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  4. Conditionally Reduce a List Via a Function

Conditionally Reduce a List through a Function

DataWeave 2.2 is compatible and bundled with Mule 4.2. This version of Mule reached its End of Life on May 2, 2023, when Extended Support ended.

Deployments of new applications to CloudHub that use this version of Mule are no longer allowed. Only in-place updates to applications are permitted.

MuleSoft recommends that you upgrade to the latest version of Mule 4 that is in Standard Support so that your applications run with the latest fixes and security enhancements.

This DataWeave example flattens the input to something simpler. For each element in the input, it conditionally includes a contentTypes field only in case it has any values. It then rearranges this content into a more readable shape. Before you begin, note that DataWeave version 2 (%dw 2.0) is for Mule 4 apps. For a Mule 3 app, refer to DataWeave 1.0 (%dw 1.0) examples, within the Mule 3.9 documentation set. For other Mule versions, you can use the Mule Runtime version selector in the table of contents.

The examples use these functions:

  • map to go through every element in the input array.

  • reduce to aggregate the multiple elements in the tags array into one field.

  • splitBy to parse the values in the "tags" array, so as to only select the first part of each string (through [0]) and discard the second.

  • ++ to concatenate these elements into one single string, with commas as separators.

  • if include the last field only if the contentTypes array is bigger than 0.

DataWeave
%dw 2.0
output application/json
fun reduceMapFor(data) = data reduce(($$ splitBy ":")[0] ++ "," ++ ($ splitBy ":")[0])
---
payload.results map
    {
        email: $.profile.email,
        name: $.profile.firstName,
        tags: reduceMapFor($.data.interests.tags[0]),
        (contenttypes: reduceMapFor($.data.interests.contenttypes[0])) if (sizeOf($.data.interests.contenttypes[0]) > 0)
    }
Input JSON
{
  "results": [
    {
      "profile": {
        "firstName": "john",
        "lastName": "doe",
        "email": "johndoe@demo.com"
      },
      "data": {
        "interests": [
          {
            "language": "English",
            "tags": [
              "digital-strategy:Digital Strategy",
              "innovation:Innovation"
            ],
            "contenttypes": []
          }
        ]
      }
    },
    {
      "profile": {
        "firstName": "jane",
        "lastName": "doe",
        "email": "janedoe@demo.com"
      },
      "data": {
        "interests": [
          {
            "language": "English",
            "tags": [
              "tax-reform:Tax Reform",
              "retail-health:Retail Health"
            ],
            "contenttypes": [
              "News",
              "Analysis",
              "Case studies",
              "Press releases"
            ]
          }
        ]
      }
    }
  ],
  "objectsCount": 2,
  "totalCount": 2,
  "statusCode": 200,
  "errorCode": 0,
  "statusReason": "OK"
}
Output JSON
[
  {
    "email": "johndoe@demo.com",
    "name": "john",
    "tags": "digital-strategy,innovation"
  },
  {
    "email": "janedoe@demo.com",
    "name": "jane",
    "tags": "tax-reform,retail-health",
    "contenttypes": "News,Analysis,Case studies,Press releases"
  }
]

See Also