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authorDavid Heinemeier Hansson <david@loudthinking.com>2015-12-17 14:28:19 +0100
committerDavid Heinemeier Hansson <david@loudthinking.com>2015-12-17 14:28:19 +0100
commit748b21db8ff850378b20a69ccd4215c06abea03e (patch)
treeb03b33698dabdea94b003af789b80fa5883535ad /activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb
parent7a53a9c13c997771797874b7549d389ced0be7b2 (diff)
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Add thread_m/cattr_accessor/reader/writer suite of methods for declaring class and module variables that live per-thread
Diffstat (limited to 'activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb')
-rw-r--r--activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb140
1 files changed, 140 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb b/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb
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+++ b/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb
@@ -0,0 +1,140 @@
+require 'active_support/core_ext/array/extract_options'
+
+# Extends the module object with class/module and instance accessors for
+# class/module attributes, just like the native attr* accessors for instance
+# attributes, but does so on a per-thread basis.
+#
+# So the values are scoped within the Thread.current space under the class name
+# of the module.
+class Module
+ # 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 # => nil
+ # Thread.current[:attr_Current_user] = "DHH"
+ # Current.user # => "DHH"
+ #
+ # 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
+ #
+ # If you want to opt out the creation on the instance reader method, pass
+ # <tt>instance_reader: false</tt> or <tt>instance_accessor: false</tt>.
+ #
+ # class Current
+ # thread_mattr_reader :user, instance_reader: false
+ # end
+ #
+ # Current.new.user # => NoMethodError
+ def thread_mattr_reader(*syms)
+ options = syms.extract_options!
+
+ syms.each do |sym|
+ raise NameError.new("invalid attribute name: #{sym}") unless sym =~ /^[_A-Za-z]\w*$/
+ class_eval(<<-EOS, __FILE__, __LINE__ + 1)
+ def self.#{sym}
+ Thread.current[:"attr_#{name}_#{sym}"]
+ end
+ EOS
+
+ unless options[:instance_reader] == false || options[:instance_accessor] == false
+ class_eval(<<-EOS, __FILE__, __LINE__ + 1)
+ def #{sym}
+ Thread.current[:"attr_#{self.class.name}_#{sym}"]
+ end
+ EOS
+ end
+ end
+ end
+ alias :thread_cattr_reader :thread_mattr_reader
+
+ # Defines a per-thread class attribute and creates a class and instance writer methods to
+ # allow assignment to the attribute.
+ #
+ # module Current
+ # thread_mattr_writer :user
+ # end
+ #
+ # Current.user = "DHH"
+ # Thread.current[:attr_Current_user] # => "DHH"
+ #
+ # If you want to opt out the instance writer method, pass
+ # <tt>instance_writer: false</tt> or <tt>instance_accessor: false</tt>.
+ #
+ # class Current
+ # thread_mattr_writer :user, instance_writer: false
+ # end
+ #
+ # Current.new.user = "DHH" # => NoMethodError
+ def thread_mattr_writer(*syms)
+ options = syms.extract_options!
+ syms.each do |sym|
+ raise NameError.new("invalid attribute name: #{sym}") unless sym =~ /^[_A-Za-z]\w*$/
+ class_eval(<<-EOS, __FILE__, __LINE__ + 1)
+ def self.#{sym}=(obj)
+ Thread.current[:"attr_#{name}_#{sym}"] = obj
+ end
+ EOS
+
+ unless options[:instance_writer] == false || options[:instance_accessor] == false
+ class_eval(<<-EOS, __FILE__, __LINE__ + 1)
+ def #{sym}=(obj)
+ Thread.current[:"attr_#{self.class.name}_#{sym}"] = obj
+ end
+ EOS
+ end
+ end
+ end
+ alias :thread_cattr_writer :thread_mattr_writer
+
+ # Defines both class and instance accessors for class attributes.
+ #
+ # class Current
+ # thread_mattr_accessor :user
+ # end
+ #
+ # Current.user = "DHH"
+ # Current.user # => "DHH"
+ # Current.new.user # => "DHH"
+ #
+ # If a subclass changes the value then that will not change the value for
+ # parent class. Similarly if parent class changes the value then that will not
+ # change the value of subclasses either.
+ #
+ # class Customer < Account
+ # end
+ #
+ # Customer.user = "CHH"
+ # Account.user # => "DHH"
+ #
+ # To opt out of the instance writer method, pass <tt>instance_writer: false</tt>.
+ # To opt out of the instance reader method, pass <tt>instance_reader: false</tt>.
+ #
+ # class Current
+ # thread_mattr_accessor :user, instance_writer: false, instance_reader: false
+ # end
+ #
+ # Current.new.user = "DHH" # => NoMethodError
+ # Current.new.user # => NoMethodError
+ #
+ # Or pass <tt>instance_accessor: false</tt>, to opt out both instance methods.
+ #
+ # class Current
+ # mattr_accessor :user, instance_accessor: false
+ # end
+ #
+ # Current.new.user = "DHH" # => NoMethodError
+ # Current.new.user # => NoMethodError
+ def thread_mattr_accessor(*syms, &blk)
+ thread_mattr_reader(*syms, &blk)
+ thread_mattr_writer(*syms, &blk)
+ end
+ alias :thread_cattr_accessor :thread_mattr_accessor
+end