Arrow 🏹 - Elegant JSON Parsing in Swift

Reason - Example - Installation

identifier <-- json["id"]
name <-- json["name"]
stats <-- json["stats"]

Reason

Why

Because parsing JSON in Swift is full of unecessary if lets, obvious casts and nil-checks
There must be a better way

How

By using a simple arrow operator that takes care of the boilerplate code for us.
Json mapping code becomes concise and maintainable ❤️

What

• Simple & Lightweight (~200lines)
• Pure Swift
• Leaves your models clean
• Implicitly casts JSON values to the right types in your model
• Automatic NSDate, NSURL, Enum, Custom model Parsing
• Converts string values to numeric types in your model
• Does not crash if JSON key is not there, nor returns nil, it simply doesn't do anything
• No overly complex obscure functional chaining operator overloading voodoo magic ?==:>>><> 😅

Example

Swift Model

struct Profile {
    var identifier = 0
    var name = ""
    var link:NSURL?
    var weekday:WeekDay = .Monday
    var stats = Stats()
    var phoneNumbers = [PhoneNumber]()
}

JSON File

{
    "id": 15678,
    "name": "John Doe",
    "link": "https://apple.com/steve",
    "weekdayInt" : 3,
    "stats": {
        "numberOfFriends": 163,
        "numberOfFans": 10987
    },
    "phoneNumbers": [{
                     "label": "house",
                     "number": "9809876545"
                     }, {
                     "label": "cell",
                     "number": "0908070656"
                     }, {
                     "label": "work",
                     "number": "0916570656"
    }]
}

Before (Chaos)

var profile = Profile()

// Int
if let id = json["id"] as? Int {
    profile.identifier = id
}  
// String
if let name = json["name"] as? String {
    profile.name = name
}
// NSURL
if let link = json["link"] as? String, url = NSURL(string:link)  {
    profile.link = link
}
// Enum
if let weekdayInt = json["weekdayInt"] as? Int, weekday = WeekDay(rawValue:weekdayInt) {
    profile.weekday = weekday
}
// Custom nested object
if let statsJson = json["stats"] as? AnyObject {
    if let numberOfFans = statsJson["numberOfFans"] as? Int {
        profile.stats.numberOfFans = numberOfFans
    }
    if let numberOfFriends = statsJson["numberOfFriends"] as? Int {
        profile.stats.numberOfFriends = numberOfFriends
    }
}
// Array of custom nested object
if let pns = json["phoneNumbers"] as? [AnyObject] {
    for pn in pns {
        phoneNumbers.append(PhoneNumber(json: pn))
    }
}

After 🎉🎉🎉

extension Profile:ArrowParsable {
    mutating func deserialize(json: JSON) {
        identifier <-- json["id"]
        link <-- json["link"]
        name <-- json["name"]
        weekday <-- json["weekdayInt"]
        stats <- json["stats"]
        phoneNumbers <-- json["phoneNumbers"]
    }
}

Usage

let profile = Profile()
profile.deserialize(json)

Installation

Carthage

github "s4cha/Arrow"

CocoaPods

pod 'Arrow'
use_frameworks!

Manually

Simply Copy and Paste Arrow.swift in your Xcode Project :) https://github.com/s4cha/Arrow/blob/master/Arrow.swift

As A Framework

Grab this repository and build the Framework target on the example project. Then Link against this framework.

How Does That Work

Notice earlier we typed :

stats <-- json["stats"]

That's because we created and extension "Stats+Arrow.swift" enabling us to use the Arrow Operator

//  Stats+Arrow.swift

import Foundation

extension Stats:ArrowParsable {
    mutating func deserialize(json: JSON) {
        numberOfFriends <-- json["numberOfFriends"]
        numberOfFans <-- json["numberOfFans"]
    }
}

Flexible you said

• DO I have to use the <-- for my sub models
• Nope, you could write it like so if you wanted :

stats.numberOfFriends <-- json["stats.numberOfFriends"]
stats.numberOfFans <-- json["stats.numberOfFans"]

• Hey I don't want to parse NSDates in every files, do you have something for me?

Sure, just set your date format once and you're done.

// Configure NSDate Parsing
Arrow.setDateFormat("yyyy-MM-dd'T'HH:mm:ssZZZZZ")
Arrow.setUseTimeIntervalSinceReferenceDate(true)

// Dates can be parsed form custom date format or timestamp
let json:JSON = JSON(["date": "2013-06-07T16:38:40+02:00", "timestamp": 392308720])
date1 <-- json["date"]
date2 <-- json["timestamp"]

What if I want a Custom NSDate format for a specific key ?

createdAt <-- json["created_at"]?.dateFormat("yyyy-MM-dd'T'HH:mm:ssZZZZZ")

Just provide it on a case per case basis ! 🎉

Accessing JSON values

Nested values

value <-- json["nested.nested.nested.nestedValue"]

Object at index

value <-- json[12]

Combine both

value <-- json[1]?["someKey"]?[2]?["something.other"]

Looping on Array

if let collection = json.collection {
    for jsonEntry in collection {
        //Do something
    }
}

Acknoledgments

This wouldn't exist without YannickDot, Damien-nd and maxkonovalov

Other repos ❤️

Arrow is part of a series of lightweight libraries aiming to make developing iOS Apps a breeze :

• Layout : Stevia
• Async code : then
• JSON WebServices : ws