遇到一个 unrecognized selector sent to instance 的问题

//ClassCalendarCollectionViewController.m
ClassCalendarDataSource *classDataSource = (ClassCalendarDataSource *)self.collectionView.dataSource;
classDataSource.configureWeekViewBlock = ^(WeekReuse *weekReuseView, NSString *kind, NSIndexPath *indexPath) {
if ([kind isEqualToString:@"WeekReuse"]) {
            for (int i = 0; i < 7; i++) {
                NSLog(@"will print: %@", weekDay[i]);
                weekReuseView.WeekTitle.text = [NSString stringWithFormat:weekDay[i], indexPath.item +1];
            }
        }
    };

//ClassCalendarDataSource.h
typedef void (^ConfigureWeekViewBlock)(WeekReuse *weekReuseView, NSString *kind, NSIndexPath *indexPath);
@interface ClassCalendarDataSource : NSObject <UICollectionViewDataSource>
@property (copy, nonatomic) ConfigureWeekViewBlock configureWeekViewBlock;
@end