LiteJSONConvertible

#LiteJSONConvertible

A minimalistic approach to JSON parsing

1. Features
2. Requirements
3. Installation
4. Usage
5. Notes
6. Medium write-up

Features

• Gereric protocol with associated type
• Generic functions
• Functional composition

Requirements

• iOS 8.0 or newer
• Swift 2.2 or newer
• CocoaPods 0.38 or newer

Installation

Add the following line to your Podfile to be able to install LiteJSONConvertible using CocoaPods:

pod 'LiteJSONConvertible', '~> 0.0.5'

You also need to make sure you're opting into using frameworks and targetin iOS8 or newer:

use_frameworks!

platform :ios, '8.0'

Usage

Array of primitive types

String

["item1", "item2", "item3", "item4"]

// Retrieve the JSON content as NSData
if let json = try? NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments) {
    let items = json.map(String.decode)
}

Bool

[true, false, true, false]

// Retrieve the JSON content as NSData
if let json = try? NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments) as? [JSON] {
    let items = json.map(Bool.decode)
}

Int

[1001, 1002, 1003, 1004]

// Retrieve the JSON content as NSData
if let json = try? NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments) as? [JSON] {
    let items = json.map(Int.decode)
}

Float

[1001.1, 1002.2, 1003.3, 1004.4]

// Retrieve the JSON content as NSData
if let json = try? NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments) as? [JSON] {
    let items = json.map(Float.decode)
}

Double

[1001.1, 1002.2, 1003.3, 1004.4]

// Retrieve the JSON content as NSData
if let json = try? NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments) as? [JSON] {
    let items = json.map(Double.decode)
}

Complex JSON content

Given a specific JSON content

{
    "locations": [{
         "label": "Home",
         "data": {
             "address": "6925 Felicity Coves",
             "city": "East Davin",
             "state": "Washington",
             "country": "USA",
             "zipCode": "22998-1456"
         }
    },
    {
        "label": "Work",
        "data": {
            "address": "0506 Gretchen River",
            "city": "Huntington Beach",
            "state": "Connecticut",
            "country": "USA",
            "zipCode": "61182-9561"
        }
    }]
}

define the appropriate classes/structs to parse it:

import LiteJSONConvertible

struct LocationData {
    
    let address: String?
    let city: String?
    let state: String?
    let country: String?
    let zipCode: String?
    
    init(address: String?,
        city: String?,
        state: String?,
        country: String?,
        zipCode: String?) {
        self.address = address
        self.city = city
        self.state = state
        self.country = country
        self.zipCode = zipCode
    }
    
}

extension LocationData: JSONDecodable {
    
    static func decode(json: JSON) -> LocationData? {
        return LocationData(
            address: json <| "address",
            city: json <| "city",
            state: json <| "state",
            country: json <| "country",
            zipCode: json <| "zipCode")
    }
    
}

struct Location {
    
    let label: String?
    let data: LocationData?
    
    init(label: String?,
        data: LocationData?) {
        self.label = label
        self.data = data
    }
    
}

extension Location: JSONDecodable {
    
    static func decode(json: JSON) -> Location? {
        return Location(
            label: json <| "label",
            data: json <| "data" >>> LocationData.decode)
    }
    
}

Then, simply retrieve the JSON content as NSData (Web Service or file) and parse it:

// Retrieve the JSON content as NSData
if let json = try? NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments) {
    let locations = json <|| "locations" >>> Location.decode
}

Notes

This library is just an experiment on minimalistic JSON parsing using generic protocols. The basic ideas behind this approach are borrowed from the following articles:

• Parsing JSON in Swift
• Efficient JSON in Swift with Functional Concepts and Generics
• Real World JSON Parsing with Swift

Medium write-up

• JSON parsing in Swift — Part I: a generic protocol for JSON parsing
• JSON parsing in Swift — Part II: a functional approach to JSON parsing