Protocol Oriented 練習：Deserialize JSON and XML

Example.swift

import Foundation

struct User {
    var username: String?
    var password: String?
}

extension User {
    init(_ node: NodeAccessable) {
        self.username = node.child("username").string
        self.password = node.child("password").string
    }
}

/**
 Example:
 
 //json
 let user: User = User(json)
 //or xml
 let user: User = User(xml)
 
 */

NodeAccessable.swift

import Foundation
import SwiftyJSON
import SWXMLHash

protocol NodeAccessable {
    func child(_ index: Int) -> NodeAccessable
    func child(_ key: String) -> NodeAccessable
    
    var string: String? { get }
    var bool: Bool? { get }
    var number: NSNumber? { get }
}

extension JSON : NodeAccessable {
    func child(_ index: Int) -> NodeAccessable {
        return self[index]
    }
    
    func child(_ key: String) -> NodeAccessable {
        return self[key]
    }
    
    //string, bool, number SwiftyJSON 本來就有實作，可省略
}

extension XMLIndexer : NodeAccessable {
    func child(_ index: Int) -> NodeAccessable {
        return self[index]
    }
    
    func child(_ key: String) -> NodeAccessable {
        return self[key]
    }
    
    var string: String? {
        if let text = self.element?.text {
            return text
        }
        return nil
    }
    
    var bool: Bool? {
        if let text = self.element?.text {
            return NSString(string: text).boolValue
        }
        return nil
    }
    
    var number: NSNumber? {
        if let text = self.element?.text {
            if let n = Int(text) {
                return NSNumber(value: n)
            }
            
            if let n = Float(text) {
                return NSNumber(value: n)
            }
            
            if let n = Double(text) {
                return NSNumber(value: n)
            }
        }
        
        return nil
    }
}