Collection View with draggable cell. 5px padding each.

FirstViewController.h

#import <UIKit/UIKit.h>

@interface FirstViewController : UIViewController <UICollectionViewDataSource, UICollectionViewDelegate>{
  
  
  CGSize cellSize;
  
}

@property (weak, nonatomic) IBOutlet UICollectionView *collectionView;

@end

FirstViewController.m

//
//  Created by Hijazi on 5/3/16.
//  Copyright © 2016 iReka Soft. All rights reserved.
//

#import "FirstViewController.h"

@interface FirstViewController ()

@end

@implementation FirstViewController

- (void)viewDidLoad {
  [super viewDidLoad];
  
  UILongPressGestureRecognizer *longPressGesture = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handleLongPressGesture:)];
  [self.collectionView addGestureRecognizer:longPressGesture];
}

- (void)handleLongPressGesture:(UILongPressGestureRecognizer *)gesture{
  
  
  
  
  
  switch (gesture.state) {
    case UIGestureRecognizerStateBegan:{
      NSIndexPath *indexPath = [self.collectionView indexPathForItemAtPoint:[gesture locationInView:self.collectionView]];
      [self.collectionView beginInteractiveMovementForItemAtIndexPath:indexPath];
    }break;
    case UIGestureRecognizerStateChanged:{
      [self.collectionView updateInteractiveMovementTargetPosition:[gesture locationInView:gesture.view]];
    }break;
    case UIGestureRecognizerStateEnded:{
      [self.collectionView endInteractiveMovement];
    }break;
      break;
      
    default:
      [self.collectionView cancelInteractiveMovement];
      
      break;
  }
  
}

- (void)didReceiveMemoryWarning {
  [super didReceiveMemoryWarning];
  // Dispose of any resources that can be recreated.
}

- (void)viewDidLayoutSubviews{
  [super viewDidLayoutSubviews];
  //  0.6213235294
  
  [self updateCellSize];
}

#pragma mark - UICollectionViewDataSource

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
  return 10;
}

// The cell that is returned must be retrieved from a call to -dequeueReusableCellWithReuseIdentifier:forIndexPath:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
  
  UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
  
  UIImageView *iv_profilePicture = [cell.contentView viewWithTag:111];
  iv_profilePicture.layer.cornerRadius = cellSize.width/2.0;
  iv_profilePicture.transform = CGAffineTransformMakeScale(0.6, 0.6);
  
  return cell;
}

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{


}

- (void)updateCellSize{
  CGFloat margin = 5.0*2.0;
  if (UIInterfaceOrientationIsPortrait([[UIApplication sharedApplication] statusBarOrientation])) {
    float cellWidth = self.collectionView.bounds.size.width/3.0-margin;
    
    cellSize = CGSizeMake(cellWidth, cellWidth*1);
  }else{
    
    float cellWidth = self.collectionView.bounds.size.width/4.0 - margin;
    
    cellSize = CGSizeMake(cellWidth, cellWidth*1);
  }
  
}

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath{
  
  return cellSize;
  

}

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section{
  
  return 5;
}

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section{
  
  return 0;
}
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section{
  return UIEdgeInsetsMake(5, 10, 5, 10);
}

- (void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath{
  
}



@end