【Serde】字符串或结构体

环境

• Time 2021-12-07


• Rust 1.57.0


• serde 1.0.130


• serde_json 1.0.72

概念

参考：https://serde.rs/string-or-struct.html

示例

main.rs

use std::collections::BTreeMap as Map;
use std::error::Error;
use std::fmt;
use std::marker::PhantomData;
use std::str::FromStr;
use serde::de::{self, MapAccess, Visitor};
use serde::{Deserialize, Deserializer};
fn main() {
let build_string = "
build: ./dir
";
let service: Service = serde_yaml::from_str(build_string).unwrap();
println!("{:?}", service);
let build_struct = "
build:
context: ./dir
dockerfile: Dockerfile-alternate
args:
buildno: '1'
";
let service: Service = serde_yaml::from_str(build_struct).unwrap();
println!("{:?}", service);
}
#[derive(Debug, Deserialize)]
struct Service {
#[serde(deserialize_with = "string_or_struct")]
build: Build,
}
#[derive(Debug, Deserialize)]
struct Build {
context: String,
dockerfile: Option,
#[serde(default)]
args: Map,
}
impl FromStr for Build {
type Err = ();
fn from_str(s: &str) -> Result {
Ok(Build {
context: s.to_string(),
dockerfile: None,
args: Map::new(),
})
}
}
fn string_or_struct<'de, T, D>(deserializer: D) -> Result
where
T: Deserialize<'de> + FromStr,
D: Deserializer<'de>,
{
struct StringOrStruct(PhantomData T>);
impl<'de, T> Visitor<'de> for StringOrStruct
where
T: Deserialize<'de> + FromStr,
{
type Value = T;
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
formatter.write_str("string or map")
}
fn visit_str(self, value: &str) -> Result
where
E: de::Error,
{
Ok(FromStr::from_str(value).unwrap())
}
fn visit_map(self, map: M) -> Result
where
M: MapAccess<'de>,
{
Deserialize::deserialize(de::value::MapAccessDeserializer::new(map))
}
}
deserializer.deserialize_any(StringOrStruct(PhantomData))
}


Cargo.toml

[package]
edition = "2021"
name = "game"
version = "0.1.0"
[dependencies]
serde = {version = "1", features = ["derive"]}
serde-transcode = "1"
serde_json = "1"
serde_yaml = "*"


总结

使用 serde 将不同的 yaml 结构转换成了相同的结构体。

附录