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JSON

Vow treats JSON like JavaScript: dynamic objects and arrays from json.parse, built with { key: value } literals, read with . and [], and serialized with json.stringify.

import json

Parse and stringify

Section titled “Parse and stringify”
let doc = match json.parse(raw) {
    Ok(v) => v,
    Err(_e) => json.null(),
};
let body = json.stringify({ ok: true, count: 3 });

Literals

Section titled “Literals”
let health = { ok: true, service: "my-app" };


var todos: JsonValue = [
    { id: 1, title: "Learn Vow", done: false },
    { id: 2, title: "Ship API", done: false },
];

Annotate JsonValue when an array holds objects or mixed JSON values.

Access

Section titled “Access”

Read

doc.title                    // JsonValue (null if missing)
doc["title"]                 // bracket
json.get_string(doc, "title", "untitled")
json.string_or(doc.title, "")

Write (primitives auto-wrap)

obj.title = "hello";
obj["count"] = 42;
obj.ok = true;

In HTTP handlers

Section titled “In HTTP handlers”
import vws from vow_web_server
import json


fn health(_req: request.Request) -> response.Response {
    return vws.json(json.stringify({ ok: true }));
}


fn create(body: String) -> response.Response {
    let title = match json.parse(body) {
        Ok(doc) => json.get_string(doc, "title", "untitled"),
        Err(_e) => "untitled",
    };
    return vws.json(201, json.stringify({ ok: true, title: title }));
}

Use vws.json_mw() middleware to validate incoming JSON bodies before handlers run.

Full demo

Section titled “Full demo”

The hello-app project (playground) is a todo API + static UI using this JSON API end-to-end:

Terminal window
cd hello-app
vpm install
vow run src/main.vow
open http://127.0.0.1:8787

Next

Section titled “Next”