claudegoodies
Skill

design-patterns

From rtk-ai

Rust design patterns for RTK. Newtype, Builder, RAII, Trait Objects, State Machine. Applied to CLI filter modules. Use when designing new modules or refactoring existing ones.

Facts

Repository
rtk-ai/rtk
Status
Actively maintained
Last commit
Declared tools
Source file
.claude/skills/design-patterns/SKILL.md

Source preview

The instructions Claude Code reads when this skill runs.

# RTK Rust Design Patterns

Patterns that apply to RTK's filter module architecture. Focused on CLI tool patterns, not web/service patterns.

## Pattern 1: Newtype (Type Safety)

Use when: wrapping primitive types to prevent misuse (command names, paths, token counts).

```rust
// Without Newtype — easy to mix up
fn track(input_tokens: usize, output_tokens: usize) { ... }
track(output_tokens, input_tokens);  // Silent bug!

// With Newtype — compile error on swap
pub struct InputTokens(pub usize);
pub struct OutputTokens(pub usize);
fn track(input: InputTokens, output: OutputTokens) { ... }
track(OutputTokens(100), InputTokens(400));  // Compile error ✅
```

```rust
// Practical RTK example: command name validation
pub struct CommandName(String);
impl CommandName {
    pub fn new(s: &str) -> Result<Self> {
        if s.contains(';') || s.contains('|') || s.contains('`') {
            anyhow::bail!("Invalid command name: shell metacharacters");
        }
        Ok(Self(s.to_string()))
    }
    pub fn as_str(&self) -> &str { &self.0 }
}
```

## Pattern 2: Builder (Complex Configuration)

Use when: a struct has 4+ optional fields, many with defaults.

```rust
#[derive(Default)]
pub struct FilterConfig {
    max_lines: Option<usize>,
    strip_ansi: bool,
    show_warnings: bool,
    truncate_at: Option<usize>,
}

impl FilterConfig {
    pub fn new() -> Self { Self::default() }
View full source on GitHub →

Other skills