[英]Rust custom deserialize implementation
我很難理解如何使用 Rust 的 serde 為自定義映射實現反序列化。 如果有人可以幫助我解決這個例子,我會很高興:
我有以下結構:
#[derive(Debug, Clone, PartialEq)]
pub struct ConnectorTopics {
pub name: String,
pub topics: Vec<String>,
}
JSON 數據格式如下:
{
"test-name": {
"topics": [
"topic1",
"topic2"
]
}
}
如您所見, name
字段是主題的包裝,因此在我的情況下,這應該反序列化為:
let _ = ConnectorTopics {
name: "test-name".into(),
topics: vec!["topic1".into(), "topic2".into()]
}
我的第一次嘗試是在 Deserialize 實現中使用自定義結構,但是,這不會編譯並且似乎不是正確的方法。
impl<'de> Deserialize<'de> for ConnectorTopics {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: Deserializer<'de>,
{
#[derive(Debug, Deserialize)]
struct Inner {
topics: Vec<String>,
}
let a = deserializer.deserialize_map(HashMap<String, Inner>).unwrap();
let value = Deserialize::deserialize::<HashMap<String, Inner>>(deserializer)?;
let (connector, inner) = value.iter().nth(0).ok_or("invalid")?.0;
Ok(ConnectorTopics {
name: connector,
topics: vec![],
})
}
}
您所做的是正確的方法,但您的 json 很奇怪:
use serde::de;
use serde::Deserialize;
use std::fmt;
#[derive(Debug, Clone, PartialEq)]
pub struct ConnectorTopics {
pub name: String,
pub topics: Vec<String>,
}
#[derive(Debug, Deserialize)]
struct Inner {
topics: Vec<String>,
}
impl<'de> de::Deserialize<'de> for ConnectorTopics {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: de::Deserializer<'de>,
{
struct ConnectorTopicsVisitor;
impl<'de> de::Visitor<'de> for ConnectorTopicsVisitor {
type Value = ConnectorTopics;
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
formatter.write_str("ConnectorTopics")
}
fn visit_map<V>(self, mut map: V) -> Result<Self::Value, V::Error>
where
V: de::MapAccess<'de>,
{
if let Some(key) = map.next_key()? {
let value: Inner = map.next_value()?;
if let Some(_) = map.next_key::<&str>()? {
Err(de::Error::duplicate_field("name"))
} else {
Ok(Self::Value {
name: key,
topics: value.topics,
})
}
} else {
Err(de::Error::missing_field("name"))
}
}
}
deserializer.deserialize_map(ConnectorTopicsVisitor {})
}
}
fn main() {
let input = r#"{
"test-name": {
"topics": [
"topic1",
"topic2"
]
}
}"#;
let result: ConnectorTopics = serde_json::from_str(input).unwrap();
let expected = ConnectorTopics {
name: "test-name".into(),
topics: vec!["topic1".into(), "topic2".into()],
};
assert_eq!(result, expected);
}
您可以使用自定義 function :
pub fn deserialize_connector_topics(data: &str) -> Result<ConnectorTopics> {
let value: Value = serde_json::from_str(data)?;
if let Some(object) = value.as_object() {
let mut it = object.into_iter();
if let Some((name, topics)) = it.next() {
let topics: Vec<String> = serde_json::from_value(topics.get("topics").unwrap().clone())?;
return Ok(ConnectorTopics {
name: name.to_string(),
topics: topics,
});
}
};
Err(Error::custom("Invalid ConnectorTopics data"))
}
請注意,它是非常臨時的,它甚至在這里和那里都有一些展開和(可能是不必要的)克隆。 您應該考慮根據需要對其進行修改。 但作為一個例子,它應該足夠了。
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