Module: ActiveRecord::ModelSchema::ClassMethods

Defined in:
activerecord/lib/active_record/model_schema.rb

Instance Method Summary collapse

Instance Method Details

#_default_attributesObject

:nodoc:


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# File 'activerecord/lib/active_record/model_schema.rb', line 253

def _default_attributes # :nodoc:
  @default_attributes ||= attributes_builder.build_from_database(
    raw_default_values)
end

#attributes_builderObject

:nodoc:


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# File 'activerecord/lib/active_record/model_schema.rb', line 233

def attributes_builder # :nodoc:
  @attributes_builder ||= AttributeSet::Builder.new(column_types, primary_key)
end

#column_defaultsObject

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


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# File 'activerecord/lib/active_record/model_schema.rb', line 249

def column_defaults
  _default_attributes.dup.to_hash
end

#column_namesObject

Returns an array of column names as strings.


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# File 'activerecord/lib/active_record/model_schema.rb', line 259

def column_names
  @column_names ||= columns.map { |column| column.name }
end

#column_typesObject

:nodoc:


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# File 'activerecord/lib/active_record/model_schema.rb', line 237

def column_types # :nodoc:
  @column_types ||= columns_hash.transform_values(&:cast_type).tap do |h|
    h.default = Type::Value.new
  end
end

#content_columnsObject

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.


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# File 'activerecord/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

#full_table_name_prefixObject

:nodoc:


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# File 'activerecord/lib/active_record/model_schema.rb', line 169

def full_table_name_prefix #:nodoc:
  (parents.detect{ |p| p.respond_to?(:table_name_prefix) } || self).table_name_prefix
end

#full_table_name_suffixObject

:nodoc:


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# File 'activerecord/lib/active_record/model_schema.rb', line 173

def full_table_name_suffix #:nodoc:
  (parents.detect {|p| p.respond_to?(:table_name_suffix) } || self).table_name_suffix
end

#inheritance_columnObject

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'

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# File 'activerecord/lib/active_record/model_schema.rb', line 186

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

#inheritance_column=(value) ⇒ Object

Sets the value of inheritance_column


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# File 'activerecord/lib/active_record/model_schema.rb', line 191

def inheritance_column=(value)
  @inheritance_column = value.to_s
  @explicit_inheritance_column = true
end

#quoted_table_nameObject

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


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# File 'activerecord/lib/active_record/model_schema.rb', line 154

def quoted_table_name
  @quoted_table_name ||= connection.quote_table_name(table_name)
end

#reset_column_informationObject

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

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# File 'activerecord/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

  initialize_find_by_cache
end

#reset_sequence_nameObject

:nodoc:


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# File 'activerecord/lib/active_record/model_schema.rb', line 204

def reset_sequence_name #:nodoc:
  @explicit_sequence_name = false
  @sequence_name          = connection.default_sequence_name(table_name, primary_key)
end

#reset_table_nameObject

Computes the table name, (re)sets it internally, and returns it.


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# File 'activerecord/lib/active_record/model_schema.rb', line 159

def reset_table_name #:nodoc:
  self.table_name = if abstract_class?
    superclass == Base ? nil : superclass.table_name
  elsif superclass.abstract_class?
    superclass.table_name || compute_table_name
  else
    compute_table_name
  end
end

#sequence_nameObject


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# File 'activerecord/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) ⇒ Object

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

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# File 'activerecord/lib/active_record/model_schema.rb', line 223

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

#table_exists?Boolean

Indicates whether the table associated with this class exists

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/model_schema.rb', line 229

def table_exists?
  connection.schema_cache.table_exists?(table_name)
end

#table_nameObject

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"

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# File 'activerecord/lib/active_record/model_schema.rb', line 125

def table_name
  reset_table_name unless defined?(@table_name)
  @table_name
end

#table_name=(value) ⇒ Object

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.


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# File 'activerecord/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

#type_for_attribute(attr_name) ⇒ Object

:nodoc:


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# File 'activerecord/lib/active_record/model_schema.rb', line 243

def type_for_attribute(attr_name) # :nodoc:
  column_types[attr_name]
end