swift - 为什么我收到此错误 EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)

Question

谁能帮助我并告诉我为什么我在第 2 行出现错误？
消息框还说：

SignIn 致命错误：在展开可选值 (lldb) 时意外发现 nil

@IBAction func done(sender: UIBarButtonItem) {

    if isSignIn == false {

        //Register code

        //Checking for empty boxes

        if self.username.text == "" || self.password.text == "" || self.riderDriverSelect.selectedSegmentIndex == -1 {

            //Red Border color for missing fields


            if self.username.text == "" {
                self.username.layer.borderColor = UIColor.redColor().CGColor
                self.username.layer.borderWidth = 1.0
            }

            if self.password.text == "" {
                self.password.layer.borderColor = UIColor.redColor().CGColor
                self.password.layer.borderWidth = 1.0
            }

            if self.riderDriverSelect.selectedSegmentIndex == -1 {
                self.riderDriverSelect.layer.borderColor = UIColor.redColor().CGColor
                self.riderDriverSelect.layer.borderWidth = 1.0

                self.showAlert("Missing field required", message: "Fill in or select missing fields in red")
            }


        }else{

Answer 1

有 1 个字符串，两个 bool，两个 bool 都是！必须改变 isSignIn Bool 吗？解决了这个问题

var buttonTitlePressed: 字符串？var isSignIn: 布尔值？var isUser：布尔！