DownloadKit. However, for new instances of DownloadKit the cache will be separate from the shared instance. The cache will automatically evict files as needed.

The default cache size is set to 150 MB.

In your AppDelegate:

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    DownloadKit.shared = DownloadKit(memorySize: 150 * 1024 * 1024) // 150 MB cache
    return true
}

Due to how Apple implemented URLCache the cache will only store a downloaded file if it's size is less than 5% of the total cache size. So take this into account when selecting a cache size.

Clearing the Cache

The cache can be cleared manually in case a fresh copy of a file is required. You can clear the entire cache with clearCache().

DownloadKit.shared.clearCache()

OR you can clear a specific file from the cache using clearCache(for:).

let url = URL(string: "https://httpbin.org/image/jpeg")

DownloadKit.shared.clearCache(for: url)

Once the cache has been cleared for a given URL, any new requests to that URL will fetch new data.

Author

moizullah, [email protected]

License

DownloadKit is available under the MIT license. See the LICENSE file for more info.