protocol による多重継承

protocol.swift

protocol ExternalAccount {}
extension ExternalAccount {
    func save() {
        print("PATCH http://api.external.com/user")
    }
}

protocol DataBaseAccount {}
extension DataBaseAccount {
    func save() {
        print("Save to Database")
    }
}

class User: DataBaseAccount, ExternalAccount {}

func updateProfile(user:ExternalAccount) {
    user.save()
}

let user = User()
updateProfile(user)
//=> PATCH http://api.external.com/user