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Merge pull request #929 from haskell-servant/cookbook-structuring-flatten

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add reference to servant-flatten in cookbook > structuring apis
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Oleg Grenrus 2018-03-21 11:32:18 +02:00 committed by GitHub
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14
doc/cookbook/structuring-apis/StructuringApis.lhs
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@ -66,9 +66,9 @@ a server for `FactoringAPI` (without the `'`) reflects the
server must be a function that takes an `Int` (the `Capture`) and server must be a function that takes an `Int` (the `Capture`) and
returns two values glued with `:<|>`, one of type `Maybe Int -> Handler Int` returns two values glued with `:<|>`, one of type `Maybe Int -> Handler Int`
and the other of type `Handler Int`. Let's provide such a server and the other of type `Handler Int`. Let's provide such a server
implementation. implementation, with those "nested types".
_Note_: you can load this module in ghci and ask for the concrete **Tip**: you can load this module in ghci and ask for the concrete
type that `Server FactoringAPI` "resolves to" by typing type that `Server FactoringAPI` "resolves to" by typing
`:kind! Server FactoringAPI`. `:kind! Server FactoringAPI`.
@ -82,6 +82,16 @@ factoringServer x = getXY :<|> postX
postX = return (x - 1) postX = return (x - 1)
``` ```
If you want to avoid the "nested types" and the need to manually
dispatch the arguments (like `x` above) to the different request
handlers, and would just like to be able to declare the API type
as above but pretending that the `Capture` is not factored out,
that every combinator is "distributed" (i.e that all endpoints
are specified like `FactoringAPI'` above), then you should
look at `flatten` from the
[servant-flatten](https://hackage.haskell.org/package/servant-flatten)
package.
Next come the two sub-APIs defined in terms of this `SimpleAPI` Next come the two sub-APIs defined in terms of this `SimpleAPI`
type, but with different parameters. That type is just a good old type, but with different parameters. That type is just a good old
Haskell type synonym that abstracts away a pretty common structure in Haskell type synonym that abstracts away a pretty common structure in