我有以下基于actix-web Database Integration sample的代码。
extern crate actix;
extern crate actix_web;
extern crate serde_json;
#[macro_use]
extern crate serde_derive;
extern crate r2d2;
extern crate r2d2_mysql;
use actix::prelude::*;
use actix_web::{middleware::Logger, server, App, FutureResponse, HttpRequest, HttpResponse};
mod dbservices {
use actix::prelude::*;
use actix_web::dev::Handler;
use model::DataDictionary;
use r2d2::Pool;
use r2d2_mysql::*;
use std::io;
pub struct MysqlConnection {
db_pool: mysql::PooledConn,
}
impl Actor for MysqlConnection {
type Context = SyncContext<Self>;
}
impl MysqlConnection {
pub fn new(db_url: &str) -> MysqlConnection {
unimplemented!();
}
}
pub struct GetDD;
impl Message for GetDD {
type Result = io::Result<Vec<DataDictionary>>;
}
impl Handler<GetDD> for MysqlConnection {
type Result = io::Result<Vec<DataDictionary>>;
fn handle(&mut self, msg: GetDD, _: &mut Self::Context) -> Self::Result {
unimplemented!();
}
}
}
mod model {
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DataDictionary {
id: i32,
name: String,
}
}
struct State {
db: Addr<MysqlConnection>,
}
fn get_dd(req: HttpRequest<State>) -> FutureResponse<HttpResponse> {
req.clone()
.state()
.db
.send(GetDD)
.from_err()
.and_then(|result| Ok.json(result))
.responder()
}
fn main() {
std::env::set_var("RUST_LOG", "actix_web=debug,info");
const db_url: str = "mysql://connstring";
let addr = SyncArbiter::start(3, move || dbservices::MysqlConnection::new(db_url));
server::new(|| {
App::new()
.middleware(Logger::default())
.middleware(Logger::new("%a %{User-Agent}i"))
.prefix("/api")
.scope("/dd", |dp_scope| {
dp_scope.resource("/", |r| r.h(dbservices::GetDD()))
})
}).bind("127.0.0.1:8088")
.unwrap()
.run();
}
编译时出现以下错误。我不确定自己在做什么错:
error[E0220]: associated type `Context` not found for `Self`
--> src/main.rs:43:50
|
43 | fn handle(&mut self, msg: GetDD, _: &mut Self::Context) -> Self::Result {
| ^^^^^^^^^^^^^ associated type `Context` not found
这是我对Cargo.toml的依赖:
[dependencies]
actix-web = "0.6.14"
actix = "0.6.1"
chrono = { version = "0.4.2", features = ["serde"] }
serde = "1.0.60"
serde_derive = "1.0.60"
serde_json = "1.0.17"
log = "0.4.1"
env_logger ="0.5.10"
futures = "0.2.1"
r2d2 = "*"
[dependencies.r2d2_mysql]
git = "https://github.com/outersky/r2d2-mysql"
version="*"
最佳答案
创建最小 MCVE几乎总是使问题更容易发现:
extern crate actix;
extern crate actix_web;
use actix::prelude::*;
use actix_web::dev::Handler;
use std::io;
pub struct MysqlConnection;
impl Actor for MysqlConnection {
type Context = SyncContext<Self>;
}
pub struct DummyMessage;
impl Message for DummyMessage {
type Result = io::Result<String>;
}
impl Handler<DummyMessage> for MysqlConnection {
type Result = io::Result<String>;
fn handle(&mut self, _: DummyMessage, _: &mut Self::Context) -> Self::Result {
unimplemented!();
}
}
fn main() {}
error[E0220]: associated type `Context` not found for `Self`
--> src/main.rs:22:53
|
22 | fn handle(&mut self, _: DummyMessage, _: &mut Self::Context) -> Self::Result {
| ^^^^^^^^^^^^^ associated type `Context` not found
问题1 —多个版本
actix-web = "0.6.14"
actix = "0.6.1"
这带来了两个不同版本的actix:
$ cargo tree -d
actix v0.5.8
└── actix-web v0.6.14
└── repro v0.1.0 (file:///private/tmp/repro)
actix v0.6.1
└── repro v0.1.0 (file:///private/tmp/repro)
选择一个,actix 0.5.8。
也可以看看:
问题2 —错误的性格
您带来
actix_web::dev::Handler
:pub trait Handler<S>: 'static {
type Result: Responder;
fn handle(&mut self, req: HttpRequest<S>) -> Self::Result;
}
您正在实现
actix::Handler
:pub trait Handler<M>
where
Self: Actor,
M: Message,
{
type Result: MessageResponse<Self, M>;
fn handle(&mut self, msg: M, ctx: &mut Self::Context) -> Self::Result;
}
actix::Handler
具有Actor
作为其 super 特性,这意味着它可以访问关联的类型Context
。 actix_web::dev::Handler
不具有上级特征,因此它不了解Self::Context
。选择适当的特征并正确实现。