The #record.key syntax is for records; Elixir structs are not records, they are maps.

DETS stores tuples, so records fit naturally.

You’ll need to either produce a tuple from your struct, so that %SomeStruct{key: 123} is stored as {123, %SomeStruct{key: 123}} or transform the struct to a record (see the Record docs for some Elixir helpers).

One possible gotcha: for the “convert to a record” case, I don’t see a clear Elixir equivalent to #record.key to get a tuple position from a field name

Edit: thanks to @lud for calling out what I totally skimmed past - if you said defrecord :user, ... then user(:some_field) is the zero-based index of some_field in the record. That will work as-is if you want to access the field with Kernel#elem, but you’ll need to explicitly add one if you pass it to ETS as keypos (which expects a 1-based index!).