我有一个枚举:
enum Role {
Administrator,
Sponsor,
Bot,
}
我的数据库中有一个名为“roles”的表,如下所示:
| user_id | administrator | sponsor | bot |
|---------|---------------|---------|-------|
| 0 | true | false | false |
| 1 | false | false | false |
| 2 | false | true | true |
如何在使用Diesel而不是原始 SQL 查询时对 a 执行匹配Role
并获取数据库中的相应列?
我可以从与角色匹配的方法返回 Diesel 表达式,但它不适用于我的插入语句:
#[macro_use]
extern crate diesel;
use diesel::{
mysql::{Mysql, MysqlConnection},
sql_types::{Bool, Nullable},
BoxableExpression, Connection, ExpressionMethods, RunQueryDsl,
};
use schema::{roles, users};
use models::{NewUser};
use std::error::Error;
mod schema {
table! {
roles (user_id) {
id -> Unsigned<Bigint>,
user_id -> Unsigned<Bigint>,
administrator -> Nullable<Bool>,
sponsor -> Nullable<Bool>,
bot -> Nullable<Bool>,
}
}
table! {
users (id) {
id -> Unsigned<Bigint>,
username -> Nullable<Varchar>,
}
}
allow_tables_to_appear_in_same_query!(
roles,
users,
);
}
mod models {
use super::schema::users;
#[derive(Insertable, PartialEq, Debug, Default)]
#[table_name = "users"]
pub struct NewUser<'a> {
username: &'a str,
}
impl<'a> NewUser<'a> {
pub fn new(username: &'a str) -> Self {
Self {
username
}
}
}
}
enum Role {
Administrator,
Sponsor,
Bot,
}
impl From<&Role> for Box<dyn BoxableExpression<roles::table, Mysql, SqlType = Nullable<Bool>>> {
fn from(r: &Role) -> Self {
match r {
Role::Administrator => Box::new(roles::dsl::administrator),
Role::Sponsor => Box::new(roles::dsl::sponsor),
Role::Bot => Box::new(roles::dsl::bot),
}
}
}
fn main() -> Result<(), Box<dyn Error>> {
let conn = MysqlConnection::establish("mysql://localhost/stquestion")?;
diesel::replace_into(users::table)
.values(&NewUser::new("test_account"))
.execute(&conn)?;
diesel::replace_into(roles::table)
.values((
roles::dsl::user_id.eq(1),
<&Role as Into<
Box<dyn BoxableExpression<roles::table, Mysql, SqlType = Nullable<Bool>>>,
>>::into(&Role::Administrator)
.eq(true),
))
.execute(&conn)?;
Ok(())
}
上面的代码给我留下了以下编译错误:
error[E0277]: the trait bound `std::boxed::Box<dyn diesel::expression::BoxableExpression<stackoverflow_questions::
schema::roles::table, diesel::mysql::backend::Mysql, SqlType = diesel::sql_types::Nullable<diesel::sql_types::Bool
>>>: diesel::query_source::Column` is not satisfied
--> src/main.rs:36:17
|
36 | .values((
| _________________^
37 | | roles::dsl::user_id.eq(1),
38 | | <&Role as Into<
39 | | Box<dyn BoxableExpression<roles::table, Mysql, SqlType = Nullable<Bool>>>,
40 | | >>::into(&Role::Administrator)
41 | | .eq(true),
42 | | ))
| |_________^ the trait `diesel::query_source::Column` is not implemented for `std::boxed::Box<dyn diesel::expr
ession::BoxableExpression<stackoverflow_questions::schema::roles::table, diesel::mysql::backend::Mysql, SqlType =
diesel::sql_types::Nullable<diesel::sql_types::Bool>>>`
|
= note: required because of the requirements on the impl of `diesel::insertable::Insertable<stackoverflow_quest
ions::schema::roles::table>` for `diesel::expression::operators::Eq<std::boxed::Box<dyn diesel::expression::Boxabl
eExpression<stackoverflow_questions::schema::roles::table, diesel::mysql::backend::Mysql, SqlType = diesel::sql_ty
pes::Nullable<diesel::sql_types::Bool>>>, diesel::expression::bound::Bound<diesel::sql_types::Nullable<diesel::sql
_types::Bool>, bool>>`
= note: required because of the requirements on the impl of `diesel::insertable::Insertable<stackoverflow_quest
ions::schema::roles::table>` for `(diesel::expression::operators::Eq<stackoverflow_questions::schema::roles::colum
ns::user_id, diesel::expression::bound::Bound<diesel::mysql::types::Unsigned<diesel::sql_types::BigInt>, u64>>, di
esel::expression::operators::Eq<std::boxed::Box<dyn diesel::expression::BoxableExpression<stackoverflow_questions:
:schema::roles::table, diesel::mysql::backend::Mysql, SqlType = diesel::sql_types::Nullable<diesel::sql_types::Boo
l>>>, diesel::expression::bound::Bound<diesel::sql_types::Nullable<diesel::sql_types::Bool>, bool>>)`
>error[E0277]: the trait bound `std::boxed::Box<dyn diesel::expression::BoxableExpression<stackoverflow_questions::schema::roles::table, diesel::mysql::backend::Mysql, SqlType = diesel::sql_types::Nullable<diesel::sql_types::Bool>>>: diesel::query_source::Column` is not satisfied
--> src/main.rs:43:10
|
43 | .execute(&conn)?;
