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An example "smart" Collection with embedded filtering abilities
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| public struct FilteringList<Element, Filter>: Collection { | |
| public typealias Filtering = (Element, Filter?) -> Bool | |
| public typealias Index = Int | |
| public typealias Element = Element | |
| public var filtering: Filtering? { | |
| didSet { filter(using: selectedFilter) } | |
| } | |
| public var selectedFilter: Filter? { | |
| didSet { filter(using: selectedFilter) } | |
| } | |
| public var elements = [Element]() { | |
| didSet { filter(using: selectedFilter) } | |
| } | |
| private var filteredElements = [Element]() | |
| public init( | |
| _ elements: [Element] = [], | |
| filtering: Filtering? = nil | |
| ) { | |
| self.elements = elements | |
| self.filtering = filtering | |
| } | |
| } | |
| public extension FilteringList { | |
| var output: [Element] { | |
| return selectedFilter == nil ? elements: filteredElements | |
| } | |
| } | |
| // MARK: - Collection | |
| public extension FilteringList { | |
| subscript(position: Int) -> Element { | |
| return filteredElements[position] | |
| } | |
| var startIndex: Int { | |
| return filteredElements.startIndex | |
| } | |
| var endIndex: Int { | |
| return filteredElements.endIndex | |
| } | |
| func index(after index: Int) -> Int { | |
| return filteredElements.index(after: index) | |
| } | |
| } | |
| // MARK: - ExpressibleByArrayLiteral | |
| extension FilteringList: ExpressibleByArrayLiteral { | |
| public init(arrayLiteral elements: Element...) { | |
| self.elements = elements | |
| } | |
| public typealias ArrayLiteralElement = Element | |
| } | |
| // MARK: - Private | |
| private extension FilteringList { | |
| mutating func filter(using selectedFilter: Filter?) { | |
| guard let filtering = self.filtering else { | |
| filteredElements = elements | |
| return SimpleLogger.warning("The filtering closure has not been set. Returning unfiltered elements...") | |
| } | |
| filteredElements = elements.filter { element -> Bool in | |
| return filtering(element, selectedFilter) | |
| } | |
| } | |
| } |
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