如何使用柴油的过滤方法？

Question

我有一个小小的actix网络项目。有这样一种模式：

#[derive(Serialize, Deserialize, Insertable, Identifiable, Queryable, PartialEq, Debug)]
#[table_name = "confirmations"]
pub struct Confirmation {
    pub id: Uuid,
    pub email: String,
    pub expires_at: chrono::NaiveDateTime
}

然后我有一个函数，我只想从数据库中获取项目。我试着这样做：

pub fn get_confirmation_item(
    id: &Uuid,
    email: &str,
    pool: &web::Data<PgDBPool>
) -> Result<Confirmation, AppError> {
    let connection = pool.get().unwrap();
    let result = confirmations
        .filter(id.eq(id))
        .filter(email.eq(email))
        .select(id)
        .first(&connection);
    Ok(result)
}

最后，我得到了一个错误：

error[E0277]: the trait bound `bool: diesel::Expression` is not satisfied
  --> src/apps/users/utils.rs:45:17
   |
45 |         .filter(id.eq(id))
   |                 ^^^^^^^^^ the trait `diesel::Expression` is not implemented for `bool`
   |
   = note: required because of the requirements on the impl of `diesel::query_dsl::filter_dsl::FilterDsl<bool>` for `diesel::query_builder::SelectStatement<schema::confirmations::table>`

error[E0277]: the trait bound `bool: diesel::expression::NonAggregate` is not satisfied
  --> src/apps/users/utils.rs:45:17
   |
45 |         .filter(id.eq(id))
   |                 ^^^^^^^^^ the trait `diesel::expression::NonAggregate` is not implemented for `bool`
   |
   = note: required because of the requirements on the impl of `diesel::query_dsl::filter_dsl::FilterDsl<bool>` for `diesel::query_builder::SelectStatement<schema::confirmations::table>`

error[E0277]: the trait bound `diesel::query_builder::SelectStatement<schema::confirmations::table, diesel::query_builder::select_clause::DefaultSelectClause, diesel::query_builder::distinct_clause::NoDistinctClause, diesel::query_builder::where_clause::WhereClause<bool>>: diesel::query_dsl::filter_dsl::FilterDsl<_>` is not satisfied
  --> src/apps/users/utils.rs:46:10
   |
46 |         .filter(email.eq(email))
   |          ^^^^^^ the trait `diesel::query_dsl::filter_dsl::FilterDsl<_>` is not implemented for `diesel::query_builder::SelectStatement<schema::confirmations::table, diesel::query_builder::select_clause::DefaultSelectClause, diesel::query_builder::distinct_clause::NoDistinctClause, diesel::query_builder::where_clause::WhereClause<bool>>`
   |
   = help: the following implementations were found:
             <diesel::query_builder::SelectStatement<F, S, D, W, O, L, Of, G, LC> as diesel::query_dsl::filter_dsl::FilterDsl<Predicate>>

error: aborting due to 3 previous errors

有人知道如何克服这个错误吗？Cargo.toml中的依赖关系：

[dependencies]
actix-web = "3.1.0"
actix-rt = "1.1.1"
diesel = { version = "1.4.5", features = ["postgres", "uuidv07", "r2d2", "chrono"] }
r2d2 = "0.8.9"
derive_more = "0.99.11"
bson = "1.1.0"
lazy_static = "1.4.0"
serde = { version = "1.0", features = ["derive"] }
serde_json = "1.0.59"
jsonwebtoken = "7.2.0"
envfile = "0.2.1"
env_logger = "0.8.1"
chrono = { version = "0.4.19", features = ["serde"] }
rust-crypto = "0.2.36"
uuid = { version = "0.8.1", features = ["serde", "v4"] }
futures = "0.3.7"
lettre = { git = "https://github.com/lettre/lettre" }

Answer 1

您将id和email与自己进行比较。您需要的是将数据库字段的值与代码中的值进行比较。

对于柴油，这通常意味着需要导入模式，如下所示：

use schema::confirmation;

// ..
.filter(confirmation::id.eq(id))
// ..

还可以查看一些示例的文档：https://diesel.rs/guides/getting-started/

与这个问题无关，你的id不是独一无二的吗？如果是这样，您还可以使用find方法，该方法允许您按主键进行搜索。

哦，而且，您也不需要使用filter两次。有一个方法.and，它允许您编写如下所示的查询：schema::id.eq(id).and(schema::email.eq(email))