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 activerecord/lib/active_record/model_schema.rb, line 371 def column_defaults load_schema @column_defaults ||= _default_attributes.to_hash end
Returns an array of column names as strings.
# File activerecord/lib/active_record/model_schema.rb, line 381 def column_names @column_names ||= columns.map(&:name) end
# File activerecord/lib/active_record/model_schema.rb, line 336 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 activerecord/lib/active_record/model_schema.rb, line 387 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
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 activerecord/lib/active_record/model_schema.rb, line 264 def inheritance_column (@inheritance_column ||= nil) || superclass.inheritance_column end
Sets the value of inheritance_column
# File activerecord/lib/active_record/model_schema.rb, line 269 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 activerecord/lib/active_record/model_schema.rb, line 314 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 activerecord/lib/active_record/model_schema.rb, line 308 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 activerecord/lib/active_record/model_schema.rb, line 232 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 activerecord/lib/active_record/model_schema.rb, line 422 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
# File activerecord/lib/active_record/model_schema.rb, line 274 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 activerecord/lib/active_record/model_schema.rb, line 301 def sequence_name=(value) @sequence_name = value.to_s @explicit_sequence_name = true end
Indicates whether the table associated with this class exists
# File activerecord/lib/active_record/model_schema.rb, line 319 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 activerecord/lib/active_record/model_schema.rb, line 206 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 activerecord/lib/active_record/model_schema.rb, line 216 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 activerecord/lib/active_record/model_schema.rb, line 361 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
# File activerecord/lib/active_record/model_schema.rb, line 433 def initialize_load_schema_monitor @load_schema_monitor = Monitor.new end
Private Instance Methods
Computes and returns a table name according to default conventions.
# File activerecord/lib/active_record/model_schema.rb, line 497 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 activerecord/lib/active_record/model_schema.rb, line 439 def inherited(child_class) super child_class.initialize_load_schema_monitor end
# File activerecord/lib/active_record/model_schema.rb, line 448 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
# File activerecord/lib/active_record/model_schema.rb, line 459 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
# File activerecord/lib/active_record/model_schema.rb, line 471 def reload_schema_from_cache @arel_table = nil @column_names = nil @attribute_types = nil @content_columns = nil @default_attributes = nil @column_defaults = 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
# File activerecord/lib/active_record/model_schema.rb, line 444 def schema_loaded? defined?(@schema_loaded) && @schema_loaded end
Guesses the table name, but does not decorate it with prefix and suffix information.
# File activerecord/lib/active_record/model_schema.rb, line 491 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