swift – viewDidLoad中之前和之后的区别
发布时间：2020-12-14 05:32:59 所属栏目：百科 来源：网络整理
导读：我试图将searchBar设置为viewDidLoad中的tableHeaderView： override func viewDidLoad() { super.viewDidLoad() // SearchController initializiation self.searchController = UISearchController.init(searchResultsController: nil) self.searchControll
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我试图将searchBar设置为viewDidLoad中的tableHeaderView：
override func viewDidLoad() {
super.viewDidLoad()
// SearchController initializiation
self.searchController = UISearchController.init(searchResultsController: nil)
self.searchController.delegate = self
self.searchController.searchBar.delegate = self
self.searchController.searchBar.sizeToFit()
self.searchController.searchResultsUpdater = self
self.searchController.searchBar.barTintColor = UIColor.white
self.searchController.searchBar.keyboardAppearance = .default
self.searchController.searchBar.backgroundColor = UIColor.white
self.searchController.hidesNavigationBarDuringPresentation = true
self.searchController.obscuresBackgroundDuringPresentation = false
self.tableView.tableHeaderView = self.searchController.searchBar
self.definesPresentationContext = true
self.fetch()
self.tableView.reloadData()
}
这个我的fetch()函数： func fetch() {
let fetchRequest:NSFetchRequest<Phone> = Phone.fetchRequest()
fetchRequest.sortDescriptors = [NSSortDescriptor.init(key: "header",ascending: true),NSSortDescriptor.init(key: "date",ascending: true)]
self.fetchedResultsController = NSFetchedResultsController.init(fetchRequest: fetchRequest,managedObjectContext: self.managedObjectContext,sectionNameKeyPath: "header",cacheName: nil)
self.fetchedResultsController.delegate = self
do {
try self.fetchedResultsController.performFetch()
self.tableView.reloadData()
} catch {}
}
但我不明白他们是不会工作的. Xcode崩溃,实际上没有发生.然后我尝试改变viewDidLoad里面的内容： override func viewDidLoad() {
super.viewDidLoad()
self.fetch()
self.tableView.reloadData()
// SearchController initializiation
self.searchController = UISearchController.init(searchResultsController: nil)
self.searchController.delegate = self
self.searchController.searchBar.delegate = self
self.searchController.searchBar.sizeToFit()
self.searchController.searchResultsUpdater = self
self.searchController.searchBar.barTintColor = UIColor.white
self.searchController.searchBar.keyboardAppearance = .default
self.searchController.searchBar.backgroundColor = UIColor.white
self.searchController.hidesNavigationBarDuringPresentation = true
self.searchController.obscuresBackgroundDuringPresentation = false
self.tableView.tableHeaderView = self.searchController.searchBar
self.definesPresentationContext = true
}
成功！工作正常我不明白有什么区别？
这是因为您设置了searchResultsUpdater和searchBar的代理,甚至在您的fetchedResultsController被初始化之前.你的代码searchResultsUpdater或searchBar的代理方法中的某些地方访问你的fetchedResultsController并且得到它,所以你的应用程序崩溃.我的建议是避免崩溃是使searchResultsController作为计算或惰性属性.
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