Module: ActiveRecord::ModelSchema::ClassMethods
Relationships & Source Files | |
Defined in: | activerecord/lib/active_record/model_schema.rb |
Instance Attribute Summary
-
#ignored_columns
rw
The list of columns names the model should ignore.
-
#ignored_columns=(columns)
rw
Sets the columns names the model should ignore.
-
#prefetch_primary_key? ⇒ Boolean
readonly
Determines if the primary key values should be selected from their corresponding sequence before the insert statement.
-
#protected_environments
rw
The array of names of environments where destructive actions should be prohibited.
-
#protected_environments=(environments)
rw
Sets an array of names of environments where destructive actions should be prohibited.
- #sequence_name rw
-
#sequence_name=(value)
rw
Sets the name of the sequence to use when generating ids to the given value, or (if the value is
nil
orfalse
) to the value returned by the given block. -
#table_exists? ⇒ Boolean
readonly
Indicates whether the table associated with this class exists.
-
#table_name
rw
Guesses the table name (in forced lower-case) based on the name of the class in the inheritance hierarchy descending directly from
::ActiveRecord::Base
. -
#table_name=(value)
rw
Sets the table name explicitly.
Instance Method Summary
-
#column_defaults
Returns a hash where the keys are column names and the values are default values when instantiating the Active Record object for this table.
-
#column_for_attribute(name)
Returns the column object for the named attribute.
-
#column_names
Returns an array of column names as strings.
- #columns
-
#content_columns
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.
-
#next_sequence_value
Returns the next value that will be used as the primary key on an insert statement.
-
#quoted_table_name
Returns a quoted version of the table name, used to construct SQL statements.
-
#reset_column_information
Resets all the cached information about columns, which will cause them to be reloaded on the next request.
-
#type_for_attribute(attr_name, &block)
Returns the type of the attribute with the given name, after applying all modifiers.
Instance Attribute Details
#ignored_columns (rw)
The list of columns names the model should ignore. Ignored columns won’t have attribute accessors defined, and won’t be referenced in SQL queries.
# File 'activerecord/lib/active_record/model_schema.rb', line 327
def ignored_columns @ignored_columns || superclass.ignored_columns end
#ignored_columns=(columns) (rw)
Sets the columns names the model should ignore. Ignored columns won’t have attribute accessors defined, and won’t be referenced in SQL queries.
A common usage pattern for this method is to ensure all references to an attribute have been removed and deployed, before a migration to drop the column from the database has been deployed and run. Using this two step approach to dropping columns ensures there is no code that raises errors due to having a cached schema in memory at the time the schema migration is run.
For example, given a model where you want to drop the “category” attribute, first mark it as ignored:
class Project < ActiveRecord::Base
# schema:
# id :bigint
# name :string, limit: 255
# category :string, limit: 255
self.ignored_columns += [:category]
end
The schema still contains “category”, but now the model omits it, so any meta-driven code or schema caching will not attempt to use the column:
Project.columns_hash["category"] => nil
You will get an error if accessing that attribute directly, so ensure all usages of the column are removed (automated tests can help you find any usages).
user = Project.create!(name: "First Project")
user.category # => raises NoMethodError
#prefetch_primary_key? ⇒ Boolean
(readonly)
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 401
def prefetch_primary_key? connection.prefetch_primary_key?(table_name) end
#protected_environments (rw)
The array of names of environments where destructive actions should be prohibited. By default, the value is ["production"]
.
# File 'activerecord/lib/active_record/model_schema.rb', line 308
def protected_environments if defined?(@protected_environments) @protected_environments else superclass.protected_environments end end
#protected_environments=(environments) (rw)
Sets an array of names of environments where destructive actions should be prohibited.
