Serde支持有趣的attributes个选项,可以用来定制类型的序列化或反序列化,同时在大多数情况下仍使用派生实现.
在您的情况下,您需要能够解码可以指定为多种类型之一的字段,而不需要来自其他字段的信息来决定如何解码有问题的字段.#[serde(deserialize_with="$path")]
注释非常适合解决您的问题.
我们需要定义一个函数,将空字符串或整数值解码为u64
.我们可以对这两个字段使用相同的函数,因为我们需要相同的行为.此函数将使用自定义Visitor
来处理字符串和整数.虽然有点长,但它会让你感激Serde为你所做的一切!
extern crate serde;
#[macro_use]
extern crate serde_derive;
extern crate serde_json;
use serde::Deserializer;
use serde::de::{self, Unexpected};
use std::fmt;
#[derive(Clone, Debug, Deserialize)]
struct WebResponse {
foo: Vec<Foo>,
}
#[derive(Clone, Debug, Deserialize)]
struct Foo {
points: Points,
}
#[derive(Clone, Debug, Deserialize)]
struct Points {
#[serde(deserialize_with = "deserialize_u64_or_empty_string")]
x: u64,
#[serde(deserialize_with = "deserialize_u64_or_empty_string")]
y: u64,
name: String,
}
struct DeserializeU64OrEmptyStringVisitor;
impl<'de> de::Visitor<'de> for DeserializeU64OrEmptyStringVisitor {
type Value = u64;
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
formatter.write_str("an integer or a string")
}
fn visit_u64<E>(self, v: u64) -> Result<Self::Value, E>
where
E: de::Error,
{
Ok(v)
}
fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
where
E: de::Error,
{
if v == "" {
Ok(0)
} else {
Err(E::invalid_value(Unexpected::Str(v), &self))
}
}
}
fn deserialize_u64_or_empty_string<'de, D>(deserializer: D) -> Result<u64, D::Error>
where
D: Deserializer<'de>,
{
deserializer.deserialize_any(DeserializeU64OrEmptyStringVisitor)
}
fn main() {
let value = serde_json::from_str::<WebResponse>(
r#"{
"foo": [
{
"points": {
"x": "",
"y": "",
"name": ""
}
},
{
"points": {
"x": 78,
"y": 92,
"name": "bar"
}
}
]
}"#,
);
println!("{:?}", value);
}
Cargo.toml
:
[dependencies]
serde = "1.0.15"
serde_json = "1.0.4"
serde_derive = "1.0.15"