第九章：State 的进一步组织 —— 总关底册可以拆成分册

use axum::extract::{FromRef, State};

#[derive(Clone)]
struct DbPool;

#[derive(Clone)]
struct AppConfig {
    service_name: String,
}

#[derive(Clone)]
struct AppState {
    db: DbPool,
    config: AppConfig,
}

impl FromRef<AppState> for DbPool {
    fn from_ref(state: &AppState) -> Self {
        state.db.clone()
    }
}

impl FromRef<AppState> for AppConfig {
    fn from_ref(state: &AppState) -> Self {
        state.config.clone()
    }
}

async fn health(State(config): State<AppConfig>) -> String {
    format!("{} OK", config.service_name)
}

总关底册 AppState
├── 数据库分册 db
└── 配置分册 config