Foreach data grouping by value

If this data is in your database, I believe you can use query aggregation functionality to group by value on a certain column and then do operations such as SUM on other column(s).

If you're looking to solve this using Appian expression language only, i.e. for on-form or other local data (not coming thru DB queries), then the steps I would do would be:

1. Create a local variable collecting a list of unique users
2. Use your a!forEach() loop over the list of unique users from step 1, and on each loop, find the items in the original list that match that user
3. Sum all matching item VALUEs in that iteration of a!forEach().

This list of steps should be doable by simply exploring the functionality available within Appian especially the documentation provided at the Appian Documentation website, and building it up iteratively.  If you need further help I may have the time to type up some example code a little later this evening or tomorrow morning (unless someone else beats me to it).

Edit: please see the below code:

a!localVariables(
  
  local!data: {
    a!map(
      id: 1,
      currency: "USD",
      createdBy: "user1@gmail.com",
      value: 1000
    ),
    a!map(
      id: 2,
      currency: "USD",
      createdBy: "user1@gmail.com",
      value: 2000
    ),
    a!map(
      id: 3,
      currency: "USD",
      createdBy: "user2@gmail.com",
      value: 2000
    )
  },
  
  local!uniqueUsers: rule!GCO_RULE_General_distinct(local!data.createdBy),
  
  a!forEach(
    local!uniqueUsers,
    a!localVariables(
      local!currentUserIndices: wherecontains(
        fv!item,
        local!data.createdBy
      ),
      
      a!map(
        currentUser: fv!item,
        totalValue: sum(
          index(
            local!data.value,
            local!currentUserIndices
          )
        )
      )
    )
  )
)