code.m

RCT_EXPORT_METHOD(pick:(NSDictionary *)options
                  resolver:(RCTPromiseResolveBlock)resolve
                  rejecter:(RCTPromiseRejectBlock)reject)
{
    mode = options[@"mode"] && [options[@"mode"] isEqualToString:@"open"] ? UIDocumentPickerModeOpen : UIDocumentPickerModeImport;
    copyDestination = options[@"copyTo"];
    UIModalPresentationStyle presentationStyle = [RCTConvert UIModalPresentationStyle:options[@"presentationStyle"]];
    [promiseWrapper setPromiseWithInProgressCheck:resolve rejecter:reject fromCallSite:@"pick"];

    NSArray *allowedUTIs = [RCTConvert NSArray:options[OPTION_TYPE]];
    UIDocumentPickerViewController *documentPicker = [[UIDocumentPickerViewController alloc] initWithDocumentTypes:allowedUTIs inMode:mode];

    documentPicker.modalPresentationStyle = presentationStyle;

    documentPicker.delegate = self;
    documentPicker.presentationController.delegate = self;

    documentPicker.allowsMultipleSelection = [RCTConvert BOOL:options[OPTION_MULTIPLE]];

    UIViewController *rootViewController = RCTPresentedViewController();

    [rootViewController presentViewController:documentPicker animated:YES completion:nil];
}