segue标识符不起作用

Question

我有一个prepareforsegue，在其中我检查segue标识符，如果它等于一个字符串，问题是这个if语句失败，尽管两个字符串相等。我注释掉了if语句和我的项目是否正常工作，但为什么这个if语句在它们看起来相等时失败了呢？

-(void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
NSLog(@"Photos stored are %@", self.photos);
if([sender isKindOfClass:[UITableViewCell class]]){
    NSIndexPath *indexPath = [self.tableView indexPathForCell:sender];
    if(indexPath){
        NSLog(@"segue identifier is %@", segue.identifier); // this outputs  segue identifier is recentPhoto 

// the if statement here fails
       if([segue.identifier isEqualToString:@"recentPhoto"]){
            if ([segue.destinationViewController respondsToSelector:@selector(setImageURL:)]) {
                NSURL *url = [FlickrFetcher urlForPhoto:self.photos[indexPath.row] format:FlickrPhotoFormatLarge];                    
                [segue.destinationViewController performSelector:@selector(setImageURL:) withObject:url];
                [segue.destinationViewController setTitle:[[self.photos objectAtIndex:indexPath.row] objectForKey:FLICKR_PHOTO_TITLE]];
            }
        }
    }
}

}