> ## Documentation Index
> Fetch the complete documentation index at: https://eo.utopy.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Service injection

> Provide Effect layers to procedures and preserve service requirement type safety.

Use `.provide(layer)` to make Effect services available to downstream procedures.

```ts title="services.ts" theme={null}
import { Effect } from "effect";

export class UsersRepo extends Effect.Service<UsersRepo>()("UsersRepo", {
  accessors: true,
  sync: () => ({
    findById: (id: string) => ({ id, name: "Ada Lovelace" }),
  }),
}) {}
```

```ts title="procedure.ts" theme={null}
import { eos } from "effect-orpc";

const effectProcedure = eos.provide(UsersRepo.Default);

const getUser = effectProcedure.effect(function* () {
  return yield* UsersRepo.findById("1");
});
```

## Missing services are type errors

If a handler yields a service that was not provided, the procedure should fail to type-check.

```ts title="missing-service.ts" theme={null}
class MissingRepo extends Context.Tag("MissingRepo")<
  MissingRepo,
  { find: () => Effect.Effect<string> }
>() {}

const procedure = eos.provide(UsersRepo.Default).effect(
  // @ts-expect-error MissingRepo was not provided.
  function* () {
    return yield* MissingRepo;
  },
);
```

## Provide multiple services

Merge services into one application layer, then provide that layer once.

```ts title="app-layer.ts" theme={null}
const AppLive = Layer.mergeAll(UsersRepo.Default, Logger.pretty, Cache.Default);

const effectProcedure = eos.provide(AppLive);
```

## Next step

Use request data to provide per-request services in [Request-scoped services](/capabilities/request-scoped-services).