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Instance Public methods
column_defaults() Link
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) Link
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>, ...>
column_names() Link
Returns an array of column names as strings.
columns() Link
content_columns() Link
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.
ignored_columns() Link
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.
ignored_columns=(columns) Link
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
next_sequence_value() Link
Returns the next value that will be used as the primary key on an insert statement.
prefetch_primary_key?() Link
Determines if the primary key values should be selected from their corresponding sequence before the insert statement.
protected_environments() Link
The array of names of environments where destructive actions should be prohibited. By default, the value is ["production"]
.
protected_environments=(environments) Link
Sets an array of names of environments where destructive actions should be prohibited.
quoted_table_name() Link
Returns a quoted version of the table name, used to construct SQL statements.
reset_column_information() Link
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[7.0]
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 537 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
sequence_name() Link
sequence_name=(value) Link
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
table_exists?() Link
Indicates whether the table associated with this class exists
table_name() Link
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”.
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
table_name=(value) Link
Sets the table name explicitly. Example:
class Project < ActiveRecord::Base
self.table_name = "project"
end
# File activerecord/lib/active_record/model_schema.rb, line 257 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
type_for_attribute(attr_name, &block) Link
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 448 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