如何仅在cpp中定义私有成员函数

class ClassName {
private:
    void privateFunctionName() {
        // 函数实现
    }
};

#include <iostream>

class MyClass {
private:
    void privateFunction() {
        std::cout << "This is a private function." << std::endl;
    }

public:
    void publicFunction() {
        std::cout << "Calling private function from public function." << std::endl;
        privateFunction();
    }
};

int main() {
    MyClass obj;
    obj.publicFunction(); // 输出: Calling private function from public function.
                          //       This is a private function.
    return 0;
}