Once Upon a Lazy Init

The article discusses the differences between the Rust crates `lazy_static` and `once_cell`, as well as the new lazy-initialization features introduced in Rust versions 1.70 and 1.80. `lazy_static`, released in 2014, allows for the declaration of static variables using a macro, while `once_cell`, introduced in 2018, provides similar functionality without macros, making it more user-friendly. The author highlights that `once_cell` is generally preferred due to its clearer syntax and better integration with Rust's type system. The article also notes that the standard library now includes equivalents for both crates, which simplifies dependency management. The author emphasizes the importance of understanding the underlying mechanics of these tools, as `lazy_static` can lead to confusing behavior and compiler errors. Additionally, the article touches on the implications of using lazy initialization in asynchronous environments and suggests that while lazy initialization can be useful, it is not always necessary and can complicate code. The author concludes by advocating for careful consideration of when to use global variables and suggests alternatives that may lead to simpler and more maintainable code.

- `once_cell` is preferred over `lazy_static` for its clearer syntax and better type handling.

- Rust's standard library now includes lazy-initialization features, reducing the need for third-party crates.

- Lazy initialization can complicate code and should be used judiciously, especially in asynchronous contexts.

- Understanding the mechanics of lazy initialization is crucial to avoid confusion and errors.

- Consider alternatives to global variables for simpler and more maintainable code.