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module ActiveRecord
module AttributeMethods
module Read
extend ActiveSupport::Concern
ATTRIBUTE_TYPES_CACHED_BY_DEFAULT = [:datetime, :timestamp, :time, :date]
included do
cattr_accessor :attribute_types_cached_by_default, :instance_writer => false
self.attribute_types_cached_by_default = ATTRIBUTE_TYPES_CACHED_BY_DEFAULT
# Undefine id so it can be used as an attribute name
undef_method(:id) if method_defined?(:id)
end
module ClassMethods
# +cache_attributes+ allows you to declare which converted attribute values should
# be cached. Usually caching only pays off for attributes with expensive conversion
# methods, like time related columns (e.g. +created_at+, +updated_at+).
def cache_attributes(*attribute_names)
cached_attributes.merge attribute_names.map { |attr| attr.to_s }
end
# Returns the attributes which are cached. By default time related columns
# with datatype <tt>:datetime, :timestamp, :time, :date</tt> are cached.
def cached_attributes
@cached_attributes ||= columns.select { |c| cacheable_column?(c) }.map { |col| col.name }.to_set
end
# Returns +true+ if the provided attribute is being cached.
def cache_attribute?(attr_name)
cached_attributes.include?(attr_name)
end
protected
def define_method_attribute(attr_name)
define_read_method(attr_name, attr_name, columns_hash[attr_name])
end
private
def cacheable_column?(column)
attribute_types_cached_by_default.include?(column.type)
end
# Define an attribute reader method. Cope with nil column.
# method_name is the same as attr_name except when a non-standard primary key is used,
# we still define #id as an accessor for the key
def define_read_method(method_name, attr_name, column)
cast_code = column.type_cast_code('v')
access_code = "(v=@attributes['#{attr_name}']) && #{cast_code}"
unless attr_name.to_s == self.primary_key.to_s
access_code.insert(0, "missing_attribute('#{attr_name}', caller) unless @attributes.has_key?('#{attr_name}'); ")
end
if cache_attribute?(attr_name)
access_code = "@attributes_cache['#{attr_name}'] ||= (#{access_code})"
end
# Where possible, generate the method by evalling a string, as this will result in
# faster accesses because it avoids the block eval and then string eval incurred
# by the second branch.
#
# The second, slower, branch is necessary to support instances where the database
# returns columns with extra stuff in (like 'my_column(omg)').
if method_name =~ ActiveModel::AttributeMethods::NAME_COMPILABLE_REGEXP
generated_attribute_methods.module_eval <<-STR, __FILE__, __LINE__
def _#{method_name}
#{access_code}
end
alias #{method_name} _#{method_name}
STR
else
generated_attribute_methods.module_eval do
define_method("_#{method_name}") { eval(access_code) }
alias_method(method_name, "_#{method_name}")
end
end
end
end
# Returns the value of the attribute identified by <tt>attr_name</tt> after it has been typecast (for example,
# "2004-12-12" in a data column is cast to a date object, like Date.new(2004, 12, 12)).
def read_attribute(attr_name)
method = "_#{attr_name}"
if respond_to? method
send method if @attributes.has_key?(attr_name.to_s)
else
_read_attribute attr_name
end
end
def _read_attribute(attr_name)
attr_name = attr_name.to_s
attr_name = self.class.primary_key if attr_name == 'id'
value = @attributes[attr_name]
unless value.nil?
if column = column_for_attribute(attr_name)
type_cast_attribute(column, value)
else
value
end
end
end
def type_cast_attribute(column, value) #:nodoc:
column.type_cast(value)
end
private
def attribute(attribute_name)
read_attribute(attribute_name)
end
end
end
end
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