カスタムオブジェクトの print を key: value 形式で吐かせる

CustomObject.swift

import UIKit

class CustomObject: NSObject {

    override var description: String {
        let mirror = Mirror(reflecting: self)
        return mirror.children.map { (element) -> String in
            let key = element.label ?? "Undefined"
            let value = element.value
            if value is CustomObject || value is NSArray {
                return "\(key): \(value.dynamicType)"
            } else {
                return "\(key): \(value)"
            }
        }.joinWithSeparator("\n")
    }

}