ios UITableView实现无数据加载占位图片

+ (void)swizzleInstanceSelector:(SEL)originalSel
      WithSwizzledSelector:(SEL)swizzledSel {

  Method originMethod = class_getInstanceMethod(self, originalSel);
  Method swizzedMehtod = class_getInstanceMethod(self, swizzledSel);
  BOOL methodAdded = class_addMethod(self, originalSel, method_getImplementation(swizzedMehtod), method_getTypeEncoding(swizzedMehtod));

  if (methodAdded) {
    class_replaceMethod(self, swizzledSel, method_getImplementation(originMethod), method_getTypeEncoding(originMethod));
  }else{
    method_exchangeImplementations(originMethod, swizzedMehtod);
  }
}

+ (void)load {
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    [self swizzleInstanceSelector:@selector(reloadData) WithSwizzledSelector:@selector(kk_reloadData)];
  });
}

- (void)kk_reloadData {
  [self kk_checkEmpty];
  [self kk_reloadData];
}

- (void)kk_checkEmpty {
  BOOL isEmpty = YES;
  id<UITableViewDataSource> src = self.dataSource;
  NSInteger sections = 1;
  if ([src respondsToSelector:@selector(numberOfSectionsInTableView:)]) {
    sections = [src numberOfSectionsInTableView:self];
  }
  for (int i = 0; i < sections; i++) {
    NSInteger rows = [src tableView:self numberOfRowsInSection:i];
    if (rows) {
      isEmpty = NO;
    }
  }
  if (isEmpty) {//数据为空，在这里添加视图
  }else{//数据不为空，在这里一处视图
  }
}

@property (nonatomic, strong) UIView *placeHolderView;

- (void)setPlaceHolderView:(UIView *)placeHolderView {
  objc_setAssociatedObject(self, @selector(placeHolderView), placeHolderView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
- (UIView *)placeHolderView {
  return objc_getAssociatedObject(self, @selector(placeHolderView));
}

if (isEmpty) {//数据为空，在这里添加视图
}else{//数据不为空，在这里一处视图
}

if (isEmpty) {
    [self.placeHolderView removeFromSuperview];
    [self addSubview:self.placeHolderView];
  }else{
    [self.placeHolderView removeFromSuperview];
  }

_tableView.placeHolderView = [[UIView alloc] init];