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module ActiveRecord
module AttributeMethods
module Read
ReaderMethodCache = Class.new(AttributeMethodCache) {
private
# We want to generate the methods via module_eval rather than
# define_method, because define_method is slower on dispatch.
# Evaluating many similar methods may use more memory as the instruction
# sequences are duplicated and cached (in MRI). define_method may
# be slower on dispatch, but if you're careful about the closure
# created, then define_method will consume much less memory.
#
# But sometimes the database might return columns with
# characters that are not allowed in normal method names (like
# 'my_column(omg)'. So to work around this we first define with
# the __temp__ identifier, and then use alias method to rename
# it to what we want.
#
# We are also defining a constant to hold the frozen string of
# the attribute name. Using a constant means that we do not have
# to allocate an object on each call to the attribute method.
# Making it frozen means that it doesn't get duped when used to
# key the @attributes in read_attribute.
def method_body(method_name, const_name)
<<-EOMETHOD
def #{method_name}
name = ::ActiveRecord::AttributeMethods::AttrNames::ATTR_#{const_name}
_read_attribute(name) { |n| missing_attribute(n, caller) }
end
EOMETHOD
end
}.new
extend ActiveSupport::Concern
module ClassMethods
protected
def define_method_attribute(name)
safe_name = name.unpack('h*').first
temp_method = "__temp__#{safe_name}"
ActiveRecord::AttributeMethods::AttrNames.set_name_cache safe_name, name
generated_attribute_methods.module_eval <<-STR, __FILE__, __LINE__ + 1
def #{temp_method}
name = ::ActiveRecord::AttributeMethods::AttrNames::ATTR_#{safe_name}
_read_attribute(name) { |n| missing_attribute(n, caller) }
end
STR
generated_attribute_methods.module_eval do
alias_method name, temp_method
undef_method temp_method
end
end
end
ID = 'id'.freeze
# Returns the value of the attribute identified by <tt>attr_name</tt> after
# it has been typecast (for example, "2004-12-12" in a date column is cast
# to a date object, like Date.new(2004, 12, 12)).
def read_attribute(attr_name, &block)
name = attr_name.to_s
name = self.class.primary_key if name == ID
_read_attribute(name, &block)
end
# This method exists to avoid the expensive primary_key check internally, without
# breaking compatibility with the read_attribute API
def _read_attribute(attr_name) # :nodoc:
@attributes.fetch_value(attr_name.to_s) { |n| yield n if block_given? }
end
private
def attribute(attribute_name)
_read_attribute(attribute_name)
end
end
end
end
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