[英]How to deserialize in Rust (using serde) optional json parameter that can be either string or string array
I am new to Rust and I am trying to deserialize JSON data using serde library.我是 Rust 的新手,我正在尝试使用 serde 库反序列化 JSON 数据。 I have following JSON structure:
我有以下 JSON 结构:
{
“foo”: “bar”,
“speech”: “something”
}
or或者
{
“foo”: “bar”,
“speech”: [“something”, “something else”]
}
or或者
{
“foo”: “bar”,
}
Ie speech is optional and it can be either string or array of strings.即语音是可选的,它可以是字符串或字符串数组。
I can handle deserializing string/array of string using following approach:我可以使用以下方法处理反序列化字符串/字符串数组:
#[derive(Debug, Serialize, Deserialize)]
struct foo {
pub foo: String,
#[serde(deserialize_with = "deserialize_message_speech")]
speech: Vec<String>
}
I can also handle deserializing optional string/string array attribute using approach:我还可以使用以下方法处理反序列化可选字符串/字符串数组属性:
#[derive(Debug, Serialize, Deserialize)]
struct foo {
pub foo: String,
#[serde(skip_serializing_if = "Option::is_none")]
speech: Option<Vec<String>>
}
or或者
struct foo {
pub foo: String,
#[serde(skip_serializing_if = "Option::is_none")]
speech: Option<String>
}
But combining it all together simply does not work.但是将它们组合在一起根本行不通。 It seems deserialize_with does not work properly with Option type.
似乎deserialize_with不适用于Option类型。 Can somebody advice most straightforward and trivial way how to implement this (serde can be pretty complex, I have seen some crazy stuff:) )?
有人可以建议最直接和最简单的方法来实现这个(serde 可能非常复杂,我见过一些疯狂的东西:))?
Try using an Enum type for the speech
field:尝试对
speech
字段使用 Enum 类型:
#[derive(Serialize, Deserialize)]
#[serde(untagged)]
enum Speech {
Str(String),
StrArray(Vec<String>),
}
#[derive(Debug, Serialize, Deserialize)]
struct foo {
pub foo: String,
speech: Option<Speech>,
}
Enum is the go-to way to represent a variant type in Rust.枚举是在 Rust 中表示变体类型的首选方式。 See https://serde.rs/enum-representations.html for more detail.
有关详细信息,请参阅https://serde.rs/enum-representations.html 。
with #[serde(untagged)] it works!与#[serde(untagged)] 一起工作!
use serde_json;
use std::result::Result;
use std::error::Error;
use serde::{Deserialize, Serialize};
#[derive(Debug, Serialize, Deserialize)]
#[serde(untagged)]
enum Speech {
Str(String),
StrArray(Vec<String>),
}
#[derive(Debug, Serialize, Deserialize)]
struct Foo {
pub foo: String,
#[serde(skip_serializing_if = "Option::is_none")]
speech: Option<Speech>,
}
fn main() -> Result<(), Box<dyn Error>> {
let json1 = r#"
{
"foo": "bar",
"speech": "something"
}
"#;
let json2 = r#"
{
"foo": "bar",
"speech": ["something", "something else"]
}
"#;
let json3 = r#"
{
"foo": "bar"
}
"#;
let foo1: Foo = serde_json::from_str(json1)?;
let back_to_str_foo1 = serde_json::to_string(&foo1).unwrap();
println!("foo1 {:#?}", foo1);
println!("back_to_str_foo1 {}", back_to_str_foo1);
let foo2: Foo = serde_json::from_str(json2)?;
let back_to_str_foo2 = serde_json::to_string(&foo2).unwrap();
println!("foo1 {:#?}", foo2);
println!("back_to_str_foo2 {}", back_to_str_foo2);
let foo3: Foo = serde_json::from_str(json3)?;
let back_to_str_foo3 = serde_json::to_string(&foo3).unwrap();
println!("foo1 {:#?}", foo3);
println!("back_to_str_foo3 {}", back_to_str_foo3);
Ok(())
}
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