code. compile. run. debug. share.
Source Code
Language
#include <iostream>
#include <memory>
#include <optional>
struct Base {
virtual void f() = 0;
virtual ~Base() {};
};
struct Helper: Base {
void f() override { std::cout << "Helper" << std::endl; }
};
struct Derived: Base {
Derived(Helper& helper): m_helper(helper) {}
void f() override { std::cout << "Derived" << std::endl; }
Helper& m_helper;
};
void test1(bool condition)
{
auto h = std::make_shared<Helper>();
std::shared_ptr<Base> p;
if (condition) {
p = std::make_shared<Derived>(*h);
} else {
p = h;
}
p->f();
}
void test2(bool condition)
{
auto h = std::make_shared<Helper>();
auto p = condition ? std::shared_ptr<Base>(new Derived(*h)) : h;
p->f();
}
void test3(bool condition)
{
Helper h;
std::optional<Derived> d;
if (condition) d.emplace(h);
Base& p = d ? *d : static_cast<Base&>(h);
p.f();
}
int main()
{
test1(true);
test1(false);
test2(true);
test2(false);
test3(true);
test3(false);
return 0;
}
Compiling Program...
Standard Input:
Interactive Console
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