Singleton: How should it be used

Answer:

Use a Singleton if:

  • You need to have one and only one object of a type in system

Do not use a Singleton if:

  • You want to save memory
  • You want to try something new
  • You want to show off how much you know
  • Because everyone else is doing it (See cargo cult programmer in wikipedia)
  • In user interface widgets
  • It is supposed to be a cache
  • In strings
  • In Sessions
  • I can go all day long

How to create the best singleton:

  • The smaller, the better. I am a minimalist
  • Make sure it is thread safe
  • Make sure it is never null
  • Make sure it is created only once
  • Lazy or system initialization? Up to your requirements
  • Sometimes the OS or the JVM creates singletons for you (e.g. in Java every class definition is a singleton)
  • Provide a destructor or somehow figure out how to dispose resources
  • Use little memory

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