对基构造函数的条件调用

class Derived : public Base {
public:
    Derived()
        : Base{ exists("myFile") ? Base{"myFile"} : Base{1, 2} } {
    }
}

exists("myFile") true ,它将构建一个临时的 Base false 它将构建一个临时的 使用第二个构造函数。不管怎样,它都将构建

class Base {
public:
    Base(std::string filname);
    Base(int a, int b);
};

class Derived : public Base {
    Derived(std::string filname) : Base(filname) {}
    Derived(int a, int b) : Base(a, b) {}
public:
    static Derived create() {
        if( /* exists("myFile") */ )
            return Derived("myFile");
        else
            return Derived(1,2);
    }
};

int main(){
    auto d = Derived::create();
}

Base 可作为成员持有( std::unique_ptr std::aligned_storage