返回在Swift中具有上限的泛型子类型?
我有以下Swift功能:返回在Swift中具有上限的泛型子类型?,swift,generics,Swift,Generics,我有以下Swift功能: private func authorizedMutableURLRequest(#ref: String) -> Result<NSMutableURLRequest> { ... } public func fetch(#ref: String) -> Result<NSURLRequest> { switch authorizedMutableURLRequest(ref: ref) { case .Su
private func authorizedMutableURLRequest(#ref: String) -> Result<NSMutableURLRequest> {
...
}
public func fetch(#ref: String) -> Result<NSURLRequest> {
switch authorizedMutableURLRequest(ref: ref) {
case .Success(let mutableURLRequestBox):
return .Success(JiveBox(mutableURLRequestBox.value))
case .Failure(let error):
return .Failure(error)
}
}
一切都会正常工作。有没有一种方法可以像Java一样,在Swift中返回一个具有上限的未指定类型
public Result<? extends NSURLRequest> fetch(String ref) {
return authorizedMutableURLRequest(ref);
}
private Result<NSMutableURLRequest> authorizedMutableURLRequest(String ref) {
...
}