I would like initialize base class by a first item form a vector which contains base classes, eg:
struct Base { ... };
struct Derived : public Base
{
Derived(const Base& baseClass)
: Base(baseClass)
{
}
Derived(const std::vector<Base*>& listOfBaseClass)
: Base(*(listOfBaseClass[0]))
{
}
};
This solution fails when listOfBaseClass
vector will be empty. How can prevent this situation. This is simplified example, so calling base class constructor like this:
std::vector<Base> baseClasses;
if(!baseClasses.empty())
{
Derived myDerived(baseClasses[0]);
}
it is not solution for my problem. Thanks in advance.
Throw an exception if the list is empty:
: Base(listOfBaseClass.empty()
? throw std::invalid_argument("Missing base class")
: *(listOfBaseClass[0])
)
Non-exception variant by request:
: Base(( (listOfBaseClass.empty() && exit(0)),
*(listOfBaseClass[0])
))
Derived(const std::vector<Base*>& listOfBaseClass)
: Base(*(listOfBaseClass->at(0)))
{
}
"at" provides exception safety. It throws out_of_range if n is out of bounds.
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