(void)beginUpdates; // allow multiple insert/delete of rows and sections to be animated simultaneously. Nestable
(void)endUpdates; // only call insert/delete/reload calls or change the editing state inside an update block. otherwise things like row count, etc. may be invalid.
使用tableview的这2个方法方法
(void)beginUpdates; // allow multiple insert/delete of rows and sections to be animated simultaneously. Nestable
(void)endUpdates; // only call insert/delete/reload calls or change the editing state inside an update block. otherwise things like row count, etc. may be invalid.