dynamic_cast" used in polymorphic classes with /GR-

reason

1. Using dynamic_cast<> will use RTTI technology, so the option "type information at runtime" needs to be enabled. /GR-means to turn off RTTI technology, /GR means to turn on RTTI technology
2. UE4 turns off RTTI by default

Solution

1. Open the project properties in vs2019->C/C+±>language, on the right side of the "Enable Runtime Type Information" item, select "Yes/GR", as shown in the figure
   

2. UE4 disables RTTI by default. If you want to use dynamic_cast, you need to enable rtti in build.cs; as shown in the figure