DefaultAssociatedTypeOverriding.swift

//: #Default associatedtype & overriding
//: Let's make an example of how can you use default associatedtype, to make clear what
//: it really does.
//: We will create generic protocol for Container, with associatedtype for ItemType.
//: Our ItemType will haave a default value of Int.

protocol Container {
    
    associatedtype ItemType = Int
    
    func getItem() -> ItemType
    func getItems() -> [ItemType]
}

class Backpack: Container { // because ItemType has default associatedtype, we don't have to specify it

    func getItem() -> Backpack.ItemType {
        return 2
    }
    
    func getItems() -> [Backpack.ItemType] {
        return [2]
    }
}

struct TypedBackpack<TypedItemType: StringLiteralConvertible>: Container { // but we can override current associatedtype quite easily
    
    func getItem() -> TypedItemType { // Because ItemType doesn't need to conform to any protocol, we can easily pass our own ItemType
        return ""
    }
    
    func getItems() -> [TypedItemType] {
        return [""]
    }
}

let backpack1 = Backpack()
let backpack2 = TypedBackpack<String>()
print(backpack1.getItem())
print(backpack2.getItem())