Search⌘ K
AI Features
Home
Courses
C++17 in Detail: A Deep Dive

Introduction

Explore how to solve factory method challenges in C++17 by using if constexpr to conditionally compile code and handle variable constructor arguments safely, improving flexibility and avoiding compilation errors.

We'll cover the following...

The Problem

In item 18 of Effective Modern C++ Scott Meyers described a method called makeInvestment:

C++
template<typename... Ts>
std::unique_ptr<Investment>
makeInvestment(Ts&&... params);

There’s a factory method that creates derived classes of Investment, and the main advantage is that it supports a variable n​umber of arguments!

For example, here are the proposed derived types:

C++
// base type:
class Investment
{
public:
    virtual ~Investment() { }
    virtual void calcRisk() = 0;
};
class Stock : public Investment
{
public:
    explicit Stock(const std::string&) { }
    void calcRisk() override { }
};
class Bond : public Investment
{
public:
    explicit Bond(const std::string&, const std::string&, int) { }
    void calcRisk() override { }
};
class RealEstate : public Investment
{
public:
    explicit RealEstate(const std::string&, double, int) { }
    void calcRisk() override { }
};

The code from the book was too idealistic, and it worked until ...