This function is called unpack <http://package.elm-lang.org/packages/elm-community/result-extra/2.0.1/Result-Extra#unpack> in elm-community/result-extra
On Sat, Nov 19, 2016 at 12:58 PM, Charlie Koster <[email protected]> wrote: > Just this morning I upgraded a 3500 line Elm 0.17 project to Elm 0.18. I > wrote down my experience that I will share at a later date but I wanted to > share a suggestion. > > My app makes a handful of Http requests. For example I have a user model > and Msgs for when the user logs in or out. > > type alias Model = > { username : String > , fullName : String > , password : String > , email : String > } > > type Msg = > | Login > | LoginSucceed Model > | LoginFail Http.Error > | Logout > | LogoutSucceed > | LogoutFail Http.Error > > A typical 0.18 Http requests looks like this > > performLogin : Model -> Cmd Msg > performLogin user = > let > request = > Http.request > { method = "POST" > , headers = [] > , url = "http://mydomain/login"; > , body = Http.jsonBody (userEncoder user) > , expect = Http.expectJson userDecoder > , timeout = Nothing > , withCredentials = False > } > in > Http.send > (\result -> > case result of > Ok user -> > LoginSucceed user > > Err err -> > LoginFail err > ) > request > > The `case result of` part in the Http.send argument is a lot of > boilerplate that I don't like seeing copy/pasted in all of my Http Cmds. > > Additionally, in most cases my success Msg takes a payload which is the > model that was decoded from the response and my fail Msg takes the Result's > Http.Error. > > I have since created a helper function that looks like this > > resultToMsg : (x -> b) -> (a -> b) -> Result x a -> b > resultToMsg errMsg okMsg result = > case result of > Ok a -> > okMsg a > > Err err -> > errMsg err > > > With that helper function my Http Cmds now look like this > > performLogin : Model -> Cmd Msg > performLogin user = > let > request = > Http.request > { method = "POST" > , headers = [] > , url = "http://mydomain/login"; > , body = Http.jsonBody (userEncoder user) > , expect = Http.expectJson userDecoder > , timeout = Nothing > , withCredentials = False > } > in > Http.send > (resultToMsg LoginFail LoginSucceed) > request > > Which results in 4 fewer lines of boilerplate (5 including the whitespace). > > I'm terrible at naming things but I propose adding a helper function to > elm-lang/core Result with basically the implementation above but with a > more appropriate name than resultToMsg. > > -- > You received this message because you are subscribed to the Google Groups > "Elm Discuss" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Elm Discuss" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
