Join array of Objects

Question

Hi ,I have a requirement to join the array1 with array2 in the same document and fetch one column from array 2 into array1 if condition matches. I can do it by splitting the arrays and join them back again. I would like to to know if i can do it in minimal way using expression language? please help&nbsp;&nbsp;studySiteId from array1 should match with&nbsp;studySiteId in array2 and get&nbsp;studySiteReferenceValue from array2 and put it in array1 with key value pair. if not matches put&nbsp;studySiteReferenceValue as null&nbsp;&nbsp;INPUT&nbsp;[{"Array1" : [{"Study": "D123","studySiteNumber":"123","studySiteId":806,"countryCode":"BR"},{"Study": "D124","studySiteNumber":"0820","studySiteId":807,"countryCode":"BR"}],"Array2" : [{"isRefFound":true,"studySiteId":806,"studySiteReferenceTypeId":100,"studySiteReferenceValue":"0SI000000006E06","sourceSystemId":22,"etlIsDeletedFlg":false},{"isRefFound":true,"studySiteId":8088,"studySiteReferenceTypeId":100,"studySiteReferenceValue":"0SI000000006E06","sourceSystemId":22,"etlIsDeletedFlg":false}]}]OUTPUT:[{"Array1" : [{"Study": "D123","studySiteNumber":"123","studySiteId":806,"countryCode":"BR","studySiteReferenceValue":"0SI000000006E06"},{"Study": "D124","studySiteNumber":"0820","studySiteId":807,"countryCode":"BR","studySiteReferenceValue":""}],"Array2" : [{"isRefFound":true,"studySiteId":806,"studySiteReferenceTypeId":100,"studySiteReferenceValue":"0SI000000006E06","sourceSystemId":22,"etlIsDeletedFlg":false},{"isRefFound":true,"studySiteId":8088,"studySiteReferenceTypeId":100,"studySiteReferenceValue":"0SI000000006E06","sourceSystemId":22,"etlIsDeletedFlg":false}]}]

koryknick · Answer

sravan&nbsp;- this is a great use case for Array Functions&nbsp;and Object Functions in SnapLogic expressions!&nbsp; Use a Mapper snap with both "Null-safe access" and "Pass through" enabled, then create a mapping expression as follows:Expression:&nbsp;
$Array1.map(a1=&gt; a1.extend(
{ studySiteReferenceValue : $Array2.find(a2=&gt; a2.studySiteId == a1.studySiteId).studySiteReferenceValue } 
)
)
Target Path:
$Array1
Let's break down that expression just a bit.
$Array1.map(a1=&gt; a1.extend(
Here we are taking the $Array1 and will iterate through each element using the map() method.&nbsp; "a1=&gt;" is the name we will use to refer to each element of the array and the "=&gt;" is how an inline (or callback) function is indicated.&nbsp; So "a1.extend" is referring to the array element we're working on, and the extend() method allows us to merge an object into the current object (remember a1 is an object in your array).
{ studySiteReferenceValue : $Array2.find(a2=&gt; a2.studySiteId == a1.studySiteId).studySiteReferenceValue } 
So here is the new object that we are adding into each array element.&nbsp; "studySiteReferenceValue" is the new field name you wanted, and the value is looking into $Array2 and using the find() method to match the array elements on studySiteId.&nbsp; Once the value is found, we're grabbing the "studySiteReferenceValue" from the found object in Array2.&nbsp; Note that if you don't use "Null safe access" on the Mapper, this will fail because you can't reference a field in null, which is what is returned if the find() method doesn't identify a matching element from the array.
Hope this helps!

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