onNull

onNull<R>(previous: Null, callback: () -> R): R

Executes a callback function if the preceding expression returns a null value and then replaces the null value with the result of the callback.

Introduced in DataWeave version 2.4.0.

Parameters

Name Description

Name	Description
`previous`	The value of the preceding expression.
`callback`	Callback that generates a new value if `previous` returns `null`.

previous

The value of the preceding expression.

callback

Callback that generates a new value if previous returns null.

Example

This example shows how onNull behaves when it receives a null value.

Source

%dw 2.0
output application/json
---
{
     "onNull": []
             reduce ((item, accumulator) -> item ++ accumulator)
             then ((result) -> sizeOf(result))
             onNull "Empty Text"
 }DataWeave

Output

{
  "onNull": "Empty Text"
}Json

onNull<T>(previous: T, callback: () -> Any): T

Helper function that enables onNull to work with a non-null value.

Introduced in DataWeave version 2.4.0.