1

我正在尝试使用 sqlite3 来掌握 rom-rb 持久性库。

我运行了以下迁移，其中包括一个NOT NULL约束：

ROM::SQL.migration do
  change do
    create_table :users do
      primary_key :id
      column :name, String, null: false
      column :age, Integer
      column :is_admin, TrueClass
    end
  end
end

这是我的简单app.rb：

require 'rom'

rom = ROM.container(:sql, 'sqlite://db/my-db-file.db') do |config|
  class Users < ROM::Relation[:sql]
    schema(infer: true)
  end

  config.relation(:users)
end

users = rom.relations[:users]
puts users.to_a.inspect # => []

create_user = users.command(:create)
create_user.call( name: 'Rob', age: 30, is_admin: true )
puts users.to_a.inspect # never reached

尝试运行此脚本会产生以下输出：

Roberts-MacBook-Pro:my-rom-demo Rob$ ruby app.rb 
[]
/Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sqlite3-1.3.13/lib/sqlite3/statement.rb:108:in `step': SQLite3::ConstraintException: NOT NULL constraint failed: users.name (ROM::SQL::NotNullConstraintError)
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sqlite3-1.3.13/lib/sqlite3/statement.rb:108:in `block in each'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sqlite3-1.3.13/lib/sqlite3/statement.rb:107:in `loop'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sqlite3-1.3.13/lib/sqlite3/statement.rb:107:in `each'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sqlite3-1.3.13/lib/sqlite3/database.rb:156:in `to_a'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sqlite3-1.3.13/lib/sqlite3/database.rb:156:in `block in execute'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sqlite3-1.3.13/lib/sqlite3/database.rb:95:in `prepare'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sqlite3-1.3.13/lib/sqlite3/database.rb:137:in `execute'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sequel-5.11.0/lib/sequel/adapters/sqlite.rb:189:in `block (2 levels) in _execute'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sequel-5.11.0/lib/sequel/database/logging.rb:38:in `log_connection_yield'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sequel-5.11.0/lib/sequel/adapters/sqlite.rb:189:in `block in _execute'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sequel-5.11.0/lib/sequel/database/connecting.rb:253:in `block in synchronize'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sequel-5.11.0/lib/sequel/connection_pool/threaded.rb:91:in `hold'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sequel-5.11.0/lib/sequel/database/connecting.rb:253:in `synchronize'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sequel-5.11.0/lib/sequel/adapters/sqlite.rb:180:in `_execute'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sequel-5.11.0/lib/sequel/adapters/sqlite.rb:146:in `execute_insert'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sequel-5.11.0/lib/sequel/dataset/actions.rb:1099:in `execute_insert'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/sequel-5.11.0/lib/sequel/dataset/actions.rb:399:in `insert'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/rom-sql-2.5.0/lib/rom/sql/relation/writing.rb:39:in `insert'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/rom-sql-2.5.0/lib/rom/sql/commands/create.rb:46:in `block in insert'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/rom-sql-2.5.0/lib/rom/sql/commands/create.rb:46:in `map'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/rom-sql-2.5.0/lib/rom/sql/commands/create.rb:46:in `insert'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/rom-sql-2.5.0/lib/rom/sql/commands/create.rb:31:in `execute'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/rom-core-4.2.1/lib/rom/command.rb:280:in `call'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/rom-sql-2.5.0/lib/rom/sql/commands/error_wrapper.rb:16:in `call'
    from /Rob.rvm/gems/ruby-2.4.0@learn-rails/gems/rom-core-4.2.1/lib/rom/commands/composite.rb:17:in `call'
    from app.rb:15:in `<main>'

为什么name在我提供属性时它认为我的属性为空？

4

1 回答 1

2

注意： 经过一些测试和了解 ops gem 版本后，我修改了我的答案

您收到NULL CONSTRAINT错误的原因是因为 ROM 没有为 users 表加载模式。

当您在下面定义容器时

rom = ROM.container(:sql, 'sqlite://db/my-db-file.db') do |config|
  class Users < ROM::Relation[:sql]
    schema(infer: true)
  end

  config.relation(:users)
end

你定义了两件事，一个绑定到一个常量的关系类Users和一个自动生成的同名关系，但实际上是在 ROM 容器中注册的。实际上，Users常数关系被忽略了。这很重要的原因是因为自动生成的关系不会自动从数据库中推断架构，因此当您将数据写出时，架构会强制删除所有未知键，从而导致错误。您发送到数据库的所有内容都是{}.

要修复错误，只需告诉关系推断架构 - 可以在下面看到一个示例。

require 'rom'
require 'rom/sql'
require 'sqlite3'

puts "ROM Version #{ROM::Core::VERSION}" # 4.2.1
puts "ROM Version #{ROM::SQL::VERSION}" # 2.5.0
puts "Sequel Version #{Sequel::VERSION}" # 5.11.0
puts "SQLite3 Gem Version #{SQLite3::VERSION}" # 1.3.13

opts = {
  adapter: :sqlite,
  database: 'c:/mydb.db'
}

rom = ROM.container(:sql, opts) do |c|
  # Just another way to write the same users table
  # c.gateways[:default].create_table(:users) do
  #   column :id,   :integer, primary_key: true
  #   column :name, :string, null: false
  #   column :age,  :integer
  #   column :is_admin, :bool
  # end

  c.gateways[:default].create_table :users do
    primary_key :id
    column :name, String, null: false
    column :age, Integer
    column :is_admin, TrueClass
  end

  c.relation(:users) do
    schema(infer: true)
  end
end

users = rom.relations[:users]
puts users.to_a.inspect # => []

create_user = users.command(:create)
create_user.call(name: 'Rob', age: 30, is_admin: true)
puts users.to_a.inspect # never reached

# Uncomment if you want to see the users schema
# puts users.dataset.db.schema(:users)

如果您想使用独立的关系类而不是容器配置 dsl，那么我建议您阅读Auto Registration system。

数据库创建问题

有很多事情可能会阻止创建 sqlite 数据库。

  • 可能是权限问题
  • 目录结构可能不存在
  • Sqlite 可能不会被编译来处理 URI（仅当您file://在路径中使用时才重要）[参见 sqlite 文档]

我的建议是在使用 sqlite 和 ROM 时，使用上面脚本中的 opts 哈希示例，并尝试使用当前工作目录中的相对路径。这似乎总是有效的。

于 2018-08-21T22:48:46.240 回答