修改UITextfield的Placeholder字体颜色

 可以通过设置UITextField的attributedPlaceholder来修改placeholder的字体颜色

UIColor *color = [UIColor colorWithWhite:1.0 alpha:0.5];

textField.attributedPlaceholder = [[NSAttributedString alloc] initWithString:@"在这输入名称" attributes:@{NSForegroundColorAttributeName: color}];