将 Option<T> 与 Diesel 的可插入特性一起使用

Question

我有以下型号：

use diesel::prelude::*;

use crate::schema::category;

#[derive(Debug, Identifiable, Queryable)]
#[table_name = "category"]
pub struct Category {
    pub id: i64,
    pub name: String,
    pub description: String,
    pub parent_id: Option<i64>,
}

#[derive(Debug, Insertable)]
#[table_name = "category"]
pub struct NewCategory<'a> {
    pub name: &'a str,
    pub description: &'a str,
    pub parent_id: &'a Option<i64>,
}

和schema.rs：

table! {
    category (id) {
        id -> Integer,
        name -> Text,
        description -> Text,
        parent_id -> Nullable<Integer>,
    }
}

但是，当我尝试编译这段代码时，出现以下错误：

error[E0277]: the trait bound `std::option::Option<i64>: diesel::Expression` is not satisfied
  --> src/models/categories.rs:15:17
   |
15 | #[derive(Debug, Insertable)]
   |                 ^^^^^^^^^^ the trait `diesel::Expression` is not implemented for `std::option::Option<i64>`
   |
   = note: required because of the requirements on the impl of `diesel::Expression` for `&std::option::Option<i64>`

error[E0277]: the trait bound `std::option::Option<i64>: diesel::Expression` is not satisfied
  --> src/models/categories.rs:15:17
   |
15 | #[derive(Debug, Insertable)]
   |                 ^^^^^^^^^^ the trait `diesel::Expression` is not implemented for `std::option::Option<i64>`
   |
   = note: required because of the requirements on the impl of `diesel::Expression` for `&'a std::option::Option<i64>`

我需要什么才能让它工作？我环顾四周，但我发现的唯一类似问题是当有人在他们的 table 中有超过 16 列时，这里不是这种情况。

Answer 1

修改 pub parent_id: &'a Option<i64> 以将 &'a 置于选项内：pub parent_id: Option<&'a i64>.

将 Option<T> 与 Diesel 的可插入特性一起使用

Using Option<T> with Diesel's Insertable trait

rust

rust-diesel