> For the complete documentation index, see [llms.txt](https://docs.aurelia.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.aurelia.io/developer-guides/error-messages/5000-to-5008/aur5002.md).

# AUR5002

## Error Message

`AUR5002: invalid config, expecting a function or an object, received {{value}}`

Where `{{value}}` is the type of the invalid parameter passed to the configure method.

## Description

This error occurs when `HttpClient.configure()` is called with a parameter that is neither a function nor a configuration object. The configure method accepts either:

1. A callback function that receives a configuration object
2. A plain configuration object

## Common Scenarios

### Passing Invalid Types

```typescript
import { HttpClient } from '@aurelia/fetch-client';

const client = new HttpClient();

// ❌ Wrong: Passing a string
client.configure('invalid'); // Throws AUR5002

// ❌ Wrong: Passing a number  
client.configure(123); // Throws AUR5002

// ❌ Wrong: Passing null/undefined
client.configure(null); // Throws AUR5002
```

## Solutions

### 1. **Use Configuration Callback (Recommended)**

```typescript
// ✅ Correct: Pass a configuration function
client.configure(config => {
  return config
    .withBaseUrl('https://api.example.com')
    .withDefaults({
      headers: { 'Content-Type': 'application/json' }
    });
});
```

### 2. **Use Configuration Object**

```typescript
// ✅ Correct: Pass a configuration object
const configObject = {
  baseUrl: 'https://api.example.com',
  defaults: {
    headers: { 'Content-Type': 'application/json' }
  }
};

client.configure(configObject);
```

## Debugging Tips

1. **Check Parameter Type**: Ensure you're passing a function or object
2. **Verify Syntax**: Make sure callback syntax is correct
3. **TypeScript**: Use TypeScript to catch type errors at compile time


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