Only fields with scalar types can be indexed from an array.

Question

Hello 
 I am facing below issue 
 I created local called 
 local!gridDataStructure: 'type!{urn:com:appian:types}CDT'( 
 role:{1,2,3} 
 . 
 . 
 . 
 . 
 . 
 ) 
 role is type of list of integer

When i try to print as local!gridDataStructure.role it throwing an error as 
 
 a!gridLayout [line 1068]: Cannot index "role" because it is an array type (List of Number (Integer)). Only fields with scalar types can be indexed from an array. 
 
 I tried applying hard coded index([1]) still it's giving a same error. Please suggest the solution

Peter Lewis · Accepted Answer

Usually this happens if you have an array of arrays. Is it possible that local!gridDataStructure also contains an array of CDT? Here's an example: a!localVariables(
 local!test: {
 'type!{urn:com:appian:types:PDL}PDL_TestNestedCDT'(
 list:{1,2,3}
 ),
 'type!{urn:com:appian:types:PDL}PDL_TestNestedCDT'(
 list: {4,5,6}
 )
 },
 index(index(local!test, 1, {}), "list")
) 
 This will work because I first index into the first item of "PDL_TestNestedCDT", then index into "list". However, it wouldn't be possible to directly enter local!test.list because that results in a list of lists. 
 If you need to display or perform a calculation with this, you can also get around this by using a!forEach() like this: 
 a!localVariables(
 local!test: {
 'type!{urn:com:appian:types:PDL}PDL_TestNestedCDT'(
 list:{1,2,3}
 ),
 'type!{urn:com:appian:types:PDL}PDL_TestNestedCDT'(
 list: {4,5,6}
 )
 },
 a!forEach(
 items: local!test,
 expression: fv!item.list
 )
)

Peter Lewis · Answer

You might need to do something with a!forEach() and update just the value of interest. For example, suppose I want to update the list for the second item - here's an expression that might work: 
 a!localVariables(
 local!test: {
 'type!{urn:com:appian:types:PDL}PDL_TestNestedCDT'(
 list:{1,2,3}
 ),
 'type!{urn:com:appian:types:PDL}PDL_TestNestedCDT'(
 list: {4,5,6}
 )
 },
 {
 a!richTextDisplayField(
 value: tostring(local!test)
 ),
 a!buttonArrayLayout(
 buttons: {
 a!buttonWidget(
 label: "Test",
 saveInto: a!save(
 target: local!test,
 value: a!forEach(
 items: local!test,
 expression: if(
 fv!index = 2 /* only update row 2 */,
 'type!{urn:com:appian:types:PDL}PDL_TestNestedCDT'(
 list: {7,8,9}
 ),
 fv!item
 )
 )
 )
 )
 }
 )
 }
)

Only fields with scalar types can be indexed from an array.

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