If I understand your problem correctly, you want to validate the phone number and normalize the entered value when it is actually written to the database, is that correct? If so, you might want to have a look at Ecto.Changeset.prepare_changes/2.

Thanks for the answer! To clarify the topic, I’ll add a little code:

def render (assigns) do
...
<.simple_form
        for={@form}
        id="some-modal-form"
        phx-target={@myself}
        phx-change="validate"
        phx-submit="save"
      >
        <.input
          field={@form[:phone]}
          id="user-phone-number"
          type="text"
          label="Phone number"
          phx-hook="PhoneInput"
        />
...

def handle_event("validate", %{"some_input" => some_input} = props, socket) do
    changeset =
      SomeInput.changeset(%SomeInput{}, some_input)

    socket = socket |> assign(:form, to_form(changeset, action: :validate))

export const PhoneInput = {
    mounted() {
        this.el.addEventListener("input", e => {
            let match = this.el.value.replace(/\D/g, "")
                .match(/^(\d{1})(\d{3})(\d{3})(\d{2})(\d{2})$/)
                        //+1 234 567 89 00
            if(match) {
            this.el.value = `+${match[1]} ${match[2]} ${match[3]} ${match[4]} ${match[5]}`
            }
        })
    }
}

  @primary_key false
  embedded_schema do
    field :phone, :string
    field :name, :string
  end

  def changeset(some_input, attrs) do
    some_input
    |> cast(attrs, [:phone, :name])
    |> validate_phone(attrs)
    |> validate_name(attrs)
  end

  def validate_phone(changeset, attrs) do
    changeset
    |> validate_format(:phone, ~r/^1/, message: "Should start with 1")
    |> validate_length(:phone,
      is: 11,
      message: "Should be 11 characters long"
    )
    # |> more validatation cases here and in db phone will be stored as a string of 11 digits
  end

Screenshot_2025-01-31_17-41-52260×151 5.41 KB

As you can see, i need to remove all non-digit symbols before validation pipes even only for validation.

I don’t think you need the hook here. You can define custom validation functions with Ecto.Changeset.validate_change/3. You can process the value in your custom validation function and then check the format. Or you can use Ecto.Changeset.update_change/3 to format the value before you run other validation functions.

You might want to consider using ExPhoneNumber for phone number validation, though. It will provide much better validation.

For storage, you should consider the e164 format. You can use ExPhoneNumber to convert the value into this format as well.

So roughly (not tested):

def changeset(schema, attrs) do
  schema
  |> cast(attrs, [:phone])
  |> validate_change(:phone, &validate_phone/2)
  |> prepare_changes(fn changeset ->
       if phone = get_change(changeset, :phone) do
         {:ok, phone_number} = ExPhoneNumber.parse(phone)
         ExPhoneNumber.format(phone_number, :e164)
       end
       changeset
     end)
end

def validate_phone(field, value) do
  case ExPhoneNumber.parse(value) do
    {:ok, _phone_number} ->
      # add further validation as needed on the parsed phone number
      []

    _ ->
      [{field, "invalid phone number"}]
  end
end