gistfile1.swift

protocol APIError {
    var domain: String { get }
    var code: ErrorCode { get }
}

struct UnexpectedAPIError : APIError {
    let domain = "An unexpected error occurred"
    let code = ErrorCode.UnexpectedAPIError
}

extension NSError {
    class func APIError<T: APIError>(error: T) -> NSError {
        return NSError(domain: error.domain, code: error.code.rawValue, userInfo: nil)
    }
}