UISearchViewController bug:
在工程中使用UISearchViewController ， 当跳出UISearchViewController 的容器视图控制器时，控制台输出以下警告信息：
Attempting to load the view of a view controller while it is deallocating is not allowed and may result in undefined behavior (<UISearchController: 0x13024c700>)
解决办法：
方式一：
- (void)viewDidLoad {
[super viewDidLoad];
}
方式二：
- (void)dealloc {
// 解决UISearchController bug
[self.searchController loadViewIfNeeded];
UIView *view = self.searchController.view;
}
