Kalecto
Kalecto
Glue between Kalends and Ecto. For saving dates, times and datetimes in Ecto.
defp deps do
[ {:kalecto, ">= 0.2.0"}, ]
end
Super quick way to get started
Here’s how to display inserted_at
and updated_at
dates using the
functionality of the Kalends library:
- Add :kalecto to your deps in your mix.exs file (see above) and run
mix deps.get
- In your Ecto models, where you have a schema definition with a
timestamps
line, adduse Kalecto.Model
at the top of the module, below the line that saysuse Ecto.Model
:
defmodule Weather do
use Ecto.Model
use Kalecto.Model
schema "weather" do
field :city, :string
timestamps
end
end
This means that your timestamps will be loaded as Kalends.DateTime structs instead of Ecto.DateTime structs and you can use the formatting functionality in Kalends.
- Format an
inserted_at
timestamp using Kalends:
@post.inserted_at |> Kalends.DateTime.Format.strftime!("%A, %e %B %Y")
It will return for instance: Monday, 9 March 2015
There are other formatting functions. For instance: http timestamp, unix timestamp, RFC 3339 (ISO 8601). You can also shift the timestamp to another timezone in order to display what date and time it was in that particular timezone. See more in the Kalends documentation.
The types
If you have a primitive type as listed below you can swap it for a Kalecto type simply by adding the type to your Ecto schema.
Primitive type | Ecto type | Kalends type |
---|---|---|
date | Kalecto.Date | Kalends.Date |
time | Kalecto.Time | Kalends.Time |
datetime | Kalecto.DateTimeUTC | Kalends.DateTime |
datetime | Kalecto.NaiveDateTime | Kalends.NaiveDateTime |
kalends_datetime | Kalecto.DateTime* | Kalends.DateTime |
If you have a datetime as a primitive type, you can use NaiveDateTime or DateTimeUTC. If you have a date as a primitive type, you can use Kalecto.Date. If you have a time as a primitive type, you can use Kalecto.Time.
*) If you are using Postgres as a database you can also use the Kalecto.DateTime type. This allows you to save any Kalends.DateTime struct. This is useful for saving for instance future times for meetings in a certain timezone. Even if timezone rules change, the “wall time” will stay the same. See the “DateTime with Postgres” heading below.
Microseconds of NaiveDateTime and DateTimeUTC are discarded/ignored if present. It is planned to include microseconds after a newer version of Ecto is released.
Example usage
In your Ecto schema:
defmodule Weather do
use Ecto.Model
use Kalecto.Model
schema "weather" do
field :city, :string
field :nice_date, Kalecto.Date
field :nice_time, Kalecto.Time
field :nice_datetime, Kalecto.DateTimeUTC
field :another_datetime, Kalecto.NaiveDateTime
timestamps
# the timestamps will be DateTimeUTC because of the `use Kalecto.Model` line
end
end
If you have a Kalends DateTime in the Etc/UTC timezone you can save it in Ecto as a DateTimeUTC.
Let’s create a new DateTime to represent “now”:
iex> example_to_be_saved_in_db = Kalends.DateTime.now_utc
%Kalends.DateTime{abbr: "UTC", day: 2, hour: 16, usec: 245828, min: 48,
month: 3, sec: 19, std_off: 0, timezone: "Etc/UTC", utc_off: 0, year: 2015}
Another way of getting a DateTime is parsing JavaScript style milliseconds:
iex> parsed_datetime = Kalends.DateTime.Parse.js_ms!("1425314899000")
%Kalends.DateTime{abbr: "UTC", day: 2, hour: 16, usec: 0, min: 48, month: 3,
sec: 19, std_off: 0, timezone: "Etc/UTC", utc_off: 0, year: 2015}
Since the field nice_datetime
is of the DateTimeUTC type, we can save
Kalends.DateTime structs there if they are in the Etc/UTC timezone:
weather_struct_to_be_saved = %Weather{nice_datetime: parsed_datetime}
When a Kalecto.DateTimeUTC type is received from the database it is loaded as a Kalends.DateTime struct. We can use the functions in Kalends to shift this UTC datetime to another time zone:
iex> example_loaded_from_db |> Kalends.DateTime.shift_zone!("Europe/Copenhagen")
%Kalends.DateTime{abbr: "CET", day: 2, hour: 17, usec: nil, min: 48,
month: 3, sec: 19, std_off: 0, timezone: "Europe/Copenhagen", utc_off: 3600,
year: 2015}
Or we could get the unix timestamp:
iex> example_loaded_from_db |> Kalends.DateTime.Format.unix
1425314899
Or format it via strftime:
iex> example_loaded_from_db |> Kalends.DateTime.Format.strftime!("The time is %T and it is %A.")
"The time is 16:48:19 and it is Monday."
DateTime with Postgres
If you are using Postgres, you can save and load DateTime structs that are not in the Etc/UTC timezone. This requires that a special type is added to the database. By running the following command you can generate a migration that adds this type:
mix kalecto.add_type_migration
Then run the migration (mix ecto.migrate
) and you can use the type
Kalecto.DateTime
Documentation
Documentation for Kalecto is available at hexdocs.
More information about Kalends functionality in the Kalends documentation.