# `GSLayer metricsValue(_:forKey:)`

*Instance Method*

Value described by a metrics key for a metric side, or `nil` when the key cannot be resolved.

## Declaration

```swift
func metricsValue(_ metric: GSMetricNumbers, forKey key: String) -> CGFloat?
```

## See Also

### Metric Values

- [`GSMetricNumbers`](/Core/GlyphsCore/GSMetricNumbers)
- [`GSLayer metricsValue:atHeight:`](/Core/GlyphsCore/GSLayer/metricsValue:atHeight:) — Metric value for a side at a measurement height.
- [`GSLayer metricsValueAndHeight(_:forKey:)`](/Core/GlyphsCore/GSLayer/metricsValueAndHeight(_:forKey:)) — Value and height described by a metrics key for a metric side, or `nil` when the key cannot be resolved.