> For the complete documentation index, see [llms.txt](https://docs.apryse.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.apryse.com/ios/get-started/samples/undoredotest.md). # UndoRedoTest Sample Obj-C code for using Apryse SDK to take snapshots of edits and move between them using the API. The Apryse SDK has a low-level facility for undo and redo operations. It is a API that applies to any edits made to a particular document (not just annotations). This sample Obj-C code shows how to use Apryse SDK to walk back and forth on a fully general, bit-exact list of document states. Saving changes in a mode that is not 'incremental' will wipe out the undo-redo state list; the API will not be able to access old snapshots anymore. See the [undoing and redoing guide](/core/pdf-editing/undoredo.md) for more information. Learn more about our [iOS SDK](/ios/guides.md). {% tabs %} {% tab title="Obj-C" %} {% code lineNumbers="true" %} ```objc //--------------------------------------------------------------------------------------- // Copyright (c) 2001-2024 by Apryse Software Inc. All Rights Reserved. // Consult legal.txt regarding legal and license information. //--------------------------------------------------------------------------------------- #import #import #include //--------------------------------------------------------------------------------------- // The following sample illustrates how to use the UndoRedo API. //--------------------------------------------------------------------------------------- int main(int argc, char *argv[]) { @autoreleasepool { int ret = 0; @try { // The first step in every application using PDFNet is to initialize the // library and set the path to common PDF resources. The library is usually // initialized only once, but calling Initialize() multiple times is also fine. [PTPDFNet Initialize: 0]; // Open the PDF document. PTPDFDoc *doc = [[PTPDFDoc alloc] initWithFilepath: @"../../TestFiles/newsletter.pdf"]; PTSDFUndoManager* undo_manager = [doc GetUndoManager]; // Take a snapshot to which we can undo after making changes. PTSDFResultSnapshot* snap0 = [undo_manager TakeSnapshot]; PTSDFDocSnapshot* snap0_state = [snap0 CurrentState]; PTElementBuilder* builder = [[PTElementBuilder alloc] init]; // Used to build new Element objects PTElementWriter* writer = [[PTElementWriter alloc] init]; // Used to write Elements to the page PTPDFRect * rect = [[PTPDFRect alloc] init]; [rect Set: 0 y1: 0 x2: 612 y2: 792]; PTPage* page = [doc PageCreate: rect]; // Start a new page [writer WriterBeginWithPage: page placement: e_ptoverlay page_coord_sys: YES compress: YES resources: NULL]; // Begin writing to this page // ---------------------------------------------------------- // Add JPEG image to the file PTImage* img = [PTImage Create: [doc GetSDFDoc] filename: @"../../TestFiles/peppers.jpg"]; PTElement* element = [builder CreateImageWithMatrix: img mtx: [[PTMatrix2D alloc] initWithA: 200 b: 0 c: 0 d: 250 h: 50 v: 500]]; [writer WritePlacedElement: element]; [writer End]; // Finish writing to the page [doc PagePushFront: page]; // Take a snapshot after making changes, so that we can redo later (after undoing first). PTSDFResultSnapshot* snap1 = [undo_manager TakeSnapshot]; if ([[snap1 PreviousState] Equals: snap0_state]) { NSLog(@"snap1 previous state equals snap0_state; previous state is correct"); } PTSDFDocSnapshot* snap1_state = [snap1 CurrentState]; [doc SaveToFile: @"../../TestFiles/Output/addimage.pdf" flags: e_ptincremental]; if ([undo_manager CanUndo]) { PTSDFResultSnapshot* undo_snap = [undo_manager Undo]; [doc SaveToFile: @"../../TestFiles/Output/addimage_undone.pdf" flags: e_ptincremental]; PTSDFDocSnapshot* undo_snap_state = [undo_snap CurrentState]; if ([undo_snap_state Equals: snap0_state]) { NSLog(@"undo_snap_state equals snap0_state; undo was successful"); } if ([undo_manager CanRedo]) { PTSDFResultSnapshot* redo_snap = [undo_manager Redo]; [doc SaveToFile: @"../../TestFiles/Output/addimage_redone.pdf" flags: e_ptincremental]; if ([[redo_snap PreviousState] Equals: undo_snap_state]) { NSLog(@"redo_snap previous state equals undo_snap_state; previous state is correct"); } PTSDFDocSnapshot* redo_snap_state = [redo_snap CurrentState]; if ([redo_snap_state Equals: snap1_state]) { NSLog(@"Snap1 and redo_snap are equal; redo was successful"); } } else { NSLog(@"Problem encountered - cannot redo."); ret = 1; } } else { NSLog(@"Problem encountered - cannot undo."); ret = 1; } } @catch(NSException *e) { NSLog(@"%@", e.reason); ret = 1; } [PTPDFNet Terminate: 0]; return ret; } } ``` {% endcode %} {% endtab %} {% endtabs %} --- # Agent Instructions This documentation is published with GitBook. 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