Use Ecto Changeset to validate a command

open_account.ex

defmodule OpenAccount do
  defstruct [:account_number, :initial_balance]
  
  @types %{
    account_number: :string,
    initial_balance: :integer      
   }
  
  def validate(params) do
    {params, @types}
    |> Changeset.cast(params, [:account_number, :initial_balance])
    |> Changeset.validate_required([:account_number, :initial_balance])
    |> Changeset.validate_number(:initial_balance, greater_than: 0)
    |> case do
      %Changeset{valid?: true, changes: changes} -> {:ok, changes}
      %Changeset{errors: errors} -> {:error, errors}
  end
end