- textField.placeholder = @"username is in here!";
- [textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];
- [textField setValue:[UIFont boldSystemFontOfSize:16] forKeyPath:@"_placeholderLabel.font"];
- 直接使用KVC模式，改变参数的值很方便
修改textField的placeholder的字体和颜色
原文：http://www.cnblogs.com/zj901203/p/4377269.html
