Trait JSONValue

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pub trait JSONValue {
    // Required method
    fn write_json<W: Write>(&self, w: &mut W) -> Result<()>;

    // Provided methods
    fn to_json_string(&self) -> String { ... }
    fn to_json_buffer(&self) -> Vec<u8> ⓘ { ... }
}

Expand description

A trait implemented by types that can be serialized to JSON

This trait can be derived for custom structs using json_in_type_derive

Required Methods§

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fn write_json<W: Write>(&self, w: &mut W) -> Result<()>

Write the object as json to the given writer

§Examples

Write a JSON object to a file

use json_in_type::JSONValue;

vec![1, 2, 3].write_json(&mut my_file);

Provided Methods§

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fn to_json_string(&self) -> String

Returns the object formatted as a json string

§Panics

If you implement JSONValue on your own types and emit invalid UTF-8 in write_json. If you use the implementations of JSONValue provided in this library, this function will never panic.

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fn to_json_buffer(&self) -> Vec<u8> ⓘ

Returns a buffer containing the bytes of a json representation of the object

Dyn Compatibility§

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementations on Foreign Types§

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impl<K: JSONString + Eq + Hash, V: JSONValue, S: BuildHasher> JSONValue for HashMap<K, V, S>

Serialize a HashMap to a JSON object. The property order is not guaranteed.

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fn write_json<W: Write>(&self, w: &mut W) -> Result<()>

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impl<T: JSONValue, I: Iterator<Item = T>> JSONValue for RefCell<I>

Allows to serialize an iterator to JSON in a streaming fashion. The iterator needs to be wrapped in a RefCell because it will be consumed as JSON is written.

§Examples

§Serialize an iterator JSON

use std::cell::RefCell;
use std::iter::repeat;
use json_in_type::JSONValue;

let my_iter = repeat(42).take(3);
let my_iter_cell = RefCell::new(my_iter);

// The iterator will be consumed as json is produced
assert_eq!("[42,42,42]", my_iter_cell.to_json_string());

// Here, the iterator has already been consumed, so there is nothing left to serialize
assert_eq!("[]", my_iter_cell.to_json_string());

§Write a large JSON to a file

In this example, we take a potentially large input file, and serialize it to a JSON file containing an array with all the lines from the input file.

The output should look like this:

[
  {"line": 1, "contents": "a line of text"},
  {"line": 2, "contents": "another line of text"}
]

use std::cell::RefCell;
use std::io::BufRead;
use std::io::BufReader;
use json_in_type::*;


let json_lines = BufReader::new(input_file)
                .lines()
                .map(|l| l.unwrap())
                .enumerate()
                .map(|(i, contents)| json_object!{line:i+1, contents:contents});

RefCell::new(json_lines).write_json(&mut output_file);

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