ios - Swift UITextField 检查第二个字符的文本

Question

我有 ViewController，上面有 2 个文本字段。 View Controller 是一个 UITextFieldDelegate。我检查此字段中的值，如果它们有效，则激活此 View Controller 按钮的返回。问题是验证是从第二个字符开始的:如果我尝试在每个字段中输入值，按钮将变为非事件状态，直到我输入第二个字符，但如果我在输入后删除该字符，返回按钮将保持事件状态。我发现问题是由 checkIfAddingAvailable() 引起的。我哪里错了？

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    guard let oldTextString = textField.text else {
        return true
    }
    let oldText = oldTextString as NSString
    let newString = oldText.replacingCharacters(in: range, with: string) as NSString

    if newString.length > 0 {
       let _ = checkIfAddingAvailable()
    } else {
       addFoodButton.isEnabled = false
    }
    return true
}

func checkIfAddingAvailable() -> Bool {
    //TODO: implement valid checking of posibility to add food
    guard let foodName = foodNameField.text else { return false }
    guard !foodName.isEmpty else {
        return false
    }

    guard let foodShelfLife = shelfLifeField.text else { return false }
    guard !foodShelfLife.isEmpty else {
        return false
    }
    guard let foodShelfLifeIntoDouble = Double(foodShelfLife) else { return false }
    guard foodShelfLifeIntoDouble > 0 else {
        return false
    }
    addFoodButton.isEnabled = true
    return true
}

Answer 1

您应该在 shouldChangeCharactersIn 处将 newstring 传递给 checkIfAddingAvailable，因为 textField 还没有最终文本

调整文本字段的代码

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        guard let oldTextString = textField.text else {
            return true
        }
        let oldText = oldTextString as NSString
        let newString = oldText.replacingCharacters(in: range, with: string) as NSString

        if newString.length > 0 {
            let _ = checkIfAddingAvailable(newString)
        } else {
            addFoodButton.isEnabled = false
        }
        return true
    }

    func checkIfAddingAvailable(_ foodNameFieldText :String) -> Bool {
        //TODO: implement valid checking of posibility to add food
        guard let foodName = foodNameFieldText else { return false }
        guard !foodName.isEmpty else {
            return false
        }

        guard let foodShelfLife = shelfLifeField.text else { return false }
        guard !foodShelfLife.isEmpty else {
            return false
        }
        guard let foodShelfLifeIntoDouble = Double(foodShelfLife) else { return false }
        guard foodShelfLifeIntoDouble > 0 else {
            return false
        }
        addFoodButton.isEnabled = true
        return true
    }