UICollectionView数据源/委托相关的异常(UICollectionView dataS

我试图动态地创建UICollectionView但我不断收到异常，当数据源或委托未设置，我们通常会得到：

*终止应用程序由于未捕获的异常 'NSInvalidArgumentException'，原因： ' - [UIView的的CollectionView：numberOfItemsInSection：]：无法识别的选择发送到实例0x8a78ce0'

但它的存在！这是我的代码：

标题：

#import <UIKit/UIKit.h>
@interface classHeader : UIViewController <UICollectionViewDelegate, UICollectionViewDataSource>

@property(nonatomic, retain) UICollectionView *collectionView;

@end

执行：

#import "classHeader.h"


@implementation classHeader

@synthesize collectionView;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];

    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];   

    UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
    [flowLayout setScrollDirection: UICollectionViewScrollDirectionHorizontal];
    [flowLayout setItemSize: CGSizeMake(0, 0, 10, 10)];

    collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 0, 50, 50) collectionViewLayout:flowLayout];

    [collectionView setDelegate:self];
    [collectionView setDataSource:self];

[collectionView registerClass:[wbcGuidedAccessManualSlideCell class] forCellWithReuseIdentifier:SlideCellIdentifier];
}

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

#pragma mark - UICollectionView Datasource
- (NSInteger)collectionView:(UICollectionView *)view numberOfItemsInSection:(NSInteger)section
{
    return 0; // No matter what value is here - exception
}

- (NSInteger)numberOfSectionsInCollectionView: (UICollectionView *)collectionView
{
    return 0; // No matter what value is here - exception
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    return nil; // No matter what value is here - exception
}

#pragma mark - UICollectionViewDelegate
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    // TODO: Select Item
}

- (void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath
{
    // TODO: Deselect item
}

#pragma mark – UICollectionViewDelegateFlowLayout
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    return CGSizeMake(50, 50);
}

- (UIEdgeInsets)collectionView: (UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
    return UIEdgeInsetsMake(0, 20, 0, 20);
}

@end

而一个有趣的说明：