Adding calculated fields to Ecto Schema - virtual field or?

Questions & Help Questions
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2

I think virtual fields are a good use case for it,
For instance:

defimpl Jason.Encoder, for: WhateverSchema do
  def encode(struct, opts) do
    struct
    |> Map.put(:avatar, RunTimeSettings.get_url_for(struct))
    # |> maybe_trim_private_fields()
    |> Jason.Encode.map(opts)
  end
end

Personally, if the full url is the only thing that makes sense for the client(s), I replace the field itself with the valid url, if the client needs/can use the field value for something, I define a virtual field and then populate that instead.