---
title: "callAsFunction(_:eventHandler:)"
framework: createmlcomponents
role: symbol
role_heading: Instance Method
path: "createmlcomponents/transformer/callasfunction(_:eventhandler:)"
---

# callAsFunction(_:eventHandler:)

Performs the transformation on a single input.

## Declaration

```swift
func callAsFunction(_ input: Self.Input, eventHandler: EventHandler? = nil) async throws -> Self.Output
```

## Parameters

- `input`: The transformer input.
- `eventHandler`: An event handler.

## Return Value

Return Value An output produced by applying the transformer to the input.

## See Also

### Transforming and predicting

- [prediction(from:)](createmlcomponents/transformer/prediction(from:).md)
- [prediction(from:eventHandler:)](createmlcomponents/transformer/prediction(from:eventhandler:).md)