Recursively get db entries

lucas0001 over 2 years ago

Hi Everyone,

I've got a CDT that has an Id as a Primary Key and then a Numeric field that is a reference to a previous same-cdt entry id.

Starting from an ID I need to back-track all the way to the first "father" entry. All should be done using Expression Rules.

To give you an example I would like to start from contract ID:4 and backtrack all the way to ID 1 (that has no father id)

I managed to achieve the backtracking with a process but I can't make it work with a reduce() or a forEach() function.

Has someone found something like this in his history?

Best regards, Luca.

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0 fredaf

Certified Lead Developer

over 2 years ago

Hi Luca,

I wouldn't recommend using this type of recursion in Appian as it's not a best practice. But, I tried it using a recursive call to the main expression rule to backtrack through the list mainly using the displayvalue function. Here's the code snippet and it returns a list of strings that u can edit as per your requirement, for this case i passed the ri value as 4 -

"FID value is 3 FID value is 2 FID value is 1 Depth reached "(Text)

a!localVariables(
  local!cdtset: {
    'type!{urn:com:appian:types}test_cdt_1'('ID': 1, 'fID': null),
    'type!{urn:com:appian:types}test_cdt_1'('ID': 2, 'fID': 1),
    'type!{urn:com:appian:types}test_cdt_1'('ID': 3, 'fID': 2),
    'type!{urn:com:appian:types}test_cdt_1'('ID': 4, 'fID': 3)
  },
  local!newvalue: displayvalue(
    ri!value,
    local!cdtset.'ID',
    local!cdtset.'fID',
    0
  ),
  if(
    or(
      a!isNullOrEmpty(local!newvalue),
      local!newvalue = 0
    ),
    { "Depth reached " & local!newvalue },
    {
      "FID value is " & local!newvalue & char(10) & rule!test_recursiveEr(local!newvalue)
    }
  )
)