---
title: validator
framework: evaluations
role: symbol
role_heading: Instance Property
path: evaluations/samplegenerator/validator
---

# validator

An optional closure that decides whether a generated sample is valid.

## Declaration

```swift
var validator: (nonisolated(nonsending) @Sendable (SampleType) async throws -> Bool)?
```

## Discussion

Discussion When provided, the generator collects rejected samples in invalidSamples.

## See Also

### Configuring generation

- [samplingStrategy](evaluations/samplegenerator/samplingstrategy-swift.property.md)
- [SampleGenerator.SamplingStrategy](evaluations/samplegenerator/samplingstrategy-swift.enum.md)