# `GSLayer axisRuleKey:rule:`

*Type Method*

A stable key for an axis rule.

## Declaration

```swift
class func axisRuleKey(_ axis: GSAxis, rule: [AnyHashable : Any]) -> String?
```

```objc
+ (NSString *) axisRuleKey:(GSAxis *) axis rule:(NSDictionary *) rule;
```

```python
axisRuleKey_rule_(axis: GSAxis, rule: dict) -> str
```

## Parameters

- `axis` — The axis described by the rule.
- `rule` — Inclusive `min` and `max` bounds in internal axis values.

## Return Value

A compact rule description, or `nil` when the rule has no bounds.