我试图在UITextField中输入一个简单的整数，并根据“正确答案”验证它-但我一直得到错误，即值为nil“致命错误：展开Optional值时意外发现nil”
我做错了什么？
在顶部我定义变量

var answerMessage = String("No Answer")
var answerLabel: SKLabelNode!
var answerField: UITextField?
var answerModal: SKNode?

然后这些是函数

func validateAnswer() {
            // Convert the entered text to an integer
            if let userAnswer = Int(answerField?.text ?? "") {
                // Use the integer value
                print("The entered number is: \(userAnswer)")
            } else {
                // Invalid input, show an error message
                print("Invalid input, please enter a valid number")
            }
           
            // Display a message with the error percentage and the correct answer
            if userAnswer == correctAnswer {
                let answerMessage = "Wow you got a PERFECT answer!! The answer was \(correctAnswer)!"
                print (answerMessage)
                //let createlabel = SKAction.sequence ([createAnswerLabel])
            }
            else {
                // Calculate the error percentage
                let diff = abs(userAnswer - correctAnswer)
                errorPercentage = Int((Double(diff) / Double(correctAnswer)) * 100)
                
                // Determine if the error is positive or negative
                let direction = userAnswer > correctAnswer ? "high" : "low"
                
                // display correct answer
                let answerMessage = "Almost! Your answer is \(errorPercentage)% \(direction), the answer is \(correctAnswer)."
                print (answerMessage)
            }
        return
        }

 func createAnswerLabel () {
        let answerLabel = SKLabelNode(text: "\(answerMessage)")
        answerLabel.fontColor = .black
        answerLabel.position = CGPoint(x: answerLabel.position.x, y: answerLabel.position.y - 50)
        answerModal!.addChild(answerLabel)
        }