Question

我正在将核心数据中的对象保存到下面列出的单元格中。 URL正在正确保存到单元格并且运行良好。我的问题是，当用户点击一个单元格时，我希望保存到该单元格的URL传递给我的detailedViewController以供使用。我有一些我尝试过的代码，但是detailedViewController中的url为nil。如果你有更好的方法来完成同样的事情，那就没问题了。代码列在下面 -

这是我将其保存到单元格的位置：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *cellIdentifier = @"Cell";
PhotoCell *cell = (PhotoCell *)[self.tableView dequeueReusableCellWithIdentifier:cellIdentifier];

if (!cell) {
    cell = [[PhotoCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:cellIdentifier];
}

// Configure the cell...
FeedEntity *feed = [_fetchedResultsController objectAtIndexPath:indexPath];
NSData *data = feed.imageData;

self.feedImage = [UIImage imageWithData:data];
cell.thumbImage = self.feedImage;

NSData *stringData = feed.urlString;
self.stringForURL = [[NSString alloc] initWithData:stringData encoding:NSUTF8StringEncoding];
self.stringForURL = [self.stringForURL stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
self.finalURL = [NSURL URLWithString:self.stringForURL];

cell.finalURL = self.finalURL;

return cell;
}

这是我从单元格中检索url并将其传递给detailedViewController的地方：

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSManagedObject *object = [[self fetchedResultsController] objectAtIndexPath:indexPath];

    // Code to create detailed view and set properties
    self.detailsViewController = [[DetailsViewController alloc] init];

    NSIndexPath *path = [self.tableView indexPathForSelectedRow];
    FeedEntity *feed = [_fetchedResultsController objectAtIndexPath:path];
    NSData *stringData = feed.urlString;
    NSString *stringURL = [[NSString alloc] initWithData:stringData encoding:NSUTF8StringEncoding];
    NSLog(@"Here is the string before: %@", stringURL);
    stringURL = [self.stringForURL stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    NSURL *urlForDetail = [NSURL URLWithString:self.stringForURL];

    NSLog(@"Here is the url before it goes to the detailed: %@", urlForDetail);

    self.detailsViewController.finalURL = urlForDetail;

    [self.navigationController pushViewController:self.detailsViewController animated:YES];

}

保存视频（在didFinishPickingMediaWithInfo中:)：

self.videoURL = [info objectForKey:UIImagePickerControllerMediaURL];

NSData *videoData = [NSData dataWithContentsOfURL:self.videoURL];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *path = [documentsDirectory stringByAppendingFormat:@"/vid1.mp4"];
self.urlForSave = [NSURL fileURLWithPath:path];

//Look at YES
[videoData writeToFile:path atomically:YES];
[self saveImageAndVideo];

这是SaveVideoAndPhoto：

- (void)saveImageAndVideo {

    NSManagedObjectContext *context = [self managedObjectContext];

    FeedEntity *feedEntity = [NSEntityDescription insertNewObjectForEntityForName:@"FeedEntity" inManagedObjectContext:context];

    NSData *imageData = UIImageJPEGRepresentation(self.thumbImage, 0.8f);
    self.photoData = imageData;

    NSString *stringForSave = [self.urlForSave absoluteString];
    NSLog(@"URL before save: %@", stringForSave);

    //NSData * stringData = [stringForSave dataUsingEncoding:NSUTF8StringEncoding];

    [feedEntity setValue:imageData forKey:@"imageData"];
    [feedEntity setValue:[NSDate date] forKey:@"timeStamp"];
    [feedEntity setValue: stringForSave forKey:@"urlString"];

    NSError *error = nil;

    if (![self.managedObjectContext save:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    } else {
        NSLog(@"URL's are being saved");
    }
}

Answer 1

您的问题出在cellForRowAtIndexPath中的代码中：

self.finalURL = [NSURL URLWithString:self.stringForURL];

您将URL设置为SELF的属性，在本例中是您的viewController。你想在CELL上设置它。从self.whatever cell创建单元格时更改所有代码。如果要将它们保存为单元格的属性，则更改。如果您在objective-c中读取范围，它可能对您有所帮助。

另外，在旁注中，您正在做的一些事情是不必要的。首先是：

NSIndexPath *path = [self.tableView indexPathForSelectedRow];

您不需要在此函数中创建indexPath对象，因为函数本身已经为变量indexPath提供了它：

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath

其次，在didSelectRowAtIndexPath内部，如果你想获取网址，你应该这样做：

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    // deselect the row if you want the cell to fade out automatically after tapping
    [tableView deselectRowAtIndexPath:indexPath animated:YES];

    // get a reference to the cell that the user tapped
    UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];

    // get the url from the cell, assuming your cell has a property called finalURL on it that you set some value
    // to originally when it was created
    NSURL *url = cell.finalURL;

    // do something with that URL here...
}

请记住，这有点不正统。你真的应该从tableView的数据源中获取信息。如果你有一个用来填充tableView的对象数组，那么简单地使用给定的indexPath从我们的数组中获取对象本身可能是一个更好的主意，而不是将信息作为属性保存在单元格中并以这种方式访问它。我强烈建议观看一些教程视频或进行一些阅读，最好是在iOS文档中，尝试学习UITableViews的最佳实践。

从单元格中检索核心数据对象

1 个答案: