ViewModelProtocol.swift

protocol ViewModelProtocol: class {
	associatedtype Item: Equatable
	init?()
	var items: [Item] { get }
	var count: Int { get }
	func getData(forResourceType resource: ResourceType) throws -> Data
	func extractItems(fromData data: Data) -> [Item]
	var resourceType: ResourceType { get }
}

extension ViewModelProtocol {
	
	var count: Int {
		return items.count
	}
	
	func getData(forResourceType resource: ResourceType) throws -> Data {
		var data: Data!
		do {
			data = try resource.load()
		} catch let err {
			throw err
		}
		return data
	}
	
	func extractItems(fromData data: Data) -> [Item] {
		let items = try? JSONDecoder().decode([Item].self, from: data)
		return items ?? []
	}
}