Attribute Macro graphql_subscription

#[graphql_subscription]

#[graphql_subscription] macro for generating a GraphQL subscription implementation for structs with computable field resolvers (declared via a regular Rust impl block).

It enables you to write GraphQL field resolvers for a type by declaring a regular Rust impl block. Under the hood, the macro implements GraphQLType/GraphQLSubscriptionValue traits.

Specifying multiple #[graphql_subscription] attributes on the same definition is totally okay. They all will be treated as a single attribute.

This macro is similar to #[graphql_object] macro and has all its properties, but requires methods to be async and return Stream of values instead of a value itself.

use juniper::graphql_subscription;

// We can declare the type as a plain struct without any members.
struct Subscription;

#[graphql_subscription]
impl Subscription {
    // WARNING: Only GraphQL fields can be specified in this `impl` block.
    //          If normal methods are required on the struct, they can be
    //          defined either in a separate "normal" `impl` block, or
    //          marked with `#[graphql(ignore)]` attribute.

    // This defines a simple, static field which does not require any
    // context.
    // Such field can return a `Stream` of any value implementing
    // `GraphQLType` and `GraphQLValue` traits.
    //
    // NOTICE: Method must be `async`.
    async fn api_version() -> BoxStream<'static, &'static str> {
        Box::pin(stream::once(async { "0.1" }))
    }
}