collectionview can not display images - objective-c

Question

I make one app that for traveler where user have to choice activity for travel. For that reason I make collectionview, but I am getting an error when first making a new file masterviewcontroller and about declaration is as shown below and make outlet in customcolumncell.h file and make breakpoint to identifier error so.. its show error in objectforkey:activityimage
{
NSMutableArray *myObject;
NSDictionary *dict;
NSString *activity_id;
NSString *activity_image;
}
-(void)viewDidLoad
{
[super viewDidLoad];
activity_id=#"Activity_ID";
activity_image= #"Activity_Image";
myObject = [[NSMutableArray alloc]init];
NSData *jsonData=[NSData dataWithContentsOfURL:[NSURL URLWithString:#"http://ezpacking.wowartndecor.com/api/Activity?Activity_id=0"]];
id jsonObjects = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:nil];
NSDictionary *arrdic=(NSDictionary *)jsonObjects;
NSMutableArray *arrdata=[arrdic objectForKey:#"Data"];
for (NSDictionary *dataDict in arrdata)
{
NSString *strActivity_ID=[dataDict objectForKey:#"Activity_ID"];
NSString *strActivity_Image=[dataDict objectForKey:#"Activity_Image"];
dict=[NSDictionary dictionaryWithObjectsAndKeys:strActivity_ID,activity_id,strActivity_Image,activity_image,nil];
[myObject addObject:dict];
}
}
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return myObject.count;
}
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
CustomColumnCell *myCell = [collectionView dequeueReusableCellWithReuseIdentifier:#"myCell"forIndexPath:indexPath];
NSDictionary *tmpDict = [myObject objectAtIndex:indexPath.row];
NSURL *url=[NSURL URLWithString:[tmpDict objectForKey:activity_image]];
NSData *data=[NSData dataWithContentsOfURL:url];
UIImage *img=[[UIImage alloc]initWithData:data];
myCell.imageview.image = img;
return myCell;
}