Instantiate object failure problem in unity

Just started to learn unity, and it always starts with the instantiate function:

Gameobject temp = (gameobject) instantiate (Bulletsource, transform.position, transform.rotation);

A common variable is then defined in the class as follows:

 Public Gameobject Bulletsource;

On the panel, the preset body is hierarchy to the first place, where the corresponding object is then entrusted to the common variables of the class.

This is no problem at first, but when the object is destroyed at a certain time, the instantiate will fail. Of course, the associated objects are gone.

The workaround is to put the object directly from the assets to the code public variable of the preset, so that the associated object does not disappear. It would be nice to create the object again with the code.

Instantiate object failure problem in unity