# File activerecord/lib/active_record/core.rb, line 56
def self.configurations
  @@configurations
end

Returns fully resolved ActiveRecord::DatabaseConfigurations object

# File activerecord/lib/active_record/core.rb, line 50
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: db/development.sqlite3

production:
  adapter: sqlite3
  database: db/production.sqlite3

…would result in ::configurations to look like this:

#<ActiveRecord::DatabaseConfigurations:0x00007fd1acbdf800 @configurations=[
  #<ActiveRecord::DatabaseConfigurations::HashConfig:0x00007fd1acbded10 @env_name="development",
    @spec_name="primary", @config={"adapter"=>"sqlite3", "database"=>"db/development.sqlite3"}>,
  #<ActiveRecord::DatabaseConfigurations::HashConfig:0x00007fd1acbdea90 @env_name="production",
    @spec_name="primary", @config={"adapter"=>"mysql2", "database"=>"db/production.sqlite3"}>
]>

# File activerecord/lib/active_record/core.rb, line 319
def initialize(attributes = nil)
  @new_record = true
  @attributes = self.class._default_attributes.deep_dup

  init_internals
  initialize_internals_callback

  assign_attributes(attributes) if attributes

  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 471
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 438
def ==(comparison_object)
  super ||
    comparison_object.instance_of?(self.class) &&
    !id.nil? &&
    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 387
    

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 396
    

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).

# File activerecord/lib/active_record/core.rb, line 423
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 459
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 465
def frozen?
  sync_with_transaction_state if @transaction_state&.finalized?
  @attributes.frozen?
end

Returns true if the attributes hash has been frozen.

# File activerecord/lib/active_record/core.rb, line 448
def hash
  if id
    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 346
def init_with(coder, &block)
  coder = LegacyYamlAdapter.convert(self.class, 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 503
def inspect
  # We check defined?(@attributes) not to issue warnings if the object is
  # allocated but not initialized.
  inspection = if defined?(@attributes) && @attributes
    self.class.attribute_names.collect do |name|
      if has_attribute?(name)
        attr = _read_attribute(name)
        value = if attr.nil?
          attr.inspect
        else
          attr = format_for_inspect(attr)
          inspection_filter.filter_param(name, attr)
        end
        "#{name}: #{value}"
      end
    end.compact.join(", ")
  else
    "not initialized"
  end

  "#<#{self.class} #{inspection}>"
end

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

# File activerecord/lib/active_record/core.rb, line 528
def pretty_print(pp)
  return super if custom_inspect_method_defined?
  pp.object_address_group(self) do
    if defined?(@attributes) && @attributes
      attr_names = self.class.attribute_names.select { |name| has_attribute?(name) }
      pp.seplist(attr_names, proc { pp.text "," }) do |attr_name|
        pp.breakable " "
        pp.group(1) do
          pp.text attr_name
          pp.text ":"
          pp.breakable
          value = _read_attribute(attr_name)
          value = inspection_filter.filter_param(attr_name, value) unless value.nil?
          pp.pp 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 494
def readonly!
  @readonly = true
end

Marks this record as read only.

# File activerecord/lib/active_record/core.rb, line 489
def readonly?
  @readonly
end

Returns true if the record is read only. Records loaded through joins with piggy-back attributes will be marked as read only since they cannot be saved.

# File activerecord/lib/active_record/core.rb, line 552
def slice(*methods)
  Hash[methods.flatten.map! { |method| [method, public_send(method)] }].with_indifferent_access
end

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