Errors
Errors are represented by values that conform to the Error protocol. They can be thrown, caught, propagated, and recovered.
Complete example
Error declaration
enum DownloadError: Error {
case unauthorized
case notEnoughSpace(mbNeeded: Int)
}
Throwing errors
func downloadFile(mbFree: Int) throws {
var userIsAuthorized = true
var mbFileSize = 1000
if !userIsAuthorized {
throw DownloadError.unauthorized
} else if mbFree < mbFileSize {
throw DownloadError.notEnoughSpace(mbNeeded: apiManager.mbFileSize)
} else {
// File download logic goes here
}
}
Catching errors
func didPressDownloadFileButton() {
do {
try downloadFile(mbFree: 500)
} catch DownloadError.unauthorized {
print("The user is not authorized to download this file.")
} catch DownloadError.notEnoughSpace(let mbNeeded) {
print("The user needs \(mbNeeded) MB to download this file.")
} catch {
print("Unknown error: \(error).")
}
}
Usage
didPressDownloadFileButton() // The user needs 1000 MB to download this file.
