将多个图像上传到Parse的正确方法

Question

I am saving multiple images by using an open source custom class called ELCImagePicker. The code to use the ELCImagePicker is found within the ViewDidLoad method of the controller for the specific tab.

ELCImagePickerController *imagePicker = [[ELCImagePickerController alloc]initImagePicker];
        imagePicker.maximumImagesCount = 20;
        imagePicker.imagePickerDelegate = self;

        [self presentViewController:imagePicker animated:YES completion:nil];

Currently, the method I am using to upload the images itself to Prase which is a backend as a service is

- (void)elcImagePickerController:(ELCImagePickerController *)picker didFinishPickingMediaWithInfo:(NSArray *)info
{
    NSData *fileData;
    NSString *fileName;
    NSString *fileType;

    for(id image in info){

        fileData = UIImagePNGRepresentation(image);
        fileName = @"image.png";

        PFFile *imageFile = [PFFile fileWithName:fileName data:fileData];
        [imageFile saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
            if (error){
                UIAlertView *errorAlert = [[UIAlertView alloc]initWithTitle:@"Image Upload Error" message:@"please try sending your image again" delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil];
                [errorAlert show];
            }else{
                PFObject *message = [PFObject objectWithClassName:@"Message"];
                [message setObject:imageFile forKey:@"imageFile"];
                [message setObject:[[PFUser currentUser] objectId] forKey:@"senderId"];
                [message setObject:[[PFUser currentUser] username] forKey:@"username"];
                [message saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
                    if (error){
                        UIAlertView *errorAlert = [[UIAlertView alloc]initWithTitle:@"Image Upload Error" message:@"please try sending your image again" delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil];
                        [errorAlert show];
                    }
                }];


            }
        }];
    }

}

First and foremost, info is an array which contains the multiple images that are selected. I am currently enumerating through the array and than using Parse's custom API to upload the images. So far I am getting an error message which reads: " 2014-04-28 11:03:58.574 One Take[42357:90b] -[__NSDictionaryM CGImage]: unrecognized selector sent to instance 0xe9749b0 2014-04-28 11:03:58.582 One Take[42357:90b] Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSDictionaryM CGImage]: unrecognized selector sent to instance 0xe9749b0' First throw call stack: "

I am wondering what is a proper method in order to upload multiple images to parse, I'm not sure if its a good practice to even do what I am currently doing.

Answer 1

The parse part isn't what's throwing the error, the id image in info is wrong. It returns dictionaries, so you're trying to convert a dictionary to a UIImage.

It should be:

for (NSDictionary * dictionary in info) {
    UIImage *image = dictionary[UIImagePickerControllerOriginalImage]; //ELC packages its dictionaries with the same key as UIImagePicker
    fileData = UIImagePNGRepresentation(image);

    // ... the rest of your code ... //

}

Your parse saves aren't necessarily a problem; however, they might be problematic because they don't keep track of which photo triggered the error. Perhaps keep track of the error photos in a separate array, then notify the user which photos failed to upload. Then give them the option to try again on just those photos.