如何使用actix-web的Json类型解决“ serde :: Deserialize的实现不够通用”的问题？

Question

我正在使用actix-web编写服务器：

use actix_web::{post, web, Responder};
use serde::Deserialize;

#[derive(Deserialize)]
struct UserModel<'a, 'b> {
    username: &'a str,
    password: &'b str,
}

#[post("/")]
pub fn register(user_model: web::Json<UserModel>) -> impl Responder {}

编译器给出此错误：

error: implementation of `user::_IMPL_DESERIALIZE_FOR_UserModel::_serde::Deserialize` is not general enough  
  --> src/user.rs:31:1  
   |  
31 | #[post("/")]  
   | ^^^^^^^^^^^^  
   |  
   = note: `user::UserModel<'_, '_>` must implement `user::_IMPL_DESERIALIZE_FOR_UserModel::_serde::Deserialize<'0>`, for any lifetime `'0`  
   = note: but `user::UserModel<'_, '_>` actually implements `user::_IMPL_DESERIALIZE_FOR_UserModel::_serde::Deserialize<'1>`, for some specific lifetime `'1`

我该如何解决？

Answer 1

从该actix-web文档：

impl<T> FromRequest for Json<T>
where
    T: DeserializeOwned + 'static, 

它基本上说，Json如果您想actix-web从请求中提取类型，则只能使用拥有该类型的拥有的数据，而不能借用该类型的数据。因此，您必须在String这里使用：

use actix_web::{post, web, Responder};
use serde::Deserialize;

#[derive(Deserialize)]
struct UserModel {
    username: String,
    password: String,
}

#[post("/")]
pub fn register(user_model: web::Json<UserModel>) -> impl Responder {
    unimplemented!()
}