Class: Copland::ServiceModel::SingletonServiceModel

Inherits:
AbstractServiceModel show all
Defined in:
lib/copland/models/singleton.rb

Overview

This service model enforces a singleton constraint on the service point it protects. That is to say, whenever the #instance method of this model is called, it will always return the same instance of the service point.

Direct Known Subclasses

SingletonDeferredServiceModel

Instance Attribute Summary

Attributes inherited from AbstractServiceModel

#service_point

Instance Method Summary collapse

Methods inherited from AbstractServiceModel

register_as

Constructor Details

#initialize(service_point) ⇒ SingletonServiceModel

Create a new SingletonServiceModel on the given service point.



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# File 'lib/copland/models/singleton.rb', line 49

def initialize( service_point )
  super
  @mutex = QueryableMutex.new
end

Instance Method Details

#instance(&init) ⇒ Object

Return the singleton instance of the service point. This is thread safe.



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# File 'lib/copland/models/singleton.rb', line 56

def instance( &init )
  return @instance if @instance

  if @mutex.self_locked?
    raise CoplandException,
      "circular dependency on #{service_point.full_name} detected"
  end

  @mutex.synchronize do
    return @instance if @instance
    new_instance( &init )
    return @instance
  end
end