matklad/once_cell

Health v2 · maintenance only

Flags: no_releases

Adoption not part of the score

2089 stars · 124 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-30, confidence not recorded

A Rust library providing single assignment cells (OnceCell) and lazy initialization types (Lazy) without macros. It offers a macro-free alternative to lazy_static! with sync and unsync variants.

Use cases

• initialize global static data lazily in Rust
• replace lazy_static! macro with plain code
• store a value that is assigned at most once
• share lazily-built HashMap or Mutex across threads
• defer expensive computation until first access

When to choose

• you need lazy statics or single-assignment cells in Rust without macros
• you want a minimal, widely-adopted dependency for lazy initialization
• you need both thread-safe and single-threaded lazy cell variants

When to avoid

• you are on Rust 1.70+ and std's OnceCell/LazyLock suffice
• you need reassignment or interior mutability beyond single assignment
• you need async-aware lazy initialization (consider async_once_cell)

Facets

library · maturity stable

concurrency developer-tools developer-tools programming-languages rust cross-platform lazy-static single-assignment no-macros initialization

Member repositories

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