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authorEugen Wissner <belka@caraus.de>2020-11-02 08:24:48 +0100
committerEugen Wissner <belka@caraus.de>2020-11-02 08:24:48 +0100
commitafcf9aaa14e925ca137ec956e3bfd47d2506c904 (patch)
treeb108a19882c9057dc7c7ad9166c58b05ed08bd80 /README.md
parent6e8d8a34a1ce07b8d9cd10d8e5c3e009d17cfdf7 (diff)
downloadgraphql-afcf9aaa14e925ca137ec956e3bfd47d2506c904.tar.gz
Write documentation out of the source tree
In a Wiki.
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# GraphQL implementation in Haskell
+[![Simple Haskell](https://www.simplehaskell.org/badges/badge.svg)](https://www.simplehaskell.org)
+[![CI/CD](https://img.shields.io/badge/CI-CD-brightgreen)](https://build.caraus.tech/go/pipelines)
+
This implementation is relatively low-level by design, it doesn't provide any
mappings between the GraphQL types and Haskell's type system and avoids
compile-time magic. It focuses on flexibility instead, so other solutions can
@@ -29,103 +32,3 @@ API documentation is available through
Further documentation will be made available in the
[Wiki](https://www.caraus.tech/projects/pub-graphql/wiki).
-
-### Getting started
-
-We start with a simple GraphQL API that provides us with some famous and less
-famous cites.
-
-```graphql
-"""
-Root Query type.
-"""
-type Query {
- """
- Provides a cite.
- """
- cite: String!
-}
-```
-
-This is called a GraphQL schema, it defines all queries supported by the API.
-`Query` is the root query type. Every GraphQL API should define a query type.
-
-`Query` has a single field `cite` that returns a `String`. The `!` after the
-type denotes that the returned value cannot be `Null`. GraphQL fields are
-nullable by default.
-
-To be able to work with this schema, we are going to implement it in Haskell.
-
-```haskell
-{-# LANGUAGE OverloadedStrings #-}
-
-import qualified Data.Aeson as Aeson
-import qualified Data.ByteString.Lazy.Char8 as ByteString.Lazy.Char8
-import qualified Data.HashMap.Strict as HashMap
-import Language.GraphQL
-import Language.GraphQL.Type
-import qualified Language.GraphQL.Type.Out as Out
-
--- GraphQL supports 3 kinds of operations: queries, mutations and subscriptions.
--- Our first schema supports only queries.
-citeSchema :: Schema IO
-citeSchema = schema queryType Nothing Nothing mempty
-
--- GraphQL distinguishes between input and output types. Input types are field
--- argument types and they are defined in Language.GraphQL.Type.In. Output types
--- are result types, they are defined in Language.GraphQL.Type.Out. Root types
--- are always object types.
---
--- Here we define a type "Query". The second argument is an optional
--- description, the third one is the list of interfaces implemented by the
--- object type. The last argument is a field map. Keys are field names, values
--- are field definitions and resolvers. Resolvers are the functions, where the
--- actual logic lives, they return values for the respective fields.
-queryType :: Out.ObjectType IO
-queryType = Out.ObjectType "Query" (Just "Root Query type.") []
- $ HashMap.singleton "cite" citeResolver
- where
- -- 'ValueResolver' is a 'Resolver' data constructor, it combines a field
- -- definition with its resolver function. This function resolves a value for
- -- a field (as opposed to the 'EventStreamResolver' used by subscriptions).
- -- Our resolver just returns a constant value.
- citeResolver = ValueResolver citeField
- $ pure "Piscis primum a capite foetat"
-
- -- The first argument is an optional field description. The second one is
- -- the field type and the third one is for arguments (we have none in this
- -- example).
- --
- -- GraphQL has named and wrapping types. String is a scalar, named type.
- -- Named types are nullable by default. To make our "cite" field
- -- non-nullable, we wrap it in the wrapping type, Non-Null.
- citeField = Out.Field
- (Just "Provides a cite.") (Out.NonNullScalarType string) HashMap.empty
-
--- Now we can execute a query. Since our schema defines only one field,
--- everything we can do is to ask to resolve it and give back the result.
--- Since subscriptions don't return plain values, the 'graphql' function returns
--- an 'Either'. 'Left' is for subscriptions, 'Right' is for queries and
--- mutations.
-main :: IO ()
-main = do
- Right result <- graphql citeSchema "{ cite }"
- ByteString.Lazy.Char8.putStrLn $ Aeson.encode result
-```
-
-Executing this query produces the following JSON:
-
-```json
-{
- "data": {
- "cite": "Piscis primum a capite foetat"
- }
-}
-```
-
-## Contact
-
-Suggestions, patches and bug reports are welcome.
-
-Should you have questions on usage, please open an issue and ask – this helps
-to write useful documentation.