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

# Fields From API

The `fieldsFromApi` method transforms raw API responses into the format defined by your collection's `fieldsSchema`. This method is called automatically when retrieving records from the external API.

## Implementation Examples

### Mapping Implementation (Recommended)

**File:** `fields-from-api.map.yml`

```yaml theme={null}
id: { $var: fields.contact_id }
email: { $var: fields.email_address }
firstName: { $var: fields.first_name }
lastName: { $var: fields.last_name }
fullName:
  $join: [' ', [{ $var: fields.first_name }, { $var: fields.last_name }]]
createdAt:
  $cond:
    - { $var: parameters.includeTimestamps }
    - { $var: fields.created_at }
    - null
updatedAt:
  $cond:
    - { $var: parameters.includeTimestamps }
    - { $var: fields.updated_at }
    - null
```

### JavaScript Implementation

**File:** `fields-from-api.js`

```javascript theme={null}
export default async function fieldsFromApi({ fields, parameters }) {
  // Transform API response to match fieldsSchema
  const transformed = {
    id: fields.contact_id,
    email: fields.email_address,
    firstName: fields.first_name,
    lastName: fields.last_name,
    // Add computed fields
    fullName: `${fields.first_name} ${fields.last_name}`,
  }

  // Add optional fields based on parameters
  if (parameters?.includeTimestamps) {
    transformed.createdAt = fields.created_at
    transformed.updatedAt = fields.updated_at
  }

  return transformed
}
```

## Input

| Property     | Type   | Description                      |
| ------------ | ------ | -------------------------------- |
| `fields`     | object | Raw fields from the API response |
| `parameters` | object | Collection parameters            |

## Return Value

The method should return an object matching the collection's `fieldsSchema`.

## Example

```javascript theme={null}
// API returns:
{
  "contact_id": "123",
  "email_address": "john@example.com",
  "first_name": "John",
  "last_name": "Doe",
  "created_at": "2024-01-01T00:00:00Z"
}

// fieldsFromApi transforms to:
{
  "id": "123",
  "email": "john@example.com",
  "firstName": "John",
  "lastName": "Doe",
  "fullName": "John Doe"
}
```