数据类型与NSMutableArray添加对象（insertObject）引起的问题

看如下代码：

NSMutableArray *favoriteData = [[NSMutableArray alloc]init];
[favoriteData addObjectsFromArray:data];
NSDictionary *favData = [[NSDictionary alloc]init];
favData = self.rowData.copy;
[favoriteData insertObject:favData atIndex:0];
for (NSMutableDictionary *dictM in favoriteData) {
if ([dictM.allKeys containsObject:@"vector"]) {
Vector *vec = [dictM objectForKey:@"vector"];
[dictM setObject:
@[[NSDecimalNumber numberWithDouble:vec.X], [NSDecimalNumber numberWithDouble:vec.Y],
[NSDecimalNumber numberWithDouble:vec.Z]] forKey:@"vector"];
}
}

由于insertObject添加是直接将NSDictionary *favData这个对象添加进了数组，故而取的时候仍旧是NSDictionary类型，所以setObject时会崩溃。

换成如下代码就可以了：

NSMutableDictionary *favData = [[NSMutableDictionary alloc]init];

favData = self.rowData.mutableCopy;