How to set up sending data to the application on share in xcode?

Question

iOS

There was a problem, we are making an application on react native and now we need to fasten the function of sending a file from share to our application. It was possible to make the application appear in the share menu, but when sharing, we need to open our application and run a certain algorithm of actions (saving the file to a specific folder, setting a name, attaching to entities, etc.). I understand that I need to dig in the direction of XCODE and object c, tell me where you can read on this topic, but it's better to look at examples.