Module: ActiveRecord::ModelSchema::ClassMethods

Defined in:
lib/active_record/model_schema.rb

Instance Method Summary collapse

Instance Method Details

#_default_attributes ⇒ Object

:nodoc:



459
460
461
462
 
# File 'lib/active_record/model_schema.rb', line 459

def _default_attributes # :nodoc:
  load_schema
  @default_attributes ||= ActiveModel::AttributeSet.new({})
end

#attribute_types ⇒ Object

:nodoc:



401
402
403
404
 
# File 'lib/active_record/model_schema.rb', line 401

def attribute_types # :nodoc:
  load_schema
  @attribute_types ||= Hash.new(Type.default_value)
end

#attributes_builder ⇒ Object

:nodoc:



383
384
385
386
387
388
389
 
# File 'lib/active_record/model_schema.rb', line 383

def attributes_builder # :nodoc:
  unless defined?(@attributes_builder) && @attributes_builder
    defaults = _default_attributes.except(*(column_names - [primary_key]))
    @attributes_builder = ActiveModel::AttributeSet::Builder.new(attribute_types, defaults)
  end
  @attributes_builder
end

#column_defaults ⇒ Object

Returns a hash where the keys are column names and the values are default values when instantiating the Active Record object for this table.



454
455
456
457
 
# File 'lib/active_record/model_schema.rb', line 454

def column_defaults
  load_schema
  @column_defaults ||= _default_attributes.deep_dup.to_hash.freeze
end

#column_for_attribute(name) ⇒ Object

Returns the column object for the named attribute. Returns an ActiveRecord::ConnectionAdapters::NullColumn if the named attribute does not exist.

class Person < ActiveRecord::Base
end

person = Person.new
person.column_for_attribute(:name) # the result depends on the ConnectionAdapter
# => #<ActiveRecord::ConnectionAdapters::Column:0x007ff4ab083980 @name="name", @sql_type="varchar(255)", @null=true, ...>

person.column_for_attribute(:nothing)
# => #<ActiveRecord::ConnectionAdapters::NullColumn:0xXXX @name=nil, @sql_type=nil, @cast_type=#<Type::Value>, ...>



445
446
447
448
449
450
 
# File 'lib/active_record/model_schema.rb', line 445

def column_for_attribute(name)
  name = name.to_s
  columns_hash.fetch(name) do
    ConnectionAdapters::NullColumn.new(name)
  end
end

#column_names ⇒ Object

Returns an array of column names as strings.



465
466
467
 
# File 'lib/active_record/model_schema.rb', line 465

def column_names
  @column_names ||= columns.map(&:name).freeze
end

#columns ⇒ Object 



396
397
398
399
 
# File 'lib/active_record/model_schema.rb', line 396

def columns
  load_schema
  @columns ||= columns_hash.values.freeze
end

#columns_hash ⇒ Object

:nodoc:



391
392
393
394
 
# File 'lib/active_record/model_schema.rb', line 391

def columns_hash # :nodoc:
  load_schema
  @columns_hash
end

#content_columns ⇒ Object

Returns an array of column objects where the primary id, all columns ending in “_id” or “_count”, and columns used for single table inheritance have been removed.



476
477
478
479
480
481
482
 
# File 'lib/active_record/model_schema.rb', line 476

def content_columns
  @content_columns ||= columns.reject do |c|
    c.name == primary_key ||
    c.name == inheritance_column ||
    c.name.end_with?("_id", "_count")
  end.freeze
end

#full_table_name_prefix ⇒ Object

:nodoc:



246
247
248
 
# File 'lib/active_record/model_schema.rb', line 246

def full_table_name_prefix #:nodoc:
  (module_parents.detect { |p| p.respond_to?(:table_name_prefix) } || self).table_name_prefix
end

#full_table_name_suffix ⇒ Object

:nodoc:



250
251
252
 
# File 'lib/active_record/model_schema.rb', line 250

def full_table_name_suffix #:nodoc:
  (module_parents.detect { |p| p.respond_to?(:table_name_suffix) } || self).table_name_suffix
end

#ignored_columns ⇒ Object

The list of columns names the model should ignore. Ignored columns won't have attribute accessors defined, and won't be referenced in SQL queries.



290
291
292
293
294
295
296
 
# File 'lib/active_record/model_schema.rb', line 290

def ignored_columns
  if defined?(@ignored_columns)
    @ignored_columns
  else
    superclass.ignored_columns
  end
end

#ignored_columns=(columns) ⇒ Object

Sets the columns names the model should ignore. Ignored columns won't have attribute accessors defined, and won't be referenced in SQL queries.

A common usage pattern for this method is to ensure all references to an attribute have been removed and deployed, before a migration to drop the column from the database has been deployed and run. Using this two step approach to dropping columns ensures there is no code that raises errors due to having a cached schema in memory at the time the schema migration is run.

