Why using the const keyword before and after method or function name?

Question

I have the following code in my application. Why do we use the const keyword with the return type and after the method name?

const T& data()         


        

Answer 1

const T& data() const { return data_; }

const after member function indicates that data is a constant member function and in this member function no data members are modified.

const return type indicates returning a constant ref to T