Ios UISearchController-目标C到Swift问题

我正在尝试对UISearchController进行子类化，以便添加自定义UISearchBar。我在Objective-C中找到了这样做的方法，但在Swift中我很难做到。以下是在Objective-C中实现此目标的两个文件：

CustomSearchController.h

@interface CustomSearchController : UISearchController <UISearchBarDelegate>

@end

我遇到的问题就是这个getter：

-(UISearchBar *)searchBar {

    if (_searchBar == nil) {
        _searchBar = [[CustomSearchBar alloc] initWithFrame:CGRectZero];
        _searchBar.delegate = self; // different from table search by apple where delegate was set to view controller where the UISearchController was instantiated or in our case where CustomSearchController was instantiated.
    }
    return _searchBar;
}

在

Swift

中，我相信我必须这样做：

var customSearchBar: CustomSearchBar?

override var searchBar: UISearchBar {
    get {
        if customSearchBar == nil {
            customSearchBar = CustomSearchBar()
            customSearchBar?.delegate = self
        }
        return customSearchBar!
    }
}

但这是最好的方法吗？

试试这个：

只有在首次访问时，

lazy

的使用才负责初始化

CustomSearchBar

实例。尽管我不确定您是否真的需要它来完成您想要完成的任务。

不要忘记在getter中使用

assert（customSearchBar！=nil，“customSearchBar为nil！”）

。

var customSearchBar: CustomSearchBar?

override var searchBar: UISearchBar {
    get {
        if customSearchBar == nil {
            customSearchBar = CustomSearchBar()
            customSearchBar?.delegate = self
        }
        return customSearchBar!
    }
}

lazy var customSearchBar: CustomSearchBar = {
    [unowned self] in
    let result = CustomSearchBar(frame:CGRectZero)
    result.delegate = self
    return result
}()

override var searchBar: UISearchBar {
    get {
        return customSearchBar
    }
}