Programming Ecto

Introducing Changesets

Changesets manage the update process by breaking it into three distinct stages: casting and filtering user input, validating the input, then sending the input to the database and capturing the result. If you think of it as a pipeline, it would look something like this:

data
|> cast_and_filter_fields
|> validate_change
|> validate_another_change
|> send_to_database

We’ll look at each step in detail, but here’s what the process looks like in code. The following example inserts a new Artist record, based on data supplied by the user:

priv/examples/changeset_01.exs

import Ecto.Changeset

params = %{name: "Gene Harris"}
changeset =
  %Artist{}
 |> cast(params, ...