ChangesetHelpers

This library provides a set of helper functions to work with Ecto Changesets.

validate_comparison(changeset, field1, operator, field2_or_value, opts)

Validates the result of the comparison of

• two fields (where at least one is a change) or
• a change and a value, where the value is an integer, a Date, a Time, a DateTime or a NaiveDateTime.

validate_comparison(changeset, :start_time, :lt, :end_time)

assert [start_time: {"must be less than 10:00:00", [validation: :comparison]}] = changeset.errors
assert [start_time: :comparison, end_time: :comparison] = changeset.validations

validate_comparison(appointment_changeset, :end_time, :lt, ~T[21:00:00])

assert [end_time: {"must be less than 21:00:00", [validation: :comparison]}] = changeset.errors
assert [end_time: :comparison] = changeset.validations

validate_not_changed(changeset, field)

Checks if the specified attribute is present in the changeset's parameters. If the attribute is present, an error is added to the changeset's :errors key.

changes = %{foo: 1, bar: 2}

changeset =
  %Appointment{}
  |> cast(changes, [:foo])
  |> validate_not_changed([:bar])
  |> validate_not_changed([:baz, :qux])

refute changeset.valid?
assert [bar: {"cannot be changed", [validation: :not_present]}] = changeset.errors

validate_list(changeset, field, validation_fun, validation_fun_args)

Validates a list of values using the given validator.

changeset =
  %Appointment{}
  |> Appointment.changeset(%{days_of_week: [1, 3, 8]})
  |> validate_list(:days_of_week, &Ecto.Changeset.validate_inclusion/3, [1..7])

assert [days_of_week: {"is invalid", [validation: :list, index: 2, validator: :validate_inclusion]}] = changeset.errors
assert [days_of_week: {:list, [validator: :validate_inclusion]}] = changeset.validations

As the validator function is from the Ecto.Changeset module, you may just write :validate_inclusion.

put_assoc(changeset, keys, value)

Puts the given nested association in the changeset through a given list of field names.

ChangesetHelpers.put_assoc(account_changeset, [:user, :config, :address], address_changeset)

Instead of giving a Changeset or a schema as the third argument, a function may also be given in order to modify the nested changeset in one go.

ChangesetHelpers.put_assoc(account_changeset, [:user, :articles],
  &(Enum.concat(&1, [%Article{} |> Ecto.Changeset.change()])))

In the code above, we change a new empty Article, and add the changeset into the articles association (typically done when we want to add a new row of form inputs to add an entity into a form handling a nested collection of entities).

put_assoc(changeset, keys, index, value)

Puts the given nested association in the changeset through a given list of field names, at the given index.

change_assoc(struct_or_changeset, keys, changes \\ %{})

Returns the nested association in a changeset. This function will first look into the changes and then fails back on data wrapped in a changeset.

Changes may be added to the given changeset through the third argument.

A tuple is returned containing the modified root changeset and the changeset of the association.

{account_changeset, address_changeset} =
  change_assoc(account_changeset, [:user, :user_config, :address], %{street: "Foo street"})

change_assoc(struct_or_changeset, keys, index, changes \\ %{})

Returns the nested association in a changeset at the given index.

update_assoc_changes(changeset, keys, changes)

Adds changes to the changed association changesets.

fetch_field(changeset, keys)

Fetches the given nested field from changes or from the data.

{:changes, street} =
  ChangesetHelpers.fetch_field(account_changeset, [:user, :config, :address, :street])

fetch_field!(changeset, keys)

Same as fetch_field/2 but returns the value or raises if the given nested key was not found.

street = ChangesetHelpers.fetch_field!(account_changeset, [:user, :config, :address, :street])

fetch_change(changeset, keys)

Fetches the given nested field from changes or from the data.

{:ok, street} =
  ChangesetHelpers.fetch_change(account_changeset, [:user, :config, :address, :street])

fetch_change!(changeset, keys)

Same as fetch_change/2 but returns the value or raises if the given nested key was not found.

street = ChangesetHelpers.fetch_change!(account_changeset, [:user, :config, :address, :street])

has_change?(changeset, keys)

ChangesetHelpers.has_change?(account_changeset, [:user, :config, :address, :street])

diff_field(changeset1, changeset2, keys)

This function allows checking if a given field is different in two changesets.

{street_changed, street1, street2} =
  diff_field(account_changeset, new_account_changeset, [:user, :user_config, :address, :street])

add_error(changeset, keys, message, extra \\ [])

Adds an error to the nested changeset.

ChangesetHelpers.add_error(account_changeset, [:user, :articles, :error_key], "Some error")

field_fails_validation?(changeset, field, validations)

Checks whether a field as the given validation error key.

ChangesetHelpers.field_fails_validation?(changeset, :email, :unsafe_unique)

field_violates_constraint?(changeset, field, constraints)

Checks whether a field as the given constraint error key.

ChangesetHelpers.field_violates_constraint?(changeset, :email, :unique)

validate_changes(changeset, fields, meta, validator)

Works like Ecto.Changeset.validate_change/3 but may receive multiple fields.

Installation

Add changeset_helpers for Elixir as a dependency in your mix.exs file:

def deps do
  [
    {:changeset_helpers, "~> 0.23"}
  ]
end

HexDocs

HexDocs documentation can be found at https://hexdocs.pm/changeset_helpers.