rust - 如何撰写经向日志？

Question

我在Rust中还很陌生，并尝试使用https://docs.rs/warp/0.2.3/warp/index.html构建Web应用程序。

我试过了:

#[tokio::main]
async fn main() {
    // GET /hello/warp => 200 OK with body "Hello, warp!"

    let cors = warp::cors()
        .allow_origin("http://localhost:8090")
        .allow_methods(vec!["GET", "POST", "DELETE"]);

    let log = warp::log("dashbaord-svc");

    let hello = warp::path!("hello" / String)
        .with(cors)
        .with(log)
        .map(|name| format!("Hello, {}!", name));


    warp::serve(hello)
        .run(([127, 0, 0, 1], 9999))
        .await;
}

编译器提示:

error[E0277]: `warp::filters::log::internal::Logged` doesn't implement `std::fmt::Display`
  --> src/main.rs:16:43
   |
16 |         .map(|name| format!("Hello, {}!", name));
   |                                           ^^^^ `warp::filters::log::internal::Logged` cannot be formatted with the default formatter
   |
   = help: the trait `std::fmt::Display` is not implemented for `warp::filters::log::internal::Logged`
   = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
   = note: required by `std::fmt::Display::fmt`
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)  

我究竟做错了什么？

Answer 1

    let hello = warp::path!("hello" / String)
    .with(cors)
    .with(log)
    .map(|name| format!("Hello, {}!", name));

过滤器传递给后续过滤器数据。在您的代码中，map函数将从最后一个过滤器(即日志过滤器)接收数据，并将数据作为“名称”传递，其类型为“warp::filters::log::internal::Logged”。此类型无法格式化!或打印!与{}一起使用，因为它没有实现显示特征。
过滤器顺序很重要。在路径过滤器之后立即更改map函数，以将路径参数接收为“名称”:

    let hello = warp::path!("hello" / String)
    .map(|name| format!("Hello, {}!", name))
    .with(cors)
    .with(log);