#include <iostream>
#include <memory>

class OtherClass {
public:
    void setOtherMember() {
        m_otherMember = 2;
        std::cout << "Other member is now 2" << std::endl;
    }

private:
    int m_otherMember = 0;
};


class TestClass {
public:
    TestClass(): m_otherClass(std::make_unique<OtherClass>())
//  TestClass()
    {}

    void myMethod() const {
        m_otherClass->setOtherMember();
//      m_otherClass.setOtherMember();
    }
private:
        std::unique_ptr<OtherClass> m_otherClass;
//      OtherClass m_otherClass; // If changing to this I get the error!!
};


int main() {
    TestClass testClass;
    testClass.myMethod();
    return 0;
}