陈老师，我尝试把MemTable与SledDb整合到一个Server中，通过config参数来动态选择MemTable还是SledDb。尝试了很久都失败了，编译器提示错误为: 50 | let resp = service_cloned.execute(msg); | ^^^^^^^ method cannot be called on `Service<Box<dyn Storage>>` due to unsatisfied trait bounds ... = note: the following trait bounds were not satisfied: `Box<dyn Storage>: Storage` 我的疑问是Box<dyn Storage>为什么不满足Storage呢？ server.rs代码如下: use anyhow::Result; use async_prost::AsyncProstStream; use futures::prelude::*; use kv::{CommandRequest, CommandResponse, MemTable, SledDb, Service, Storage}; use tokio::net::TcpListener; use kv::service::ServiceInner; use tracing::info; use clap::{Parser, ArgEnum}; #[derive(Parser)] #[clap(name = "kv server")] struct Cli { ​#[clap(arg_enum, long, short, default_value="memory")] ​storage: StorageType, ​#[clap(long, short='d', default_value="./sled")] ​sled_dir: String, } #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, ArgEnum)] enum StorageType { ​Memory, ​Sled, } #[tokio::main] async fn main() -> Result<()> { ​tracing_subscriber::fmt::init(); ​let args: Cli = Cli::parse(); ​let addr = "127.0.0.1:9527"; ​let listener = TcpListener::bind(addr).await?; ​info!("Start listening on {}", addr); ​let db : Box<dyn Storage> = match args.storage { ​StorageType::Memory => Box::new(MemTable::default()), ​StorageType::Sled => Box::new(SledDb::new(args.sled_dir)), ​}; ​let service: Service<Box<dyn Storage>> = ServiceInner::new(db).into(); ​loop { ​let (stream, addr) = listener.accept().await?; ​info!("Client {:?} connected", addr); ​let service_cloned = service.clone(); ​tokio::spawn(async move { ​let mut stream = ​AsyncProstStream::<_, CommandRequest, CommandResponse, _>::from(stream).for_async(); ​while let Some(Ok(msg)) = stream.next().await { ​info!("Got a new command: {:?}", msg); ​let resp = service_cloned.execute(msg); ​info!("Response: {:?}", resp); ​stream.send(resp).await.unwrap(); ​} ​info!("Client {:?} disconnected", addr); ​}); ​}