Struct JsonLinesReader

Source

pub struct JsonLinesReader<R> { /* private fields */ }

Expand description

A structure for reading JSON values from JSON Lines input.

A JsonLinesReader wraps a std::io::BufRead instance and parses each line as a serde::de::DeserializeOwned value in JSON.

§Example

use serde::Deserialize;
use serde_jsonlines::JsonLinesReader;
use std::fs::{write, File};
use std::io::BufReader;

#[derive(Debug, Deserialize, PartialEq)]
pub struct Structure {
    pub name: String,
    pub size: i32,
    pub on: bool,
}

fn main() -> std::io::Result<()> {
    write(
        "example.jsonl",
        concat!(
            "{\"name\": \"Foo Bar\", \"on\":true,\"size\": 42 }\n",
            "{ \"name\":\"Quux\", \"on\" : false ,\"size\": 23}\n",
            " {\"name\": \"Gnusto Cleesh\" , \"on\": true, \"size\": 17}\n",
        ),
    )?;
    let fp = BufReader::new(File::open("example.jsonl")?);
    let reader = JsonLinesReader::new(fp);
    let items = reader
        .read_all::<Structure>()
        .collect::<std::io::Result<Vec<_>>>()?;
    assert_eq!(
        items,
        [
            Structure {
                name: "Foo Bar".into(),
                size: 42,
                on: true,
            },
            Structure {
                name: "Quux".into(),
                size: 23,
                on: false,
            },
            Structure {
                name: "Gnusto Cleesh".into(),
                size: 17,
                on: true,
            },
        ]
    );
    Ok(())
}

Implementations§

Source §

impl<R> JsonLinesReader<R>

Source

pub fn new(reader: R) -> Self

Construct a new JsonLinesReader from a std::io::BufRead instance

Source

pub fn into_inner(self) -> R

Consume the JsonLinesReader and return the underlying reader

Source

pub fn get_ref(&self) -> &R

Get a reference to the underlying reader

Source

pub fn get_mut(&mut self) -> &mut R

Get a mutable reference to the underlying reader

Source

pub fn read_all<T>(self) -> JsonLinesIter<R, T> ⓘ

Consume the JsonLinesReader and return an iterator over the deserialized JSON values from each line.

The returned iterator has an Item type of std::io::Result<T>. Each call to next() has the same error conditions as read().

Note that all deserialized values will be of the same type. If you wish to read lines of varying types, use the read() method instead.

Source §

impl<R: BufRead> JsonLinesReader<R>

Source

pub fn read<T>(&mut self) -> Result<Option<T>>
where T: DeserializeOwned,

Read & deserialize a line of JSON from the underlying reader.

If end-of-file is reached, this method returns Ok(None).

Note that separate calls to this method may read different types of values.

§Errors

Has the same error conditions as std::io::BufRead::read_line() and serde_json::from_str(). Note that, in the latter case (which can be identified by the std::io::Error having a serde_json::Error value as its payload), continuing to read from the JsonLinesReader afterwards will pick up on the next line as though the error never happened, so invalid JSON can be easily ignored if you so wish.