JSON: Reading

● Intermediate3 min

json.parse gives a Json value; doc["key"] and doc[i] read into it, and .text(), .int() and the others give the value as an optional.

use std.json

fn main() ! Error {
    const body = "\{\"user\": \{\"name\": \"asha\"}, \"tags\": [\"vip\", \"new\"]}"
    const doc = try json.parse(body)
    print(doc["user"]["name"].text() ?? "guest")
    print(doc["user"]["email"].text() ?? "no email")
    print(doc["tags"][0].text() ?? "none")
    print(doc["tags"].len())
}

kavach run dynamic.kav

ashano emailvip2

Reading never panics: a missing key, an index out of range, or reading into something that isn't an object gives Null, so reads chain safely.
The method then gives none, and ?? gives a fallback.

use std.json

fn main() ! Error {
    const body = "\{\"name\": \"asha\", \"age\": 31, \"extra\": \{\"vip\": true}}"
    const doc = try json.parse(body)
    print(doc["name"].text() ?? "nobody")
    print(doc["age"].int() ?? 0)
    print(doc["extra"]["vip"].bool() ?? false)
    print(doc["missing"]["deeper"].text() ?? "not there")
    for (key, value) in doc.object() ?? [:] {
        print("{key}: {value}")
    }
}

kavach run unknown-fields.kav

asha31truenot therename: "asha"age: 31extra: {"vip":true}