UITextField右对齐时，会有以下问题：
1.第一个字符输入空格，光标会跳到左侧；
2.如果先输入其它字符，然后输入空格，此时输入的空格不会立即显示，直到再次输入其它字符时该空格会与输入的字符同时显示出来；
3.输入内容末尾是空格时，结束输入后，空格不展示，只在编辑的时候显示

解决方案1：

private lazy var contentTextField: UITextField = {
        let textField = UITextField()
        textField.font = UIFont.normalFont()
        textField.textAlignment = .Right
        textField.delegate = self
        textField.addTarget(self, action: #selector(textChange(_:)), forControlEvents: .EditingChanged)
        return textField
}()

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
        if range.location == textField.text?.length && string == " " {
            textField.text = textField.text?.stringByAppendingString("\u{00a0}")
            // 调用一次textChange(textField)，解决拦截代理方法textField: shouldChangeCharactersInRange: replacementString:对于空格返回false时，不能监听UITextFieldTextDidChangeNotification的问题。
            textChange(textField)
            return false
        }
        return true
}

@objc private func textChange(textField : UITextField) {
        guard let text = textField.text else {
            return
        }
        // 使用时需要将空格替换回去
        if let callBack = callBackOfTextFieldEndEditing {
            let contentSpace = textField.text!.stringByReplacingOccurrencesOfString("\u{00a0}", withString: " ")
            let content = contentSpace.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceCharacterSet())
            callBack(text: content)
        }
}

解决方案2：

private lazy var contentTextField: UITextField = {
        let textField = UITextField()
        textField.font = UIFont.normalFont()
        textField.textAlignment = .Right
        textField.addTarget(self, action: #selector(textChange(_:)), forControlEvents: .EditingChanged)
        return textField
}()

@objc private func textChange(textField : UITextField) {
        guard let text = textField.text else {
            return
        }
        let range = textField.markedTextRange
        if range != nil {
            return
        }

        let textRange = textField.selectedTextRange
        textField.text = text.stringByReplacingOccurrencesOfString(" ", withString: "\u{00a0}")
        textField.selectedTextRange = textRange
        
        // 使用时需要将空格替换回去
        if let callBack = callBackOfTextFieldEndEditing {
            let contentSpace = textField.text!.stringByReplacingOccurrencesOfString("\u{00a0}", withString: " ")
            let content = contentSpace.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceCharacterSet())
            callBack(text: content)
        }
    }