how to store a ConstPtr msg into a vector?

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Hi, I am a ROS and C++ beginner. My aim is to merge frontiers of multiple robot exploration based on frontier exploration. I've tried several ways to achieve that, but the easiest one is to merge frontiers pose together, and the problem here is about how to create a vector to store many robot/frontiers topic output msgs. Those msgs are ConstPtr, so it cannot be directly stored into vector, otherwise some errors happened in the terminal. Could someone have any suggestions? Thanks a lot.