以编程方式更改UITextField的占位符文本颜色

我有一个带占位符的 UITextField 。当用户想要提交表单并且他/她没有在文本字段中输入任何内容时，我希望占位符的文本颜色变为红色。以下是我的问题：

I have a UITextField with a placeholder. When the user wants to submit the form and he/she hasn't typed anything in the textfield, I would like the placeholder's text color become red. Here are my questions:

• 这会违反Apple的用户界面指南吗？我不希望我的应用被拒绝，因为这么小的细节。


• 我该怎么办？

我知道我可以在 UITextField 的子类中覆盖 drawPlaceholderInRect：方法。但是，如果我这样做，文本将始终是红色的，正如我之前写的那样，我希望它根据用户定义的操作变为红色。

I know I can override the method drawPlaceholderInRect: in a subclass of UITextField. But if I did this, the text would be always red and as I wrote before, I would like it to become red depending on a user defined action.

唯一的解决方案我可以想到的是为我的 UITextField （占位符的文本）使用默认文本，只要用户没有键入任何内容就显示为浅灰色我需要时用红色显示。换句话说，我只是嘲笑占位符的行为。但当然，这不是很优雅。

The only solution I can think of is to use a "default" text for my UITextField (the placeholder's text), display it in light grey as long as the user hasn't typed anything and display it in red when I need it. In other words, I would just mock the placeholder's behavior. But of course, this is not very elegant.

任何想法？