Overriding Classes

PSPDFKit has a rather unique and easy-to-use system that allows you to subclass classes that are used deeply within the framework without having to know where they are all instantiated.

The PSPDFConfiguration object has an overrideClass:withClass: method in the builder, which is where you can register your subclasses to be used instead of the vanilla PSPDF objects.

Let's say you want to move the PSPDFScrubberBar all the way to the top. Classes usually don't manage their placement themselves, so in this example, the class is managed by the PSPDFUserInterfaceView, requiring you to override the class. We usually expose a variety of hooks that are meant to be modified in a subclass:

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extension PSPDFUserInterfaceView {

    /// Update these to manually set the frame.
    open func updateDocumentLabelFrame(animated: Bool)
    open func updatePageLabelFrame(animated: Bool)
    open func updateThumbnailBarFrame(animated: Bool)
    open func updateScrubberBarFrame(animated: Bool)
}
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@interface PSPDFUserInterfaceView (SubclassingHooks)

// Update these to manually set the frame.
- (void)updateDocumentLabelFrameAnimated:(BOOL)animated;
- (void)updatePageLabelFrameAnimated:(BOOL)animated;
- (void)updateThumbnailBarFrameAnimated:(BOOL)animated;
- (void)updateScrubberBarFrameAnimated:(BOOL)animated;
@end

Here we're interested in modifying the updateScrubberBarFrameAnimated: method.

First, we create a custom subclass where we override this method:

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class PSCCustomUserInterfaceView: PSPDFUserInterfaceView {

    override func updateScrubberBarFrame(animated: Bool) {
        super.updateScrubberBarFrame(animated: animated)

        // Stick scrubber bar to the top.
        guard var newFrame = dataSource?.contentRect else { return }
        newFrame.size.height = 44
        scrubberBar.frame = newFrame
    }
}
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@interface PSCCustomUserInterfaceView : PSPDFUserInterfaceView @end
@implementation PSCCustomUserInterfaceView

- (void)updateScrubberBarFrameAnimated:(BOOL)animated {
    [super updateScrubberBarFrameAnimated:animated];

    // Stick scrubber bar to the top.
    CGRect newFrame = self.dataSource.contentRect;
    newFrame.size.height = 44.f;
    self.scrubberBar.frame = newFrame;
}

@end

Next, we register our custom subclass:

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let pdfController = PSPDFViewController(document: document, configuration: PSPDFConfiguration { builder in
    builder.overrideClass(PSPDFUserInterfaceView.self, with: PSCCustomUserInterfaceView.self)
})
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PSPDFViewController *pdfController = [[PSPDFViewController alloc] initWithDocument:document configuration:[PSPDFConfiguration configurationWithBuilder:^(PSPDFConfigurationBuilder *builder) {
    [builder overrideClass:PSPDFUserInterfaceView.class withClass:PSCCustomUserInterfaceView.class];
}]];

That's it! From now on, every time PSPDFKit creates a PSPDFUserInterfaceView, it actually uses PSCCustomUserInterfaceView.

Things to Keep in Mind

  • Your subclass must be an actual subclass or we'll throw an exception to warn you.
  • Most methods require that you call super on them.
  • Model-related classes need to be registered in PSPDFDocument's overrideClass:withClass:.
  • Overrides need to be registered before calling any other method on the object (e.g. trying to set an override on the document after unlockWithPassword: has been called will silently fail — it would be too expensive to check all calls for timing correctness.)
  • If you see a getter/setter property pair or a read-only getter, unless specifically documented, do not override it. In most cases, this will lead to unexpected/inconsistent/buggy behavior. PSPDFKit will even detect and assert some of these attempts, but we can't possibly anticipate every use and every way to dynamically override properties. In most cases there will be a better way to achieve what you're trying to do — ping us on support; we're happy to help.