# File activerecord/lib/active_record/core.rb, line 119
class_attribute :attributes_for_inspect, instance_accessor: false, default: :all

Specifies the attributes that will be included in the output of the inspect method:

Post.attributes_for_inspect = [:id, :title]
Post.first.inspect #=> "#<Post id: 1, title: "Hello, World!">"

When set to ‘:all` inspect will list all the record’s attributes:

Post.attributes_for_inspect = :all
Post.first.inspect #=> "#<Post id: 1, title: "Hello, World!", published_at: "2023-10-23 14:28:11 +0000">"

# File activerecord/lib/active_record/core.rb, line 77
def self.configurations
  @@configurations
end

Returns a fully resolved ActiveRecord::DatabaseConfigurations object.

# File activerecord/lib/active_record/core.rb, line 71
def self.configurations=(config)
  @@configurations = ActiveRecord::DatabaseConfigurations.new(config)
end

Contains the database configuration - as is typically stored in config/database.yml - as an ActiveRecord::DatabaseConfigurations object.

For example, the following database.yml…

development:
  adapter: sqlite3
  database: storage/development.sqlite3

production:
  adapter: sqlite3
  database: storage/production.sqlite3

…would result in ActiveRecord::Base.configurations to look like this:

#<ActiveRecord::DatabaseConfigurations:0x00007fd1acbdf800 @configurations=[
  #<ActiveRecord::DatabaseConfigurations::HashConfig:0x00007fd1acbded10 @env_name="development",
    @name="primary", @config={adapter: "sqlite3", database: "storage/development.sqlite3"}>,
  #<ActiveRecord::DatabaseConfigurations::HashConfig:0x00007fd1acbdea90 @env_name="production",
    @name="primary", @config={adapter: "sqlite3", database: "storage/production.sqlite3"}>
]>

# File activerecord/lib/active_record/core.rb, line 196
def self.current_preventing_writes
  connected_to_stack.reverse_each do |hash|
    return hash[:prevent_writes] if !hash[:prevent_writes].nil? && hash[:klasses].include?(Base)
    return hash[:prevent_writes] if !hash[:prevent_writes].nil? && hash[:klasses].include?(connection_class_for_self)
  end

  false
end

Returns the symbol representing the current setting for preventing writes.

ActiveRecord::Base.connected_to(role: :reading) do
  ActiveRecord::Base.current_preventing_writes #=> true
end

ActiveRecord::Base.connected_to(role: :writing) do
  ActiveRecord::Base.current_preventing_writes #=> false
end

# File activerecord/lib/active_record/core.rb, line 159
def self.current_role
  connected_to_stack.reverse_each do |hash|
    return hash[:role] if hash[:role] && hash[:klasses].include?(Base)
    return hash[:role] if hash[:role] && hash[:klasses].include?(connection_class_for_self)
  end

  default_role
end

Returns the symbol representing the current connected role.

ActiveRecord::Base.connected_to(role: :writing) do
  ActiveRecord::Base.current_role #=> :writing
end

ActiveRecord::Base.connected_to(role: :reading) do
  ActiveRecord::Base.current_role #=> :reading
end

# File activerecord/lib/active_record/core.rb, line 177
def self.current_shard
  connected_to_stack.reverse_each do |hash|
    return hash[:shard] if hash[:shard] && hash[:klasses].include?(Base)
    return hash[:shard] if hash[:shard] && hash[:klasses].include?(connection_class_for_self)
  end

  default_shard
end

Returns the symbol representing the current connected shard.

ActiveRecord::Base.connected_to(role: :reading) do
  ActiveRecord::Base.current_shard #=> :default
end

ActiveRecord::Base.connected_to(role: :writing, shard: :one) do
  ActiveRecord::Base.current_shard #=> :one
end

# File activerecord/lib/active_record/core.rb, line 47
class_attribute :destroy_association_async_batch_size, instance_writer: false, instance_predicate: false, default: nil

Specifies the maximum number of records that will be destroyed in a single background job by the dependent: :destroy_async association option. When nil (default), all dependent records will be destroyed in a single background job. If specified, the records to be destroyed will be split into multiple background jobs.

# File activerecord/lib/active_record/core.rb, line 27
def self.destroy_association_async_job
  if _destroy_association_async_job.is_a?(String)
    self._destroy_association_async_job = _destroy_association_async_job.constantize
  end
  _destroy_association_async_job
rescue NameError => error
  raise NameError, "Unable to load destroy_association_async_job: #{error.message}"
end

The job class used to destroy associations in the background.

