pattmehta / serializednavpath Goto Github PK

Swift package to enable persistence layer over NavigationPath. Package also provides a few navigation utils. Package consists of six main things

1. SerializedNavPath type, which is an Observable that wraps the built-in NavigationPath
2. Read-only pathBinding property which provides Binding to the above path property
3. SerializedNavPath provides persistence from its initialization stage itself by reading the (saved) serialized data from disk, unless we want to create a new object

   init(filenameWithExtension: String, createNew: Bool = false)

4. An internal property navPathLib of type SerializedNavPathLib is also used, as it contains useful methods listed as following (these methods are only accessible within the package)

   - func readSerializedData(filenameWithExtension: String? = nil) -> Data?
   - func writeSerializedData(_ data: Data) -> Bool
   - func eraseSerializedData()
   - func log(_ message: String)

5. Package provides the following routing utils and properties, which are available outside the package

   // methods
   - func createNew()
   - func getNavPathForNavigationStack() -> Binding<NavigationPath>
   - func append(_ route: Route)
   - func removeLast()
   // properties
   - var count: Int
   - var routes: [Route]

6. Package provides the following disk utils, which are available outside the package

   - func save()
   - func erase()

As seen in the SerializedNavPathExampleApp, the SerializedNavPath object needs be initialized with the filenameWithExtension parameter. The initialization stage itself will load the path data from disk, and set the path by de-serializing (or, decoding) this path data. Almost instantly, this SerializedNavPath is read by the NavigationStack, defined as following. Here, the getNavPathForNavigationStack method simply returns the pathBinding.

NavigationStack(path: navPath.getNavPathForNavigationStack())

Internal

• readSerializedData: Mutating method of SerializedNavPathLib to read serialized data from file, where filename is obtained using filenameWithExtension param, or _filenameWithExtension property.
• writeSerializedData: Method of SerializedNavPathLib for the corresponding write operation, that returns true on success.
• eraseSerializedData: Another method that removes file using _filenameWithExtension property.

Public

• save: Saves json encoded NavigationPath data to disk using writeSerializedData method of navPathLib.
• erase: Calls eraseSerializedData method of navPathLib.
• createNew: Erases the serialized data and assigns a new NavigationPath object to the path property.
• getNavPathForNavigationStack: This method returns the private property pathBinding.
• append: This method appends a new element to the NavigationPath, and saves the path data to disk.
• count: Computed property that represents the number of elements in the NavigationPath.
• removeLast: If count is non-zero, this method removes the last element from the NavigationPath.
• routes: Computed property obtained by the transformation of NavigationPath data to a collection of Route type, returns an empty collection if there is no data.

Debugging can be turned on by setting the SerializedNavPath.debug flag. The example app view sets this debug flag in its init method. Running the app shows two kinds of logs. The file-io logs show when serialized data is written to the json file, or when this file is removed. The other logs are for information only, for e.g. when attempt is made to modify the pathBinding property, the log prints pathBinding is readonly.

In the first example recording, clicking the Login button appends "home" Route to NavigationPath, and calls the save method of SerializedNavPath, which in turn calls navPathLib.writeSerializedData method, passing it the updated path data. If this step produces error, the log prints could not save path, else it prints data written, followed by the filename with extension.

• macOS v13 and above
• iOS v16 and above

First recording shows navigation b/w views, and write logs (for file MainNavPath.json). Most importantly, it shows the navPath.count and navPath.routes properties in the view. At the end it shows that pathBinding is read-only, and calls navPath.erase for demo purposes only. Second recording shows the persistence of navigation path b/w app launches — as a feature of the SerializedNavPath package.

1. The above recordings are from SerializedNavPathExampleApp view.
2. This view initializes a navPath of type SerializedNavPath using a filename constant.
3. The title property retrieves the first route's path from navPath, or a default title if no route exists.
4. View body is a NavigationStack with conditional navigation destinations based on the route path.
5. Each destination (LoginView, HomeView, OtherHomeView) receives and stores the navPath for calling the corresponding methods.