For example, given a model where you want to drop the “category” attribute, first mark it as ignored:

class Project < ActiveRecord::Base
  # schema:
  #   id         :bigint
  #   name       :string, limit: 255
  #   category   :string, limit: 255

  self.ignored_columns = [:category]
end

The schema still contains “category”, but now the model omits it, so any meta-driven code or schema caching will not attempt to use the column:

Project.columns_hash["category"] => nil

You will get an error if accessing that attribute directly, so ensure all usages of the column are removed (automated tests can help you find any usages).

user = Project.create!(name: "First Project")
user.category # => raises NoMethodError



329
330
331
332
 
# File 'lib/active_record/model_schema.rb', line 329

def ignored_columns=(columns)
  reload_schema_from_cache
  @ignored_columns = columns.map(&:to_s).freeze
end

#inheritance_column ⇒ Object

Defines the name of the table column which will store the class name on single-table inheritance situations.

The default inheritance column name is type, which means it's a reserved word inside Active Record. To be able to use single-table inheritance with another column name, or to use the column type in your own model for something else, you can set inheritance_column:

self.inheritance_column = 'zoink'



278
279
280
 
# File 'lib/active_record/model_schema.rb', line 278

def inheritance_column
  (@inheritance_column ||= nil) || superclass.inheritance_column
end

#inheritance_column=(value) ⇒ Object

Sets the value of inheritance_column



283
284
285
286
 
# File 'lib/active_record/model_schema.rb', line 283

def inheritance_column=(value)
  @inheritance_column = value.to_s
  @explicit_inheritance_column = true
end

#next_sequence_value ⇒ Object

Returns the next value that will be used as the primary key on an insert statement.



374
375
376
 
# File 'lib/active_record/model_schema.rb', line 374

def next_sequence_value
  connection.next_sequence_value(sequence_name)
end

#prefetch_primary_key? ⇒ Boolean

Determines if the primary key values should be selected from their corresponding sequence before the insert statement.

Returns:

  • (Boolean) 


368
369
370
 
# File 'lib/active_record/model_schema.rb', line 368

def prefetch_primary_key?
  connection.prefetch_primary_key?(table_name)
end

#protected_environments ⇒ Object

The array of names of environments where destructive actions should be prohibited. By default, the value is ["production"].



256
257
258
259
260
261
262
 
# File 'lib/active_record/model_schema.rb', line 256

def protected_environments
  if defined?(@protected_environments)
    @protected_environments
  else
    superclass.protected_environments
  end
end

#protected_environments=(environments) ⇒ Object

Sets an array of names of environments where destructive actions should be prohibited.



265
266
267
 
# File 'lib/active_record/model_schema.rb', line 265

def protected_environments=(environments)
  @protected_environments = environments.map(&:to_s)
end

#quoted_table_name ⇒ Object

Returns a quoted version of the table name, used to construct SQL statements.



231
232
233
 
# File 'lib/active_record/model_schema.rb', line 231

def quoted_table_name
  @quoted_table_name ||= connection.quote_table_name(table_name)
end

#reset_column_information ⇒ Object

Resets all the cached information about columns, which will cause them to be reloaded on the next request.

The most common usage pattern for this method is probably in a migration, when just after creating a table you want to populate it with some default values, eg:

class CreateJobLevels < ActiveRecord::Migration[6.0]
  def up
    create_table :job_levels do |t|
      t.integer :id
      t.string :name

      t.timestamps
    end

    JobLevel.reset_column_information
    %w{assistant executive manager director}.each do |type|
      JobLevel.create(name: type)
    end
  end

  def down
    drop_table :job_levels
  end
end



510
511
512
513
514
515
516
517
 
# File 'lib/active_record/model_schema.rb', line 510

def reset_column_information
  connection.clear_cache!
  ([self] + descendants).each(&:undefine_attribute_methods)
  connection.schema_cache.clear_data_source_cache!(table_name)

  reload_schema_from_cache
  initialize_find_by_cache
end

#reset_sequence_name ⇒ Object

:nodoc:



342
343
344
345
 
# File 'lib/active_record/model_schema.rb', line 342

def reset_sequence_name #:nodoc:
  @explicit_sequence_name = false
  @sequence_name          = connection.default_sequence_name(table_name, primary_key)
end

#reset_table_name ⇒ Object

Computes the table name, (re)sets it internally, and returns it.



236
237
238
239
240
241
242
243
244
 
# File 'lib/active_record/model_schema.rb', line 236

def reset_table_name #:nodoc:
  self.table_name = if abstract_class?
    superclass == Base ? nil : superclass.table_name
  elsif superclass.abstract_class?
    superclass.table_name || compute_table_name
  else
    compute_table_name
  end
end

#sequence_name ⇒ Object 



334
335
336
337
338
339
340
 
# File 'lib/active_record/model_schema.rb', line 334

def sequence_name
  if base_class?
    @sequence_name ||= reset_sequence_name
  else
    (@sequence_name ||= nil) || base_class.sequence_name
  end
end

#sequence_name=(value) ⇒ Object

Sets the name of the sequence to use when generating ids to the given value, or (if the value is nil or false) to the value returned by the given block. This is required for Oracle and is useful for any database which relies on sequences for primary key generation.

