How to write block definition using properties? - ios

Question

I am writing a class for getting image from Photos Library.
I want one single method that will return selected image from library.
So i started writing a class named MediaBrowser.
I used block that will give selected image. But I am confused where to write block definition. Please correct the code if i am going wrong.
In MediaBrowser.h
#interface MediaBrowser : NSObject
typedef UIImage* (^MediaBrowserCompletionHandler)(void);
+ (id)sharedInstance;
- (BOOL)startMediaBrowserFromViewController:(UIViewController*)controller
completionHandler:(MediaBrowserCompletionHandler)completion;
#end
In MediaBrowser.m
#interface MediaBrowser () <UIImagePickerControllerDelegate, UINavigationControllerDelegate>
#property (nonatomic, strong) MediaBrowserCompletionHandler completionHandler;
#end
#implementation MediaBrowser
static MediaBrowser *sharedMediaBrowser = nil;
+ (id)sharedInstance
{
if (nil != sharedMediaBrowser) {
return sharedMediaBrowser;
}
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
sharedMediaBrowser = [[MediaBrowser alloc] init];
});
return sharedMediaBrowser;
}
- (BOOL)startMediaBrowserFromViewController:(UIViewController *)controller completionHandler:(MediaBrowserCompletionHandler)completion
{
self.completionHandler = [completion copy];
if (([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeSavedPhotosAlbum] == NO)
|| (controller == nil))
return NO;
UIImagePickerController *mediaUI = [[UIImagePickerController alloc] init];
mediaUI.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
// Displays saved pictures from the Camera Roll album.
mediaUI.mediaTypes = [[NSArray alloc] initWithObjects:(NSString *)kUTTypeImage, nil];
// Hides the controls for moving & scaling pictures, or for
// trimming movies. To instead show the controls, use YES.
mediaUI.allowsEditing = NO;
mediaUI.delegate = self;
[controller presentModalViewController:mediaUI animated:YES];
return YES;
}
// UIImagePickerControllerDelegate
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
NSString *mediaType = [info objectForKey: UIImagePickerControllerMediaType];
UIImage *imageToUse;
// Handle a still image picked from a photo album
if (CFStringCompare ((CFStringRef) mediaType, kUTTypeImage, 0) == kCFCompareEqualTo) {
imageToUse = (UIImage *) [info objectForKey:UIImagePickerControllerOriginalImage];
// Do something with imageToUse
if (self.completionHandler) {
// Pass here UIImage
self.completionHandler();
}
}
[picker dismissModalViewControllerAnimated:YES];
}
#end

Answer 1

I figured out the answer. I wanted to send selected image from UIImagePickerController to the calling class. I was writing wrong block. See corrected code below.
In MediaBrowser.h
block declaration shoudld be :
typedef void (^MediaBrowserCompletionHandler)(UIImage *selectedImage);
And in MediaBroser.m
Calling block should be :
if (self.completionHandler) {
self.completionHandler(imageToUse);
}

Answer 2

typedef UIImage* (^MediaBrowserCompletionHandler)(void);
#interface MediaBrowser : NSObject
#property (nonatomic,copy) MediaBrowserCompletionHandler handler;
#end

Answer 3

This should be fine.
typedef UIImage* (^MediaBrowserCompletionHandler)(void);
#interface MediaBrowser : NSObject
....
#end