throwing.swift

enum InstanceError: Error {
    case parentNotFound
    case notFullJSON
}

func createInstance(data: [String: Any]) throws {
    guard let id = data["id"] as? String else {
        throw InstanceError.notFullJSON
    }
}

do {
    try createInstance(data: [:])
} catch InstanceError.parentNotFound {
    print("Be sure that you have parent instance")
} catch InstanceError.notFullJSON {
    print("The initial JSON data isn't full")
}