监听键盘输入更改的方法
self.textFieldBuyOrSell.addTarget(self, action: #selector(self.textFieldChange), for: UIControlEvents.editingChanged)
监听键盘输入更改的方法
self.textFieldBuyOrSell.addTarget(self, action: #selector(self.textFieldChange), for: UIControlEvents.editingChanged)