小编Sev*_*rin的帖子

我有以下方法:

@IBAction func postcodeTextfieldDidChanged(_ sender: UITextField) {

        if (postcodeTextField.text?.characters.count == 4) {
            self.postcode = postcodeTextField.text
            postcodeHas4Chars = true
        } else {
            postcodeHas4Chars = false
        }
    }

而准备方法:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        if segue.identifier == "CoffeeShopListWithPostcode" {
            if (postcodeHas4Chars == true) {
                if let list = segue.destination as? CoffeeShopListVC {
                    list.postcode = postcode
                } else {
                    print("Data NOT Passed!")
                }
            }
        } else { print("Id doesnt match with Storyboard segue Id")
        }
    }

代码工作,我可以将邮政编码发送到下一个ViewController,但是如何更改代码以在第四次输入后自动调用该方法？此时,用户必须手动退出输入才能执行.