ios - Swift async method and return / completion block -

i'm trying create async method in project takes input parameters. if parameters correct stuff , call completion block.

however, if input parameters not correct won't stuff (and completion block won't run , i'd have call myself).

anyway, i'm wondering best approach this...

i'm thinking have method return status enum includes wrong input , have completion block.

the problem there error completion block. maybe should different error type?

something this... (using login example).

enum loginrequeststatus {     case missingemail     case missingpassword     case requestinglogin } 

and error completion might be...

enum loginerror: error {     case nouserfound     case invalidpassword     case success } 

then function might this...

func login(withemail email: string, password: string, completion: (loginerror?) -> ()) -> loginstatus {     if email.isempty() {         return loginstatus.missingemail     }     if password.isempty() {         return loginstatus.missingpassword     }      //make async request here or something...      //... if error...     completion(loginerror.invalidpassword)      return loginstatus.requestinglogin } 

does make sense? swifty (i hate word portrays mean)? there different way approach altogether?

thanks

from point of view possible use throws simplify interaction method. write small example. implementation quite easy not miss error because of exceptions. , clear response status show if request successful.

throws errors:

enum loginerror: errortype {     case missingemail     case missingpassword } 

response status:

enum loginrequeststatus {     case nouserfound     case invalidpassword     case success } 

function implementation:

func login(withemail email: string, password: string) throws -> loginrequeststatus {      guard email.characters.count > 0 else{         throw loginerror.missingemail     }      guard password.characters.count > 0 else{         throw loginerror.missingpassword     }      // request      return loginrequeststatus.success }