If a sequence name is not explicitly set when using Oracle, it will default to the commonly used pattern of: ##table_name_seq

If a sequence name is not explicitly set when using PostgreSQL, it will discover the sequence corresponding to your primary key for you.

class Project < ActiveRecord::Base
  self.sequence_name = "projectseq"   # default would have been "project_seq"
end



361
362
363
364
 
# File 'lib/active_record/model_schema.rb', line 361

def sequence_name=(value)
  @sequence_name          = value.to_s
  @explicit_sequence_name = true
end

#symbol_column_to_string(name_symbol) ⇒ Object

:nodoc:



469
470
471
472
 
# File 'lib/active_record/model_schema.rb', line 469

def symbol_column_to_string(name_symbol) # :nodoc:
  @symbol_column_to_string_name_hash ||= column_names.index_by(&:to_sym)
  @symbol_column_to_string_name_hash[name_symbol]
end

#table_exists? ⇒ Boolean

Indicates whether the table associated with this class exists

Returns:

  • (Boolean) 


379
380
381
 
# File 'lib/active_record/model_schema.rb', line 379

def table_exists?
  connection.schema_cache.data_source_exists?(table_name)
end

#table_name ⇒ Object

Guesses the table name (in forced lower-case) based on the name of the class in the inheritance hierarchy descending directly from ActiveRecord::Base. So if the hierarchy looks like: Reply < Message < ActiveRecord::Base, then Message is used to guess the table name even when called on Reply. The rules used to do the guess are handled by the Inflector class in Active Support, which knows almost all common English inflections. You can add new inflections in config/initializers/inflections.rb.

Nested classes are given table names prefixed by the singular form of the parent's table name. Enclosing modules are not considered.

Examples

class Invoice < ActiveRecord::Base
end

file                  class               table_name
invoice.rb            Invoice             invoices

class Invoice < ActiveRecord::Base
  class Lineitem < ActiveRecord::Base
  end
end

file                  class               table_name
invoice.rb            Invoice::Lineitem   invoice_lineitems

module Invoice
  class Lineitem < ActiveRecord::Base
  end
end

file                  class               table_name
invoice/lineitem.rb   Invoice::Lineitem   lineitems

Additionally, the class-level table_name_prefix is prepended and the table_name_suffix is appended. So if you have “myapp_” as a prefix, the table name guess for an Invoice class becomes “myapp_invoices”. Invoice::Lineitem becomes “myapp_invoice_lineitems”.

You can also set your own table name explicitly:

class Mouse < ActiveRecord::Base
  self.table_name = "mice"
end



205
206
207
208
 
# File 'lib/active_record/model_schema.rb', line 205

def table_name
  reset_table_name unless defined?(@table_name)
  @table_name
end

#table_name=(value) ⇒ Object

Sets the table name explicitly. Example:

class Project < ActiveRecord::Base
  self.table_name = "project"
end



215
216
217
218
219
220
221
222
223
224
225
226
227
228
 
# File 'lib/active_record/model_schema.rb', line 215

def table_name=(value)
  value = value && value.to_s

  if defined?(@table_name)
    return if value == @table_name
    reset_column_information if connected?
  end

  @table_name        = value
  @quoted_table_name = nil
  @arel_table        = nil
  @sequence_name     = nil unless defined?(@explicit_sequence_name) && @explicit_sequence_name
  @predicate_builder = nil
end

#type_for_attribute(attr_name, &block) ⇒ Object

Returns the type of the attribute with the given name, after applying all modifiers. This method is the only valid source of information for anything related to the types of a model's attributes. This method will access the database and load the model's schema if it is required.

The return value of this method will implement the interface described by ActiveModel::Type::Value (though the object itself may not subclass it).

attr_name The name of the attribute to retrieve the type for. Must be a string or a symbol.



421
422
423
424
425
426
427
428
429
430
 
# File 'lib/active_record/model_schema.rb', line 421

def type_for_attribute(attr_name, &block)
  attr_name = attr_name.to_s
  attr_name = attribute_aliases[attr_name] || attr_name

  if block
    attribute_types.fetch(attr_name, &block)
  else
    attribute_types[attr_name]
  end
end

#yaml_encoder ⇒ Object

:nodoc:



406
407
408
 
# File 'lib/active_record/model_schema.rb', line 406

def yaml_encoder # :nodoc:
  @yaml_encoder ||= ActiveModel::AttributeSet::YAMLEncoder.new(attribute_types)
end