删除当前地图上已经添加的标注数组报错

代码如下：

[_mapview removeAnnotations:_mapview.annotations];

运行崩溃，错误信息如下：

 BaiduMapSW[7782:707] *** Terminating app due to uncaught exception 'NSGenericException', reason: '*** Collection <__NSArrayM: 0x2c1690> was mutated while being enumerated.'
*** First throw call stack:

解决方法：

    NSArray* array = [NSArray arrayWithArray:_mapView.annotations];

    [_mapView removeAnnotations:array];