objective-c 是 c 的超集，而不是 c++，因此它不支持 static_cast.你可以只使用 c-style cast:

objective-c is a superset of c, not c++ so static_cast is not supported in it. You can just use c-style cast:

[pPacket SetHeaderSequenceNumber:(char)(m_transmitSequenceNumber + ASCII_ZERO)];