We've also found a useful Ecto Cheatsheet More specifically, consider reading up on the four main Ecto modules. The functions cast/4 and change/2 are the usual entry points for creating changesets. There is an example of working with changesets in the introductory documentation in the Ecto module. We highly recommend the Ecto documentation. Changesets allow filtering, casting, validation and definition of constraints when manipulating structs. For now, we're armed with the basics of Ecto.
#Ecto changeset install#
install ( Further ReadingĮcto is a massive topic that we will cover throughout the course. This post at least provides a line in the sand that I can revisit as I build up more experience in using and observing changesets in the wild.Mix. It feels like it has been caught between two opposing principles and has thus been pulled in two different directions.Ĭhangesets want to offer welcome convenience in building web applications and they want to follow the Elixir and Phoenix principles of separation of concerns and decoupled code. It doesn’t decompose as neatly as I might like.
Changesets are responsible for casting, filtering, validating, change tracking, and receiving feedback from the data repository.While changesets have been successfully decoupled from forms on the one side and queries on the other there remains evidence of a previous coupling: action, repo, repo_opts, constraints.It could be that there’s something to be improved here, despite how embedded changesets in the mindset of a Phoenix developer. It could be simply that this is a thorny problem to solve and dealing with different responsibilities is simply a fact of life. This could of course be down to my lack of experience and the resultant failure to fully appreciate the abstraction. With changesets on the other hand I’m a seeing a forest because of all the trees. Ecto.Query is a beautiful, thin layer of abstraction over SQL. Plug offers a very elegant way of handling the request-response cycle. In other parts of Phoenix this clean separation of responsibilities can be clearly seen. There is nothing wrong with /3, in some cases it makes sense to use it, for values that cant come through the API for any reason, if you need a mapping between the value sent via API and your datastore, or if you need to nullify a field. One of the claims is that ‘Rails is not your application’ with Phoenix building on this Clean Architecture mantra by separating out lib and web folders and functionality, introducing contexts, and encouraging a more decoupled application design.Ĭhangesets therefore provide an interesting litmus test of this philosophy. In addition of course to the introduction of a programming model that fits hand in glove with the requirements of the web ( Phoenix.PubSub, Phoenix.Presence, Phoenix.LiveView). Phoenix is a framework which supposedly learns from the limitations of Rails to bring something that is explicit (over Rails’ implicitness), straightforward (over Rails’ indirection) and simple (over Rails’ complexity). Indeed if we trace the heritage of Elixir in general and Phoenix in particular then there is a strong current of being better across a chosen set of criteria.Įlixir borrows Ruby’s friendly syntax but inhabits a world of performance, concurrency and fault tolerance which Ruby finds difficult to match. Certainly these are all united by the goal of preparing, controlling and executing a set of changes but I can’t help but get the feeling that it is doing too much.ĭoing too much was always a criticism of ActiveRecord in Ruby on Rails. The first thing that strikes me about this is that a changeset is responsible for several different things. So far in What is a Changeset? and Validations we have seen how an Ecto Changeset is an immutable data structure which is transformed by applying different kinds of functions for different purposes.
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