[self ReadAllImagesFromPhotosLibrary];

[self WriteFewImagestoDirectory];

[self GettingBackAllImagesFromFolder];

[self MoveToNextView];

BLOCK A(NEXT BLOCK reference){
->Do the the required Task
->If(next Block reference)
--->Then call that block
->Else
--->Exit or have a callback on mainthread
}

dispatch_queue_t serialQueue = dispatch_queue_create("com.unique.name.queue", DISPATCH_QUEUE_SERIAL);

dispatch_async(serialQueue, ^{
        [self ReadAllImagesFromPhotosLibrary];
             dispatch_async(serialQueue, ^{
                     [self WriteFewImagestoDirectory];
                     dispatch_async(serialQueue, ^{
                         [self GettingBackAllImagesFromFolder];
                         dispatch_async(serialQueue, ^{
                              [self MoveToNextView];
                         });
                   });
              });
    });

dispatch_async(serialQueue, ^{
        [self ReadAllImagesFromPhotosLibrary];
    });
dispatch_async(serialQueue, ^{
         [self WriteFewImagestoDirectory];
});
dispatch_async(serialQueue, ^{
    [self GettingBackAllImagesFromFolder];
});
dispatch_async(serialQueue, ^{
    [self MoveToNextView];
});