我将按照以下指南开始使用hanami：
https://guides.hanamirb.org/v2.0/introduction/getting-started/
我更喜欢Sequel，而不是ROM，但我偶然发现了它的持久性：
https://guides.hanamirb.org/v2.0/introduction/getting-started/#persisting-books
在我的gemfile中，我使用了sequel和pg，而不是rom。
我将以下内容添加到config/app.rb：

require "sequel"

config/providers/persistence.rb包含以下内容：

Hanami.app.register_provider :persistence, namespace: true do
  prepare do

    #config = ROM::Configuration.new(:sql, target["settings"].database_url)
    config = DB = Sequel.connect(database_url) 

    register "config", config
    register "db", config.gateways[:default].connection
  end

  start do
    config = target["persistence.config"]

    # config.auto_registration(
    #   target.root.join("lib/bookshelf/persistence"),
    #   namespace: "Bookshelf::Persistence"
    # )

    register "sequel", DB
  end
end

config/settings.rb：

module Bookshelf
  class Settings < Hanami::Settings
    # Define your app settings here, for example:
    #
    # setting :my_flag, default: false, constructor: Types::Params::Bool

    setting :database_url, constructor: Types::String
  end
end

最后在.env和.env.test文件中定义database_url。

# .env
DATABASE_URL=postgres://thiebo@localhost:5432/bookshelf_development

从hanami控制台运行此命令可以正常工作：

moi@Hugo bookshelf % bundle exec hanami console
bookshelf[development]> Hanami.app["settings"].database_url
=> "postgres://moi@localhost:5432/bookshelf_development"
bookshelf[development]>

Sequel允许将迁移作为rake任务运行：www.example.comhttp://sequel.jeremyevans.net/rdoc/files/doc/migration_rdoc.html#label-Running+migrations+from+a+Rake+task
我的Rakefile：

require "sequel"

namespace :db do
  desc "Run migrations"
  task :migrate, [:version] do |t, args|
    require "sequel/core"
    Sequel.extension :migration
    version = args[:version].to_i if args[:version]
    Sequel.connect(ENV.fetch("DATABASE_URL")) do |db|
      Sequel::Migrator.run(db, "db/migrations", target: version)
    end
  end
end

但是......当我运行时，尝试从控制台运行迁移，如Sequel文档所示：

thiebo@Hugo bookshelf % rake db:migrate           
rake aborted!
KeyError: key not found: "DATABASE_URL"
/Users/thiebo/bookshelf/Rakefile:12:in `fetch'
/Users/thiebo/bookshelf/Rakefile:12:in `block (2 levels) in <top (required)>'
/Users/thiebo/.rvm/gems/ruby-3.0.0/gems/rake-13.0.6/exe/rake:27:in `<top (required)>'
/Users/thiebo/.rvm/gems/ruby-3.0.0/bin/ruby_executable_hooks:22:in `eval'
/Users/thiebo/.rvm/gems/ruby-3.0.0/bin/ruby_executable_hooks:22:in `<main>'
Tasks: TOP => db:migrate
(See full trace by running task with --trace)

(it也不适用于database_url而不是DATABASE_URL。同样的错误...）