Ios 如何在文件管理器中拾取pdf文件？

我正在尝试在我的应用程序中开发载体表单，这里我正在尝试在我的应用程序中实现恢复上载文件上载。这里我正在为open file manager编写代码，但我不知道如何在file manager中选择pdf文件。请任何人帮助完成此操作。提前感谢

 UIButton *button = (UIButton *)sender;
    NSURL *URL = [[NSBundle mainBundle] URLForResource:@"test" withExtension:@"pdf"];

    if (URL) {
        // Initialize Document Interaction Controller
        self.documentInteractionController = [UIDocumentInteractionController interactionControllerWithURL:URL];

        //Configure Document Interaction Controller
        [self.documentInteractionController setDelegate:self];

        // Present Open In Menu
        [self.documentInteractionController presentOpenInMenuFromRect:[button frame] inView:self.view animated:YES];

    }

这是我用于open file manager的代码。

试试这个

 NSArray *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,            
 NSUserDomainMask, YES); 
 NSString *docsDirectory = [path objectAtIndex:0]; 
 NSString *filePath = [docsDirectory stringByAppendingPathComponent:@“sample.pdf"];
 NSURL *pdfUrl = [NSURL fileURLWithPath:filePath];
 pdf = CGPDFDocumentCreateWithURL((CFURLRef)pdfURL);

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欢迎来到Stackoverflow。请阅读并确保包含您所询问的代码。此处是哪种数据类型的pdf变量？CGPDFDocumentReleasepdf；