# File 'activerecord/lib/active_record/model_schema.rb', line 317
def protected_environments=(environments) @protected_environments = environments.map(&:to_s) end
#sequence_name (rw)
[ GitHub ]# File 'activerecord/lib/active_record/model_schema.rb', line 367
def sequence_name if base_class? @sequence_name ||= reset_sequence_name else (@sequence_name ||= nil) || base_class.sequence_name end end
#sequence_name=(value) (rw)
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 394
def sequence_name=(value) @sequence_name = value.to_s @explicit_sequence_name = true end
#table_exists? ⇒ Boolean
(readonly)
Indicates whether the table associated with this class exists
# File 'activerecord/lib/active_record/model_schema.rb', line 412
def table_exists? connection.schema_cache.data_source_exists?(table_name) end
#table_name (rw)
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 ActiveRecord::ModelSchema.table_name_prefix is prepended and the ActiveRecord::ModelSchema.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”.
Active Model Naming’s model_name
is the base name used to guess the table name. In case a custom Active Model Name is defined, it will be used for the table name as well:
class PostRecord < ActiveRecord::Base
class << self
def model_name
ActiveModel::Name.new(self, nil, "Post")
end
end
end
PostRecord.table_name
# => "posts"
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 255
def table_name reset_table_name unless defined?(@table_name) @table_name end
#table_name=(value) (rw)
Sets the table name explicitly. Example:
class Project < ActiveRecord::Base
self.table_name = "project"
end
# File 'activerecord/lib/active_record/model_schema.rb', line 265
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
Instance Method Details
#column_defaults
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 497
def column_defaults load_schema @column_defaults ||= _default_attributes.deep_dup.to_hash.freeze end
#column_for_attribute(name)
Returns the column object for the named attribute. Returns an ::ActiveRecord::ConnectionAdapters::NullColumn
if the named attribute does not exist.
class Person < ActiveRecord::Base
end
person = Person.new
person.column_for_attribute(:name) # the result depends on the ConnectionAdapter
# => #<ActiveRecord::ConnectionAdapters::Column:0x007ff4ab083980 @name="name", @sql_type="varchar(255)", @null=true, ...>
person.column_for_attribute(:nothing)
# => #<ActiveRecord::ConnectionAdapters::NullColumn:0xXXX @name=nil, @sql_type=nil, @cast_type=#<Type::Value>, ...>
# File 'activerecord/lib/active_record/model_schema.rb', line 488
def column_for_attribute(name) name = name.to_s columns_hash.fetch(name) do ConnectionAdapters::NullColumn.new(name) end end
#column_names
Returns an array of column names as strings.
# File 'activerecord/lib/active_record/model_schema.rb', line 508
def column_names @column_names ||= columns.map(&:name).freeze end
#columns
[ GitHub ]# File 'activerecord/lib/active_record/model_schema.rb', line 429
def columns load_schema @columns ||= columns_hash.values.freeze end
#content_columns
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 519
def content_columns @content_columns ||= columns.reject do |c| c.name == primary_key || c.name == inheritance_column || c.name.end_with?("_id", "_count") end.freeze end
#next_sequence_value
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 407
def next_sequence_value connection.next_sequence_value(sequence_name) end
#quoted_table_name
Returns a quoted version of the table name, used to construct SQL statements.
# File 'activerecord/lib/active_record/model_schema.rb', line 281
def quoted_table_name @quoted_table_name ||= connection.quote_table_name(table_name) end
#reset_column_information
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, e.g.:
class CreateJobLevels < ActiveRecord::Migration[7.1]
def up
create_table :job_levels do |t|
t.integer :id
t.string :name
t.
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 553
def reset_column_information connection.clear_cache! ([self] + descendants).each(&:undefine_attribute_methods) connection.schema_cache.clear_data_source_cache!(table_name) reload_schema_from_cache initialize_find_by_cache end
#type_for_attribute(attr_name, &block)
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 or a symbol.
# File 'activerecord/lib/active_record/model_schema.rb', line 464
def type_for_attribute(attr_name, &block) attr_name = attr_name.to_s attr_name = attribute_aliases[attr_name] || attr_name if block attribute_types.fetch(attr_name, &block) else attribute_types[attr_name] end end