gistfile1.txt

import Foundation
import SwiftyJSON

extension JSON {
    func update(keyPath: String, value: JSON?) -> JSON {
        let keys = keyPath.componentsSeparatedByString(".")
        guard let targetKey = keys.first else {
            return self
        }
        
        let targetValue: JSON?
        if 1 < keys.count {
            let subPath = keyPath.substringFromIndex(keyPath.startIndex.advancedBy(targetKey.characters.count + 1))
            targetValue = self[targetKey].update(subPath, value: value)
        } else {
            targetValue = value
        }
        
        var result = JSON([:])
        for (key, subJson) in self {
            if key == targetKey {
                if let targetValue = targetValue {
                    result[key] = targetValue
                }
            } else {
                result[key] = subJson
            }
        }
        
        return result
    }
}