domain：错误域
code：错误编码
userInfo：错误原因
NSString *domain = @"xxxxxx";
NSString *desc = NSLocalizedString(@"xxx", @"xxx");//NSLocalizedString国际化
NSDictionary *userInfo = @{NSLocalizedDescriptionKey : desc };
NSError *error = [NSError errorWithDomain:domain code:-101 userInfo:userInfo];
原文：https://www.cnblogs.com/lulushen/p/10689677.html