$devvkit learn --librarie serde-guide

Serde Guide

[rust][serialization][json]

Rust

Install

cargo add serde --features derive
cargo add serde_json

Serde is the standard serialization framework for Rust. Compile-time derive macros generate ser/de impls.

Supports JSON, YAML, TOML, BSON, MessagePack, and 50+ other formats via data format crates.

The derive API means zero runtime reflection — serialization is as fast as hand-written code.

Setup

Add deps— Cargo.toml entries.

cargo add serde --features derive
cargo add serde_json

Derive Macros

Derive basics— Standard ser/de.

#[derive(Serialize, Deserialize, Debug)]
struct User {
    id: u64,
    name: String,
    email: String,
}

Rename fields— Change serialized names.

#[derive(Serialize, Deserialize)]
struct User {
    #[serde(rename = "user_id")]
    id: u64,
    #[serde(rename = "full_name")]
    name: String,
}

Skip field— Omit from serialization.

#[derive(Serialize)]
struct User {
    name: String,
    #[serde(skip_serializing_if = "Option::is_none")]
    age: Option<u32>,
}

Default values— Defaults on deserialize.

#[derive(Deserialize, Default)]
struct Config {
    #[serde(default = "default_port")]
    port: u16,
    #[serde(default)]
    host: String,
}

JSON

Serialize to JSON— Struct to JSON string.

let user = User { id: 1, name: "Alice".into(), email: "a@b.com".into() };
let json = serde_json::to_string(&user)?;
println!("{json}");

Deserialize from JSON— JSON string to struct.

let json = r#"{"id":1,"name":"Alice","email":"a@b.com"}"#;
let user: User = serde_json::from_str(json)?;

Custom Serialization

Custom deserialize— Manual deserialization.

impl Visitor<'_> for ColorVisitor {
    type Value = Color;
    fn expecting(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "a hex color") }
    fn visit_str<E: de::Error>(&self, v: &str) -> Result<Color, E> {
        Color::from_hex(v).ok_or_else(|| de::Error::custom("invalid color"))
    }
}

Advanced

Flatten— Inline nested struct.

#[derive(Serialize)]
struct Response {
    status: String,
    #[serde(flatten)]
    data: User,
}  // {"status":"ok","id":1,"name":"Alice"}