Moveit! How to do collision checking between the user-defined object during planning?

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Hi guys,

Recently I use moveit! to do the motion planning. The task of the robot arm is to pick up an object and put it into a box. I can add both the object and the box to the world using C++ code

planning_scene_interface.addCollisionObjects(collision_objects);

and I can also attach the object to the end effector of the robot arm.

But when I do the motion planning,the planner ignores the collision check between the object that the robot arm picked up and the box.

I have tried to add the object to the urdf file of the robot,It surely can work but it is obviously not a good idea.

So what should I do to make the planner do the collision checkinig between the object which the robot arm picked up and the other objects in the world?