module ActiveRecord::ModelSchema::ClassMethods - activerecord-4.2.4 Documentation

# module ActiveRecord::ModelSchema::ClassMethods

### Public Instance Methods

column_defaults() click to toggle source

Returns a hash where the keys are column names and the values are default values when instantiating the AR object for this table.

    # File lib/active_record/model_schema.rb, line 249
    def column_defaults
      _default_attributes.to_hash
    end

column_names() click to toggle source

Returns an array of column names as strings.

    # File lib/active_record/model_schema.rb, line 259
    def column_names
      @column_names ||= columns.map { |column| column.name }
    end

content_columns() click to toggle source

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 265
    def content_columns
      @content_columns ||= columns.reject { |c| c.name == primary_key || c.name =~ /(_id|_count)$/ || c.name == inheritance_column }
    end

inheritance_column() click to toggle source

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 186
    def inheritance_column
      (@inheritance_column ||= nil) || superclass.inheritance_column
    end

inheritance_column=(value) click to toggle source

Sets the value of #inheritance_column

    # File lib/active_record/model_schema.rb, line 191
    def inheritance_column=(value)
      @inheritance_column = value.to_s
      @explicit_inheritance_column = true
    end

quoted_table_name() click to toggle source

Returns a quoted version of the table name, used to construct SQL statements.

    # File lib/active_record/model_schema.rb, line 154
    def quoted_table_name
      @quoted_table_name ||= connection.quote_table_name(table_name)
    end

reset_column_information() click to toggle source

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
      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 295
    def reset_column_information
      connection.clear_cache!
      undefine_attribute_methods
      connection.schema_cache.clear_table_cache!(table_name)

      @arel_engine        = nil
      @column_names       = nil
      @column_types       = nil
      @content_columns    = nil
      @default_attributes = nil
      @inheritance_column = nil unless defined?(@explicit_inheritance_column) && @explicit_inheritance_column
      @relation           = nil
    end

sequence_name() click to toggle source

    # File lib/active_record/model_schema.rb, line 196
    def sequence_name
      if base_class == self
        @sequence_name ||= reset_sequence_name
      else
        (@sequence_name ||= nil) || base_class.sequence_name
      end
    end

sequence_name=(value) click to toggle source

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 223
    def sequence_name=(value)
      @sequence_name          = value.to_s
      @explicit_sequence_name = true
    end

table_exists?() click to toggle source

Indicates whether the table associated with this class exists

    # File lib/active_record/model_schema.rb, line 229
    def table_exists?
      connection.schema_cache.table_exists?(table_name)
    end

table_name() click to toggle source

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

Alternatively, you can override the #table_name method to define your own computation. (Possibly using `super` to manipulate the default table name.) Example:

    class Post < ActiveRecord::Base
      def self.table_name
        "special_" + super
      end
    end
    Post.table_name # => "special_posts"

    # File lib/active_record/model_schema.rb, line 125
    def table_name
      reset_table_name unless defined?(@table_name)
      @table_name
    end

table_name=(value) click to toggle source

Sets the table name explicitly. Example:

    class Project < ActiveRecord::Base
      self.table_name = "project"
    end

You can also just define your own `self.table_name` method; see the documentation for ActiveRecord::Base#table_name.

    # File lib/active_record/model_schema.rb, line 138
    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
      @relation          = Relation.create(self, arel_table)
    end

### Private Instance Methods

compute_table_name() click to toggle source

Computes and returns a table name according to default conventions.

    # File lib/active_record/model_schema.rb, line 318
    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

raw_default_values() click to toggle source

    # File lib/active_record/model_schema.rb, line 335
    def raw_default_values
      columns_hash.transform_values(&:default)
    end

undecorated_table_name(class_name = base_class.name) click to toggle source

Guesses the table name, but does not decorate it with prefix and suffix information.

    # File lib/active_record/model_schema.rb, line 312
    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