hoeppner

hoeppner

From Ruby to Elixir — warning about invalid association when doing mix ecto.create (page 97)

Hi @sb8244,

I get a warning when I try to do the migrations on page 97 with mix ecto.create:

warning: invalid association sms_messages in schema PhoneApp.Conversations.Schema.Contact: associated schema PhoneApp.Conversations.Schema.SmsMessage does not have field contact_id
lib/phone_app/conversations/schema/contact.ex:1

I wanted to ask if this is because of the following:

The “SmsMessage” module has a clause that says schema "sms_messages" do. That is, the name of the module has the singular form, but the name of the schema is plural.
In case of the “Contact” module, the situation is reversed. It has an equivalent clause that says schema "contacts" do.

My confusion starts here:

The “SmsMessage” module refers to the contact s via belongs_to :contact (note the singular form in the token), while the “Contact” module refers to the SMS messages via has_many :sms_messages (note the plural).

Do the tokens’ (:contact, :sms_messages) forms (singular/plural) need to agree with the words in the schema clauses (i.e., schema "contacts" do and schema "sms_messages" do)?

Most Liked

sb8244

sb8244

Author of From Ruby to Elixir and Real-Time Phoenix

Which page are on on when you get this? One section of the chapter calls out that you’ll get a warning because we haven’t set up the other side of the association yet. In that case, the warning goes away a few pages later.

The plurality in the book is correct. Has many is plural, belongs to is singular. Schema modules are singular but the table name is plural (table name actually doesn’t matter.)

Where Next?

Popular Pragmatic Bookshelf topics Top

ianwillie
Hello Brian, I have some problems with running the code in your book. I like the style of the book very much and I have learnt a lot as...
New
jamis
The following is cross-posted from the original Ray Tracer Challenge forum, from a post by garfieldnate. I’m cross-posting it so that the...
New
sdmoralesma
Title: Web Development with Clojure, Third Edition - migrations/create not working: p159 When I execute the command: user=> (create-...
New
gilesdotcodes
In case this helps anyone, I’ve had issues setting up the rails source code. Here were the solutions: In Gemfile, change gem 'rails' t...
New
swlaschin
The book has the same “Problem space/Solution space” diagram on page 18 as is on page 17. The correct Problem/Solution space diagrams ar...
New
leonW
I ran this command after installing the sample application: $ cards add do something --owner Brian And got a file not found error: Fil...
New
AufHe
I’m a newbie to Rails 7 and have hit an issue with the bin/Dev script mentioned on pages 112-113. Iteration A1 - Seeing the list of prod...
New
redconfetti
Docker-Machine became part of the Docker Toolbox, which was deprecated in 2020, long after Docker Desktop supported Docker Engine nativel...
New
SlowburnAZ
Getting an error when installing the dependencies at the start of this chapter: could not compile dependency :exla, "mix compile" failed...
New
roadbike
From page 13: On Python 3.7, you can install the libraries with pip by running these commands inside a Python venv using Visual Studio ...
New

Other popular topics Top

AstonJ
If it’s a mechanical keyboard, which switches do you have? Would you recommend it? Why? What will your next keyboard be? Pics always w...
New
DevotionGeo
I know that these benchmarks might not be the exact picture of real-world scenario, but still I expect a Rust web framework performing a ...
New
AstonJ
You might be thinking we should just ask who’s not using VSCode :joy: however there are some new additions in the space that might give V...
New
AstonJ
poll poll Be sure to check out @Dusty’s article posted here: An Introduction to Alternative Keyboard Layouts It’s one of the best write-...
New
AstonJ
There’s a whole world of custom keycaps out there that I didn’t know existed! Check out all of our Keycaps threads here: https://forum....
New
PragmaticBookshelf
Rust is an exciting new programming language combining the power of C with memory safety, fearless concurrency, and productivity boosters...
New
PragmaticBookshelf
Author Spotlight: Peter Ullrich @PJUllrich Data is at the core of every business, but it is useless if nobody can access and analyze ...
New
New
New
RobertRichards
Hair Salon Games for Girls Fun Girls Hair Saloon game is mainly developed for kids. This game allows users to select virtual avatars to ...
New

Sub Categories: