Check if iOS app supports background downloads

README.md

Background Download Support

An SDK may need to check if the UIAppDelegate function for background events is defined to determine if it will handle background downloads. Since Swift does not support reflection this is one way to do it using some lower level functions.

• Downloading Files in the Background (Apple)

Code.swift

var supportsBackgroundDownloads: Bool {
    guard let appDelegate = UIApplication.shared.delegate else {
        return false
    }

    let signature = "application:handleEventsForBackgroundURLSession:completionHandler:"

    var methodCount: UInt32 = 0
    guard let methodList = class_copyMethodList(type(of: appDelegate), &methodCount) else {
        return false
    }

    let range = 0..<Int(methodCount)
    let found = range.reduce(into: []) { result, index in
        let selName = sel_getName(method_getName(methodList[index]))
        let methodName = String(cString: selName, encoding: .utf8)!
        result.append(methodName)
    }.first(where: { $0 == signature }) != nil

    return found
}