将结构存储在通用数组中

Question

I'm trying to create a struct which acts as a storage for the results being returned from a web API. This API returns different JSON results which are modeled as a set of struct s.

These results need to be stored in an array inside of a storage class which will need to be generic as it should be able to store arrays of any of the types returned. I'm struggling, however, with adding generic data to an array… and this is where you guys might come in.

This is the storage class :

class FooStorage<F: Fooable> {
    private var storage: [F] = []
    
    func add<F: Fooable>(_ someFoo: F) {
        storage.append(someFoo)
    }
}

These are two sample structs modeling what the API mentioned will return:

struct FooA: Fooable, Decodable {
    var foo: String
}

struct FooB: Fooable, Decodable {
    var foo: String
    var bar: String
}

And finally, this is the protocol I created in order to specify that all of these structs are results of the same API:

protocol Fooable {}

The compiler error I get is this:

No exact matches in call to instance method append

And it is thrown on the storage.append(_:) method of the FooStorage class. Tried to add Equatable and Hashable conformance to the FooX protocols but to no avail. Seems I need some enlightenment here… thanks in advance!

Answer 1

In your add function, remove the generic part & let it use the class generic:

class FooStorage<F: Fooable> {
    private var storage: [F] = []
    
    func add(_ someFoo: F) {
        storage.append(someFoo)
    }
}