View Source ArangoXEcto.Changeset (ArangoX Ecto v2.0.0)

Methods to manipulate an Ecto Changeset

The methods within the module are specific to ArangoXEcto and only exist here if there isn't an adequite function available already in the Ecto.Changeset module.

When working with changesets you need to cast or put assocs, well you need to do that for graph relations to. However, you need to use a special version of the function called ArangoXEcto.Changeset.cast_graph/3. This works like the following.

defmodule MyApp.User do
  import Ecto.Changeset
  import ArangoXEcto.Changeset

  ...

  def changeset(user, attrs \ %{}) do
    user
    |> cast(attrs, [...])
    |> cast_graph(:my_content, with: %{
      Post => [:title],
      Comment => [:text]
    })
  end
end

You can also use the put version (ArangoXEcto.Changeset.put_graph/4) just like you would use put_assoc/4.

cast_graph vs cast_assoc

cast_graph and cast_assoc (also the put versions) are very similar in functionality but with some key differences. Firstly, the syntax. You would have seen above that cast_graph/3 allows for a module or a mapper. Secondly, cast_graph/3 allows for the special multiple nodes to edges behaviour as seen above.

Note

cast_assoc/3 and put_assoc/4 will NOT work properly because of how the graph relations work. So you will need to make sure to use the cast_graph/3 and put_graph/4 functions.

Summary

Functions

cast_graph(changeset, name, opts \\ [])

Casts the given graph association with the changeset parameters.

put_graph(changeset, name, value, opts \\ [])

Puts the given graph association entry or entries into a graph association.

Functions

cast_graph(changeset, name, opts \\ [])

(since 2.0.0) 
@spec cast_graph(Ecto.Changeset.t(), atom(), Keyword.t()) :: Ecto.Changeset.t()

Casts the given graph association with the changeset parameters.

This operates simarly to Ecto.Changeset.cast_assoc/3 (and indeed was based on the implementation) but allows for a relation to represent multiple possible options. For example, in the following :my_content can represent either a post or a comment.

# Implicit use the module changesets
ArangoXEcto.Changeset.cast_graph(changeset, :my_content)

# Explicit use the module changesets
ArangoXEcto.Changeset.cast_graph(changeset, :my_content, with: %{
  Post => &Post.changeset/2,
  Comment => &Comment.changeset/2,
})

Like with Ecto.Changeset.cast_assoc/3, the changeset must have explicitly preloaded the graph association before being cast. Refer to the Ecto docs for more info.

Parameters

  • changeset - The Ecto changeset to cast
  • name - The name of the field to cast
  • opts - Options to use (described below)

Options

  • :required - if the graph association is a required field. A non-empty list is satisfactory.

  • :required_message - the message on failure, defaults to "can't be blank"

  • :invalid_message - the message on failure, defaults to "is invalid"

  • :force_update_on_change - force the parent record to be updated in the repository if there is a change, defaults to true

  • :with - can either be a function or a map where the keys are a schema module and the values is the function to use. The function is used to build the changeset from params. Defaults to the changeset/2 function of the associated module. It can be an anonymous function that expects two arguments: the associated struct to be cast and its parameters. It must return a changeset. Functions with arity 3 are accepted, and the third argument will be the position of the associated element in the list, or nil, if the association is being replaced.

  • :drop_param - the parameter name which keeps a list of indexes to drop from the relation parameters

  • :sort_param - the parameter name which keeps a list of indexes to sort from the relation parameters. Unknown indexes are considered to be new entries. Non-listed indexes will come before any sorted ones.

put_graph(changeset, name, value, opts \\ [])

(since 2.0.0) 
@spec put_graph(Ecto.Changeset.t(), atom(), term(), Keyword.t()) :: Ecto.Changeset.t()

Puts the given graph association entry or entries into a graph association.

This operates simarly to Ecto.Changeset.put_assoc/4 (and indeed was based off of the implementation) but allows for a relation to represent multiple possible options. For example, in the following :my_content can represent either a post or a comment.

ArangoXEcto.Changeset.put_graph(changeset, :my_content, [
  %Post{title: "abc"},
  %Comment{text: "cba"}
])

This operates on the graph association as a whole. So for example the above will replace the :my_content edges between the nodes. This works exactly the same as Ecto.Changeset.put_assoc/4. Therefore, if you want to update the content you will have to preload the value and update from there. The :on_replace value for the field applies here.

An empty list can be given too.

The data provided is the same as the available options in Ecto.Changeset.put_assoc/4. I.e. you can provide a map, a keyword list, a changeset or a struct as the options in the list.

Although it accepts an opts argument, there are no options currently supported by put_graph/4.

Parameters

  • changeset - The Ecto changeset to apply the change to
  • name - The name of the field to put the value to
  • value - The value of the field to apply
  • opts - none available currently