在Java中,有时可以使用泛型而不必关心实际类型。在Swift中是否可以这样做?
例如,
还有其他方法吗?
例如,
MyClass<AnyObject>
与Java中的MyClass<?>
不同,我希望它们能够以相同的方式工作。还有其他方法吗?
介绍一个类型参数;编译器将允许它接受任何类型。尝试:
func executeRequest<T> (request: APIRequest<T>) {
// ...
}
例如:
class APIRequest<T> {}
class Movie {}
class MovieRequest : APIRequest<Movie> {}
let m = MovieRequest()
//print(m)
func executeRequest<T> (request: APIRequest<T>) {
print(request)
}
executeRequest(m)
protocol Resource {}
class Movie : Resource {}
class Song : Resource {}
class APIRequest<T:Resource> { /* ... */ }
func executeRequest<T:Resource> (request: APIRequest<T>) { /* ... */ }
// start with a common protocol
protocol Requestable {
func execute()
func processData(input: Any)
}
// protocol with type constraint
protocol APIRequest : Requestable {
typealias ContentType
var content : ContentType { get }
func processInput(input: ContentType)
}
extension APIRequest {
func processData(input: Any) {
if let input = input as? ContentType {
processInput(input)
} else {
// probably should throw an error here
}
}
}
// Either define a Generic function to execute with a specific type
func executeRequest<RequestType:APIRequest>(request: RequestType) {
request.execute()
}
// Or define a function taking a protocol conforming type
func executeRequest(request: Requestable) {
request.execute()
}
// process the data with a specific request and input
func processRequest<RequestType:APIRequest>(request: RequestType, input: RequestType.ContentType) {
request.processInput(input)
}
// process the data with input of arbitrary type
func processRequest(request: Requestable, data: Any) {
request.processData(data)
}
class Movie {
}
class MovieRequest : APIRequest {
var content : Movie
init(movie: Movie) {
self.content = movie
}
func execute() {
// do something here
}
func processInput(input: Movie) {
// do something with the movie input
}
}
let movieRequest = MovieRequest(movie: Movie())
executeRequest(movieRequest)
MyClass<Any>
,其中Any
确实是任何类型(类、结构体、枚举、类型、函数、元组等),但再次说一遍,它可能就是通配符的作用,我无法完全记住它在Java中是如何工作的。 - Kametrixomclass MoviesAPIRequest: APIRequest<Movie>
实例调用方法func executeRequest(request: APIRequest<Any>)
,但是我得到了一个编译错误,提示“无法将类型为MoviesAPIRequest的值转换为预期的参数类型APIRequest<Any>”。 - Cosmin