@interface WWCollectionView : NSScrollView
// 布局对象
@property (retain) WWCollectionViewLayout *layout;
// 数据源
@property (weak) id dataSource;
// 事件响应
@property (weak) id delegate;
// 重加载数据
(void)reloadData;
// 重排布
(void)invalidateLayout;
// 取消返回选中
(void)unSelectedAll;
// 注册重用对象
(void)registerClass:(Class)cellClass forCellWithReuseIdentifier:(NSString *)identifier;
// 对象重用
(id)dequeueReusableCellWithReuseIdentifier:(NSString )identifier forIndexPath:(NSIndexPath )indexPath;
// 设置选中对象
(void)selectItemAtIndexPath:(NSIndexPath *)indexPath animated:(BOOL)animated;
// 当前选中对象
(NSIndexPath *)selectedItem;
// 重加载indexPath item
(void)reloadItemsAtIndexPath:(NSIndexPath *)indexPath;
// 插入
(void)insertItemsAtIndexPath:(NSIndexPath *)indexPath withAnimate:(BOOL)animate;
// 删除
(void)deleteItemsAtIndexPath:(NSIndexPath *)indexPath withAnimate:(BOOL)animate;
// 重新排列
(void)relayoutWithAnimation:(BOOL)animated completion:(void (^)(BOOL finished))completion;
// 滚动到aPoint
(void)scrollToPoint:(NSPoint)aPoint withAnimate:(BOOL)animate;
@end

@protocol WWCollectionViewDataSource 
// 返回indexPath下标的cell
(WWCollectionCellView )collectView:(WWCollectionView )collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath;
// 总cell个数
(NSInteger)numberOfItemInCollectionView:(WWCollectionView *)collectionView;
// cell的数据
(id)collectionView:(WWCollectionView )colletionView objectValueAtIndexPath:(NSIndexPath )indexPath;
@end

@protocol WWCollectionViewDelegate 
// indexPath元素被选中
(void)collectionView:(WWCollectionView )collectionView didSelectItemAtIndexPath:(NSIndexPath )indexPath;
// 是否支持选中
(BOOL)collectionView:(WWCollectionView )collectionView shouldSelectItemsAtIndexPaths:(NSIndexPath )indexPath;
@end

@interface WWCollectionViewLayout : NSObject
// 布局基类
@property (weak) WWCollectionView *collectionView;
// 每个cell元素大小
@property (assign) NSSize itemSize;
// edgeInsets
@property (assign) NSEdgeInsets edgeInsets;
// scrollview使用，表示整个画布大小
@property (assign) NSSize viewContentSize;
(instancetype)initWithCollectionView:(WWCollectionView *)collectionView;
(void)invalidateLayout;
// 返回index的cell大小
(NSRect)frameForIndexPath:(NSIndexPath *)index total:(NSInteger)total;
(NSSize)collectionViewContentSize;
@end
// 横向布局控件
@interface WWFlowCollectionViewLayout : WWCollectionViewLayout
@property (assign) CGFloat headMargin;
@property (assign) CGFloat tailMargin;
@end
// grid布局控件
@interface WWGridCollectionViewLayout : WWCollectionViewLayout
// 每行多少个
@property (assign) NSInteger numberPerRow;
@property (assign) CGFloat headMargin;
@property (assign) CGFloat tailMargin;
@end

@implementation WWFlowCollectionViewLayout

(void)invalidateLayout {
NSInteger cellCount = [self.collectionView.dataSource numberOfItemInCollectionView:self.collectionView];
CGRect bounds = self.collectionView.bounds;
// 画布宽度
CGFloat width = _headMargin + _tailMargin + (cellCount - 1) (self.edgeInsets.left + self.edgeInsets.right) + self.itemSize.width cellCount;
if (width < bounds.size.width) {
width = bounds.size.width;
}
self.viewContentSize = NSMakeSize(width, bounds.size.height);
[super invalidateLayout];
}
(NSRect)frameForIndexPath:(NSIndexPath *)index total:(NSInteger)total {
CGFloat leftPos = self.headMargin + [index indexAtPosition:0] * (self.itemSize.width + self.edgeInsets.left + self.edgeInsets.right);
// 返回cell的rect
return NSMakeRect(leftPos, self.edgeInsets.top, self.itemSize.width, self.itemSize.height);
}
@end

@interface WWCollectionCellView : NSView
// 当前cell被选中
@property (nonatomic, assign) BOOL selected;
// 数据
@property (nonatomic, retain) id dataValue;
// 使用前重置展示效果
(void)reset;
@end