Calling a non-static variable from a static function

Question

I am a novice C ++ programmer and do PoC for my company. Therefore, I apologize for my main question.

class TestOne{
  private:
    TestTwo* t2;

  void createInstance(TestTwo* param){
    t2 = param;
  }

  static void staticFunctionToAccessT2(){
    // Now here I want to access "t2" here in the current instance of the class
    // By current instance I mean "this" in non-static context
    // currently there is no function to get object, but can be created
    // ** we cannot call new TestOne(), because that will create a new instance
    // ** of the current class and that I don't want.
  }
}

Any help in this regard would be greatly appreciated.

thank

=== UPDATE ===

This can be seen as a scenario in which I am developing an application in QT Creator, where I have a static function of a predefined signature and you want to access user interface elements for changing text (for example, TextEdit)

Answer 1

You cannot do this, even in Java.

staticmethods are just local helper functions for all instances of a class without access to a separate state of the class (for example, t2).

static , - a static, , .

EDIT:

, SDK , , t2. public static. , staticFunctionToAccessT2 :

public: void mutateT2();

, mutateT2 on, :

TestOne foo;

SDK , :

std::bind(&TestOne::mutateT2, foo)

, , SDK std::function, .

Answer 2

- " ".

, Singleton (anti-), Singleton ++. , , , -.

, RAII , std::unique_ptr<TestOne> safeInstance;, getInstance(), Android.

Singleton, , . , , .

, "", , "", singleton, , . singleton.

Answer 3

; -.

, API ( ), . ; , :

static TestOne * bodge;
static void staticFunctionToAccessT2(){
    TestTwo * t2 = bodge->t2;
}

API

TestOne::bodge = my_t1;
broken_api(&TestOne::staticFunctionToAccessT2);

bodge - , API , .

API , " "; , void*, . :

static void staticFunctionToAccessT2(void * p) {
    TestOne * t1 = static_cast<TestOne*>(p);
    TestTwo * t2 = t1->t2;
}

less_broken_api(&TestOne::staticFunctionToAccessT2, my_t1);

API , :

void memberFunctionToAccessT2() {
    TestTwo * t2 = this->t2;
}

nice_api([=]{my_t1->memberFunctionToAccessT2();});