rust - 通过 FromRequest 传递数据库引用

Question

我在 Rust 中使用 Rocket Web 框架，并且我有一个数据库池（DbConn）。

#[database("redirect-api")]
pub struct DbConn(diesel::PgConnection);

我已经能够将 DbConn 传递给每条路由，但是在尝试将它传递给 from_request 调用的函数时遇到了麻烦。在 get_redirects 中，我使用了 ApiKey 结构，我如何理解它，FromRequest 是一个检查输入的守卫。在 from_request 中，我调用了 is_valid 函数，但不能将其传递给 DbConn，就像我从路由调用 is_valid 一样，比如直接从 get_redirects 调用。

我希望能够在 is_valid 函数中使用 DbConn，但是如果我尝试使用 &DbConn，则会收到此错误

the trait `diesel::Connection` is not implemented for `fn(PooledConnection<<diesel::PgConnection as Poolable>::Manager>) -> DbConn {DbConn}`

   |
43 |         .load::<Token>(&DbConn)
   |                        ^^^^^^^ the trait `diesel::Connection` is not implemented for `fn(PooledConnection<<diesel::PgConnection as Poolable>::Manager>) -> DbConn {DbConn}`
   |
   = note: required because of the requirements on the impl of `LoadQuery<fn(PooledConnection<<diesel::PgConnection as Poolable>::Manager>) -> DbConn {DbConn}, models::Token>` for `diesel::query_builder::SelectStatement<schema::tokens::table, query_builder::select_clause::DefaultSelectClause, query_builder::distinct_clause::NoDistinctClause, query_builder::where_clause::WhereClause<diesel::expression::operators::Eq<schema::tokens::columns::token, diesel::expression::bound::Bound<diesel::sql_types::Text, std::string::String>>>, query_builder::order_clause::NoOrderClause, query_builder::limit_clause::LimitClause<diesel::expression::bound::Bound<BigInt, i64>>>`

#![feature(decl_macro)]
use rocket::{catchers, routes};

#[macro_use]
extern crate diesel;
#[macro_use]
extern crate rocket_contrib;
use diesel::prelude::*;
// --snip--

#[database("redirect-api")]
pub struct DbConn(diesel::PgConnection);
// --snip--

fn is_valid(key: &str) {
    // ... use key, hash is, etc
    // check if hash is in database
    // this function needs the database pool or DbConn
    // but it can't be passed through FromRequest
}

impl<'a, 'r> FromRequest<'a, 'r> for ApiKey {
    type Error = ApiKeyError;

    fn from_request(request: &'a Request<'r>) -> request::Outcome<Self, Self::Error> {
        let keys: Vec<_> = request.headers().get("x-api-key").collect();
        match keys.len() {
            0 => Outcome::Failure((Status::BadRequest, ApiKeyError::Missing)),
            1 if is_valid(keys[0]) => Outcome::Success(ApiKey(keys[0].to_string())),
            1 => Outcome::Failure((Status::BadRequest, ApiKeyError::Invalid)),
            _ => Outcome::Failure((Status::BadRequest, ApiKeyError::BadCount)),
        }
    }
}
// --snip--

#[get("/redirects")]
pub fn get_redirects(_key: ApiKey, conn: DbConn) -> String {
    // ... do database things with conn
    format!("something {}", some_value_from_db)
}

// --snip--

fn main() {
    rocket::ignite()
        .register(catchers![not_found])
        .attach(DbConn::fairing())
        .mount("/", routes![root, get_redirect])
        .launch();
}

标签： rustrust-dieselrust-rocket