Casting polymorphic objects

Imagine that some programmer designed such an awful interface as follows (this is a good example of how interfaces should not be written):

struct object { 
    virtual ~object() {} 
}; 

struct banana: public object { 
    void eat() const {} 
    virtual ~banana(){} 
}; 

struct penguin: public object { 
    bool try_to_fly() const {
        return false; // penguins do not fly
    }
    virtual ~penguin(){} 
}; 

object* try_produce_banana(); 

Our task is to make a function that eats bananas, and throws exceptions if something different came instead of banana ( try_produce_banana() may return nullptr)so if we dereference a value returned by it without checking we are in danger of dereferencing a null pointer.

Getting started

Basic knowledge of C++ is required for this recipe.

How to do it...

So we need to write the following code:

void try_eat_banana_impl1() { 
    const object* obj = try_produce_banana(); 
    if (!obj) { 
        throw std::bad_cast(); 
    } 
 ...