Macro rocket_contrib::json

source ·
macro_rules! json {
    ($($json:tt)+) => { ... };
Expand description

A macro to create ad-hoc JSON serializable values using JSON syntax.


To import the macro, add the #[macro_use] attribute to the extern crate rocket_contrib invocation:

#[macro_use] extern crate rocket_contrib;

The return type of a json! invocation is JsonValue. A value created with this macro can be returned from a handler as follows:

use rocket_contrib::json::JsonValue;

fn get_json() -> JsonValue {
        "key": "value",
        "array": [1, 2, 3, 4]

The Responder implementation for JsonValue serializes the value into a JSON string and sets it as the body of the response with a Content-Type of application/json.


Create a simple JSON object with two keys: "username" and "id":

let value = json!({
    "username": "mjordan",
    "id": 23

Create a more complex object with a nested object and array:

let value = json!({
    "code": 200,
    "success": true,
    "payload": {
        "features": ["serde", "json"],
        "ids": [12, 121],

Variables or expressions can be interpolated into the JSON literal. Any type interpolated into an array element or object value must implement serde’s Serialize trait, while any type interpolated into a object key must implement Into<String>.

let code = 200;
let features = vec!["serde", "json"];

let value = json!({
   "code": code,
   "success": code == 200,
   "payload": {
       features[0]: features[1]

Trailing commas are allowed inside both arrays and objects.

let value = json!([
    "comma -->",