uvm_resource中get_by_name/get_by_type会返回一个uvm_object类型的resource,但resource实际有int/string/object/bit/byte等多种类型,在实现一个resource时,往往需要根据resource的类型来重新定义get_by_name/get_by_type函数。uvm_resource_specializations.svh即提供了几种常用的派生自uvm_resource的resource基类: uvm_resource中get_by_name/get_by_type会返