I made a custom barButtonItem in my toolbar. I want to change the string of the NSAttributedString when the barButtonItem has been tapped. But as the apple document said the performance of the function is charged by the customView, not the barButtonItem any more, how can I access and do some change to the details of it according to events?

```
    let button1 = UIButton(type: .System)
    button1.sizeToFit()
    let attributes1 = [NSForegroundColorAttributeName: UIColor.grayColor(), NSFontAttributeName: UIFont.systemFontOfSize(13)]
    let attributedString1 = NSAttributedString(string: "Hello", attributes: attributes1)
    button1.setAttributedTitle(attributedString1, forState: .Normal)
    button1.addTarget(self, action: #selector(ActionViewController.switchAccounts), forControlEvents: .TouchUpInside)
    let account = UIBarButtonItem(customView: button1)

    setToolbarItems([account], animated: true)

```

I'm a new swifter. OC can also be read by me.
Any advice is welcome. Thanks.