Validates the structure of a URL field in an Ecto changeset. It does not make it required field.

If the field in the changeset is a URL, this function ensures that it has a scheme (defaulting to "https://" if none is present), and then checks the URL's structure against a regular expression.

If the URL's structure is invalid, the error_message is attached to the field in the changeset's errors.

Parameters

• changeset: The Ecto changeset containing the URL to validate.
• field: The key (atom) for the field in the changeset containing the URL.
• error_message: The error message to attach to the field in the changeset if the URL is invalid.

Examples

iex> types = %{url: :string}
iex> params = %{url: "https://www.example.com/"}
iex> Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
...> |> validate_url(:url, "is not a valid url")
#Ecto.Changeset<action: nil, changes: %{url: "https://www.example.com/"}, errors: [], data: %{}, valid?: true, ...>

iex> types = %{url: :string}
iex> params = %{url: "www.example.com/"}
iex> Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
...> |> validate_url(:url, "is not a valid url")
#Ecto.Changeset<action: nil, changes: %{url: "https://www.example.com/"}, errors: [], data: %{}, valid?: true, ...>

iex> types = %{url: :string}
iex> params = %{url: nil}
iex> Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
...> |> validate_url(:url, "is not a valid url")
#Ecto.Changeset<action: nil, changes: %{}, errors: [], data: %{}, valid?: true, ...>

iex> types = %{url: :string}
iex> params = %{url: "some@invalid_url"}
iex> Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
...> |> validate_url(:url, "is not a valid url")
#Ecto.Changeset<action: nil, changes: %{url: "https://some@invalid_url"}, errors: [url: {"is not a valid url", [validation: :format]}], data: %{}, valid?: false, ...>

iex> types = %{url: :string}
iex> params = %{url: "Just some random text"}
iex> Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
...> |> validate_url(:url, "is not a valid url")
#Ecto.Changeset<action: nil, changes: %{url: "https://Just some random text"}, errors: [url: {"is not a valid url", [validation: :format]}], data: %{}, valid?: false, ...>