feat(dialog): implement save API on iOS (#1707)

.changes/ios-dialog-save.md

@@ -0,0 +1,5 @@
+---
+"dialog": patch:feat
+---
+
+Implement `save` API on iOS.

plugins/dialog/ios/Sources/DialogPlugin.swift

@@ -17,10 +17,10 @@ enum FilePickerEvent {
 }
 
 struct MessageDialogOptions: Decodable {
-  let title: String?
+  var title: String?
   let message: String
-  let okButtonLabel: String?
+  var okButtonLabel: String?
-  let cancelButtonLabel: String?
+  var cancelButtonLabel: String?
 }
 
 struct Filter: Decodable {
@@ -30,13 +30,18 @@ struct Filter: Decodable {
 struct FilePickerOptions: Decodable {
   var multiple: Bool?
   var filters: [Filter]?
+  var defaultPath: String?
+}
+
+struct SaveFileDialogOptions: Decodable {
+  var fileName: String?
+  var defaultPath: String?
 }
 
 class DialogPlugin: Plugin {
 
   var filePickerController: FilePickerController!
-  var pendingInvoke: Invoke? = nil
+  var onFilePickerResult: ((FilePickerEvent) -> Void)? = nil
-  var pendingInvokeArgs: FilePickerOptions? = nil
 
   override init() {
     super.init()
@@ -66,8 +71,16 @@ class DialogPlugin: Plugin {
       }
     }
 
-    pendingInvoke = invoke
+    onFilePickerResult = { (event: FilePickerEvent) -> Void in
-    pendingInvokeArgs = args
+      switch event {
+      case .selected(let urls):
+        invoke.resolve(["files": urls])
+      case .cancelled:
+        invoke.resolve(["files": nil])
+      case .error(let error):
+        invoke.reject(error)
+      }
+    }
 
     if uniqueMimeType == true || isMedia {
       DispatchQueue.main.async {
@@ -104,6 +117,9 @@ class DialogPlugin: Plugin {
       let documentTypes = parsedTypes.isEmpty ? ["public.data"] : parsedTypes
       DispatchQueue.main.async {
         let picker = UIDocumentPickerViewController(documentTypes: documentTypes, in: .import)
+        if let defaultPath = args.defaultPath {
+          picker.directoryURL = URL(string: defaultPath)
+        }
         picker.delegate = self.filePickerController
         picker.allowsMultipleSelection = args.multiple ?? false
         picker.modalPresentationStyle = .fullScreen
@@ -112,6 +128,46 @@ class DialogPlugin: Plugin {
     }
   }
 
+  @objc public func saveFileDialog(_ invoke: Invoke) throws {
+    let args = try invoke.parseArgs(SaveFileDialogOptions.self)
+
+    // The Tauri save dialog API prompts the user to select a path where a file must be saved
+    // This behavior maps to the operating system interfaces on all platforms except iOS,
+    // which only exposes a mechanism to "move file `srcPath` to a location defined by the user"
+    //
+    // so we have to work around it by creating an empty file matching the requested `args.fileName`,
+    // and using it as `srcPath` for the operation - returning the path the user selected
+    // so the app dev can write to it later - matching cross platform behavior as mentioned above
+    let fileManager = FileManager.default
+    let srcFolder = fileManager.urls(for: .documentDirectory, in: .userDomainMask).first!
+    let srcPath = srcFolder.appendingPathComponent(args.fileName ?? "file")
+    if !fileManager.fileExists(atPath: srcPath.path) {
+      // the file contents must be actually provided by the tauri dev after the path is resolved by the save API
+      try "".write(to: srcPath, atomically: true, encoding: .utf8)
+    }
+
+    onFilePickerResult = { (event: FilePickerEvent) -> Void in
+      switch event {
+      case .selected(let urls):
+        invoke.resolve(["file": urls.first!])
+      case .cancelled:
+        invoke.resolve(["file": nil])
+      case .error(let error):
+        invoke.reject(error)
+      }
+    }
+
+    DispatchQueue.main.async {
+      let picker = UIDocumentPickerViewController(url: srcPath, in: .exportToService)
+      if let defaultPath = args.defaultPath {
+        picker.directoryURL = URL(string: defaultPath)
+      }
+      picker.delegate = self.filePickerController
+      picker.modalPresentationStyle = .fullScreen
+      self.presentViewController(picker)
+    }
+  }
+
   private func presentViewController(_ viewControllerToPresent: UIViewController) {
     self.manager.viewController?.present(viewControllerToPresent, animated: true, completion: nil)
   }
@@ -133,14 +189,7 @@ class DialogPlugin: Plugin {
   }
 
   public func onFilePickerEvent(_ event: FilePickerEvent) {
-    switch event {
+    self.onFilePickerResult?(event)
-    case .selected(let urls):
-      pendingInvoke?.resolve(["files": urls])
-    case .cancelled:
-      pendingInvoke?.resolve(["files": nil])
-    case .error(let error):
-      pendingInvoke?.reject(error)
-    }
   }
 
   @objc public func showMessageDialog(_ invoke: Invoke) throws {

plugins/dialog/src/commands.rs

@@ -197,10 +197,6 @@ pub(crate) async fn save<R: Runtime>(
     dialog: State<'_, Dialog<R>>,
     options: SaveDialogOptions,
 ) -> Result<Option<FilePath>> {
-    #[cfg(target_os = "ios")]
-    return Err(crate::Error::FileSaveDialogNotImplemented);
-    #[cfg(any(desktop, target_os = "android"))]
-    {
     let mut dialog_builder = dialog.file();
     #[cfg(any(windows, target_os = "macos"))]
     {
@@ -231,7 +227,6 @@ pub(crate) async fn save<R: Runtime>(
     }
 
     Ok(path.map(|p| p.simplified()))
-    }
 }
 
 fn message_dialog<R: Runtime>(

plugins/dialog/src/error.rs

@@ -18,9 +18,6 @@ pub enum Error {
     #[cfg(mobile)]
     #[error("Folder picker is not implemented on mobile")]
     FolderPickerNotImplemented,
-    #[cfg(target_os = "ios")]
-    #[error("File save dialog is not implemented on iOS")]
-    FileSaveDialogNotImplemented,
     #[error(transparent)]
     Fs(#[from] tauri_plugin_fs::Error),
     #[error("URL is not a valid path")]