oop - C++ prefered way to share objects between methods within the same class -

given class has 2 methods need share variable best way pass/share variable between them? assuming variable not needed anywhere else in class. if variable stl container, change anything?

i'm considering following 3 options:

instantiate variable in 1 method , return pointer, delete in other method.

class myclass {     public:         std::vector<int>* method1();         void method2(); };  std::vector<int>* myclass::method1() {     std::vector<int> *my_int_vector = new std::vector<int>;     //manipulate vector in way     return my_int_vector; }  void myclass::method2() {     std::vector<int> *myvector;     myvector = this->method1();     //manipulate vector in way     delete myvector; } 

this separates new , delete between methods seems to begging go wrong.

alternatively can use class private member property hold variable.

class myclass {     private:         std::vector<int> myvector;     public:         void method1();         void method2(); };  void myclass::method1() {     //manipulate this->myvector }  void myclass::method2() {     this->method1();     //manipulate this->myvector } 

this unnecessarily exposes variable rest of class.

finally, can create object in 1 method , pass reference.

class myclass {     public:         void method1(std::vector<int> *my_int_vector);         void method2(); };  void myclass::method1(std::vector<int> *my_int_vector) {     //manipulate my_int_vector in way }  void myclass::method2() {     std::vector<int> myvector;     this->method1(&myvector);     //manipulate myvector in way } 

to me seems best solution not calling new or delete , variable not available whole class.

is assessment of alternatives correct , have missed other options better?

the preferred way make variable member if passing parameter 1 function other not possible.

so yes third option might best.

if variable stl container, change anything?

no. containers in c++ standard library normal objects too.

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about second option:

this separates new , delete between methods seems to begging go wrong.

yes. using raw new , delete in first place begging trouble. don't allocate dynamically when don't have to. , when do, use smart pointers.

so in case pass vector value. or if function going called lot maybe make vector static , return reference.

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you mentioned second option it

unnecessarily exposes variable rest of class.

if really problem class might big and/or trying much. should consider splitting class smaller classes clear, minimal, well-defined responsibilities (srp).

which brings fourth option, might or might not make sense in case: store vector in own class, , make 2 methods members of class. store class member of myclass.