M02 Resource

This is a decision framework for choosing between Box, Rc, Arc, and other smart pointers in Rust. It walks you through ownership patterns (single vs shared), threading context (Rc vs Arc), and cycle prevention (when to use Weak). The error table is smart, it reframes "use Weak" as "is the cycle necessary in design?" instead of just throwing syntax at you. The trace up/down sections connect pointer choices to broader architecture questions, which is useful when you're stuck deciding between Rc and Arc but the real issue is whether you actually need shared ownership at all. Comes with a flowchart and anti-pattern warnings about overusing Arc or RefCell everywhere.

skills.sh installs: 3.6K
GitHub stars: 1.6K
last updated: Aug 21, 2026

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Install

$ npx -y skills add actionbook/rust-skills --skill m02-resource --agent claude-code

Installs into .claude/skills of the current project.

Files

Resource Management

Layer 1: Language Mechanics

Core Question

What ownership pattern does this resource need?

Before choosing a smart pointer, understand:

Is ownership single or shared?
Is access single-threaded or multi-threaded?
Are there potential cycles?

Error → Design Question

Error	Don't Just Say	Ask Instead
"Need heap allocation"	"Use Box"	Why can't this be on stack?
Rc memory leak	"Use Weak"	Is the cycle necessary in design?
RefCell panic	"Use try_borrow"	Is runtime check the right approach?
Arc overhead complaint	"Accept it"	Is multi-thread access actually needed?

Thinking Prompt

Before choosing a smart pointer:

What's the ownership model?
- Single owner → Box or owned value
- Shared ownership → Rc/Arc
- Weak reference → Weak
What's the thread context?
- Single-thread → Rc, Cell, RefCell
- Multi-thread → Arc, Mutex, RwLock
Are there cycles?
- Yes → One direction must be Weak
- No → Regular Rc/Arc is fine