error enumeration.swift

public enum Error: ErrorType, CustomDebugStringConvertible {

    // Add error enumerations here
    case FirstError(source: String, reason: String)
    
    public var debugDescription: String {
        
        let mirror = Mirror(reflecting: self)
        guard let item = mirror.children.first else {fatalError("Missing error enumeration item")}
        guard let myEnumeration = item.label else {fatalError("Missing error enumeration label")}
        
        let itemMirror = Mirror(reflecting:item.value)
        guard let sourceItem = itemMirror.children.first else {fatalError("Missing error source child")}
        guard let reasonItem = itemMirror.children.dropFirst().first else {fatalError("Missing  error reason child")}
        
        let (_, sourceStringItem) = sourceItem
        let (_, reasonStringItem) = reasonItem
        guard let reasonString = reasonStringItem as? String else {fatalError("Missing error reason string value")}

        return "\(mirror.subjectType).\(myEnumeration): \(sourceStringItem)" + (reasonString.isEmpty ? "" : ", \"\(reasonString)\"")
    }
    
    // Call with Error.build(type:Error.FirstError)
    // Or Error.build(reason:"reason text", type:Error.FirstError)

    static func build(
        file : String = __FILE__,
        function : String = __FUNCTION__,
        line : Int = __LINE__,
        reason : String = "",
        type errorType: (String, String) -> Error) -> Error {
            return errorType("File \(file), Line \(line)", reason)
    }
}

let f = Error.build(type:Error.FirstError)
let e = Error.build(reason:"Something", type:Error.FirstError)
print(f)
print(e)