问题描述
我编写了一个通用函数,但在使用该函数时出现错误。这个错误的原因是什么?我将 Codable 添加到我的模型中。我找不到这个问题的原因。
Type 'MovieSearchContainer.Type' cannot conform to 'Decodable'; only struct/enum/class types can conform to protocols
模型
struct MovieSearchContainer: Codable {
var page: Int
var results: [MovieSearch]
}
struct MovieSearch: Codable {
var id: Int
var title: String
}
电影服务
class MovieBaseService {
func fetchNewspaper<T: Codable>(stringUrl: String,model: T,completion: @escaping (T) -> ()) {
if let url = URL(string:stringUrl) {
let session = URLSession(configuration: .default)
var request = URLRequest(url: url)
request.httpMethod = "GET"
request.addValue("application/json",forHTTPHeaderField: "Content-Type")
request.addValue("application/json",forHTTPHeaderField: "Accept")
let task = session.dataTask(with: request as URLRequest) { (data,response,error) in
if error == nil {
let decoder = JSONDecoder()
if let movieData = data {
do {
let results = try decoder.decode(T.self,from: movieData)
completion(results)
} catch {
print(error)
}
}
}
}
task.resume()
}
}
}
SearchMovieVM
class SearchMovieVM: ObservableObject {
var searchMovieService = MovieBaseService()
@Published var searchedMovie: [MovieSearch] = []
@Published var query: String = ""
@Published var page: Int = 1
func getSearchingMovie() {
self.searchMovieService.fetchNewspaper(stringUrl: "https://api.themoviedb.org/3/search/movie?api_key=594b8eb4999a8b44ad5136ee3ed1ebdb&language=tr-TR&query=\(query)&page=1&include_adult=false",model: MovieSearchContainer) { (result) in
}
}
}
解决方法
编译器可以推断出泛型 T,并在您的情况下使用完成闭包
func fetchNewspaper<T: Codable>(stringUrl: String,completion: @escaping (T) -> ())
service.fetchNewspaper(stringUrl: url) { (result: MovieSearchContainer) in
// ...
}
除非在这种情况下您想显式传递模型类型
func fetchNewspaper<T: Codable>(stringUrl: String,model: T.Type,completion: @escaping (T) -> ())
service.fetchNewspaper(stringUrl: url,model: MovieSearchContainer.self) { result in
// ...
}
有关 Swift 泛型的更多信息,请参阅 official docs