For development, I don't guess configuring Dockerfile and docker-compose (just if you want, sure) is necessary.

Pre-reqs

This short tutorial was built using WSL2, integrated docker, ruby 3.2.2 and rails 7.0.6.

Getting Started

We're going to basically create a new rails application, raise and connect the docker postgresql container with the app.

I like creating my projects in ~/projects
$ mkdir ~/projects && cd projects
$ rails new myapp -d postgresql

You don't need the postgresql installed, just the necessary packages to run it. If you have a problem with the pg gem, make sure the following packages are installed.

on ubuntu
$ sudo apt-get install libpq-dev

on arch $ yay -S postgresql-libs or just $ sudo pacman -S postgresql-libs

After this, you can raise the container with the postgres replacing the {} for the name that you want.

$ docker run --name {container_name} -e POSTGRES_PASSWORD={password} -e POSTGRES_USER={username} -p 5432:5432 -v $HOME/docker/volumes/postgres:/var/lib/postgresql/data -d postgres:14.2-alpine

This command will raise the container binding the 5432 port and setting the volume, you can change the postgres:14.2-alpine for another image.

Now you have to set the /config/database.yml with the right params to connect in the postgres container.

Your file will be like this:

default: &default
  adapter: postgresql
  encoding: unicode
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  host: localhost
  port: 5432
  password: {your_password}
  username: {your_username}

development:
  <<: *default
  database: {myapp_development_db}

test:
  <<: *default
  database: {myapp_test_db}

production:
  <<: *default
  database: {myapp_production_db}
  username: {your_prod_username}
  password: {your_prod_password}

I put the password and username in default, but the best is to have a user and password for the dev, test and prod. And put all the values on a .env file.

If all occur well you just have to run
$ rails s
and you can start your app development.