| ^^^^^^^ the trait `diesel::query_source::Column` is not implemented for `std::boxed::Box<dyn diesel::expression::BoxableExpression<stackoverflow_questions::schema::roles::table, diesel::mysql::backend::Mysql, SqlType = diesel::sql_types::Nullable<diesel::sql_types::Bool>>>`
|
= note: required because of the requirements on the impl of `diesel::insertable::InsertValues<stackoverflow_questions::schema::roles::table, diesel::mysql::backend::Mysql>` for `diesel::insertable::ColumnInsertValue<std::boxed::Box<dyn diesel::expression::BoxableExpression<stackoverflow_questions::schema::roles::table, diesel::mysql::backend::Mysql, SqlType = diesel::sql_types::Nullable<diesel::sql_types::Bool>>>, diesel::expression::bound::Bound<diesel::sql_types::Nullable<diesel::sql_types::Bool>, bool>>`
= note: required because of the requirements on the impl of `diesel::insertable::InsertValues<stackoverflow_questions::schema::roles::table, diesel::mysql::backend::Mysql>` for `(diesel::insertable::ColumnInsertValue<stackoverflow_questions::schema::roles::columns::user_id, diesel::expression::bound::Bound<diesel::mysql::types::Unsigned<diesel::sql_types::BigInt>, u64>>, diesel::insertable::ColumnInsertValue<std::boxed::Box<dyn diesel::expression::BoxableExpression<stackoverflow_questions::schema::roles::table, diesel::mysql::backend::Mysql, SqlType = diesel::sql_types::Nullable<diesel::sql_types::Bool>>>, diesel::expression::bound::Bound<diesel::sql_types::Nullable<diesel::sql_types::Bool>, bool>>)`
= note: required because of the requirements on the impl of `diesel::query_builder::QueryFragment<diesel::mysql::backend::Mysql>` for `diesel::query_builder::insert_statement::ValuesClause<(diesel::insertable::ColumnInsertValue<stackoverflow_questions::schema::roles::columns::user_id, diesel::expression::bound::Bound<diesel::mysql::types::Unsigned<diesel::sql_types::BigInt>, u64>>, diesel::insertable::ColumnInsertValue<std::boxed::Box<dyn diesel::expression::BoxableExpression<stackoverflow_questions::schema::roles::table, diesel::mysql::backend::Mysql, SqlType = diesel::sql_types::Nullable<diesel::sql_types::Bool>>>, diesel::expression::bound::Bound<diesel::sql_types::Nullable<diesel::sql_types::Bool>, bool>>), stackoverflow_questions::schema::roles::table>`
= note: required because of the requirements on the impl of `diesel::query_builder::QueryFragment<diesel::mysql::backend::Mysql>` for `diesel::query_builder::insert_statement::InsertStatement<stackoverflow_questions::schema::roles::table, diesel::query_builder::insert_statement::ValuesClause<(diesel::insertable::ColumnInsertValue<stackoverflow_questions::schema::roles::columns::user_id, diesel::expression::bound::Bound<diesel::mysql::types::Unsigned<diesel::sql_types::BigInt>, u64>>, diesel::insertable::ColumnInsertValue<std::boxed::Box<dyn diesel::expression::BoxableExpression<stackoverflow_questions::schema::roles::table, diesel::mysql::backend::Mysql, SqlType = diesel::sql_types::Nullable<diesel::sql_types::Bool>>>, diesel::expression::bound::Bound<diesel::sql_types::Nullable<diesel::sql_types::Bool>, bool>>), stackoverflow_questions::schema::roles::table>, diesel::query_builder::insert_statement::Replace>`
= note: required because of the requirements on the impl of `diesel::query_dsl::load_dsl::ExecuteDsl<_, diesel::mysql::backend::Mysql>` for `diesel::query_builder::insert_statement::InsertStatement<stackoverflow_questions::schema::roles::table, diesel::query_builder::insert_statement::ValuesClause<(diesel::insertable::ColumnInsertValue<stackoverflow_questions::schema::roles::columns::user_id, diesel::expression::bound::Bound<diesel::mysql::types::Unsigned<diesel::sql_types::BigInt>, u64>>, diesel::insertable::ColumnInsertValue<std::boxed::Box<dyn diesel::expression::BoxableExpression<stackoverflow_questions::schema::roles::table, diesel::mysql::backend::Mysql, SqlType = diesel::sql_types::Nullable<diesel::sql_types::Bool>>>, diesel::expression::bound::Bound<diesel::sql_types::Nullable<diesel::sql_types::Bool>, bool>>), stackoverflow_questions::schema::roles::table>, diesel::query_builder::insert_statement::Replace>`
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0277`.
error: could not compile `stackoverflow-questions`.
To learn more, run the command again with --verbose.
我在这里为这个问题创建了一个可重现的示例。