Thanks for bringing AnyHashable to my attention.
It works, but the types are now erased. I want to have a union of the two sets
because I want to loop over it to treat each contained item as Named, so I can
process them as though they are of the same type. Is this type of use case
really should be addressed using super class?
> On 11 Jul 2017, at 7:38 PM, Howard Lovatt <howard.lov...@gmail.com> wrote:
>
> You can have a set of AnyHashable:
>
>> var item = Set<AnyHashable>()
>> item.insert(AnyHashable(Foo()))
>> item.insert(AnyHashable(Bar()))
>
> Depends what you will do with the set if this is viable or not. You can also
> use classes and ObjectID.
>
> You might want this though:
>
>> var item = [AnyHashable: Any]
> extension Dictionary where Key == AnyHashable, Value: Hashable {
> func insert(_ value: Value) {
> self[AnyHashable(value)] == value
> }
> }
>> item.insert(Foo())
>> item.insert(Bar())
>
> So you get at the stored value.
>
> -- Howard.
>
> On 11 Jul 2017, at 8:09 pm, Glen Huang via swift-users <swift-users@swift.org
> <mailto:swift-users@swift.org>> wrote:
>
>> Hi,
>>
>> I want to store some heterogeneous items all conform to a protocol inside a
>> set, is it something possible to do in swift?
>>
>> I tried this example:
>>
>> ```
>> protocol Named: Hashable {
>> var name: String { get }
>> }
>>
>> extension Named {
>> var hashValue: Int {
>> return name.hashValue
>> }
>>
>> static func ==(lhs: Self, rhs: Self) -> Bool {
>> return lhs.name == rhs.name
>> }
>> }
>>
>> struct Foo: Named {
>> var name = "foo"
>> }
>>
>> struct Bar: Named {
>> var name = "bar"
>> }
>>
>> var item = Set<Named>()
>> item.insert(Foo())
>> item.insert(Bar())
>> ```
>>
>> But it failed at `Set<Named>()` where it complained "Using 'Named' as a
>> concrete type conforming to protocol 'Hashable' is not supported”.
>>
>> After watching the WWDC session "Protocol-Oriented Programming in Swift” by
>> Dave Abrahams, I try to use protocols whenever possible. But I can’t seem to
>> overcome this barrier. Set.Element must confirm to Hashable, which inherits
>> from Equatable, which has self requirement, which ultimately means that
>> Set.Element all must be of the same type. So it seems it’s impossible to
>> have heterogeneous items using protocol. Is that the case?
>>
>> My use case is this:
>>
>> I have an object that can contain two sets of other objects:
>>
>> ```
>> class Parent {
>> var foos: Set<Foo>
>> var bars: Set<Bar>
>> }
>> ```
>>
>> I want to define a computed property “all” that is the union of the two
>> sets. Foo and Bar conform to the same protocol. I wonder what return type I
>> should use for the union? Do I have to go back to OOP and define a super
>> class for Foo and Bar?
>>
>> Thanks.
>> _______________________________________________
>> swift-users mailing list
>> swift-users@swift.org <mailto:swift-users@swift.org>
>> https://lists.swift.org/mailman/listinfo/swift-users
>> <https://lists.swift.org/mailman/listinfo/swift-users>
_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users
