Adding paragraph to generic cookbook
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@ -10,6 +10,79 @@ case](../namedRoutes/NamedRoutes.html) cookbook that broaches the subject.
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Shall we begin?
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## Why would I want to use `Records` over the alternative `:<|>` operator?
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With a record-based API, we don’t need to care about the declaration order of the endpoints.
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For example, with the `:<|>` operator there’s room for error when the order of the API type
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```haskell,ignore
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type API1 = "version" :> Get '[JSON] Version
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:<|> "movies" :> Get '[JSON] [Movie]
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```
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does not follow the `Handler` implementation order
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```haskell,ignore
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apiHandler :: ServerT API1 Handler
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apiHandler = getMovies
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:<|> getVersion
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```
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GHC could scold you with a very tedious message such as :
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```console
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• Couldn't match type 'Handler NoContent'
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with 'Movie -> Handler NoContent'
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Expected type: ServerT MovieCatalogAPI Handler
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Actual type: Handler Version
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:<|> ((Maybe SortBy -> Handler [Movie])
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:<|> ((MovieId -> Handler (Maybe Movie))
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:<|> ((MovieId -> Movie -> Handler NoContent)
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:<|> (MovieId -> Handler NoContent))))
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• In the expression:
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versionHandler
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:<|>
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movieListHandler
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:<|>
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getMovieHandler :<|> updateMovieHandler :<|> deleteMovieHandler
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In an equation for 'server':
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server
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= versionHandler
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:<|>
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movieListHandler
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:<|>
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getMovieHandler :<|> updateMovieHandler :<|> deleteMovieHandler
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226 | server = versionHandler
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```
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On the contrary, with the record-based technique, we refer to the routes by their name:
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```haskell,ignore
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data API mode = API
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{ list :: "list" :> ...
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, delete :: "delete" :> ...
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}
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```
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and GHC follows the lead :
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```console
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• Couldn't match type 'NoContent' with 'Movie'
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Expected type: AsServerT Handler :- Delete '[JSON] Movie
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Actual type: Handler NoContent
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• In the 'delete' field of a record
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In the expression:
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MovieAPI
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{get = getMovieHandler movieId,
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update = updateMovieHandler movieId,
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delete = deleteMovieHandler movieId}
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In an equation for 'movieHandler':
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movieHandler movieId
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= MovieAPI
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{get = getMovieHandler movieId,
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update = updateMovieHandler movieId,
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delete = deleteMovieHandler movieId}
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252 | , delete = deleteMovieHandler movieId
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```
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So, records are more readable for a human, and GHC gives you more accurate error messages.
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What are we waiting for?
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```haskell
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{-# LANGUAGE DataKinds #-}
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{-# LANGUAGE DeriveGeneric #-}
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