Communicate with C++ from Blueprints

Is it possible to access c++ classes from Blueprints?How can I connect a blueprint to some objects in my C++ project?
I mean,I know that basically I can create blueprint in C++ but how can I dispatch event or trigger some methods of the pure C++ objects in the project?

For example,I have some widgets in UMG GUI.I want to delegate the events to the objects I wrote in C++.So basically I want to be able to have some C++ object observe the blueprint actions and data flow.

Sorry,my question is wrong.I will change it,