iOS 修改TextField中的placeholder字体大小和颜色

1.在iOS6.0之前提供的attributedPlaceholder属性：

textField.placeholder = @"请输入用户名!";
 [textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"]; [textField setValue:[UIFont boldSystemFontOfSize:16] forKeyPath:@"_placeholderLabel.font"];

2.在iOS6.0之后提供的attributedPlaceholder属性：

UITextField *textField = [[UITextField alloc] initWithFrame:CGRectMake(0, 0, 200, 200)];
NSString *holderText = @"请输入密码！";
 NSMutableAttributedString *placeholder = [[NSMutableAttributedString alloc] initWithString:holderText];
 [placeholder addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:NSMakeRange(0, holderText.length)];
 [placeholder addAttribute:NSFontAttributeName value:[UIFont boldSystemFontOfSize:16] range:NSMakeRange(0, holderText.length)];textField.attributedPlaceholder = placeholder;
 [cell.contentView addSubview:textField];