---
schema_version: "1"
id: 86ca566cf1dbfa101e0c745801c4b5c1d08cc473c7b918568697c49035e308be
title: Use Dynamic Writer Properties
collection: mulesoft
version: current
locale: en-us
portal_url: https://docs.salesforce.com/mulesoft/current/en-us/dataweave/2.4/dataweave-cookbook-writer-prop-mule.md
canonical_url: https://docs.mulesoft.com/dataweave/2.4/dataweave-cookbook-writer-prop-mule
source_site: docs.mulesoft.com
content_type: documentation
content_hash: 9e481fd47a213ad4cfb9feaaf3be4e2ee6780862b29e855c57322825bdec7415
description: MuleSoft Documentation Site
release: "2.4"
latest: false
---
---
product: DataWeave
version: 2.4
---

# Use Dynamic Writer Properties

> For the full documentation index, see: https://docs.mulesoft.com/llms.txt

The following example shows a Mule flow that transforms comma-separated CSV data into pipe-separated
(`|`) CSV data. Instead of setting a literal value in the script, the example selects the pipe value
from a [Mule variable](https://docs.mulesoft.com/mule-runtime/latest/about-mule-variables), which is part of a Mule
event that travels through data-processing components in the flow. The example uses the DataWeave
writer function in the body of the script to change the comma-separated input to pipe-separated
output.

The Scheduler component (`<scheduler/>`) in the example generates a Mule event each time it triggers
the flow.

The Set Variable component (`<set-variable/>`) creates a Mule variable named `delimiter` with the
value `'|'`. In Studio, the value is created as an **fx** expression (`value="#['|']"`), rather than
a simple string (`value="'|'"`).

The Transform Message component (`<ee:transform-message/>`) contains a DataWeave script that reads
comma-separated CSV input and uses the Mule variable to write pipe-separated CSV output.

The Logger component (`<logger/>`), which is set to `payload`, writes the pipe-separated output as
INFO in its `LoggerMessageProcessor` message: `macaroni | rigatoni | ravioli | spaghetti`.

Mule Flow:

```xml
<flow name="ex-use-mule-var-as-prop-config-val" >
  <scheduler doc:name="Scheduler" >
    <scheduling-strategy >
      <fixed-frequency frequency="45" timeUnit="SECONDS"/>
    </scheduling-strategy>
  </scheduler>
  <set-variable value="#['|']" doc:name="Set Variable" variableName="delimiter" />
  <ee:transform doc:name="Transform Message" >
    <ee:message>
      <ee:set-payload><![CDATA[%dw 2.0
var myVar = read("macaroni , rigatoni , ravioli , spaghetti", "application/csv" , {"header":false, separator:','})
output application/csv with binary
---
write(myVar, "application/csv", {"header":false, "separator":vars.delimiter})]]></ee:set-payload>
    </ee:message>
  </ee:transform>
  <logger level="INFO" doc:name="Logger" message="#[payload]"/>
</flow>
```

To provide comma-separated input for the example, the script in the Transform Message component uses
a [read](https://docs.mulesoft.com/dataweave/2.4/dw-core-functions-read) function as a value to a DataWeave variable, `myVar`:

`var myVar = read("macaroni , rigatoni , ravioli , spaghetti", "application/csv" , {"header":false, separator:','})`

To write pipe-separated output, the DataWeave [write](https://docs.mulesoft.com/dataweave/2.4/dw-core-functions-write) function in the body
of the script changes the comma-separated input to pipe-separated output. To select the pipe value
from the Mule variable (`delimiter`), the function passes the writer property configuration
`"separator":vars.delimiter` as an argument:

`write(myVar, "application/csv", {"header":false, "separator":vars.delimiter})`

The script uses the following DataWeave `output` directive in the script’s header:
`output application/csv with binary`. It is necessary to append the `with binary` setting
([introduced in Mule 4.3.0](https://docs.mulesoft.com/dataweave/2.4/dataweave-formats#set_mime_types)) to invoke the binary writer because
the `write` function returned CSV output. Without the setting, DataWeave would attempt to write CSV
again and produce the following issue:
`CSV Structure should be an Array<Object> or Object but got String, while writing CSV.`

Note that if you want to see pipe-separated content from the Tranform Message component’s
**Preview** screen in the Studio UI, you must create sample data for it:

1.  Double-click the Transform Message component from the **Message Flow** area of the Studio app.

2.  Right-click **delimiter: _String_** in the **Context** tab, which is located on the bottom left
    of the configuration UI for the component.

3.  Select **Edit Sample Data** to open a **vars-delimiter** tab.

4.  Replace any content in the **vars-delimiter** with the following sample data for the `delimiter`
    value: `"|"`. You must put the delimiter in quotation marks.

For further guidance with sample data, see
[Previewing the Output of a Transformation](https://docs.mulesoft.com/mule-runtime/latest/transform-preview-transformation-output-studio-task).

## See Also

- [DataWeave Formats](https://docs.mulesoft.com/dataweave/2.4/dataweave-formats)

- [Core Components](https://docs.mulesoft.com/mule-runtime/latest/about-components)

- [DataWeave Cookbook](https://docs.mulesoft.com/dataweave/2.4/dataweave-cookbook)