About resource release (free, relealse, freeandnil) in Delphi)

According to the daily programming experience, some experiences about resource release in Delphi are obtained.

Assume that the object obj is of the tobject type:

1) After obj. Free releases the resource directly, the ondestroy event is called, but the OBJ pointer value is not set to nil.

2) obj. Release: Release the resource after waiting for the resource to be no longer used. The OBJ pointer is also not modified to nil. Therefore, it is best to use release to release the resource in ondestroy.

3) When releasing resources with local variables, you can use freeandnil () to release resources. This increases the efficiency and improves the memory utilization.

4) It is not enough to judge whether an object has been created by using assigned (OBJ) alone, because if the object is released through free/release, OBJ points to an unknown address rather than nil, so you need to use (not assigned (OBJ) and (not (obj is tobject )) to determine whether the object has been created in the memory.