Introduce #assign_preserving method about store_model

[DmitryTsepelev]

Hi @FunkyloverOne!

Thanks for the reaching out, I like the idea! Let's design the API for it 🙂

I think it should be possible to patch the .attributedefinition to accept preserve: argument:

class Site
  class Settings
    include StoreModel::Model

    attribute :twitter_handle, :string
    # ...

    attribute :colours, ColourScheme.to_type, default: -> { ColourScheme.new }, preserve: true
    attribute :style, Styling.to_type, default: -> { Styling.new }, preserve: true
    attribute :footer_pages, FooterPage.to_array_type, default: -> { [] }
  end
end

In this case #assign_preserving can be moved to StoreModel::Model, and we should also make sure that if preserve: true is passed than type is either JsonType or ArrayType. What do you think?

[FunkyloverOne]

Hey @DmitryTsepelev, one important thing is that we also need to have that #assign_preserving on a parent ActiveRecord model.

Arrays preservation is not that easy as singular JSONs. You see, we need a way of identifying each individual element, updating/removing it, adding new ones. It is supposed to be similar to ActiveRecord's accepts_nested_attributes_for API.

But we could start without arrays preservation support, it's already good enough 😄

[DmitryTsepelev]

Makes sense. We should probably change the name to something that can be easily associated with StoreModel (like assign_preserving_nested_store_models but less verbose)