Module: ActiveRecord::AttributeMethods::ClassMethods

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

Instance Method Summary collapse

Instance Method Details

#attribute_method?(attribute) ⇒ Boolean

Returns true if attribute is an attribute method and table exists, false otherwise.

class Person < ActiveRecord::Base
end

Person.attribute_method?('name')   # => true
Person.attribute_method?(:age=)    # => true
Person.attribute_method?(:nothing) # => false

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 140

def attribute_method?(attribute)
  super || (table_exists? && column_names.include?(attribute.to_s.sub(/=$/, "")))
end

#attribute_names ⇒ Object

Returns an array of column names as strings if it’s not an abstract class and table exists. Otherwise it returns an empty array.

class Person < ActiveRecord::Base
end

Person.attribute_names
# => ["id", "created_at", "updated_at", "name", "age"]



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# File 'activerecord/lib/active_record/attribute_methods.rb', line 152

def attribute_names
  @attribute_names ||= if !abstract_class? && table_exists?
    attribute_types.keys
  else
    []
  end
end

#column_for_attribute(name) ⇒ Object

Returns the column object for the named attribute. Returns a 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>, ...>



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# File 'activerecord/lib/active_record/attribute_methods.rb', line 185

def column_for_attribute(name)
  name = name.to_s
  columns_hash.fetch(name) do
    ConnectionAdapters::NullColumn.new(name)
  end
end

#dangerous_attribute_method?(name) ⇒ Boolean

A method name is ‘dangerous’ if it is already (re)defined by Active Record, but not by any ancestors. (So ‘puts’ is not dangerous but ‘save’ is.)

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 99

def dangerous_attribute_method?(name) # :nodoc:
  method_defined_within?(name, Base)
end

#dangerous_class_method?(method_name) ⇒ Boolean

A class method is ‘dangerous’ if it is already (re)defined by Active Record, but not by any ancestors. (So ‘puts’ is not dangerous but ‘new’ is.)

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 117

def dangerous_class_method?(method_name)
  return true if RESTRICTED_CLASS_METHODS.include?(method_name.to_s)

  if Base.respond_to?(method_name, true)
    if Object.respond_to?(method_name, true)
      Base.method(method_name).owner != Object.method(method_name).owner
    else
      true
    end
  else
    false
  end
end

#define_attribute_methods ⇒ Object

Generates all the attribute related methods for columns in the database accessors, mutators and query methods.



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# File 'activerecord/lib/active_record/attribute_methods.rb', line 48

def define_attribute_methods # :nodoc:
  return false if @attribute_methods_generated
  # Use a mutex; we don't want two threads simultaneously trying to define
  # attribute methods.
  generated_attribute_methods.synchronize do
    return false if @attribute_methods_generated
    superclass.define_attribute_methods unless base_class?
    super(attribute_names)
    @attribute_methods_generated = true
  end
end

#has_attribute?(attr_name) ⇒ Boolean

Returns true if the given attribute exists, otherwise false.

class Person < ActiveRecord::Base
end

Person.has_attribute?('name')   # => true
Person.has_attribute?(:age)     # => true
Person.has_attribute?(:nothing) # => false

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 168

def has_attribute?(attr_name)
  attribute_types.key?(attr_name.to_s)
end

#inherited(child_class) ⇒ Object

:nodoc:



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# File 'activerecord/lib/active_record/attribute_methods.rb', line 32

def inherited(child_class) #:nodoc:
  child_class.initialize_generated_modules
  super
end

#initialize_generated_modules ⇒ Object

:nodoc:



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# File 'activerecord/lib/active_record/attribute_methods.rb', line 37

def initialize_generated_modules # :nodoc:
  @generated_attribute_methods = const_set(:GeneratedAttributeMethods, GeneratedAttributeMethods.new)
  private_constant :GeneratedAttributeMethods
  @attribute_methods_generated = false
  include @generated_attribute_methods

  super
end

#instance_method_already_implemented?(method_name) ⇒ Boolean

Raises an ActiveRecord::DangerousAttributeError exception when an Active Record method is defined in the model, otherwise false.

class Person < ActiveRecord::Base
  def save
    'already defined by Active Record'
  end
end

Person.instance_method_already_implemented?(:save)
# => ActiveRecord::DangerousAttributeError: save is defined by Active Record. Check to make sure that you don't have an attribute or method with the same name.

Person.instance_method_already_implemented?(:name)
# => false

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 81

def instance_method_already_implemented?(method_name)
  if dangerous_attribute_method?(method_name)
    raise DangerousAttributeError, "#{method_name} is defined by Active Record. Check to make sure that you don't have an attribute or method with the same name."
  end

  if superclass == Base
    super
  else
    # If ThisClass < ... < SomeSuperClass < ... < Base and SomeSuperClass
    # defines its own attribute method, then we don't want to overwrite that.
    defined = method_defined_within?(method_name, superclass, Base) &&
      ! superclass.instance_method(method_name).owner.is_a?(GeneratedAttributeMethods)
    defined || super
  end
end

#method_defined_within?(name, klass, superklass = klass.superclass) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 103

def method_defined_within?(name, klass, superklass = klass.superclass) # :nodoc:
  if klass.method_defined?(name) || klass.private_method_defined?(name)
    if superklass.method_defined?(name) || superklass.private_method_defined?(name)
      klass.instance_method(name).owner != superklass.instance_method(name).owner
    else
      true
    end
  else
    false
  end
end

#undefine_attribute_methods ⇒ Object

:nodoc:



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# File 'activerecord/lib/active_record/attribute_methods.rb', line 60

def undefine_attribute_methods # :nodoc:
  generated_attribute_methods.synchronize do
    super if defined?(@attribute_methods_generated) && @attribute_methods_generated
    @attribute_methods_generated = false
  end
end