c++ - What is the best way to handle a collection of derived objects in a derived class -

imagine have class 'basea' contains collection of items 'itema'. want extend 'basea' add capabilities, derive 'deriveda' 'basea'. 1 characteristic of 'deriveda' has handle more sophisticated 'deriveditema' items instead of 'itema' ones.

class basea { protected:     vector<itema> x;     void m1(int i) { x.m1(i); } };  class itema { protected:     void m1(int i) { ... } };  class deriveditema : public itema {     void m2(int i) { ... } }; 

now handle of sort:

class deriveda : public basea {     vector<deriveditema> x;     void m2(int i) { x[i].m2(); } }; 

i.e. have derived class handle derived items. above definition of x incorrect clashes 1 in basea. idea want able reuse methods in basea handle x long deal itema elements , have extended methods in deriveda handle intricacies of deriveditema type of data

any suggestion? current thoughts in lines of defining new datatype x (vectorofitema instance) , derive vectorofderiveditema. wonder if there simpler / better solution.

thanks

i believe need have pointers in vectors in order handle this. i'm little confused value pass m1 , m2 since appears index, here's guess:

class basea { protected:     vector<itema*> x;     void m1(int i) { x[i]->m1(i); } };  class itema { protected:     void m1(int i) { ... } };  class deriveditema : public itema {     void m2(int i) { ... } };  class deriveda : public basea {     vector<deriveditema*> y; //don't shadow base class vector!     void m2(int i) { y[i]->m2(i); } }; 

then, when add item in deriveda, add both x , y. way basea can it's thing pointer in x , deriveda can thing on pointer in y.

edit: you'll need provide virtual method adding items otherwise might things added basea.x don't added deriveda.y.