The CollectionView has a getError property that provides validation support. To use it, set getError to a function that takes two parameters containing the data item being validated and the property to validate, and returns a string describing the error condition (or null if there are no errors),
The getError property goes beyond basic HTML5 validation based only on the value itself (such as min, max, required, pattern, etc). It allows you to specify conditions that involve multiple properties.
The getError property allows you to include the validation logic in the collection itself, rather than in the UI used for editing items. The same method can then be used by input forms or by controls such as the FlexGrid.