# ResolveReplFn

**Kind:** Class

**Source:** [`packages/core/repl/native-functions/resolve-repl-fn.ts`](https://github.com/nestjs/nest/blob/master/packages/core/repl/native-functions/resolve-repl-fn.ts#L5)

**Part of:** [Core](subsystem-packages-core)

`ResolveReplFn` is a native REPL function that performs the resolve operation exposed by the interactive REPL environment. Its `action()` method executes the resolution workflow asynchronously and returns the resulting value to the REPL runtime.

**Extends:** `ReplFunction`

## Methods

| Method | Signature | Returns |
|---|---|---|
| `action` | `action(token: string | symbol | Function | Type<any>, contextId: any)` | `Promise<any>` |

## Properties

| Property | Type |
|---|---|
| `fnDefinition` | `ReplFnDefinition` |

## Diagram

```mermaid
graph LR
  User[REPL user input] --> Repl[REPL runtime]
  Repl --> ResolveReplFn[ResolveReplFn]
  ResolveReplFn --> Action[action()]
  Action --> Resolver[Resolution workflow]
  Resolver --> Result[Promise result]
  Result --> Repl
```

## Usage

```ts
import { ResolveReplFn } from "./native-functions/resolve-repl-fn";

// ResolveReplFn is typically constructed and registered by the REPL runtime.
declare const resolveFn: ResolveReplFn;

async function runResolve(): Promise<void> {
  const result = await resolveFn.action();

  console.log("Resolve result:", result);
}

void runResolve();
```

## AI Coding Instructions

- Keep `action()` asynchronous and return the resolution result through its `Promise`.
- Treat this class as a REPL integration point; ensure it is registered or instantiated through the same native-function flow as other REPL commands.
- Preserve the result shape expected by the REPL renderer or caller when changing resolution behavior.
- Handle resolution failures consistently with other native REPL functions so errors are surfaced clearly to interactive users.

## How it works

## `ResolveReplFn`

`ResolveReplFn` is a built-in REPL function class that extends `ReplFunction`. Its metadata registers the function under the name `resolve`, with the displayed signature `(token: InjectionToken, contextId: any) => Promise<any>`. [packages/core/repl/native-functions/resolve-repl-fn.ts:5-11]

`ReplContext` includes `ResolveReplFn` in its built-in function classes. During initialization, it constructs the class, stores it in `nativeFunctions` under its metadata name, and binds its `action` method into the REPL global scope as `resolve`. [packages/core/repl/repl-context.ts:168-184] [packages/core/repl/repl-context.ts:122-150] Thus a REPL user can invoke it as `resolve(...)`. The bound function also has a non-enumerable `help` getter that writes a generated help message to standard output. [packages/core/repl/repl-context.ts:152-162] The help text is generated from this class’s description, name, and signature. [packages/core/repl/repl-function.ts:27-35]