MuleSoft Dataweave Tutorial: Part II - Functions

User Defined Functions

Here is a example from Mule document:

%dw 1.0
%output application/json
%function toUser(user) { firstName: user.givenName, lastName: user.sn }
---
{
  "user" : toUser({ givenName : "Annie", sn : "Point" })
}

Output from the result:

{
  "user": {
    "firstName": "Annie",
    "lastName": "Point"
  }
}

Mule document did not provide much explanation. What does this function do?

 %function toUser(user) { firstName: user.givenName, lastName: user.sn }

First, we can see it declares the user object, which has {givenName, sn}. When we use the function in the body, we parse an object of user in the form of:

 toUser({ givenName : "Annie", sn : "Point" }) 

Where

 { givenName : "Annie", sn : "Point" } 

is an user object. This tell us how you can initialize an object and pass to a function.

Using Build-in Function: GroupBy

If we want to group object by attribute, we can groupBy and pluck together. Here is the simple Dataweave code:

%dw 1.0
%output application/json
---
payload groupBy $.state

Here is the input data:

[
 {
  "name": "John Smith",
  "street": "1234 JS Ln",
  "city": "Allen",
  "state": "TX",
  "zip": "75123" 
 },
 {
  "name": "Framk Chambers",
  "street": "1234  Colleage Rd",
  "city": "Stillwater",
  "state": "OK",
  "zip": "73001" 
 },
 {
  "name": "Robert Goll",
  "street": "1234 Bush Dr",
  "city": "Plano",
  "state": "TX",
  "zip": "75127" 
 },
  {
  "name": "Billie Chambers",
  "street": "1234 College Rd",
  "city": "Stillwater",
  "state": "OK",
  "zip": "73001" 
 }
]

And here is the output:

[
  {
    "name": "John Smith"
  },
  {
    "name": "Robert Goll"
  },
  {
    "name": "Framk Chambers"
  },
  {
    "name": "Billie Chambers"
  }
]