UITextField - 向左滚动

Question

我正在创建UITextField programmaticaly，用于收集电子邮件地址以发送电子邮件。当用户输入多个电子邮件地址并且文本长度超过文本字段长度时，通常文本在左侧移动。 但如果我想编辑我输入的第一个电子邮件地址，我就无法滚动到左侧。

以下是创建Textfield的代码：

    let ToTextField = UITextField(frame: CGRectMake(140, 150, 500, 40))
    ToTextField.text = "To"
    ToTextField.textColor = UIColor(red:204/255, green:204/255, blue:204/255, alpha:1.0)
    ToTextField.font = UIFont.systemFontOfSize(15)
    ToTextField.borderStyle = UITextBorderStyle.RoundedRect
    ToTextField.autocorrectionType = UITextAutocorrectionType.No
    ToTextField.autocapitalizationType = UITextAutocapitalizationType.None
    ToTextField.keyboardType = UIKeyboardType.Default
    ToTextField.returnKeyType = UIReturnKeyType.Done
    ToTextField.clearButtonMode = UITextFieldViewMode.WhileEditing
    ToTextField.contentVerticalAlignment = .Center
    ToTextField.contentHorizontalAlignment = .Left
    ToTextField.tag=776756
    ToTextField.delegate = self
    self.SendMessageForm.addSubview(ToTextField)

有没有办法让它水平向左右方向滚动？