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 379

def _default_attributes # :nodoc:
  @default_attributes ||= AttributeSet.new({})
end

#attribute_typesObject

:nodoc:


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# File 'activerecord/lib/active_record/model_schema.rb', line 348

def attribute_types # :nodoc:
  load_schema
  @attribute_types ||= Hash.new(Type::Value.new)
end

#attributes_builderObject

:nodoc:


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# File 'activerecord/lib/active_record/model_schema.rb', line 330

def attributes_builder # :nodoc:
  @attributes_builder ||= AttributeSet::Builder.new(attribute_types, primary_key) do |name|
    unless columns_hash.key?(name)
      _default_attributes[name].dup
    end
  end
end

#column_defaultsObject

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


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# File 'activerecord/lib/active_record/model_schema.rb', line 374

def column_defaults
  load_schema
  _default_attributes.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 384

def column_names
  @column_names ||= columns.map(&:name)
end

#columnsObject


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# File 'activerecord/lib/active_record/model_schema.rb', line 343

def columns
  load_schema
  @columns ||= columns_hash.values
end

#columns_hashObject

:nodoc:


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# File 'activerecord/lib/active_record/model_schema.rb', line 338

def columns_hash # :nodoc:
  load_schema
  @columns_hash
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 390

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 254

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 258

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 271

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 276

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

#next_sequence_valueObject

Returns the next value that will be used as the primary key on an insert statement.


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# File 'activerecord/lib/active_record/model_schema.rb', line 321

def next_sequence_value
  connection.next_sequence_value(sequence_name)
end

#prefetch_primary_key?Boolean

Determines if the primary key values should be selected from their corresponding sequence before the insert statement.

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/model_schema.rb', line 315

def prefetch_primary_key?
  connection.prefetch_primary_key?(table_name)
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 239

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[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

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# File 'activerecord/lib/active_record/model_schema.rb', line 420

def reset_column_information
  connection.clear_cache!
  undefine_attribute_methods
  connection.schema_cache.clear_data_source_cache!(table_name)

  reload_schema_from_cache
end

#reset_sequence_nameObject

:nodoc:


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# File 'activerecord/lib/active_record/model_schema.rb', line 289

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 244

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 281

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 308

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 326

def table_exists?
  connection.schema_cache.data_source_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

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# File 'activerecord/lib/active_record/model_schema.rb', line 213

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

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

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) ⇒ Object

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


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# File 'activerecord/lib/active_record/model_schema.rb', line 364

def type_for_attribute(attr_name, &block)
  if block
    attribute_types.fetch(attr_name, &block)
  else
    attribute_types[attr_name]
  end
end