ios - Error handling with custom messages? -

how can throw error messages (i.e errortype) custom messages?

for example:

catch let error myerror {   print(error.custommessage) } 

i found clean version out. idea implement both string , errortype protocols , use error's rawvalue.

enum uservalidationerror: string, errortype {   case nofirstnameprovided = "please insert first name."   case nolastnameprovided = "please insert last name."   case noageprovided = "please insert age."   case noemailprovided = "please insert email." } 

usage:

do {   try user.define(firstname,                   lastname: lastname,                   age: age,                   email: email,                   gender: gender,                   location: location,                   phone: phone) } catch let error user.uservalidationerror {   print(error.rawvalue)   return }