---
url: https://masyaka.github.io/injecute/errors/already-registered.md
description: The key is already registered in this container or a parent
---

# `INJECUTE_ALREADY_REGISTERED`

**The key is already registered in this container or a parent.**

## How to fix it

Pass { replace: true } to replace the registration, or use another key. In a fork, { replace: true } is needed to override a parent's key too, and the override reaches only services resolved in the fork: services registered in the parent keep the parent's one. To replace it for every service, use fork({ isolated: true }).

## Example

```ts
app.addInstance('logger', console).addInstance('logger', pino()); // throws

app.addInstance('logger', pino(), { replace: true }); // replaces it
app.fork().addInstance('logger', pino()); // throws: the parent has "logger"
app.fork().addInstance('logger', pino(), { replace: true }); // overrides it in the fork
```

## Overriding a parent's key in a fork

A fork needs `{ replace: true }` to register a key its parent has, because the override doesn't reach
everything. In a plain fork it reaches only the services resolved in the fork: a service registered in
the parent runs and is cached in the parent, so it keeps the parent's instance. The error names those
services:

```ts
const app = new DIContainer()
  .addSingleton('tx', (db) => db.begin(), ['db'])
  .addSingleton('report', Report, ['tx']);

app.fork().addSingleton('tx', (db) => db.begin(), ['db']);
// throws: "report" (registered in a parent) depends on "tx" and keeps the parent's "tx"
```

What to do depends on what you want:

* **Only the fork's own services should use the new one:** pass `{ replace: true }`.
* **A parent service should use it too:** register that service in the fork as well (for a scope's
  services, in a [scope module](../guide/request-state.md#scope-modules)), and don't register the key in
  the root.
* **Every service should use it** (tests, a variant of the app): use an
  [isolated fork](../guide/containers.md#isolated-forks), with `{ replace: true }`.

To wrap the existing service instead of replacing it, depend on its own key (see
[Decorating a service](../guide/registration.md#decorating-a-service)).

## Handling it in code

```ts
import { InjecuteError } from 'injecute';

try {
  // ...
} catch (error) {
  if (error instanceof InjecuteError && error.code === 'INJECUTE_ALREADY_REGISTERED') {
    // error.message explains what happened; error.path is the resolution chain
  }
}
```

[All error codes](./index.md)