rust 28 lines · 7 steps

Serializing config to JSON in Rust

Turn typed config structs into pretty JSON on disk with serde, skipping empty fields along the way.

Explained by highlit
Intermediate serialization serde file-io error-handling buffered-writing
1use std::fs::File;
2use std::io::{self, BufWriter};
3use std::path::Path;
4 
5use serde::Serialize;
6 
7#[derive(Serialize)]
8struct ServerConfig {
9 hostname: String,
10 port: u16,
11 #[serde(skip_serializing_if = "Vec::is_empty")]
12 allowed_origins: Vec<String>,
13 tls: TlsConfig,
14}
15 
16#[derive(Serialize)]
17struct TlsConfig {
18 enabled: bool,
19 #[serde(skip_serializing_if = "Option::is_none")]
20 cert_path: Option<String>,
21}
22 
23fn write_config(config: &ServerConfig, path: impl AsRef<Path>) -> io::Result<()> {
24 let file = File::create(path)?;
25 let mut writer = BufWriter::new(file);
26 serde_json::to_writer_pretty(&mut writer, config)?;
27 writer.flush()
28}
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Deriving Serialize lets serde map struct fields to JSON without hand-written conversion code.
  2. 2skip_serializing_if keeps output clean by omitting empty or absent optional fields.
  3. 3Wrapping a File in BufWriter batches writes, but you must flush to guarantee the bytes hit disk.

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