How to create ActiveRecord tableless Model in Rails 5?

Question

I tried create new model which has auto type casting without table in database. I've tried to inherit from ActiveRecord::Base it's thrown exception ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR: relation "people" does not exist

Class implementation:

class Person < ActiveRecord::Base

  def self.columns
    @columns ||= [];
  end

  def self.column(name, sql_type = nil, default = nil, null = true)
    @columns << ActiveRecord::ConnectionAdapters::Column.new(name.to_s, default, sql_type.to_s, null)
  end

  columns

  column :from_email, :string
  column :to_email, :string
  column :article_id, :integer
  column :message, :text

  def initialize
  end

end

stack trace:

ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR:  relation "people" does not exist
LINE 8:                WHERE a.attrelid = '"people"'::regclass
^
  :               SELECT a.attname, format_type(a.atttypid, a.atttypmod),
                         pg_get_expr(d.adbin, d.adrelid), a.attnotnull, a.atttypid, a.atttypmod,
                         (SELECT c.collname FROM pg_collation c, pg_type t
                         WHERE c.oid = a.attcollation AND t.oid = a.atttypid AND a.attcollation <> t.typcollation),
                         col_description(a.attrelid, a.attnum) AS comment
FROM pg_attribute a LEFT JOIN pg_attrdef d
ON a.attrelid = d.adrelid AND a.attnum = d.adnum
WHERE a.attrelid = '"people"'::regclass
AND a.attnum > 0 AND NOT a.attisdropped
ORDER BY a.attnum

from /activerecord-5.0.1/lib/active_record/connection_adapters/postgresql/database_statements.rb:88:in `async_exec'
from /activerecord-5.0.1/lib/active_record/connection_adapters/postgresql/database_statements.rb:88:in `block in query'
from /activerecord-5.0.1/lib/active_record/connection_adapters/abstract_adapter.rb:589:in `block in log'
from /activesupport-5.0.1/lib/active_support/notifications/instrumenter.rb:21:in `instrument'
from /activerecord-5.0.1/lib/active_record/connection_adapters/abstract_adapter.rb:583:in `log'
from /activerecord-5.0.1/lib/active_record/connection_adapters/postgresql/database_statements.rb:87:in `query'
from /activerecord-5.0.1/lib/active_record/connection_adapters/postgresql_adapter.rb:739:in `column_definitions'
from /activerecord-5.0.1/lib/active_record/connection_adapters/postgresql/schema_statements.rb:227:in `columns'
from /activerecord-5.0.1/lib/active_record/connection_adapters/schema_cache.rb:56:in `columns'
from /activerecord-5.0.1/lib/active_record/connection_adapters/schema_cache.rb:62:in `columns_hash'
from /activerecord-5.0.1/lib/active_record/model_schema.rb:441:in `load_schema!'
from /activerecord-5.0.1/lib/active_record/attributes.rb:233:in `load_schema!'
from /activerecord-5.0.1/lib/active_record/attribute_decorators.rb:28:in `load_schema!'
from /activerecord-5.0.1/lib/active_record/model_schema.rb:436:in `load_schema'
from /activerecord-5.0.1/lib/active_record/model_schema.rb:349:in `attribute_types'
from /activerecord-5.0.1/lib/active_record/attribute_methods.rb:179:in `has_attribute?'
... 3 levels...
from /railties-5.0.1/lib/rails/commands/console_helper.rb:9:in `start'
from /railties-5.0.1/lib/rails/commands/commands_tasks.rb:78:in `console'
from /railties-5.0.1/lib/rails/commands/commands_tasks.rb:49:in `run_command!'
from /railties-5.0.1/lib/rails/commands.rb:18:in `<top (required)>'
from /activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
from /activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `block in require'
from /activesupport-5.0.1/lib/active_support/dependencies.rb:259:in `load_dependency'
from /activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
from /project/rails/bin/rails:9:in `<top (required)>'
from /activesupport-5.0.1/lib/active_support/dependencies.rb:287:in `load'
from /activesupport-5.0.1/lib/active_support/dependencies.rb:287:in `block in load'
from /activesupport-5.0.1/lib/active_support/dependencies.rb:259:in `load_dependency'
from /activesupport-5.0.1/lib/active_support/dependencies.rb:287:in `load'

EDIT:

Neither

extend ActiveModel::Naming

nor

include ActiveModel::Model

cannot implement the implicit type conversion.

Answer 1

You can use

class Person
  include ActiveModel::Model
  attr_accessor :name, :email
  ...
end

and then you get a lot of the functionality of an activerecord model, like validations.