NSCollectionViewItems don't reload when scrolling <OSX - Objective C> - objective-c

Question

I'm new to learning Objective-C and I have a problem with NSCollectionView which I couldn't find any ways to resolve it.
My problem is:
I wrote a button event to create a NSCollectionView named thoughtCollectionView and added onto my contentView to display NSCollectionViewItems.
When I run the simulator, items look okay, but they don't reload when I scroll.
Here's my code:
MainViewController.m
- (void)thoughtShow{
// Add Collection View
thoughtCollectionView = [[ThoughtCollection alloc] initWithFrame:NSMakeRect(0, 0, contentWidth, contentHeight)];
NSCollectionViewFlowLayout *layout = [[NSCollectionViewFlowLayout alloc] init];
[thoughtCollectionView setCollectionViewLayout:layout];
[layout setScrollDirection:NSCollectionViewScrollDirectionVertical];
layout.itemSize = NSMakeSize(50, 50);
layout.minimumInteritemSpacing = 20;
layout.sectionInset = NSEdgeInsetsMake(20, 20, 20, 20);
[thoughtCollectionView registerClass:ThoughtItems.self forItemWithIdentifier:#"ThoughtItems"];
thoughtScrollView = [[NSScrollView alloc] initWithFrame:NSMakeRect(0, 0, contentWidth, contentHeight)];
thoughtScrollView.documentView = thoughtCollectionView;
[contentView addSubview:thoughtScrollView];
[thoughtCollectionView reloadData];
[thoughtCollectionView setNeedsDisplay:YES];
[thoughtCollectionView layoutSubtreeIfNeeded];
}
MainViewController.h
#interface MainViewController : NSViewController <NSCollectionViewDelegateFlowLayout, NSCollectionViewDelegate, NSCollectionViewDataSource>
#end
ThoughtCollectionView.h
#interface ThoughtCollection : NSCollectionView <NSCollectionViewDataSource, NSCollectionViewDelegate, NSCollectionViewDelegateFlowLayout>
{
NSMutableArray * ar;
}
#end
ThoughtCollectionView.m
#implementation ThoughtCollection
- (NSCollectionViewItem *)collectionView:(NSCollectionView *)collectionView itemForRepresentedObjectAtIndexPath:(NSIndexPath *)indexPath{
ThoughtItems *item = [collectionView makeItemWithIdentifier:#"ThoughtItems" forIndexPath:indexPath];
NSLog(#"Reloading item");
return item;
}
- (void)collectionView:(NSCollectionView *)collectionView willDisplayItem:(nonnull NSCollectionViewItem *)item forRepresentedObjectAtIndexPath:(nonnull NSIndexPath *)indexPath{
}
- (void)collectionView:(NSCollectionView *)collectionView didEndDisplayingItem:(nonnull NSCollectionViewItem *)item forRepresentedObjectAtIndexPath:(nonnull NSIndexPath *)indexPath{
}
- (NSInteger)collectionView:(NSCollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
NSLog(#"Collection view count : %lu", [ar count]);
return [ar count];
}
- (NSInteger)numberOfSectionsInCollectionView:(NSCollectionView *)collectionView{
return 1;
}
-(BOOL)shouldInvalidateLayoutForBoundsChange:(NSRect)newBounds
{
return YES;
}
- (void)viewDidMoveToWindow {
NSLog(#"My collection View");
self.delegate = self;
self.dataSource = self;
ar = [[NSMutableArray alloc] init];
for (int n = 0; n < 1000; n++) {
[ar addObject:#"Hello"];
}
[self reloadData];
[self setNeedsDisplay:YES];
[self layoutSubtreeIfNeeded];
}
#end
Simulator display:
enter image description here
Scroll:
enter image description here
ThoughtItem.m
#import "ThoughtItems.h"
#interface ThoughtItems ()
#end
#implementation ThoughtItems
- (void)viewDidLoad {
[super viewDidLoad];
[self.view setWantsLayer:YES];
[self.view.layer setBackgroundColor:[[NSColor orangeColor] CGColor]];
}
#end
ThoughtItem.h
#import <Cocoa/Cocoa.h>
#interface ThoughtItems : NSCollectionViewItem
#end

Answer 1

I found out that what's the problem with the CollectionItem.
I have to add an Object in the ThoughtItem.xib file, then change the object class name to "ThoughtItem".
And I change -(void)viewDidMoveToWindow to a method which I can call it from MainViewController.
(or create NSCollectionView in the MainViewController is a way to solve it too)
Then all the problems are solved!