iOS开发调用SearchBar报错：
Access to UISearchBar's _searchField ivar is prohibited. This is an application bug'
出现原因： iOS 13 系统禁止通过 KVC 访问一些方式
UITextField*textfield = [searchBarvalueForKey:@"_searchField"];[textfieldsetValue:KFont(12)forKeyPath:@"_placeholderLabel.font"];
解决办法：
UITextField*textfield = [searchBarvalueForKey:@"searchField"];[textfieldsetValue:KFont(12)forKeyPath:@"placeholderLabel.font"];
