尝试添加搜索功能时，我收到以下错误消息“无法在属性初始化程序中使用实例成员'country'；属性初始化程序在'self'可用之前运行”。我不确定为什么会发生这种情况，如果将变量“ country”移动到viewdidload，我不仅会收到很多错误（我应该将其移动到viewwillappear吗？），任何帮助将不胜感激。下面是导致问题的视图控制器的所有代码。
class PresetGenreViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {
@IBOutlet weak var collectionView: UICollectionView!
var country = [countries]()
let searchController = UISearchController(searchResultsController: nil)
var passValue:String = ""
var filteredCountries = [country]()
override func viewDidLoad() {
super.viewDidLoad()
country = [countries(name: "Afghanistan"), countries(name: "Africa"), countries(name: "Alabama"),countries(name: "Alaska"),countries(name: "Albania"),countries(name: "Algeria"),countries(name: "Andorra"),countries(name: "Angola"),countries(name: "Antigua and Barbuda"),countries(name: "Arabic"),countries(name: "Argentina"),countries(name: "Armenia"),countries(name: "Aruba"),countries(name: "Australia"),countries(name: "Austria"),countries(name: "Azerbaijan"),countries(name: "Bahamas"),countries(name: "Bangladesh"),countries(name: "Barbados"),countries(name: "Belarus"),countries(name: "Belgium"),countries(name: "Belize"),countries(name: "Benin"),countries(name: "Bermuda"),countries(name: "Bolivia"),countries(name: "Bosnia and Herzegovina"),countries(name: "Brazil"),countries(name: "Brunei"),countries(name: "Bulgaria"),countries(name: "Burkina Faso"),countries(name: "Burundi"),countries(name: "Cambodia"),countries(name: "Cameroon"),countries(name: "Canada"),countries(name: "Cayman Island"),countries(name: "Chile"),countries(name: "China"),countries(name: "Colombia"),countries(name: "Congo"),countries(name: "Costa Rica"),countries(name: "Croatia"),countries(name: "Cuba"),countries(name: "Curacao"),countries(name: "Cyprus"),countries(name: "Czech Republic"),countries(name: "Denmark"),countries(name: "Dominica"),countries(name: "Dominican Republic"),countries(name: "Ecuador"),countries(name: "Egypt"),countries(name: "El Salvador"),countries(name: "English"),countries(name: "Estonia"),countries(name: "Ethiopia"),countries(name: "Faroe Islands"),countries(name: "Fiji"),countries(name: "Finland"),countries(name: "France"),countries(name: "Gambia"),countries(name: "Georgia"),countries(name: "Germany"),countries(name: "Ghana"),countries(name: "Greece"),countries(name: "Greenland"),countries(name: "Grenada"),countries(name: "Guadeloupe"),countries(name: "Guatemala"),countries(name: "Guinea"),countries(name: "Guyana"),countries(name: "Haiti"),countries(name: "Honduras"),countries(name: "Hong Kong"),countries(name: "Hungary"),countries(name: "Iceland"),countries(name: "India"),countries(name: "Indonesia"),countries(name: "Iran"),countries(name: "Iraq"),countries(name: "Ireland"),countries(name: "Israel"),countries(name: "Italy"),countries(name: "Ivory Coast"),countries(name: "Jamaica"),countries(name: "Japan"),countries(name: "Jordan"),countries(name: "Kazakhstan"),countries(name: "Kenya"),countries(name: "Korea"),countries(name: "Kosovo"),countries(name: "Kuwait"),countries(name: "Kyrgyzstan"),countries(name: "Latvia"),countries(name: "Lebanon"),countries(name: "Liberia"),countries(name: "Lithuania"),countries(name: "Luxembourg"),countries(name: "Macedonia"),countries(name: "Madagascar"),countries(name: "Malaysia"),countries(name: "Maldives"),countries(name: "Mali"),countries(name: "Malta"),countries(name: "Martinique"),countries(name: "Mauritius"),countries(name: "Mexico"),countries(name: "Moldova"),countries(name: "Monaco"),countries(name: "Mongolia"),countries(name: "Montenegro"),countries(name: "Morocco"),countries(name: "Namibia"),countries(name: "Nepal"),countries(name: "Netherlands"),countries(name: "Netherlands Antilles"),countries(name: "New Zealand"),countries(name: "Nicaragua"),countries(name: "Nigeria"),countries(name: "Norway"),countries(name: "Oman"),countries(name: "Pakistan"),countries(name: "Palestine"),countries(name: "Panama"),countries(name: "Paraguay"),countries(name: "Persian"),countries(name: "Peru"),countries(name: "Philippines"),countries(name: "Poland"),countries(name: "Portugal"),countries(name: "Puerto Rico"),countries(name: "Qatar"),countries(name: "Romania"),countries(name: "Russia"),countries(name: "Rwanda"),countries(name: "Saint Kitts and Nevis"),countries(name: "Saint Lucia"),countries(name: "Saint Vincent"),countries(name: "Saudi Arabia"),countries(name: "Senegal"),countries(name: "Serbia"),countries(name: "Singapore"),countries(name: "Slovakia"),countries(name: "Slovenia"),countries(name: "Somalia"),countries(name: "South Africa"),countries(name: "South Korea"),countries(name: "Spain"),countries(name: "Sri Lanka"),countries(name: "Sudan"),countries(name: "Suriname"),countries(name: "Sweden"),countries(name: "Switzerland"),countries(name: "Syria"),countries(name: "Taiwan"),countries(name: "Tajikistan"),countries(name: "Tamil"),countries(name: "Tanzania"),countries(name: "Thailand"),countries(name: "Trinidad and Tobago"),countries(name: "Tunisia"),countries(name: "Turkey"),countries(name: "Uganda"),countries(name: "UK"),countries(name: "Ukraine"),countries(name: "United Arab Emirates"),countries(name: "Uruguay"),countries(name: "USA"),countries(name: "Uzbekistan"),countries(name: "Venezuela"),countries(name: "Vietnam"),countries(name: "Virgin Islands"),countries(name: "Zambia"),countries(name: "Zimbabwe")]
// Setup the Search Controller
searchController.searchResultsUpdater = self
searchController.obscuresBackgroundDuringPresentation = false
searchController.searchBar.placeholder = "Search Countries"
navigationItem.searchController = searchController
definesPresentationContext = true
}
func searchBarIsEmpty() -> Bool {
// Returns true if the text is empty or nil
return searchController.searchBar.text?.isEmpty ?? true
}
func filterContentForSearchText(_ searchText: String, scope: String = "All"){
filteredCountries = country.filter({ (Country: countries) -> Bool in
return Country.name.lowercased().contains(searchText.lowercased())
})
collectionView.reloadData()
}
func isFiltering() -> Bool {
return searchController.isActive && !searchBarIsEmpty()
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
if (isFiltering()){
return filteredCountries.count
} else {
return country.count
}
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! CollectionViewCell
let Country: countries
if (isFiltering()){
Country = filteredCountries[indexPath.row]
} else {
Country = country[indexPath.row]
}
cell.label.text = Country.name
return cell
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
collectionView.allowsSelection = true
let currentCell = collectionView.cellForItem(at: indexPath) as! CollectionViewCell
currentCell.label.text = passValue
}
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
// Get the new view controller using segue.destination.
// Pass the selected object to the new view controller.
if (segue.identifier == "discover"){
let viewcontroller = segue.destination as! PresetViewController
viewcontroller.passedValue = passValue
}
}
extension PresetGenreViewController: UISearchResultsUpdating {
// MARK: - UISearchResultsUpdating Delegate
func updateSearchResults(for searchController: UISearchController) {
filterContentForSearchText(searchController.searchBar.text!)
}
}
答案 0 :(得分：1)
您的初始化都是错误的。 country和filteredCountries似乎都是类型为Country的数组，将这样声明。
var filteredCountries = [Country]()
我认为您对数组的类型感到困惑。您似乎在设置类型时以为它应该表示数组内容的来源。但这不是那样。该类型仅说明特定变量中包含哪种数据。因此，即使您的filteredCountries从countries那里得到了满足。国家类型为Country，这意味着fitleredCountries的类型也应为Country。
重要说明：类，结构等的名称应为{em> Swift API guidelines中所述的 upperCamelCase 。