Get a list of chapters of pdf document in Objective C?

I need to get a list of chapters of pdf document programmatically开发者_如何学运维 in Objective C. I've googled, someone said that CGPDFDocumentGetCatalog may helpful but I don't know how to use it.

Use the PDFDocument class in the PDFKit Framework, something like this:

PDFDocument* pdfDoc = [[PDFDocument alloc] initWithURL:... ];
PDFOutline* pdfOutline = [pdfDoc outlineRoot];