未为`diesel_geography::types::GeogPoint`实现特征``serde：：trait <‘_>`

Question

我正在尝试使用Diesel和diesel_geography从使用Rust的PostGIS数据库读取数据。

下面是我得到的错误：

error[E0277]: the trait bound `diesel_geography::types::GeogPoint: serde::Serialize` is not satisfied
  --> src/models.rs:11:5
   |
11 |     pub coordinates: GeogPoint,
   |     ^^^ the trait `serde::Serialize` is not implemented for `diesel_geography::types::GeogPoint`
   |
   = note: required by `serde::ser::SerializeStruct::serialize_field`

error[E0277]: the trait bound `diesel_geography::types::GeogPoint: serde::Deserialize<'_>` is not satisfied
  --> src/models.rs:11:5
   |
11 |     pub coordinates: GeogPoint,
   |     ^^^ the trait `serde::Deserialize<'_>` is not implemented for `diesel_geography::types::GeogPoint`
   |
   = note: required by `serde::de::SeqAccess::next_element`

error[E0277]: the trait bound `diesel_geography::types::GeogPoint: serde::Deserialize<'_>` is not satisfied
  --> src/models.rs:11:5
   |
11 |     pub coordinates: GeogPoint,
   |     ^^^ the trait `serde::Deserialize<'_>` is not implemented for `diesel_geography::types::GeogPoint`
   |
   = note: required by `serde::de::MapAccess::next_value`

环顾四周，我发现当使用多个版本的serde作为依赖项时，也会发生类似的错误，这可以使用cargo tree -d进行检查。我试过了，serde没有显示为重复的依赖项。

这是我到目前为止的代码：

Cargo.toml

[package]
name = "123"
version = "0.1.0"
authors = ["ASD"]
edition = "2018"

[dependencies]
diesel = { version = "1.4.2", features = ["postgres"] }
serde = { version = "1.0", features = ["derive"] } 
serde_json="1.0"

dotenv = "0.14.1"

diesel-geography = "0.2.0"

schema.rs

table! {
    use diesel::sql_types::*;
    use diesel_geography::sql_types::*;

    users (email) {
        email -> Varchar,
        password -> Varchar,
        coordinates -> Geography
    }
}

models.rs

use diesel_geography::types::*;
use crate::schema::users;
use serde::{Serialize, Deserialize};

#[derive(Debug, Serialize, Deserialize, Queryable, Insertable)]
#[table_name = "users"]
pub struct User {
    pub email: String,
    pub password: String,
    pub coordinates: GeogPoint
}

main.rs

extern crate serde;
extern crate dotenv;
#[macro_use] extern crate diesel;
//#[macro_use] extern crate serde_derive;

mod models;
mod schema;
use diesel::PgConnection;
use dotenv::dotenv;
use std::env;

use diesel::prelude::*;

fn main() {
    dotenv().ok();

    let database_url = env::var("DATABASE_URL")
        .expect("DATABASE_URL must be set");

    let connection = PgConnection::establish(&database_url)
        .expect(&format!("Error connecting to {}", database_url));

    use crate::schema::users::dsl::*;
    use crate::models::User;

    let results = users
        .limit(5)
        .load::<User>(&connection)
        .expect("Error loading users");

    println!("Displaying {} users", results.len());

    for user in results {
        println!("{}", user.email);
        println!("----------\n");
        println!("{}", user.password);
    }
}

Answer 1

Serde是一个optional dependency of diesel-geography。您需要开启该功能：

[dependencies]
diesel-geography = { version = "0.2.0", features = ["serde"] }