FileBackedDictionary

public struct FileBackedDictionary<T> where T : Decodable, T : Encodable

Encapsulates a [String:T] dictionary whose values are automatically persisted (each in its own file).

Exposes methods and properties similar to those of the Swift Dictionary.

Usage examples:

Create a FileBackedDictionary instance, using Documents subdirectory named Resources and struct Resource as the value type.

      let directoryName = "Resources"
      var fbDict = FileBackedDictionary<Resource>(directoryName: directoryName)

Add resource instances

      fbDict["apples"] = Resource(name: "apples", value: 1, quantity: 1)
      fbDict["oranges"] = Resource(name: "oranges", value: 2, quantity: 2)
      fbDict["mangos"] = Resource(name: "mangos", value: 3, quantity: 3)

Look up the resource info

      let count = bDict.count // 3
      let keys = fbDict.keys  // ["apples", "oranges", "mangos"])
      let values = fbDict.values // ...
      let myOranges = fbDict["oranges"]

Remove resources

       fbDict["oranges"] = nil
       fbDict.removeAll()

At its initialization (typically at the application start), an instance of FileBackedDictionary recovers the keys and values from the file storage.

  • Declaration

    Swift

    private(set) var dictionary: [String : T] { get }

  • Initialize the backed-up storage

    Remark

    if the directory for the backup files does not exist, creates it. Initiallizes the local dict from files in the directory (if any)

    Declaration

    Swift

    public init(directoryName: String)

    Parameters

    directoryName

    names the backup directory

  • Support for dictionary style setting and getting of a value by key

    Declaration

    Swift

    public subscript(key: String) -> T? { get set }

  • Return sorted keys

    Declaration

    Swift

    public var keys: [String] { get }

  • Return values sorted by keys

    Declaration

    Swift

    public var values: [T] { get }

  • Remove the value for key from the dictionary and from the file

    Declaration

    Swift

    public mutating func removeValue(forKey key: String)

    Parameters

    forKey

    key

  • Remove all values from dictionary and from files

    Declaration

    Swift

    public mutating func removeAll()

  • Return the dictionary item count

    Declaration

    Swift

    public var count: Int { get }