當沒有數據時，設置一張背景圖片提示無數據

#import "UIView+AutoLayout.h"

@property (nonatomic, weak) UIImageView *noDataView;


- (UIImageView *)noDataView
{
    if (!_noDataView) {
        // 添加一個"沒有數據"的提醒
        UIImageView *noDataView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"icon_deals_empty"]];
        [self.view addSubview:noDataView];
        [noDataView autoCenterInSuperview];
        self.noDataView = noDataView;
    }
    return _noDataView;
}