B. Command line argument parsing

#[derive(Parser)]
struct Cli {
    #[arg(short, long)]
    name: String,
}

B. Serialization/Deserialization

#[derive(Serialize, Deserialize)]
struct Data { /* ... */ }
```text

</details>

---

# คำถาม 20.3

`anyhow` crate ใช้ทำอะไร?

A. Async runtime  
B. Easy error handling  
C. Web framework  
D. Database ORM

<details>
<summary>ดูเฉลย</summary>

**B. Easy error handling**

```rust,ignore
fn main() -> anyhow::Result<()> {
    // ใช้ ? ได้กับทุก error types
    Ok(())
}

B. แยก modules ตาม responsibility

src/
├── main.rs
├── lib.rs
├── models/
├── handlers/
└── utils/

B. Optimized, production-ready

• cargo build = debug, fast compile
• cargo build --release = optimized, slower compile