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# NSRuleEditorDelegate

The `NSRuleEditorDelegate` protocol defines the optional methods implemented by delegates of [`NSRuleEditor`](/documentation/AppKit/NSRuleEditor) objects.

```
protocol NSRuleEditorDelegate : NSObjectProtocol
```

## Topics

### Providing Data

[`ruleEditor(_:child:forCriterion:with:)`](/documentation/AppKit/NSRuleEditorDelegate/ruleEditor(_:child:forCriterion:with:))

Returns the child of a given item at a given index.

[`ruleEditor(_:displayValueForCriterion:inRow:)`](/documentation/AppKit/NSRuleEditorDelegate/ruleEditor(_:displayValueForCriterion:inRow:))

Returns the value for a given criterion.

[`ruleEditor(_:numberOfChildrenForCriterion:with:)`](/documentation/AppKit/NSRuleEditorDelegate/ruleEditor(_:numberOfChildrenForCriterion:with:))

Returns the number of child items of a given criterion or row type.

[`ruleEditor(_:predicatePartsForCriterion:withDisplayValue:inRow:)`](/documentation/AppKit/NSRuleEditorDelegate/ruleEditor(_:predicatePartsForCriterion:withDisplayValue:inRow:))

Returns a dictionary representing the parts of the predicate determined by the given criterion and value.

[`NSRuleEditor.PredicatePartKey`](/documentation/AppKit/NSRuleEditor/PredicatePartKey)

These strings are used as keys to the dictionary returned from the delegate’s [`ruleEditor(_:predicatePartsForCriterion:withDisplayValue:inRow:)`](/documentation/AppKit/NSRuleEditorDelegate/ruleEditor(_:predicatePartsForCriterion:withDisplayValue:inRow:)) optional method. To construct a valid predicate, the union of the dictionaries for each item in the row must contain the required parts.

### Monitoring Row Changes

[`ruleEditorRowsDidChange(_:)`](/documentation/AppKit/NSRuleEditorDelegate/ruleEditorRowsDidChange(_:))

Notifies the receiver that a rule editor’s rows changed.


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