Mule 4 - How to Pass Dynamic Values for "keys" in Key-Value Pair

Hello Muleys,

You might have quite often encountered a situation where you need to have dynamic "keys" in a key-value pair.

We know that we can pass dynamic values directly using the syntax like below  : 

%dw 2.0

output application/java

---

{

"message" : vars.message

}

But even the key "message" has to be dynamic. Then what's the syntax we have to use?

Simple! - 

Define a local variable,

"$(a)"  - Just wrap  within double quotes and give your local var within ()

Double quotes are very important. Or else you will have a syntactical error.

Also its () not {} . There's a difference between $() and ${}

${} is used to retrieve property value. Whereas $() is used to retrieve dynamic value.

Eg:

x

%dw 2.0

output application/json

var a = "message"

---

{

"$(a)" : payload

}

The above syntax returns:

xxxxxxxxxx

{

    "message": "Hello Muleys"

}

If you want dynamic keys for an array of objects,

then you can use like ($.xyz) you need to wrap in ().

xxxxxxxxxx

%dw 2.0

output application/json

var a = "OrderInformation"

var orders = [

    {orderId : 134 , orderName :  "Soap"},

    {orderId : 222 , orderName :  "Tumbler"},

    {orderId : 389 , orderName :  "NoteBook"}

]

--- 

"$(a)" : orders map {

    ($.orderId) : $.orderName

                    }

Result :

xxxxxxxxxx

{

  "OrderInformation": [

    {

      "134": "Soap"

    },

    {

      "222": "Tumbler"

    },

    {

      "389": "NoteBook"

    }

  ]

}

So basically 2 different syntaxes for dynamic keys. 

One:  When you want to use the local variable as the key-value - "$(a)"

Two: When you want to use the array of values as keys  -  ($.xyz)

Here's the video for the same :

Simple and Short!
Happy Learning!