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Tips and Traps¶

1. std::cell::OnceCell is a partial implementation of once_cell in the Rust standard library.

2. There are 2 Rust crates lazy_static and once_cell for (lazy) once assignment (which can be used to create singletons). once_cell

An implementation of the singleton pattern must:

• ensure that only one instance of the singleton class ever exists;
• and provide global access to that instance.

Typically, this is done by:

• declaring all constructors of the class to be private;
• and providing a static method that returns a reference to the instance.

The instance is usually stored as a private static variable; the instance is created when the variable is initialized, at some point before the static method is first called. The following is a sample implementation written in Java.