相关疑难解决方法(0)

我正在使用Erica Sadun的异步下载方法(此处链接到项目文件:下载),但是她的方法不适用于具有大尺寸(50 mb或更高)的文件.如果我尝试下载超过50 MB的文件,它通常会因内存崩溃而崩溃.无论如何我可以调整这段代码,以便它也适用于大文件？这是我在DownloadHelper类中的代码(已经在下载链接中):

.H

@protocol DownloadHelperDelegate <NSObject>
@optional
- (void) didReceiveData: (NSData *) theData;
- (void) didReceiveFilename: (NSString *) aName;
- (void) dataDownloadFailed: (NSString *) reason;
- (void) dataDownloadAtPercent: (NSNumber *) aPercent;
@end

@interface DownloadHelper : NSObject 
{
    NSURLResponse *response;
    NSMutableData *data;
    NSString *urlString;
    NSURLConnection *urlconnection;
    id <DownloadHelperDelegate> delegate;
    BOOL isDownloading;
}
@property (retain) NSURLResponse *response;
@property (retain) NSURLConnection *urlconnection;
@property (retain) NSMutableData *data;
@property (retain) NSString *urlString;
@property (retain) id delegate;
@property (assign) BOOL isDownloading;

+ …

import UIKit
import WebKit

class ViewController: UIViewController, UIDocumentInteractionControllerDelegate {

    var docController: UIDocumentInteractionController!

    override func viewDidLoad() {
        super.viewDidLoad()

        docController = UIDocumentInteractionController.init(url: URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(urlVal!))
        docController.delegate = self
        docController.presentPreview(animated: true)       
    }


    func documentInteractionControllerViewControllerForPreview(_ controller: UIDocumentInteractionController) -> UIViewController {
            return self
     }
}

上面的代码我无法显示pdf文件。有人可以帮忙吗？