# Create array in logstash -\> elastic
**URL:** https://discuss.elastic.co/t/create-array-in-logstash-elastic/100512
**Category:** Logstash
**Created:** [September 14, 2017, 10:24am UTC](https://discuss.elastic.co/t/create-array-in-logstash-elastic/100512 "2017-09-14T10:24:39Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Frances\_Buontempo](https://discuss.elastic.co/u/Frances_Buontempo)
#### Post date: [September 14, 2017, 10:24am UTC](https://discuss.elastic.co/t/create-array-in-logstash-elastic/100512/1 "2017-09-14T10:24:39Z")
I want to update documents, and add some of the fields to an array, e.g. with documents from json like
{ "name": "bill, "hobbies": "a" , "id": 1}
if I run logstash on more data like
{ "name": "ted, "hobbies": "a" , "id": 2}
{ "name": "bill, "hobbies": "c" , "id": 1}
I'd like to end up with ted having ["a"] as hobbies, and bill with ["a", "c"].
Looking at [Creating/updating array of objects in elasticsearch logstash output](https://discuss.elastic.co/t/creating-updating-array-of-objects-in-elasticsearch-logstash-output/59139) and [Add new values in the nested field - Logstash to Elasticsearch](https://discuss.elastic.co/t/add-new-values-in-the-nested-field-logstash-to-elasticsearch/62253) I've tried adding a script to the output plugin for elasticsearch
```
script => '
if (ctx._source.hobbies != null) {
ctx._source.hobbies.add(params.event.get("hobbies"))
} else {
ctx._source.hobbies = [params.event.get("hobbies")]
}'
```
This fails on the update because the field is a string;
"reason"=\>"Unable to find dynamic method [add] with [1] arguments for class [java.lang.String]."}
How do I persuade it to be an array?
Is this possible? Is there another option?
Cheers.
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [October 12, 2017, 10:24am UTC](https://discuss.elastic.co/t/create-array-in-logstash-elastic/100512/2 "2017-10-12T10:24:39Z")
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