textField.placeholder=@"username is in here!";
[textField ?setValue:[UIColorredColor] ?forKeyPath:@"_placeholderLabel.textColor"];
[textField ?setValue:[UIFontboldSystemFontOfSize:16] ?forKeyPath:@"_placeholderLabel.font"];
這里是使用了KVC的方式,是不是很簡單呢坟募?呵呵!