The Morpheus GQL client enables the use of GQL queries and mutations on HTTP servers and also the subscription of specific topics to GQL subscriptions using websockets.
Suppose we have the following GQL schema from which we want to retrieve information about the hero Poseidon.
type Deity {
name: String!
power: String
realm: Realm!
bornAt: City
}
enum Realm {
Sky
Sea
Underworld
}
type Query {
deity(name: String!, realm: Realm): Deity!
}
we should start with declareGlobalTypes to declare haskell type for Realm
declareGlobalTypes "assets/mythology.gql"
now we can declare haskell type for qurey GetHero.
declareLocalTypesInline
"assets/mythology.gql"
[raw|
query GetHero ($name: String!, realm: Sea)
{
deity (name:$name) {
name
power
}
}
|]
at the last stage, we can define Morpheus HTTP client with URL and custom headers which can be used to fetch Hero.
client :: GQLClient
client = "http://localhost:3000" `withHeaders` [("custom-header", "custom-value")]
fetchHero :: IO (ResponseStream GetHero)
fetchHero = request client GetHeroArgs {name = "poseidon"}
Suppose we have the following GQL schema, from which we want to subscribe information about the new users.
type User {
name: String!
email: String!
}
type Query {
user: User!
}
type Subscription {
newUser: User!
}
as in the example above, we will start with the declaration of global and subscription types
declareGlobalTypes "assets/users.gql"
declareLocalTypesInline
"assets/users.gql"
[raw|
subscription NewUsers
{
newUser {
name
email
}
}
|]
as in previous example we will define client with websockets URL and use it.
However, now it results stream of NewUsers instead of the single response. To print these results each time
we receive a new user, we can use the function forEach.
client :: GQLClient
client = "ws://localhost:3000"
newUsers :: IO (ResponseStream NewUsers)
newUsers = request client ()
subscribeUSers :: IO ()
subscribeUSers = newUsers >>= forEach print