# File activerecord/lib/active_record/core.rb, line 87
class_attribute :enumerate_columns_in_select_statements, instance_accessor: false, default: false

Force enumeration of all columns in SELECT statements. e.g. SELECT first_name, last_name FROM ... instead of SELECT * FROM ... This avoids PreparedStatementCacheExpired errors when a column is added to the database while the app is running.

# File activerecord/lib/active_record/core.rb, line 22
class_attribute :logger, instance_writer: false

Accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then passed on to any new database connections made. You can retrieve this logger by calling logger on either an Active Record model class or an Active Record model instance.

# File activerecord/lib/active_record/core.rb, line 460
def initialize(attributes = nil)
  @new_record = true
  @attributes = self.class._default_attributes.deep_dup

  init_internals
  initialize_internals_callback

  super

  yield self if block_given?
  _run_initialize_callbacks
end

New objects can be instantiated as either empty (pass no construction parameter) or pre-set with attributes but not yet saved (pass a hash with key names matching the associated table column names). In both instances, valid attribute keys are determined by the column names of the associated table – hence you can’t have attributes that aren’t part of the table columns.

Example

# Instantiates a single new object
User.new(first_name: 'Jamie')

# File activerecord/lib/active_record/core.rb, line 654
def <=>(other_object)
  if other_object.is_a?(self.class)
    to_key <=> other_object.to_key
  else
    super
  end
end

Allows sort on objects

# File activerecord/lib/active_record/core.rb, line 620
def ==(comparison_object)
  super ||
    comparison_object.instance_of?(self.class) &&
    primary_key_values_present? &&
    comparison_object.id == id
end

Returns true if comparison_object is the same exact object, or comparison_object is of the same type and self has an ID and it is equal to comparison_object.id.

Note that new records are different from any other record by definition, unless the other record is the receiver itself. Besides, if you fetch existing records with select and leave the ID out, you’re on your own, this predicate will return false.

Note also that destroying a record preserves its ID in the model instance, so deleted models are still comparable.

# File activerecord/lib/active_record/core.rb, line 512
    

Identical to Ruby’s clone method. This is a “shallow” copy. Be warned that your attributes are not copied. That means that modifying attributes of the clone will modify the original, since they will both point to the same attributes hash. If you need a copy of your attributes hash, please use the dup method.

user = User.first
new_user = user.clone
user.name               # => "Bob"
new_user.name = "Joe"
user.name               # => "Joe"

user.object_id == new_user.object_id            # => false
user.name.object_id == new_user.name.object_id  # => true

user.name.object_id == user.dup.name.object_id  # => false

# File activerecord/lib/active_record/core.rb, line 529
    

Duped objects have no id assigned and are treated as new records. Note that this is a “shallow” copy as it copies the object’s attributes only, not its associations. The extent of a “deep” copy is application specific and is therefore left to the application to implement according to its need. The dup method does not preserve the timestamps (created|updated)_(at|on) and locking column.

# File activerecord/lib/active_record/core.rb, line 576
def encode_with(coder)
  self.class.yaml_encoder.encode(@attributes, coder)
  coder["new_record"] = new_record?
  coder["active_record_yaml_version"] = 2
end

Populate coder with attributes about this record that should be serialized. The structure of coder defined in this method is guaranteed to match the structure of coder passed to the init_with method.

Example:

class Post < ActiveRecord::Base
end
coder = {}
Post.new.encode_with(coder)
coder # => {"attributes" => {"id" => nil, ... }}

# File activerecord/lib/active_record/core.rb, line 643
def freeze
  @attributes = @attributes.clone.freeze
  self
end

Clone and freeze the attributes hash such that associations are still accessible, even on destroyed records, but cloned models will not be frozen.

# File activerecord/lib/active_record/core.rb, line 649
def frozen?
  @attributes.frozen?
end

Returns true if the attributes hash has been frozen.

# File activerecord/lib/active_record/core.rb, line 763
def full_inspect
  inspect_with_attributes(all_attributes_for_inspect)
end

Returns all attributes of the record as a nicely formatted string, ignoring .attributes_for_inspect.

