Nim: How to parse JSON | Glenn Gillen
Nim: How to parse JSON

Nim: How to parse JSON

Mar 21, 2022

To parse a JSON string into an object, use the json import from the standard library:

import json
let jsonObject = """{"first_name": "glenn", "last_name": "gillen"}"""
let jsonArray = """[7, 8, 9]"""
let parsedObject = parseJson(jsonObject)
let parsedArray = parseJson(jsonArray)

This will create a series of nodes, on which you'll need to call getStr(), getInt(), getFloat(), or getBool() to retrieve the actual value:

ech parsedObject["first_name"].getStr() # glenn
echo parsedArray[1].getInt() # 8

If you've a nested JSON object Nim will automatically parse the nesting and you'll only need to call the get*() on the edge node:

import json
let jsonObject = """{
"names": {
"first": "glenn",
"last": "gillen"
}
}"""
let parsedObject = parseJson(jsonObject)
echo parsedObject["names"]["first"].getStr() # glenn

To parse into an object, you'll need to define an object that matches your expected structure:

import json
type
Person = object
first_name: string
last_name: string
let jsonObject = parseJson("""{"first_name": "glenn", "last_name": "gillen"}""")
let person = to(jsonObject, Person)
echo person.first_name # glenn
Hi, I'm Glenn! 👋 I've spent most of my career working with or at startups. I'm currently the Director of Product @ Ockam where I'm helping developers build applications and systems that are secure-by-design. It's time we started securely connecting apps, not networks.

Previously I led the Terraform product team @ HashiCorp, where we launched Terraform Cloud and set the stage for a successful IPO. Prior to that I was part of the Startup Team @ AWS, and earlier still an early employee @ Heroku. I've also invested in a couple of dozen early stage startups.