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Day 1: a confusing Rails error message
Today I started an Recurse Center batch! I got to meet a few people, and started on a tiny fun Rails project. I think I won’t talk too much about what the project actually is today, but here are some quick notes on a day with Rails:
some notes on getting started
The main thing I learned about setting up a Rails project is that
- it uses sqlite by default, you have to tell it to use Postgres
- there are a ton of things that Rails includes by default that you can disable.
I installed and rm -rf’d Rails maybe 7 times before I was satisfied with it and ended up with this incantation:
rails new . -d postgresql --skip-sprockets --skip-javascript`
Basically because I definitely wanted to use Postgres and not sqlite, and skipping sprockets and javascript seemed to make installing Rails faster, and I figured I could install them later if I decided I wanted them.
the official Rails guide is really good
I used 2 main resources for creating my starter Rails app:
- DHH’s original Rails talk from 2005 https://www.youtube.com/watch?v=Gzj723LkRJY (which I didn’t watch this time, but I watched the last time I spent a day with Rails, and I found it pretty inspiring and helpful)
- The official Rails “getting started” guide, which seems pretty short and clear https://guides.rubyonrails.org/v5.0/getting_started.html
a mysterious error message: undefined method 'user'
I love bugs, so here’s a weird Rails error I ran into today! I had some code that looked like this:
@user = User.new(user_params)
@user.save
Pretty simple, right? But when that code ran, I got this baffling error message:
undefined method `user' for #<User:0x00007fb6f4012ab8> Did you mean? super
I was EXTREMELY confused about what was going on here because I hadn’t called a method called user. I’d called .save. What???? I stayed confused and frustrated about this for maybe 20 minutes, and then finally I looked at my User model and found this code:
class User < ApplicationRecord
has_secure_password
validates :user, presence: true, uniqueness: true
end
validates :user... was supposed to be some Rails magic validating that every User had a username, and that usernames had to be unique. But I’d made a typo, and I’d written user and not username. I fixed this and then everything worked! hooray!
I still don’t understand how I was supposed to debug this though: the stack trace told me the problem was with the @user.save line, and never mentioned that validates :user thing at all. I feel like there must be a way to debug this but I don’t know what it is.
The whole point of me playing with Rails is to see how the Rails magic plays out in practice so this was a fun bug to hit early on.
a simple user management system
I decided I wanted users in my toy app. Some Googling showed me that there’s an extremely popular gem called devise that handles users. I found the README a little overwhelming and I knew that I wanted a very minimal user management system in my toy app, so instead I followed this guide called Authentication from Scratch with Rails 5.2 which seems to be working out so far. Rails seems to already have a bunch of built in stuff for managing users – I was really surprised by how short that guide was and how little code I needed to write.
I learned while implementing users that Rails has a built in magical session management system (see How Rails Sessions Work. By default all the session data seems to be stored in a cookie on the user’s computer, though I guess you can also store the session data in a database if it gets too big for a cookie.
It’s definitely kind of strange to already have a session management system and cookies and users without quite knowing what’s going on exactly, but it’s also kind of fun! We’ll see how it goes.
tomorrow: more rails!
Maybe tomorrow I can actually make some progress on implementing my fun rails app idea!
via: https://jvns.ca/blog/2020/11/09/day-1--a-little-rails-/
作者：Julia Evans 选题：lujun9972 译者：译者ID 校对：校对者ID