Thread::Local

Per-Class Instance

By default, classes are instantiated using self.new:

require 'thread/local'

class MyClass
	extend Thread::Local
end

p MyClass.instance

Extensions

If you need to change the behaviour of an existing thread local, you can prepend a module to wrap the call to self.new:

require 'thread/local'

class MyClass
	extend Thread::Local
	
	attr_accessor :data
end

module MyExtension
	def local
		instance = super
		
		# Do something with the thread local instance, e.g.:
		instance.data = [1, 2, 3]
		
		return instance
	end
end

MyClass.extend(MyExtension)

p MyClass.instance

Assignment

Generally, you should avoid assigning to the thread-local instance. You should prefer extensions as outlined above. However, in some situations (e.g. testing) you may prefer to directly assign to the thread local:

require 'thread/local'

class MyClass
	extend Thread::Local
end

# Change the instance for the current thread:
MyClass.instance = Object.new

p MyClass.instance

Per-Module Instance

By default, you cannot instantiate a module. So, you must implement your own self.new method:

require 'thread/local'

module MyModule
	extend Thread::Local
	
	def self.new
		Object.new
	end
end

p MyModule.instance

Definitions

def local
	self.new
end

def instance
	thread = Thread.current
	name = self.name
	
	unless instance = thread.thread_variable_get(name)
		if instance = self.local
			thread.thread_variable_set(name, instance)
		end
	end
	
	return instance
end

def instance= instance
	thread = Thread.current
	thread.thread_variable_set(self.name, instance)
end