# `GSLayer metricsValue:forKey:value:atHeight:`

*Instance Method*

Evaluates a metrics key for a metric side.

## Declaration

```objc
- (BOOL) metricsValue:(GSMetricNumbers) metric forKey:(NSString *) key value:(CGFloat *) value atHeight:(NSInteger *) atHeight;
```

```python
metricsValue_forKey_value_atHeight_(metric: GSMetricNumbers, key: str, value: float, atHeight: int) -> bool
```

## Parameters

- `metric` — The metric side that the key is evaluated for.
- `key` — The metrics key to evaluate.
- `value` — On return, the resolved metric value.
- `atHeight` — On return, the height qualifier from the key, or `NSNotFound`.

## Return Value

`YES` when the key syntax is valid.

## 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 metricsValue:forKey:`](/Core/GlyphsCore/GSLayer/metricsValue:forKey:) — Value described by a metrics key for a metric side.