EXC_BAD_INSTRUCTION（代码= EXC_I386_INVOP，子代码= 0x0）更改uibutton的标题大小更改时出现thihs错误

Question

当我想更改uibuttons标题大小时，我收到此错误。

不幸的是，这只适用于一个按钮，但是当我尝试使用多个按钮时，它不起作用。

这是我的代码，它适用于一个按钮

 override func viewDidLoad() {
   btnconfidentiality.setTitle("CONFIDENTIALITY AGREEMENT", forState: .Normal)
    btnconfidentiality.titleLabel?.adjustsFontSizeToFitWidth = true



}

@IBAction func onclickconfidentiality(sender: AnyObject) {
    sender.titleLabel?!.textColor = UIColor.blueColor()
    btnconfidentiality.titleLabel!.font =  UIFont(name: "HelveticaNeue", size: 25.0)
    btncontact.titleLabel!.font =  UIFont(name: "HelveticaNeue", size: 25.0)
}

但当我尝试另一个按钮时，我收到错误

override func viewDidLoad() {
   btnconfidentiality.setTitle("CONFIDENTIALITY AGREEMENT", forState: .Normal)
    btnconfidentiality.titleLabel?.adjustsFontSizeToFitWidth = true

    btnbyticket.setTitle("BUY A TICKET", forState: .Normal)


}

@IBAction func onclickconfidentiality(sender: AnyObject) {
    sender.titleLabel?!.textColor = UIColor.blueColor()
    btnconfidentiality.titleLabel!.font =  UIFont(name: "HelveticaNeue", size: 25.0)
    btncontact.titleLabel!.font =  UIFont(name: "HelveticaNeue", size: 25.0)
}

@IBAction func onclickbuyaticket(sender: AnyObject) {
    btnbyticket.titleLabel!.font =  UIFont(name: "HelveticaNeue", size: 25.0)
}

Answer 1

viewDidLoad内的第一条指令应该是super：

override func viewDidLoad() {
   super.viewDidLoad()
}