# Rust Development ## Project Structure ``` my-project/ ├── Cargo.toml ├── src/ │ ├── main.rs │ ├── lib.rs │ └── handlers/ │ └── mod.rs └── tests/ └── integration.rs ``` ## Error Handling ```rust use thiserror::Error; #[derive(Error, Debug)] pub enum AppError { #[error("User not found: {0}")] NotFound(String), #[error("Database error: {0}")] Database(#[from] sqlx::Error), #[error("Validation error: {0}")] Validation(String), } // Using Result async fn get_user(id: &str) -> Result { let user = sqlx::query_as!(User, "SELECT * FROM users WHERE id = $1", id) .fetch_optional(&pool) .await? .ok_or_else(|| AppError::NotFound(id.to_string()))?; Ok(user) } // Using ? operator fn process() -> Result<(), AppError> { let user = get_user("123")?; validate(&user)?; save(&user)?; Ok(()) } ``` ## Ownership & Borrowing ```rust // Ownership transfer fn take_ownership(s: String) { println!("{}", s); } // s is dropped here // Borrowing (immutable) fn borrow(s: &String) { println!("{}", s); } // Mutable borrowing fn mutate(s: &mut String) { s.push_str(" world"); } // Lifetimes fn longest<'a>(x: &'a str, y: &'a str) -> &'a str { if x.len() > y.len() { x } else { y } } ``` ## Async with Tokio ```rust use tokio; #[tokio::main] async fn main() { let result = fetch_data().await; } async fn fetch_all(urls: Vec) -> Vec { let futures: Vec<_> = urls .into_iter() .map(|url| tokio::spawn(async move { fetch(&url).await })) .collect(); let results = futures::future::join_all(futures).await; results.into_iter().filter_map(|r| r.ok()).collect() } ``` ## Axum Web Handler ```rust use axum::{ extract::{Path, State}, http::StatusCode, Json, }; async fn get_user( State(pool): State, Path(id): Path, ) -> Result, (StatusCode, String)> { let user = sqlx::query_as!(User, "SELECT * FROM users WHERE id = $1", id) .fetch_optional(&pool) .await .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))? .ok_or((StatusCode::NOT_FOUND, "User not found".to_string()))?; Ok(Json(user)) } ``` ## Testing ```rust #[cfg(test)] mod tests { use super::*; #[test] fn test_validation() { let result = validate("valid@email.com"); assert!(result.is_ok()); } #[tokio::test] async fn test_async_operation() { let result = fetch_data().await; assert!(result.is_ok()); } } ``` ## Tooling ```bash # Format cargo fmt # Lint cargo clippy -- -D warnings # Test cargo test # Build release cargo build --release ``` ---