Merge pull request #929 from K6F/patch-1

修改UIScrollView+MJRefresh.m

MJRefresh/UIScrollView+MJRefresh.m

@@ -39,7 +39,7 @@ - (void)setMj_header:(MJRefreshHeader *)mj_header
         
         // 存储新的
         objc_setAssociatedObject(self, &MJRefreshHeaderKey,
-                                 mj_header, OBJC_ASSOCIATION_ASSIGN);
+                                 mj_header, OBJC_ASSOCIATION_RETAIN);
     }
 }
 
@@ -59,7 +59,7 @@ - (void)setMj_footer:(MJRefreshFooter *)mj_footer
         
         // 存储新的
         objc_setAssociatedObject(self, &MJRefreshFooterKey,
-                                 mj_footer, OBJC_ASSOCIATION_ASSIGN);
+                                 mj_footer, OBJC_ASSOCIATION_RETAIN);
     }
 }