---
title: "rulerView(_:shouldAdd:)"
framework: appkit
role: symbol
role_heading: Instance Method
path: "appkit/nstextview/rulerview(_:shouldadd:)"
---

# rulerView(_:shouldAdd:)

Returns whether a new marker can be added.

## Declaration

```swift
func rulerView(_ ruler: NSRulerView, shouldAdd marker: NSRulerMarker) -> Bool
```

## Parameters

- `ruler`: The ruler view sending the message.
- `marker`: The marker to be added.

## Return Value

Return Value true if aMarker can be added, false otherwise.

## Discussion

Discussion The receiver checks for permission to make the change by invoking shouldChangeText(in:replacementString:) and returning the return value of that message. If the change is allowed, the receiver is then sent a rulerView(_:didAdd:) message.

## See Also

### Supporting the ruler view

- [rulerView(_:didMove:)](appkit/nstextview/rulerview(_:didmove:).md)
- [rulerView(_:willMove:toLocation:)](appkit/nstextview/rulerview(_:willmove:tolocation:).md)
- [rulerView(_:shouldMove:)](appkit/nstextview/rulerview(_:shouldmove:).md)
- [rulerView(_:didRemove:)](appkit/nstextview/rulerview(_:didremove:).md)
- [rulerView(_:shouldRemove:)](appkit/nstextview/rulerview(_:shouldremove:).md)
- [rulerView(_:didAdd:)](appkit/nstextview/rulerview(_:didadd:).md)
- [rulerView(_:willAdd:atLocation:)](appkit/nstextview/rulerview(_:willadd:atlocation:).md)
- [rulerView(_:handleMouseDownWith:)](appkit/nstextview/rulerview(_:handlemousedownwith:).md)