★ Navigationの戻るボタンを設定する
// 文字列のボタンを生成
let leftBarbuttnoItem = UIBarButtonItem(title: "戻る", style: .Plain, target: self, action: #selector(NextViewController.backAction(_:)))
self.navigationItem.leftBarButtonItem = leftBarbuttnoItem
// ボタン押下時のアクション
func backAction(sender: UIBarButtonItem) {
self.navigationController?.popViewControllerAnimated(true)
}
★ UIBarButtonItemStyle
public enum UIBarButtonItemStyle : Int {
case Plain
case Done
}