使用多个关系时，rom-rb形成验证。

Question

我正在尝试http://rom-rb.org/，但我想不出如何在多个源模型的存在下通过存在性验证。我希望下面的脚本可以保存一个新的活动和组织者，但是它说event_name不存在。

我遗漏了什么？

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'
  gem 'rom'
  gem 'rom-sql'
  gem 'rom-rails'
  gem 'activemodel'
  gem 'sqlite3'
  gem 'activesupport'
end

require 'rom'
require 'rom-rails'

`rm -Rf /tmp/romtest.sqlite`
ROM.setup(:sql, 'sqlite:///tmp/romtest.sqlite')

class Events < ROM::Relation[:sql]
end

class Organisers < ROM::Relation[:sql]
end

class CreateEvent < ROM::Commands::Create[:sql]
  relation :events
  register_as :create
  result :one

  associates :organiser, key: [:organiser_id, :id]
end

class CreateOrganiser < ROM::Commands::Create[:sql]
  relation :organisers
  register_as :create
  result :one
end

class CreateEventWithOrganiser < ROM::Model::Form
  commands organisers: :create, events: :create

  input do
    attribute :email
    attribute :event_name
  end

  validations do
    validates :event_name, presence: true
  end

  def commit!
    command = organisers.create.with(
      email: email,
    ) >> events.create.with(
      name: event_name,
    )

    command.transaction do
      command.call
    end
  end
end

ROM.finalize
rom = ROM.env
gateway = rom.gateways.fetch(:default)
migration = gateway.migration do
  change do
    create_table :organisers do
      primary_key :id
      column :email, String, null: false
    end

    create_table :events do
      primary_key :id
      column :name, String, null: false
      column :organiser_id, Integer, null: false
    end
  end
end

migration.apply(gateway.connection, :up)

f = CreateEventWithOrganiser.build(
  email:      'test@example.com',
  event_name: 'Test Event'
)

# Unexpectedly fails
f.save
puts f.errors.full_messages
# => "Event name can't be blank"

Answer 1

下面是您的脚本的更新版本，该版本工作如下：

require 'rom'
require 'rom-rails'

`rm -Rf /tmp/romtest.sqlite`
ROM.setup(:sql, 'sqlite:///tmp/romtest.sqlite')

class Events < ROM::Relation[:sql]
end

class Organisers < ROM::Relation[:sql]
end

class CreateEvent < ROM::Commands::Create[:sql]
  relation :events
  register_as :create
  result :one

  associates :organiser, key: [:organiser_id, :id]
end

class CreateOrganiser < ROM::Commands::Create[:sql]
  relation :organisers
  register_as :create
  result :one
end

class CreateEventWithOrganiser < ROM::Model::Form
  inject_commands_for :organisers, :events

  input do
    attribute :email
    attribute :event_name
  end

  validations do
    validates :event_name, presence: true
  end

  def commit!
    validate!

    return if errors.any?

    command = organisers.create.with(
      email: email
    ) >> events.create.with(
      name: event_name
    )

    command.transaction do
      command.call
    end
  end
end

ROM.finalize
rom = ROM.env
gateway = rom.gateways.fetch(:default)
migration = gateway.migration do
  change do
    create_table :organisers do
      primary_key :id
      column :email, String, null: false
    end

    create_table :events do
      primary_key :id
      column :name, String, null: false
      column :organiser_id, Integer, null: false
    end
  end
end

migration.apply(gateway.connection, :up)

f = CreateEventWithOrganiser.build(
  email:      'test@example.com',
  event_name: 'Test Event'
)

puts f.save.result.inspect
# #<ROM::Commands::Result::Success:0x007fa92b589ea0 @value={:id=>1, :name=>"Test Event", :organiser_id=>1}>

它不能使用commands的原因是该方法将为您的表单生成命令对象，并为每个命令设置提供的验证，只有在使用单个命令时才能正确工作。否则，每个命令都会使用相同的验证器，这是没有意义的。当您使用inject_commands_for时，它将获取您自己的命令，其中没有设置验证器，因此您可以自己处理验证。

我认为我们应该停止对命令设置验证器，这将使您的原始示例工作，但请注意，您需要自己调用validate!。

我希望这能帮到你。

我还创建了一个要点，演示如何在没有表单的情况下进行相同的操作：https://gist.github.com/solnic/3b68342482cf1414f719