# `EctoCommons.DateValidator`
[🔗](https://github.com/achedeuzot/ecto_commons/blob/v0.3.7/lib/validators/date.ex#L1)

This module provides validators for `Date`s.

You can use the following checks:

  * `:is` to check if a `Date` is exactly some `Date`. You can also provide a `:delta` option (in days)
     to specify a delta around which the `Date` is still considered identical.
  * `:before` to check if a `Date` is before some `Date`
  * `:after` to check if a `Date` is after some `Date`

You can also combine the given checks for complex checks. Errors won't be stacked though, the first error
encountered will be returned and subsequent checks will be skipped.
If you want to check everything at once, you'll need to call this validator multiple times.

Also, instead of providing a `Date`, you can also provide some special atoms:

  * `:utc_today` will compare the given `Date` with the `Date` at runtime, by calling `Date.utc_today()`.

## Example:

    iex> types = %{birthdate: :date}
    iex> params = %{birthdate: ~D[2016-05-24]}
    iex> Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
    ...> |> validate_date(:birthdate)
    #Ecto.Changeset<action: nil, changes: %{birthdate: ~D[2016-05-24]}, errors: [], data: %{}, valid?: true, ...>

    # Using :is to ensure a date is identical to another date
    iex> types = %{birthdate: :date}
    iex> params = %{birthdate: ~D[2016-05-24]}
    iex> Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
    ...> |> validate_date(:birthdate, is: ~D[2016-05-24])
    #Ecto.Changeset<action: nil, changes: %{birthdate: ~D[2016-05-24]}, errors: [], data: %{}, valid?: true, ...>

    iex> types = %{birthdate: :date}
    iex> params = %{birthdate: ~D[2016-05-24]}
    iex> Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
    ...> |> validate_date(:birthdate, is: ~D[2017-05-24])
    #Ecto.Changeset<action: nil, changes: %{birthdate: ~D[2016-05-24]}, errors: [birthdate: {"should be %{is}.", [validation: :date, kind: :is, is: ~D[2017-05-24]]}], data: %{}, valid?: false, ...>

    # Using :is with :delta to ensure a date is near another another date
    iex> types = %{birthdate: :date}
    iex> params = %{birthdate: ~D[2016-05-20]}
    iex> Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
    ...> |> validate_date(:birthdate, is: ~D[2016-05-24], delta: 7)
    #Ecto.Changeset<action: nil, changes: %{birthdate: ~D[2016-05-20]}, errors: [], data: %{}, valid?: true, ...>

    iex> types = %{birthdate: :date}
    iex> params = %{birthdate: ~D[2016-04-24]}
    iex> Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
    ...> |> validate_date(:birthdate, is: ~D[2016-05-24], delta: 7)
    #Ecto.Changeset<action: nil, changes: %{birthdate: ~D[2016-04-24]}, errors: [birthdate: {"should be %{is}.", [validation: :date, kind: :is, is: ~D[2016-05-24]]}], data: %{}, valid?: false, ...>

    # Using :is with a function to allow for dynamic date comparison
    iex> types = %{start: :date, finish: :date}
    iex> params = %{start: ~D[2000-01-01], finish: ~D[2000-01-31]}
    iex> changeset = Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
    iex> result = validate_date(changeset, :finish, is: fn chgst, _opts -> Ecto.Changeset.get_field(chgst, :start) |> Date.add(30) end)
    iex> result.valid?
    true

    iex> types = %{start: :date, finish: :date}
    iex> params = %{start: ~D[2000-01-01], finish: ~D[2000-01-02]}
    iex> changeset = Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
    iex> result = validate_date(changeset, :finish, is: fn chgst, _opts -> Ecto.Changeset.get_field(chgst, :start) |> Date.add(30) end)
    iex> result.errors
    [finish: {"should be %{is}.", [validation: :date, kind: :is, is: ~D[2000-01-31]]}]

    # Using :before to ensure date is before given date
    iex> types = %{birthdate: :date}
    iex> params = %{birthdate: ~D[2016-05-24]}
    iex> Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
    ...> |> validate_date(:birthdate, before: ~D[2017-05-24])
    #Ecto.Changeset<action: nil, changes: %{birthdate: ~D[2016-05-24]}, errors: [], data: %{}, valid?: true, ...>

    iex> types = %{birthdate: :date}
    iex> params = %{birthdate: ~D[2016-05-24]}
    iex> Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
    ...> |> validate_date(:birthdate, before: ~D[2015-05-24])
    #Ecto.Changeset<action: nil, changes: %{birthdate: ~D[2016-05-24]}, errors: [birthdate: {"should be before %{before}.", [validation: :date, kind: :before, before: ~D[2015-05-24]]}], data: %{}, valid?: false, ...>

    # Using :before with a function to allow for dynamic date comparison
    iex> types = %{start: :date, finish: :date}
    iex> params = %{start: ~D[2000-01-01], finish: ~D[2000-01-31]}
    iex> changeset = Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
    iex> result = validate_date(changeset, :start, before: fn chgst, _opts -> Ecto.Changeset.get_field(chgst, :finish) end)
    iex> result.valid?
    true

    iex> types = %{start: :date, finish: :date}
    iex> params = %{start: ~D[2000-01-01], finish: ~D[1999-01-31]}
    iex> changeset = Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
    iex> result = validate_date(changeset, :start, before: fn chgst, _opts -> Ecto.Changeset.get_field(chgst, :finish) end)
    iex> result.errors
    [start: {"should be before %{before}.", [validation: :date, kind: :before, before: ~D[1999-01-31]]}]

    # Using :after to ensure date is after given date
    iex> types = %{birthdate: :date}
    iex> params = %{birthdate: ~D[2016-05-24]}
    iex> Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
    ...> |> validate_date(:birthdate, after: ~D[2015-05-24])
    #Ecto.Changeset<action: nil, changes: %{birthdate: ~D[2016-05-24]}, errors: [], data: %{}, valid?: true, ...>

    iex> types = %{birthdate: :date}
    iex> params = %{birthdate: ~D[2016-05-24]}
    iex> Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
    ...> |> validate_date(:birthdate, after: ~D[2017-05-24])
    #Ecto.Changeset<action: nil, changes: %{birthdate: ~D[2016-05-24]}, errors: [birthdate: {"should be after %{after}.", [validation: :date, kind: :after, after: ~D[2017-05-24]]}], data: %{}, valid?: false, ...>

    iex> types = %{start: :date, finish: :date}
    iex> params = %{start: ~D[2000-01-01], finish: ~D[2000-01-31]}
    iex> changeset = Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
    iex> result = validate_date(changeset, :finish, after: fn chgst, _opts -> Ecto.Changeset.get_field(chgst, :start) end)
    iex> result.valid?
    true

    iex> types = %{start: :date, finish: :date}
    iex> params = %{start: ~D[2000-01-01], finish: ~D[1999-01-31]}
    iex> changeset = Ecto.Changeset.cast({%{}, types}, params, Map.keys(types))
    iex> result = validate_date(changeset, :finish, after: fn chgst, _opts -> Ecto.Changeset.get_field(chgst, :start) end)
    iex> result.errors
    [{:finish, {"should be after %{after}.", [validation: :date, kind: :after, after: ~D[2000-01-01]]}}]

# `validate_date`

---

*Consult [api-reference.md](api-reference.md) for complete listing*