rust - 火箭的“响应者”特征未针对“结果”实现

Question

我最近开始学习Rust，目前正在尝试创建一个小型API。我为API响应创建了自己的结构，为错误创建了枚举:

// API Response Structure
pub struct ApiResponse {
    pub body: JsonValue,
    pub status: Status,
}

// Enum for my "custom errors"
#[derive(Debug, Snafu, Clone, Serialize)]
pub enum Errors {
    #[snafu(display("Unable to retrieve the specified entry."))]
    NotFound,

    #[snafu(display("Internal Server Error, unable to process the data."))]
    ISE,
}

然后，我为我的API Response结构实现了 Responder<'_>特性:

impl<'r> Responder<'r> for ApiResponse {
    fn respond_to(self, req: &Request) -> Result<Response<'r>, Status> {
        Response::build_from(self.body.respond_to(req).unwrap())
            .status(self.status)
            .header(ContentType::JSON)
            .ok()
    }
}

但是，当我尝试使用所提到的内容时，似乎无法让我的函数返回 Result<JsonValue, Errors>。我对这个问题不太确定，我也不太熟悉Rust，所以任何文档/指针都将不胜感激。

这是返回响应类型的函数。

#[put("/users/<user_id>", format = "json", data = "<new_user>")]
pub fn update_user(
    conn: DbConnection,
    user_id: i32,
    new_user: Json<NewUser>,
) -> Result<JsonValue, ApiResponse> {

    match users::table.find(user_id).load::<User>(&*conn) {
        Ok(result) => {
            if result.len() < 1 {
                let response = ApiResponse {
                    body: json!({
                        "message": Errors::NotFound
                    }),
                    status: Status::NotFound
                };

                return Err(response)
            }
        },

        Err(e) => {
            let response = ApiResponse {
                body: json!({
                    "message": Errors::ISE
                }),
                status: Status::InternalServerError
            };

            return Err(response);
        },
    }

    match diesel::update(users::table.filter(id.eq(user_id)))
        .set((
            user_name.eq(new_user.user_name.to_string()),
            age.eq(new_user.age),
            gender.eq(new_user.gender.to_string()),
        ))
        .get_result::<User>(&*conn)
    {
        Ok(result) => Ok(json!(result)),
        Err(_) => {
            let res = ApiResponse {
                body: json!({
                    "message": Errors::ISE
                }),
                status: Status::InternalServerError
            };

            return Err(res);
        },
    }
}

旁注:请记住，我仍然是Rust的初学者，而且我的错误处理/代码通常不是最好的。

编辑:我忘了包括错误堆栈:

error[E0277]: the trait bound `std::result::Result<rocket_contrib::json::JsonValue, api_cont::ApiResponse>: rocket::response::Responder<'_>` is not satisfied
   --> src/routes.rs:72:6
    |
72  | ) -> Result<JsonValue, ApiResponse> {
    |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `rocket::response::Responder<'_>` is not implemented for `std::result::Result<rocket_contrib::json::JsonValue, api_cont::ApiResponse>`
    | 
   ::: /home/kenneth/.cargo/registry/src/github.com-1ecc6299db9ec823/rocket-0.4.4/src/handler.rs:202:20
    |
202 |     pub fn from<T: Responder<'r>>(req: &Request, responder: T) -> Outcome<'r> {
    |                    ------------- required by this bound in `rocket::handler::<impl rocket::Outcome<rocket::Response<'r>, rocket::http::Status, rocket::Data>>::from`
    |
    = help: the following implementations were found:
              <std::result::Result<R, E> as rocket::response::Responder<'r>>
              <std::result::Result<R, E> as rocket::response::Responder<'r>>

Answer 1

我也遇到了这个错误。
API Docs中提到了以下内容:

A type implementing Responder should implement the Debug trait when possible. This is because the Responder implementation for Result requires its Err type to implement Debug. Therefore, a type implementing Debug can more easily be composed.

这意味着您必须实现Debug，因为您将 ApiResponse用作 Err类型。

#[derive(Debug)]
pub struct ApiResponse {
    pub body: JsonValue,
    pub status: Status,
}