# Field reference with a split event

**URL:** <https://discuss.elastic.co/t/field-reference-with-a-split-event/263315>\
**Category:** Logstash\
**Created:** [February 4, 2021, 11:31pm UTC](https://discuss.elastic.co/t/field-reference-with-a-split-event/263315 "2021-02-04T23:31:40Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![jiacob](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@jiacob](https://discuss.elastic.co/u/jiacob)\
**Post date:** [February 4, 2021, 11:31pm UTC](https://discuss.elastic.co/t/field-reference-with-a-split-event/263315/1 "2021-02-04T23:31:40Z")

</div>

Hello,

I'm looking into trying to split a nested field that uses a field reference and I'm not sure which is the right way of doing it.

`split { field => "[field1][field2]['%{[field3]}']" }`

This gives me a field reference error and causes the logstash instance to crash.

---

<div class="post-metadata">

**Author:** ![Badger](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/badger/32/25190_2.png) [@Badger](https://discuss.elastic.co/u/Badger)\
**Post date:** [February 5, 2021, 12:20am UTC](https://discuss.elastic.co/t/field-reference-with-a-split-event/263315/2 "2021-02-05T00:20:25Z")

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I think you would need to use ruby to do that reference. I have not tested it, but something like

```
ruby {
    code => '
        fieldName = event.get("field3")
        someObject = event.get("[field1][field2]")
        value = someObject[fieldName]
        event.set("[@metadata][value]", value)
    '
}
split { field => "[@metadata][value]" }
ruby {
    code => '
        fieldName = event.get("field3")
        value = event.get("[@metadata][value]")
        event.set("[field1][field2][#{fieldName}]", value)
    '
}

```

You would have to add tests so that if event.get returns nil the code does not blow up.

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [March 5, 2021, 12:20am UTC](https://discuss.elastic.co/t/field-reference-with-a-split-event/263315/3 "2021-03-05T00:20:57Z")

</div>

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