Flatten Elements of Arrays
DataWeave can flatten subarrays of an array and collections of key-value pairs
within DataWeave objects, arrays, and subarrays.
Before you begin, note that DataWeave version 2 (%dw 2.0) is for Mule 4 apps. For a
Mule 3 app, refer to DataWeave version 1
(%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.
Flatten Subarrays with Key-Value Pairs into an Array of Objects
This example shows how flatten acts on key-value pairs of the input array
defined by the variable arrayOne. Notice that every key-value pair in the
array becomes a separate DataWeave object.
The example uses this function:
-
flattento move the elements from the subarrays to the parent array, eliminate the subarrays, and covert all key-value pairs into a list of objects within the parent array.
%dw 2.0
var arrayOne = [
[
"keyOne" : 1,
"keyTwo" : 2
],
[
"keyThree" : 3,
"keyFour" : 4,
"keyFive" : 5
],
"keySix" : 6
]
output application/json
---
flatten(arrayOne)[
{
"keyOne": 1
},
{
"keyTwo": 2
},
{
"keyThree": 3
},
{
"keyFour": 4
},
{
"keyFive": 5
},
{
"keySix": 6
}
]Flatten Combined Arrays
Like the previous DataWeave example, the following returns an array that combines and flattens the
elements from two arrays. This second example applies the selector fruit
to select only the values of the key fruit and to exclude other values in
the array.
This example uses:
-
++to combine the objects of two arrays (arrayOneandarrayTwo) into a single array. -
flattento flatten the combined array into a list of key-value pairs.
%dw 2.0
var arrayOne = [
[
"fruit" : "orange",
"fruit" : "apple"
],
[
"fruit" : "grape",
"notfruit" : "something else"
]
]
var arrayTwo = [
[
{ "fruit" : "kiwi" }
],
"fruit" : "strawberry",
"fruit" : "plum",
{ "fruit" : "banana" },
"notfruit" : "something else"
]
output application/json
---
flatten(arrayOne ++ arrayTwo)[
{ "fruit": "orange" },
{ "fruit": "apple" },
{ "fruit": "grape" },
{ "notfruit": "something else" },
{ "fruit": "kiwi" },
{ "fruit": "strawberry" },
{ "fruit": "plum" },
{ "fruit": "banana" },
{ "notfruit": "something else" }
]The only difference between the previous example and the
following example is the addition of the .fruit selector to the body expression
to select all the fruit values and to exclude values
of the notfruit keys from the output array.
%dw 2.0
var arrayOne = [
[
"fruit" : "orange",
"fruit" : "apple"
],
[
"fruit" : "grape",
"notfruit" : "something else"
]
]
var arrayTwo = [
[
{ "fruit" : "kiwi" }
],
"fruit" : "strawberry",
"fruit" : "plum",
{ "fruit" : "banana" },
"notfruit" : "something else"
]
output application/json
---
flatten(arrayOne ++ arrayTwo).fruit[
"orange",
"apple",
"grape",
"kiwi",
"strawberry",
"plum",
"banana"
]The next example uses ..*fruit as a selector in the body expression instead
of .fruit to return all nested fruit values in the flattened array. It also
flattens three combined arrays instead of two.
%dw 2.0
var arrayOne = [
[
"fruit" : "orange",
"fruit" : "apple"
],
[
"fruit" : "grape",
"notfruit" : "something else"
]
]
var arrayTwo = [
[
{ "fruit" : "kiwi" }
],
"fruit" : "strawberry",
"fruit" : "plum",
{ "fruit" : "banana" },
"notfruit" : "something else"
]
var arrayThree = [
{ parentOne :
[
{ child :
[
{ grandchild :
{
"fruit" : "watermelon",
"notfruit" : "something else"
}
},
{
fruit : "cantaloupe",
"notfruit" : "something else"
}
]
},
{
fruit : "honeydew",
"notfruit" : "something else"
}
]
},
{ parentTwo:
[
fruit : "cherry",
"notfruit" : "something else"
]
}
]
output application/json
---
flatten(arrayOne ++ arrayTwo ++ arrayThree)..*fruit[
"orange",
"apple",
"grape",
"kiwi",
"strawberry",
"plum",
"banana",
"watermelon",
"cantaloupe",
"honeydew",
"cherry"
]Flatten Subarrays into the Parent Array
This example shows how the flatten function acts on a variety of data types,
including numbers, DataWeave objects, subarrays, a string, a null value, and
and a key-value pair. Notice that elements of the subarrays become elements of
the parent array, and the subarrays are no longer present.
The example uses this function:
-
flattento flatten the subarrays into their parent arrays.
%dw 2.0
var myArray = [
1,
[2,3],
{ a : "b"},
"my string",
[ [4,5], { c : "d"}, 6 ],
null,
"e" : "f"
]
output application/json
---
flatten(myArray)[
1,
2,
3,
{
"a": "b"
},
"my string",
[
4,
5
],
{
"c": "d"
},
6,
null,
{
"e": "f"
}
]