shared_ptr

class myClass{
public: 
      myClass(); 
      ~myClass(){}
private: 
      std::shared_ptr<someClass> scObj;
};
myClass::myClass() : scObj(new someClass) //works{ 
      scObj = new someClass; //<< error 
      scObj(new someClass); //<< error
}

The initialization list after the : works, but for the purpose of satisfying my curiosity, I would like to know why the other initialization methods do not work.
Thanks for your help!