Skip to main content

Factory Method and Automatic Pointers

In general when a factory method returns an instance of the created object, in C++, it is a pointer to a dynamically created memory or a resource.

Resource* factory(); // allocates dynamically

Factory method pattern does not talk about the lifetime of the object it creates. It depends upon the caller of the factory to release the resource. It can do better here. A factory method can act smarter by returing the dynamically allocated pointer by wrapping it in an automatic pointer (auto_ptr).

auto_ptr <Resource> factory(); // allocates dynamically

Returning an automatic pointer strongly indicates ownership transfer as well as
takes care of releasing the resource.

{
auto_ptr <Resource> rtemp;
rtemp = factory();
.
.
.
} // rtemp freed here automatically even in the face of exceptions!!
-----
SRC: Scott Meyers

Comments

i thought your blog was cool and i think you may like this cool Website. now just Click Here
Exciting blog. Your site was amazing and will be
back again! I never get tired of looking for blogs
just like this one.
Want to see top notch work, peep my cash advance blog site for the bomb work!
Terrific blog. I search the internet everytime I
get a moment to find blogs. Its better than cold iced
tea and I have to visit it one more time!
Where you been? You have got to look at my 1800contacts com coupon blog!
Prodigious blog. Loved it so much I went to it
again! Just go online and search for blogs that are
worth the value as yours.
Please take a journey to my blog.
Energizing blog. It blew me away and I loved your
site. when I have the time to surf the net, i try
finding blogs as good as your site.
I'm looking at the possibility of checking your coupon codes 1800contacts blog.
lightly-blended said…
Captivate blog. I surf the web for blogs this
nature.The site are wonderful and will be returned to
again!
Search for my blog, please!
stunned said…
Charming blog. Your site was off the chain and I
will return! When I get the time I look for blog like
this one.
Look who checking out my 1800contacts com coupon blog?
Sensational blog. I took pleasure in the site and I
will go back! Surfing online for blogs like this one
is worth my time.
Stop by and visiit my blog!
after-while said…
Hot blog. When I get to seraching on the web for
blogs, its got to be like yours! And the site is off
the hook! I just kept coming back!
Go and find my blog.
Charming blog. Your site was off the chain and I
will return! When I get the time I look for blog like
this one.
I'm looking at the possibility of checking your coupon 1800contacts blog.
Great blog. I'm always finding blog like yours. It
got my attention and I will go to the site again!
My risk of plastic surgery blog, is something you need to peep out!
manho valentine said…
Sensational blog. I took pleasure in the site and I
will go back! Surfing online for blogs like this one
is worth my time.
Stop by and visiit my blog!
gclub

Popular posts from this blog

Multi-dimensional arrays in C++11

What new can be said about multi-dimensional arrays in C++? As it turns out, quite a bit! With the advent of C++11, we get new standard library class std::array. We also get new language features, such as template aliases and variadic templates. So I'll talk about interesting ways in which they come together.

It all started with a simple question of how to define a multi-dimensional std::array. It is a great example of deceptively simple things. Are the following the two arrays identical except that one is native and the other one is std::array?

int native[3][4];
std::array<std::array<int, 3>, 4> arr;

No! They are not. In fact, arr is more like an int[4][3]. Note the difference in the array subscripts. The native array is an array of 3 elements where every element is itself an array of 4 integers. 3 rows and 4 columns. If you want a std::array with the same layout, what you really need is:

std::array<std::array<int, 4>, 3> arr;

That's quite annoying for two r…

Folding Monadic Functions

In the previous two blog posts (Understanding Fold Expressions and Folding Functions) we looked at the basic usage of C++17 fold expressions and how simple functions can be folded to create a composite one. We’ll continue our stride and see how "embellished" functions may be composed in fold expressions.

First, let me define what I mean by embellished functions. Instead of just returning a simple value, these functions are going to return a generic container of the desired value. The choice of container is very broad but not arbitrary. There are some constraints on the container and once you select a generic container, all functions must return values of the same container. Let's begin with std::vector.
// Hide the allocator template argument of std::vector. // It causes problems and is irrelevant here. template <class T> struct Vector : std::vector<T> {}; struct Continent { }; struct Country { }; struct State { }; struct City { }; auto get_countries…

Covariance and Contravariance in C++ Standard Library

Covariance and Contravariance are concepts that come up often as you go deeper into generic programming. While designing a language that supports parametric polymorphism (e.g., templates in C++, generics in Java, C#), the language designer has a choice between Invariance, Covariance, and Contravariance when dealing with generic types. C++'s choice is "invariance". Let's look at an example.
struct Vehicle {}; struct Car : Vehicle {}; std::vector<Vehicle *> vehicles; std::vector<Car *> cars; vehicles = cars; // Does not compile The above program does not compile because C++ templates are invariant. Of course, each time a C++ template is instantiated, the compiler creates a brand new type that uniquely represents that instantiation. Any other type to the same template creates another unique type that has nothing to do with the earlier one. Any two unrelated user-defined types in C++ can't be assigned to each-other by default. You have to provide a c…