---
title: MLMetricKey
framework: coreml
role: symbol
role_heading: Class
path: coreml/mlmetrickey
---

# MLMetricKey

A key for the metrics dictionary in an update context.

## Declaration

```swift
class MLMetricKey
```

## Topics

### Getting the keys

- [lossValue](coreml/mlmetrickey/lossvalue.md)
- [epochIndex](coreml/mlmetrickey/epochindex.md)
- [miniBatchIndex](coreml/mlmetrickey/minibatchindex.md)

### Supporting types

- [MLKey](coreml/mlkey.md)

## Relationships

### Inherits From

- [MLKey](coreml/mlkey.md)

### Conforms To

- [CVarArg](swift/cvararg.md)
- [CustomDebugStringConvertible](swift/customdebugstringconvertible.md)
- [CustomStringConvertible](swift/customstringconvertible.md)
- [Equatable](swift/equatable.md)
- [Hashable](swift/hashable.md)
- [NSCoding](foundation/nscoding.md)
- [NSCopying](foundation/nscopying.md)
- [NSObjectProtocol](objectivec/nsobjectprotocol.md)
- [NSSecureCoding](foundation/nssecurecoding.md)

## See Also

### Evaluating the update

- [metrics](coreml/mlupdatecontext/metrics.md)