下面是一個不起作用的代碼示例：
use serde_json::json;
#[derive(Serialize, Deserialize, Clone, Debug)]
pub struct Model<T>
where
T: DeserializeOwned,
{
pub id: i32,
pub info: Option<T>,
}
fn main() {
#[derive(Serialize, Deserialize, Debug, Clone)]
struct Info {
name: String,
}
let some_model_1: Model<Info> = serde_json::from_value(json!({
"id": 43,
"info": {
"name": "some_model_name"
}
}))
.unwrap();
println!("some_model_1: {:#?}", some_model_1);
let some_model_2: Model<Info> = serde_json::from_value(json!({
"id": 43
}))
.unwrap();
println!("some_model_2: {:#?}", some_model_2);
}
錯誤如下：cannot satisfy 'T: Deserialize<'de>。
所以我補充說：
#[serde(deserialize_with = "Option::deserialize")]
pub info: Option<T>,
現在代碼可以編譯，但是盡管使用了 Option 型別，但缺少的“info”物件some_model_2會導致錯誤：
thread 'main' panicked at 'called 'Result::unwrap()' on an 'Err' value: Error("missing field 'info'", line: 0, column: 0)', src\main.rs:34:6
我的最后一個解決方案是使用自定義函式對info欄位進行反序列化：
use serde::{de::DeserializeOwned, Deserialize, Deserializer, Serialize};
use serde_json::{json, Value};
#[derive(Serialize, Deserialize, Clone, Debug)]
pub struct Model<T>
where
T: DeserializeOwned,
{
pub id: i32,
#[serde(deserialize_with = "ok_or_none")]
pub info: Option<T>,
}
fn ok_or_none<'de, D, T>(deserializer: D) -> Result<Option<T>, D::Error>
where
D: Deserializer<'de>,
T: Deserialize<'de>,
{
let v = Value::deserialize(deserializer)?;
Ok(T::deserialize(v).ok())
}
fn main() {
#[derive(Serialize, Deserialize, Debug, Clone)]
struct Info {
name: String,
}
let some_model_1: Model<Info> = serde_json::from_value(json!({
"id": 43,
"info": {
"name": "some_model_name"
}
}))
.unwrap();
println!("some_model_1: {:#?}", some_model_1);
let some_model_2: Model<Info> = serde_json::from_value(json!({
"id": 43
}))
.unwrap();
println!("some_model_2: {:#?}", some_model_2);
}
這種變化沒有幫助，同樣的恐慌錯誤仍然存??在。該ok_or_none函式甚至沒有被呼叫。
以下是我的依賴項：
serde = { version = "1.0.94", features = ["derive"] }
serde_json = "1.0.40"
我不知道我還能做些什么來完成這項作業。
預先感謝您的幫助！
uj5u.com熱心網友回復：
你不需要使用DeserializeOwned，一個簡單T的就足夠了，當從 serde 派生時，它會檢查你的屬性是否可以序列化/反序列化：
use serde::{Deserialize, Serialize};
use serde_json::json;
#[derive(Serialize, Deserialize, Clone, Debug)]
pub struct Model<T> {
pub id: i32,
pub info: Option<T>,
}
fn main() {
#[derive(Serialize, Deserialize, Debug, Clone)]
struct Info {
name: String,
}
let some_model_1: Model<Info> = serde_json::from_value(json!({
"id": 43,
"info": {
"name": "some_model_name"
}
}))
.unwrap();
println!("some_model_1: {:#?}", some_model_1);
let some_model_2: Model<Info> = serde_json::from_value(json!({
"id": 43
}))
.unwrap();
println!("some_model_2: {:#?}", some_model_2);
}
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