When defined as below in Objective-C code, how can I specify Item protocol from Swift?
// Objective-C
@protocol Item <NSObject>
@end
@interface Item : NSObject<Item>
@end
@implementation Item
@end
// Swift
var item = Item() // item interface, but I'd like to define as Item protocol.
Should I define as distinct name?
You cannot instantiate a protocol type, therefore Item() will always refer to @interface Item. You should explicitly specify that you mean a protocol in your declaration:
var item: protocol<Item>
By the way, the thing you've done in Objective-C cannot be done in Swift – it requires all declarations in the same scope to be uniquely named. Your equivalent, following Apple's conventions, would look like this:
@objc(Item) protocol ItemType {
}
class Item: ItemType {
}
NSObject protocol into NSObjectProtocol for the same reason.ItemType or ItemProtocol in your Objective-C code and it will become more safe and readable.