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

johnp
Running the examples in chapter 5 c under pytest 5.4.1 causes an AttributeError: ‘module’ object has no attribute ‘config’. In particula...
New
mikecargal
Title: Hands-On Rust (Chap 8 (Adding a Heads Up Display) It looks like ​.with_simple_console_no_bg​(SCREEN_WIDTH*2, SCREEN_HEIGHT*2...
New
Charles
In general, the book isn’t yet updated for Phoenix version 1.6. On page 18 of the book, the authors indicate that an auto generated of ro...
New
oaklandgit
Hi, I completed chapter 6 but am getting the following error when running: thread 'main' panicked at 'Failed to load texture: IoError(O...
New
taguniversalmachine
Hi, I am getting an error I cannot figure out on my test. I have what I think is the exact code from the book, other than I changed “us...
New
rainforest
Hi, I’ve got a question about the implementation of PubSub when using a Phoenix.Socket.Transport behaviour rather than channels. Before ...
New
Henrai
Hi, I’m working on the Chapter 8 of the book. After I add add the point_offset, I’m still able to see acne: In the image above, I re...
New
tkhobbes
After some hassle, I was able to finally run bin/setup, now I have started the rails server but I get this error message right when I vis...
New
SlowburnAZ
Getting an error when installing the dependencies at the start of this chapter: could not compile dependency :exla, "mix compile" failed...
New
dachristenson
@mfazio23 Android Studio will not accept anything I do when trying to use the Transformations class, as described on pp. 140-141. Googl...
New

Other popular topics Top

PragmaticBookshelf
Stop developing web apps with yesterday’s tools. Today, developers are increasingly adopting Clojure as a web-development platform. See f...
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
DevotionGeo
The V Programming Language Simple language for building maintainable programs V is already mentioned couple of times in the forum, but I...
New
PragmaticBookshelf
Use WebRTC to build web applications that stream media and data in real time directly from one user to another, all in the browser. ...
New
PragmaticBookshelf
Author Spotlight Rebecca Skinner @RebeccaSkinner Welcome to our latest author spotlight, where we sit down with Rebecca Skinner, auth...
New
PragmaticBookshelf
Author Spotlight: VM Brasseur @vmbrasseur We have a treat for you today! We turn the spotlight onto Open Source as we sit down with V...
New
hilfordjames
There appears to have been an update that has changed the terminology for what has previously been known as the Taskbar Overflow - this h...
New
sir.laksmana_wenk
I’m able to do the “artistic” part of game-development; character designing/modeling, music, environment modeling, etc. However, I don’t...
New
AstonJ
Curious what kind of results others are getting, I think actually prefer the 7B model to the 32B model, not only is it faster but the qua...
New
PragmaticBookshelf
A concise guide to MySQL 9 database administration, covering fundamental concepts, techniques, and best practices. Neil Smyth MySQL...
New

Sub Categories: