overlap between pimpl idiom and builder patterns?

Question

I was reading about builder patters from the http://en.wikibooks.org/wiki/C%2B%2B_Programming/Code/Design_Patterns#Creational_Patterns link and the code below seems to use idea similar to pimpl idiom by having a pointer to pizzaBuilder in the Class Cook as the private member. Is there any overlap between pimp idioms and how it used in designer patterns?

class Cook
{
        public:
                void setPizzaBuilder(PizzaBuilder* pb)
                {
                        m_pizzaBuilder = pb;
                }
                Pizza* getPizza()
                {
                        return m_pizzaBuilder->getPizza();
                }
                void constructPizza()
                {
                        m_pizzaBuilder->createNewPizzaProduct();
                        m_pizzaBuilder->buildDough();
                        m_pizzaBuilder->buildSauce();
                        m_pizzaBuilder->buildTopping();
                }
        private:
                PizzaBuilder* m_pizzaBuilder;
};

milleniumbug · Accepted Answer · 2013-06-14T01:33:39.520

2

No. While language features used (pointers, private fields) may be similar, intended result is completely different.

PIMPL fairly transparent to the user of the class - and that's the point. You don't see CookPimpl used in interface of the Cook - it's hidden in .cpp file, caller can't even do anything meaningful to it.

Builder class on the other hand is self-sufficient, and could be used directly, in Cook class or in PizzaRestaurant.

What is more, PIMPL idiom is C++-specific (adding or removing private member leads to recompilation everywhere, since definitions are copy-pasted), while design patterns strive to be language agnostic.

edited Jun 14 '13 at 01:33

answered Jun 14 '13 at 01:10

milleniumbug

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Isn't pImpl mostly because of the compiler needing to know the size of the object, rather than due to a lack of modules? – templatetypedef Jun 14 '13 at 01:26
@templatetypedef Oh wait, you're right. Let me correct my answer. – milleniumbug Jun 14 '13 at 01:31

overlap between pimpl idiom and builder patterns?

1 Answers1