GJSON

Very simple JSON parser written in Swift 3 based on case sensitive string paths.

Goal

We all need to use JSON structs in our projects, but unfortunately there is no any stable repository about JSON updated to Swift 3 syntax. So I've decided to make my own, very simple JSON parser that allows you to manage JSON values.

This is not a library, you can just copy & paste my code inside your project. Please feel free to use & modify this code for your projects' requirements.

Usage

GJSON uses simple string paths (components must be separated with slash /) to extract values from valid JSON objects.
The first option is to extract optional value of Any? type. It does not produce any errors or exceptions during parsing, if there is no value that you've requested - you will just receive nil as a result and small log message containing information about what was happened.
Also you can extract optional "strictly typed" values (they just need to be unwrapped, this allow you to extract null values safely).
As a special feature you can extract a concrete item from an internal JSON array by specifying string component prefixed by :, for example: Result/Items/:2 (index starts from zero, instead of 2 you can print any index inside json array's bounds).

Quick Guide

Please note that path strings are case sensitive.
Use number, string, bool, array or object instance-level methods of the GJSON class to get strictly typed values as a result. These method will return nil if JSON code does not contain specified value types at specified paths.
Use strict valueAt(_, of:) method which will return strictly typed value or throw an exception if any error occured during parsing.
Use any instance-level method or GJSON.path(_, json:) class-level method to extract value of type Any?. Just don't forget to unwrap them when it's necessary.
Use special myJson/jsonArrayItem/:3 index specifying to extract the concrete item of an array.

Example

Let's take this JSON code on some server address https://myserver.com/json:

{
	"glossary": {
		"title": "example",
		"items": [
			{ "Id": 5, "text": "some item" },
			{ "Id": 28, "text": "some another item" }
		],
		"GlossList": {
			"GlossEntry": {
				"ID": "SGML",
				"SortDesc": true,
				"GlossDef": {
					"GlossSeeAlso": ["GML", "XML"]
				},
				"GlossSee": "markup"
			}
		}
	}
}

Here are an example of items extraction:

// receive our JSON with async URLSession data task
let urlString = "https://myserver.com/json"
let url = URL(string: urlString)
var request = URLRequest(url: url!)
request.httpMethod = "GET"
// send async task
let task = URLSession.shared.dataTask(with: request) { (data, res, err) in
  let object = try! JSONSerialization.jsonObject(with: data!, options: .allowFragments)
  App.parseJSON(object)
}
task.resume()

...

class App {
  static func parseJSON(_ json: Any?) {
    let parser = GJSON(json)
    let glossary = GJSON(parser.any("glossary")!)!
    print(glossary.number("items/:0/Id")!) // extract the "Id" property of the first item of an array
    print(glossary.string("GlossList/GlossEntry/ID")!)
    print(glossary.bool("GlossList/GlossEntry/SortDesc")!)
    print(GJSON.path("glossary/GlossList/GlossEntry/GlossSee", json: json) as! String)
  }
}

This will print the following lines:

5
SGML
true
markup

License