module ActiveRecord::ModelSchema::ClassMethods
Public Instance Methods
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 287 def column_defaults load_schema _default_attributes.to_hash end
Returns an array of column names as strings.
# File lib/active_record/model_schema.rb, line 297 def column_names @column_names ||= columns.map(&:name) end
# File lib/active_record/model_schema.rb, line 260 def columns load_schema @columns ||= columns_hash.values end
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 303 def content_columns @content_columns ||= columns.reject { |c| c.name == primary_key || c.name =~ /(_id|_count)$/ || c.name == inheritance_column } end
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 192 def inheritance_column (@inheritance_column ||= nil) || superclass.inheritance_column end
Sets the value of #inheritance_column
# File lib/active_record/model_schema.rb, line 197 def inheritance_column=(value) @inheritance_column = value.to_s @explicit_inheritance_column = true end
Returns the next value that will be used as the primary key on an insert statement.
# File lib/active_record/model_schema.rb, line 242 def next_sequence_value connection.next_sequence_value(sequence_name) end
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 236 def prefetch_primary_key? connection.prefetch_primary_key?(table_name) end
Returns a quoted version of the table name, used to construct SQL statements.
# File lib/active_record/model_schema.rb, line 160 def quoted_table_name @quoted_table_name ||= connection.quote_table_name(table_name) end
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 333 def reset_column_information connection.clear_cache! undefine_attribute_methods connection.schema_cache.clear_data_source_cache!(table_name) reload_schema_from_cache end
# File lib/active_record/model_schema.rb, line 202 def sequence_name if base_class == self @sequence_name ||= reset_sequence_name else (@sequence_name ||= nil) || base_class.sequence_name end end
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 229 def sequence_name=(value) @sequence_name = value.to_s @explicit_sequence_name = true end
Indicates whether the table associated with this class exists
# File lib/active_record/model_schema.rb, line 247 def table_exists? connection.schema_cache.data_source_exists?(table_name) end
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 134 def table_name reset_table_name unless defined?(@table_name) @table_name end
Sets the table name explicitly. Example:
class Project < ActiveRecord::Base self.table_name = "project" end
# File lib/active_record/model_schema.rb, line 144 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
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 281 def type_for_attribute(attr_name) attribute_types[attr_name] end
Private Instance Methods
Computes and returns a table name according to default conventions.
# File lib/active_record/model_schema.rb, line 390 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
# File lib/active_record/model_schema.rb, line 347 def load_schema unless schema_loaded? load_schema! end end
# File lib/active_record/model_schema.rb, line 353 def load_schema! @columns_hash = connection.schema_cache.columns_hash(table_name).except(*ignored_columns) @columns_hash.each do |name, column| warn_if_deprecated_type(column) define_attribute( name, connection.lookup_cast_type_from_column(column), default: column.default, user_provided_default: false ) end end
# File lib/active_record/model_schema.rb, line 366 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 @attribute_names = nil direct_descendants.each do |descendant| descendant.send(:reload_schema_from_cache) end end
# File lib/active_record/model_schema.rb, line 343 def schema_loaded? defined?(@columns_hash) && @columns_hash end
Guesses the table name, but does not decorate it with prefix and suffix information.
# File lib/active_record/model_schema.rb, line 384 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
# File lib/active_record/model_schema.rb, line 407 def warn_if_deprecated_type(column) return if attributes_to_define_after_schema_loads.key?(column.name) if column.respond_to?(:oid) && column.sql_type.start_with?("point") if column.array? array_arguments = ", array: true" else array_arguments = "" end ActiveSupport::Deprecation.warn(" The behavior of the `:point` type will be changing in Rails 5.1 to return a `Point` object, rather than an `Array`. If you'd like to keep the old behavior, you can add this line to #{self.name}: attribute :#{column.name}, :legacy_point#{array_arguments} If you'd like the new behavior today, you can add this line: attribute :#{column.name}, :point#{array_arguments} ".strip_heredoc) end end