Method: Module#thread_mattr_reader

Defined in:
lib/active_support/core_ext/module/attribute_accessors_per_thread.rb

#thread_mattr_reader(*syms, instance_reader: true, instance_accessor: true, default: nil) ⇒ Object Also known as: thread_cattr_reader

Defines a per-thread class attribute and creates class and instance reader methods. The underlying per-thread class variable is set to nil, if it is not previously defined.

module Current
  thread_mattr_reader :user
end

Current.user = "DHH"
Current.user # => "DHH"
Thread.new { Current.user }.value # => nil

The attribute name must be a valid method name in Ruby.

module Foo
  thread_mattr_reader :"1_Badname"
end
# => NameError: invalid attribute name: 1_Badname

To omit the instance reader method, pass instance_reader: false or instance_accessor: false.

class Current
  thread_mattr_reader :user, instance_reader: false
end

Current.new.user # => NoMethodError



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# File 'lib/active_support/core_ext/module/attribute_accessors_per_thread.rb', line 41

def thread_mattr_reader(*syms, instance_reader: true, instance_accessor: true, default: nil) # :nodoc:
  syms.each do |sym|
    raise NameError.new("invalid attribute name: #{sym}") unless /^[_A-Za-z]\w*$/.match?(sym)

    # The following generated method concatenates `object_id` because we want
    # subclasses to maintain independent values.
    if default.nil?
      class_eval(<<-EOS, __FILE__, __LINE__ + 1)
        def self.#{sym}
          @__thread_mattr_#{sym} ||= "attr_#{sym}_\#{object_id}"
          ::ActiveSupport::IsolatedExecutionState[@__thread_mattr_#{sym}]
        end
      EOS
    else
      default = default.dup.freeze unless default.frozen?
      singleton_class.define_method("#{sym}_default_value") { default }

      class_eval(<<-EOS, __FILE__, __LINE__ + 1)
        def self.#{sym}
          @__thread_mattr_#{sym} ||= "attr_#{sym}_\#{object_id}"
          value = ::ActiveSupport::IsolatedExecutionState[@__thread_mattr_#{sym}]

          if value.nil? && !::ActiveSupport::IsolatedExecutionState.key?(@__thread_mattr_#{sym})
            ::ActiveSupport::IsolatedExecutionState[@__thread_mattr_#{sym}] = #{sym}_default_value
          else
            value
          end
        end
      EOS
    end

    if instance_reader && instance_accessor
      class_eval(<<-EOS, __FILE__, __LINE__ + 1)
        def #{sym}
          self.class.#{sym}
        end
      EOS
    end
  end
end