'int' is a primitive and doesn't support nested properties: Azure Data Factory v2 - azure-data-factory

Question

I am trying to find a substring of a string as a part of an activity in ADF. Say for instance I want to extract out the subsctring 'de' out of a string 'abcde'. I have tried:
#substring(variables('target_folder_name'), 3, (int(variables('target_folder_name_length'))-3))
where int(variables('target_folder_name_length')) has a value of 5 and variables('target_folder_name') has a value of 'abcde'
But it gives me: Unrecognized expression: (int(variables('target_folder_name_length'))-3)
On the other hand, if I try this: #substring(variables('target_folder_name'), 2, int(variables('target_folder_name_length'))-3)
This gives me: 'int' is a primitive and doesn't support nested properties
Where am I going wrong?

Answer 1

Use indexof. See my example below:
#substring(variables('testString'), indexof(variables('testString'), variables('de')), length(variables('de')))
Output of 'result' variable:

Answer 2

Since your preceding values are static, you can use below dynamic expression to achieve the substring value as per your requirement.
#substring(variables('varInputFolderName'), 3, sub(length(variables('varInputFolderName')), 3))
Where varInputFolderName = String = abcde as per this sample.
Here is the pipeline JSON payload for this sample. You can play around with it for further testing.
{
"name": "pipeline_FindSubstring",
"properties": {
"activities": [
{
"name": "setSubstringValue",
"type": "SetVariable",
"dependsOn": [],
"userProperties": [],
"typeProperties": {
"variableName": "varSubstringOutput",
"value": {
"value": "#substring(variables('varInputFolderName'), 3, sub(length(variables('varInputFolderName')), 3))",
"type": "Expression"
}
}
}
],
"variables": {
"varInputFolderName": {
"type": "String",
"defaultValue": "abcde"
},
"varSubstringOutput": {
"type": "String"
}
},
"annotations": []
}
}