module ActiveRecord::ModelSchema::ClassMethods

Public Instance Methods

column_defaults() click to toggle source

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

# File lib/active_record/model_schema.rb, line 382
def column_defaults
  load_schema
  _default_attributes.to_hash
end
column_names() click to toggle source

Returns an array of column names as strings.

# File lib/active_record/model_schema.rb, line 392
def column_names
  @column_names ||= columns.map(&:name)
end
columns() click to toggle source
# File lib/active_record/model_schema.rb, line 347
def columns
  load_schema
  @columns ||= columns_hash.values
end
content_columns() click to toggle source

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.

# File lib/active_record/model_schema.rb, line 398
def content_columns
  @content_columns ||= columns.reject do |c|
    c.name == primary_key ||
    c.name == inheritance_column ||
    c.name.end_with?("_id") ||
    c.name.end_with?("_count")
  end
end
inheritance_column() click to toggle source

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'
# File lib/active_record/model_schema.rb, line 275
def inheritance_column
  (@inheritance_column ||= nil) || superclass.inheritance_column
end
inheritance_column=(value) click to toggle source

Sets the value of #inheritance_column

# File lib/active_record/model_schema.rb, line 280
def inheritance_column=(value)
  @inheritance_column = value.to_s
  @explicit_inheritance_column = true
end
next_sequence_value() click to toggle source

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

# File lib/active_record/model_schema.rb, line 325
def next_sequence_value
  connection.next_sequence_value(sequence_name)
end
prefetch_primary_key?() click to toggle source

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

# File lib/active_record/model_schema.rb, line 319
def prefetch_primary_key?
  connection.prefetch_primary_key?(table_name)
end
quoted_table_name() click to toggle source

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

# File lib/active_record/model_schema.rb, line 243
def quoted_table_name
  @quoted_table_name ||= connection.quote_table_name(table_name)
end
reset_column_information() click to toggle source

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[5.0]
  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
# File lib/active_record/model_schema.rb, line 433
def reset_column_information
  connection.clear_cache!
  undefine_attribute_methods
  connection.schema_cache.clear_data_source_cache!(table_name)

  reload_schema_from_cache
  initialize_find_by_cache
end
sequence_name() click to toggle source
# File lib/active_record/model_schema.rb, line 285
def sequence_name
  if base_class == self
    @sequence_name ||= reset_sequence_name
  else
    (@sequence_name ||= nil) || base_class.sequence_name
  end
end
sequence_name=(value) click to toggle source

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
# File lib/active_record/model_schema.rb, line 312
def sequence_name=(value)
  @sequence_name          = value.to_s
  @explicit_sequence_name = true
end
table_exists?() click to toggle source

Indicates whether the table associated with this class exists

# File lib/active_record/model_schema.rb, line 330
def table_exists?
  connection.schema_cache.data_source_exists?(table_name)
end
table_name() click to toggle source

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
# File lib/active_record/model_schema.rb, line 217
def table_name
  reset_table_name unless defined?(@table_name)
  @table_name
end
table_name=(value) click to toggle source

Sets the table name explicitly. Example:

class Project < ActiveRecord::Base
  self.table_name = "project"
end
# File lib/active_record/model_schema.rb, line 227
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) click to toggle source

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

# File lib/active_record/model_schema.rb, line 372
def type_for_attribute(attr_name, &block)
  if block
    attribute_types.fetch(attr_name, &block)
  else
    attribute_types[attr_name]
  end
end

Protected Instance Methods

initialize_load_schema_monitor() click to toggle source
# File lib/active_record/model_schema.rb, line 444
def initialize_load_schema_monitor
  @load_schema_monitor = Monitor.new
end

Private Instance Methods

compute_table_name() click to toggle source

Computes and returns a table name according to default conventions.

# File lib/active_record/model_schema.rb, line 508
def compute_table_name
  base = base_class
  if self == base
    # Nested classes are prefixed with singular parent table name.
    if parent < Base && !parent.abstract_class?
      contained = parent.table_name
      contained = contained.singularize if parent.pluralize_table_names
      contained += "_"
    end

    "#{full_table_name_prefix}#{contained}#{undecorated_table_name(name)}#{full_table_name_suffix}"
  else
    # STI subclasses always use their superclass' table.
    base.table_name
  end
end
inherited(child_class) click to toggle source
Calls superclass method
# File lib/active_record/model_schema.rb, line 450
def inherited(child_class)
  super
  child_class.initialize_load_schema_monitor
end
load_schema() click to toggle source
# File lib/active_record/model_schema.rb, line 459
def load_schema
  return if schema_loaded?
  @load_schema_monitor.synchronize do
    return if defined?(@columns_hash) && @columns_hash

    load_schema!

    @schema_loaded = true
  end
end
load_schema!() click to toggle source
# File lib/active_record/model_schema.rb, line 470
def load_schema!
  @columns_hash = connection.schema_cache.columns_hash(table_name).except(*ignored_columns)
  @columns_hash.each do |name, column|
    define_attribute(
      name,
      connection.lookup_cast_type_from_column(column),
      default: column.default,
      user_provided_default: false
    )
  end
end
reload_schema_from_cache() click to toggle source
# File lib/active_record/model_schema.rb, line 482
def reload_schema_from_cache
  @arel_engine = nil
  @arel_table = nil
  @column_names = nil
  @attribute_types = nil
  @content_columns = nil
  @default_attributes = nil
  @inheritance_column = nil unless defined?(@explicit_inheritance_column) && @explicit_inheritance_column
  @attributes_builder = nil
  @columns = nil
  @columns_hash = nil
  @schema_loaded = false
  @attribute_names = nil
  @yaml_encoder = nil
  direct_descendants.each do |descendant|
    descendant.send(:reload_schema_from_cache)
  end
end
schema_loaded?() click to toggle source
# File lib/active_record/model_schema.rb, line 455
def schema_loaded?
  defined?(@schema_loaded) && @schema_loaded
end
undecorated_table_name(class_name = base_class.name) click to toggle source

Guesses the table name, but does not decorate it with prefix and suffix information.

# File lib/active_record/model_schema.rb, line 502
def undecorated_table_name(class_name = base_class.name)
  table_name = class_name.to_s.demodulize.underscore
  pluralize_table_names ? table_name.pluralize : table_name
end