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# shouldChangeText(in:replacementString:)

Initiates a series of delegate messages (and general notifications) to determine whether modifications can be made to the characters and attributes of the receiver’s text.

```
func shouldChangeText(in affectedCharRange: NSRange, replacementString: String?) -> Bool
```

## Parameters

`affectedCharRange`

The range of characters affected by the proposed change.

`replacementString`

The characters that will replace those in `affectedCharRange`. If only text attributes are being changed, `replacementString` is `nil`.

## Return Value

<doc://com.apple.documentation/documentation/Swift/true> to allow the change, <doc://com.apple.documentation/documentation/Swift/false> to prohibit it.

## Discussion

This method checks with the delegate as needed using [`textShouldBeginEditing(_:)`](/documentation/AppKit/NSTextDelegate/textShouldBeginEditing(_:)) and [`textView(_:shouldChangeTextIn:replacementString:)`](/documentation/AppKit/NSTextViewDelegate/textView(_:shouldChangeTextIn:replacementString:)).

This method must be invoked at the start of any sequence of user-initiated editing changes. If your subclass of `NSTextView` implements methods that modify the text, make sure to invoke this method to determine whether the change should be made. If the change is allowed, complete the change by invoking the [`didChangeText()`](/documentation/AppKit/NSTextView/didChangeText()) method.

### Special Considerations

If you override this method, you must call `super` at the beginning of the override.

If the receiver is not editable, this method automatically returns <doc://com.apple.documentation/documentation/Swift/false>. This result prevents instances in which a text view could be changed by user actions even though it had been set to be non-editable.

In macOS 10.4 and later, if there are multiple selections, this method acts on the first selected subrange.

## See Also

[`editable`](/documentation/AppKit/NSTextView/isEditable)

A Boolean value that controls whether the text views sharing the receiver’s layout manager allow the user to edit text.


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