Post.first.full_inspect
#=> "#<Post id: 1, title: "Hello, World!", published_at: "2023-10-23 14:28:11 +0000">"

# File activerecord/lib/active_record/core.rb, line 630
def hash
  id = self.id

  if primary_key_values_present?
    self.class.hash ^ id.hash
  else
    super
  end
end

Delegates to id in order to allow two records of the same type and id to work with something like:

[ Person.find(1), Person.find(2), Person.find(3) ] & [ Person.find(1), Person.find(4) ] # => [ Person.find(1) ]

# File activerecord/lib/active_record/core.rb, line 487
def init_with(coder, &block)
  coder = LegacyYamlAdapter.convert(coder)
  attributes = self.class.yaml_encoder.decode(coder)
  init_with_attributes(attributes, coder["new_record"], &block)
end

Initialize an empty model object from coder. coder should be the result of previously encoding an Active Record model, using encode_with.

class Post < ActiveRecord::Base
end

old_post = Post.new(title: "hello world")
coder = {}
old_post.encode_with(coder)

post = Post.allocate
post.init_with(coder)
post.title # => 'hello world'

# File activerecord/lib/active_record/core.rb, line 753
def inspect
  inspect_with_attributes(attributes_for_inspect)
end

Returns the attributes of the record as a nicely formatted string.

Post.first.inspect
#=> "#<Post id: 1, title: "Hello, World!", published_at: "2023-10-23 14:28:11 +0000">"

The attributes can be limited by setting .attributes_for_inspect.

Post.attributes_for_inspect = [:id, :title]
Post.first.inspect
#=> "#<Post id: 1, title: "Hello, World!">"

# File activerecord/lib/active_record/core.rb, line 769
def pretty_print(pp)
  return super if custom_inspect_method_defined?
  pp.object_address_group(self) do
    if @attributes
      attr_names = attributes_for_inspect.select { |name| _has_attribute?(name.to_s) }
      pp.seplist(attr_names, proc { pp.text "," }) do |attr_name|
        attr_name = attr_name.to_s
        pp.breakable " "
        pp.group(1) do
          pp.text attr_name
          pp.text ":"
          pp.breakable
          value = attribute_for_inspect(attr_name)
          pp.text value
        end
      end
    else
      pp.breakable " "
      pp.text "not initialized"
    end
  end
end

Takes a PP and prettily prints this record to it, allowing you to get a nice result from pp record when pp is required.

# File activerecord/lib/active_record/core.rb, line 735
def readonly!
  @readonly = true
end

Marks this record as read only.

customer = Customer.first
customer.readonly!
customer.save # Raises an ActiveRecord::ReadOnlyRecord

# File activerecord/lib/active_record/core.rb, line 671
def readonly?
  @readonly
end

Returns true if the record is read only.

# File activerecord/lib/active_record/core.rb, line 583
    

Returns a hash of the given methods with their names as keys and returned values as values.

topic = Topic.new(title: "Budget", author_name: "Jason")
topic.slice(:title, :author_name)
=> { "title" => "Budget", "author_name" => "Jason" }

# File activerecord/lib/active_record/core.rb, line 709
def strict_loading!(value = true, mode: :all)
  unless [:all, :n_plus_one_only].include?(mode)
    raise ArgumentError, "The :mode option must be one of [:all, :n_plus_one_only] but #{mode.inspect} was provided."
  end

  @strict_loading_mode = mode
  @strict_loading = value
end

Sets the record to strict_loading mode. This will raise an error if the record tries to lazily load an association.

user = User.first
user.strict_loading! # => true
user.address.city
=> ActiveRecord::StrictLoadingViolationError
user.comments.to_a
=> ActiveRecord::StrictLoadingViolationError

Parameters

• value - Boolean specifying whether to enable or disable strict loading.

• :mode - Symbol specifying strict loading mode. Defaults to :all. Using :n_plus_one_only mode will only raise an error if an association that will lead to an n plus one query is lazily loaded.

Examples

user = User.first
user.strict_loading!(false) # => false
user.address.city # => "Tatooine"
user.comments.to_a # => [#<Comment:0x00...]

user.strict_loading!(mode: :n_plus_one_only)
user.address.city # => "Tatooine"
user.comments.to_a # => [#<Comment:0x00...]
user.comments.first.ratings.to_a
=> ActiveRecord::StrictLoadingViolationError

# File activerecord/lib/active_record/core.rb, line 676
def strict_loading?
  @strict_loading
end

Returns true if the record is in strict_loading mode.

# File activerecord/lib/active_record/core.rb, line 726
def strict_loading_all?
  @strict_loading_mode == :all
end

Returns true if the record uses strict_loading with :all mode enabled.

# File activerecord/lib/active_record/core.rb, line 721
def strict_loading_n_plus_one_only?
  @strict_loading_mode == :n_plus_one_only
end

Returns true if the record uses strict_loading with :n_plus_one_only mode enabled.

# File activerecord/lib/active_record/core.rb, line 598
    

Returns an array of the values returned by the given methods.

topic = Topic.new(title: "Budget", author_name: "Jason")
topic.values_at(:title, :author_name)
=> ["Budget", "Jason"]