Question

I am new to oop and objective-c. I have a collectionView which loads photos from my phone. I want to segue to another ViewController so that my asset is displayed @ full resolution.I followed this post: set UIImageView.image in prepareForSegue by Rob Mayoff and came up with this, here is my code for the main VC :

 - (void)viewDidLoad
    {
        [super viewDidLoad];

        void (^assetEnumerator)(ALAsset *, NSUInteger, BOOL *) = ^(ALAsset *result, NSUInteger index, BOOL *stop)
        {
            if (result != NULL)
            {
                NSLog(@"See Asset: %@", result);
                [_gallery addObject:result];
            }

        };




        void (^assetGroupEnumerator)(ALAssetsGroup *, BOOL *) =  ^(ALAssetsGroup *group, BOOL *stop)
        {
            if(group != nil)
            {
                [group enumerateAssetsUsingBlock: assetEnumerator];

            }

           [self.collectionView reloadData];
        };

        _gallery = [[NSMutableArray alloc]init];

        _library = [[ALAssetsLibrary alloc] init];

        [_library enumerateGroupsWithTypes: ALAssetsGroupAlbum
                               usingBlock: assetGroupEnumerator
                             failureBlock: ^(NSError *error)
         {
             NSLog(@"Failure");
         }];
    }





    -(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
    {

        return 1;

    }


    -(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
    {
        return _gallery.count;

    }


    -(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
    {

        ViewControllerCell *myCell = [collectionView dequeueReusableCellWithReuseIdentifier:@"myCell" forIndexPath:indexPath];



        _asset = [_gallery objectAtIndex:indexPath.row];


        _photo =[UIImage imageWithCGImage:[_asset thumbnail]] ;

        myCell.myImage.image = _photo;

        return myCell;
    }



    -(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
    {
        _asset = [_gallery objectAtIndex:indexPath.row];
        _photo = [UIImage imageWithCGImage:[_asset thumbnail]];
        ALAssetRepresentation *rep = [_asset defaultRepresentation];
        CGImageRef ref = [rep fullResolutionImage];
        _img = [UIImage imageWithCGImage: ref];


    }

     //the segue is set to modal
    - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
    {

        if ([segue.identifier isEqualToString:@"ShowPhoto"]) {


           PhotoZoomController *photoZoom = segue.destinationViewController;

            photoZoom.object = sender;


        }
    }

Now to show my full image I do this in my viewDidLoad method in the destination VC :

- (void)viewDidLoad
{
    ViewController *vc = [[ViewController alloc] init];

    _image = vc.img;

     [super viewDidLoad];


    _largePhoto.image = _image;   / *largePhoto is the UIImageView @property declared        
                                    in destination VC.h */

}

I am getting a blank imageView. I certainly have done something wrong and really need your help. I just don’t know what to do anymore Thanks in advance.

Answer 1

I think you misunderstood how prepareForSegue: method works. It basically provides you a possibility to interact with viewController to which you are navigating to, like setting a property. So your PhotoZoomController should have a property UIImageView to which you pass the image. Then you can do something like this:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([segue.identifier isEqualToString:@"ShowPhoto"]) {
           PhotoZoomController *photoZoom = segue.destinationViewController;
            photoZoom.imageView = myCreatedImageView;
        }
    }

This way once your modal view is displayed, its UIImageView property should be set properly. There is no need to create new view controller ViewController *vc, like you do.