ios修改textField的placeholder的字体颜色大小

设置UITextField的placeholder的颜色代码片段：

textField.placeholder = @"username is in here!";
[textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];
[textField setValue:[UIFont boldSystemFontOfSize:16] forKeyPath:@"_placeholderLabel.font"];

直接在iOS6.0之后提供的attributedPlaceholder属性：

 UITextField *textField = [[UITextField alloc] initWithFrame:CGRectMake(0, 0, 200, 200)];
NSString *holderText = @"这是一段测试文字！";
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];