Concatenate strings in reduce() with shorthand syntax "+"

UIView+RecursiveDescription.swift

//
//  UIView+RecursiveDescription.swift
//
//  Created by Logan Moseley on 12/11/15.
//

import UIKit

extension UIView {
    var recursiveDescription: String {
        return indentedRecursiveDescription("")
    }
    
    private func indentedRecursiveDescription(currentIndentation: String) -> String {
        let myDescription = "\(self.indentedDescriptionLine(currentIndentation))\n"
        let newIndentation = currentIndentation.stringByAppendingString("    ")
        let subviewDescriptions = subviews.map { $0.indentedRecursiveDescription(newIndentation) }
        return subviewDescriptions.reduce(myDescription, combine: +)
    }
    
    private func indentedDescriptionLine(indentation: String) -> String {
        return indentation.stringByAppendingString(self.description)
    }
}