Environment

class Environment

The Environment combines all the things that Relay.swift needs to be able to work. You use an environment to fetch queries and load stored records. Any views in your app that need to use Relay will need access to the environment to do so.

Creating an environment

init

init(

network: Network,

store: Store,

handlerProvider: HandlerProvider = DefaultHandlerProvider()

)

An environment needs two things at a minimum:

• A Network Layer to tell it how to communicate with your GraphQL API
• A Store for keeping track of data locally

Once you've created it, you probably want to keep the same Environment instance for the lifetime of your app. In SwiftUI, you can use relayEnvironment() to provide this to your views.

Fetching data outside a view

fetchQuery

func fetchQuery<Op: Operation>(

_ operation: Op,

cacheConfig: CacheConfig = .init()

) -> AnyPublisher<Op.Data?, Error>

The fetchQuery method allows you to perform a query without displaying the data in a view. Sometimes this can be useful to update the local store with new data in response to an event, or if you need access to a query's data in a background task.

If you want to show query data in a SwiftUI view, use the @Query property wrapper.

Running mutations outside a view

commitMutation

func commitMutation<Op: Operation>(

_ operation: Op,

optimisticResponse: [String: Any]? = nil,

optimisticUpdater: SelectorStoreUpdater? = nil,

updater: SelectorStoreUpdater? = nil

) -> AnyPublisher<Op.Data?, Error>

The commitMutation method allows you to execute a mutation to update data on the server. You can use this if you need to execute a mutation outside your views.

Note that you need to subscribe to the publisher that is returned (using sink or assign) in order for your mutation to actually execute, and if that subscription is canceled early for some reason, you may not see the updates you expect.

If you want to run a mutation in response to input from a SwiftUI view, use the @Mutation property wrapper, which manages this for you and makes it easy to show progress state in your UI while the mutation is running.

For more information about how to use the updater and optimisticUpdater parameters, see Updater functions.

Updating the store manually

commitUpdate(_:)

func commitUpdate(

_ updater: @escaping StoreUpdater

)

The commitUpdate method allows you to perform updates to Relay's store outside the context of a mutation.

The main reason to do this is to add client-only data to the store. The StoreUpdater function you pass in is similar to the SelectorStoreUpdater used for mutations, but without the methods and arguments for information provided by the mutation's response.

note

We may document Environment's other public methods at some point, but they're largely there to implement higher-level APIs like RelaySwiftUI.