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A factory is a way of organizing certain things based on a certain need.
It applies to most (probably all) Object Oriented languages.
I can also state that although a bit odd you can create something similar in C.
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Quote: A factory is a way of organizing certain things based on a certain need.
You make factory sound like a vague notion, to my knowledge it`s a well defined pattern to create objects.
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CalinNegru wrote: to my knowledge it`s a well defined pattern to create objects. I didn't see where they implied otherwise.
"the debugger doesn't tell me anything because this code compiles just fine" - random QA comment
"Facebook is where you tell lies to your friends. Twitter is where you tell the truth to strangers." - chriselst
"I don't drink any more... then again, I don't drink any less." - Mike Mullikins uncle
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why the rhetoric? I wasn`t arguing I was only seeking explanations.
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It depends what you mean by a "factory". The Factory Pattern is a well defined method of creating certain objects, based on a class structure. But you can still write well structure projects without using it.
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What is the default approach for creating objects using a factory? When one is creating several objects of the same class using a factory is the factory class retaining the objects as an array/std container and returning through a function a pointer to the object that has been created (which can be stored into an array/container outside the factory class)?
this is code for creating a single object
#include <iostream>
using namespace std;
class Vehicle {
public:
virtual void printVehicle() = 0;
static Vehicle* Create(VehicleType type);
};
class TwoWheeler : public Vehicle {
public:
void printVehicle() {
cout << "I am two wheeler" << endl;
}
};
Vehicle* Vehicle::Create() {
return new TwoWheeler();
}
class Client {
public:
Client()
{
}
~Client() {
if (pVehicle) {
delete[] pVehicle;
pVehicle = NULL;
}
}
void BuildVehicle()
{
pVehicle = Vehicle::Create();
}
Vehicle* getVehicle() {
return pVehicle;
}
private:
Vehicle *pVehicle;
};
int main() {
Client *pClient = new Client();
pClient->BuildVechicle();
Vehicle * pVehicle = pClient->getVehicle();
pVehicle->printVehicle();
return 0;
}
how should the modified version of main() look like if you want more than one vehicle to be created
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I`ve had a look at Snesh`s profile, thank you.
Quote: That is not really about a Factory, just about creating objects
I know. But things are meant to be learned in a certain order. Factory seems to be the next thing to learn after the "c++ class" lesson. Factory stands for more than just one thing, but those things designated with the word 'factory' although different they still somehow resemble. Basically the factory pattern upgrades the understanding of constructor and destructor concepts. It`s like traditional German house windows, everybody knows Germans are the best car makers. That means they gave a good grip on the things that go into making a car. Germans had the best tanks in WWII so that explains why Germans have a good grip on the concept of car body/frame. The problem is tanks didn`t had windows (and still don`t till this day) so someone arranged things such that Germans have a good grip on the concept of physical windows too, German houses have a two layer windows system (which is basically two windows in one): the usual window made of glass and metal/wood frame and then the wooden only layer/covering meant to protect the windows from physical damage.
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CalinNegru wrote: I`ve had a look at Snesh`s profile, thank you. I meant you to read her articles, if you really want to understand Factories in programming.
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Thanks.
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Some projects are as you describe. The only way to analyze dependencies is by #include directives, which aren't even reliable. Ones that aren't needed don't necessarily get removed. And others that should be added aren't, because the header in question gets accidentally included, transitively. Sometimes A.cpp #include s B.h, and B.cpp #include s A.h for reasons of collaboration. Such circular dependencies are sometimes unavoidable.
Layering is the main way to impose higher level structure. The software is organized into static or dynamic libraries that preclude circular dependencies. That is, if library B has a file that #includes a file in library A, then no file in A can #include anything in B. This allows libraries to be tested independently and also allows an application to be developed without having to use a monolithic code base that contains various things that the application doesn't need.
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CalinNegru wrote: Looking at a large project
Depends on what "large" actually means...
In the real world companies end up with software that was created by many people over time.
As with everything else that humans are involved in quality tends towards the average. That includes design which impacts what you refer to as 'structure'.
Programmers also like to think that they know for certain that the best way to do something is the way they know. Which is completely subjective.
So they create new 'better' solutions willy-nilly and hack them into existing code bases because of that. Then they leave the company and someone else starts doing it. Overtime this leads to significant organizational problems.
Even in the best systems there are real world business requirements that only come up long after the original design and for which the original design did not account. And the company is not willing to pay to refactor the entire code base when this happens. Even worse if it wasn't well designed. Or with 'better' ways on top of it.
And developers seldom consider the long term impact on maintenance when they make radical decisions to go in a different direction on a code base. It is known (multiple studies) that maintenance costs are always 2 to 10 times higher than the original cost to develop the product. And 100 times higher is probably reasonable for some.
Might note that although I point out developers in the above I have never seen a company that was actually willing to recognize the maintenance costs much less put an emphasis on mitigating for that.
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Background
I have a WPF app in which I'm using DevExpress Reporting.
To create a report based off a List<t> there is a wizard which allows you to choose "Object Data Source". When you choose that you see a list of entities in your app that are marked with the attribute "[HighlightedClass]". This attribute is defined in the namespace "DevExpress.DataAccess.ObjectBinding".
My WPF UI, DAL, BL, and entities are all defined in seperate projects. This all works fine.
Problem
Now I'm working on a Xamarin Forms project that will use the same DAL, BL, and entities to pull data from the WPF project into an Android app.
My shared mobile project has references to the DAL, BL, and entities. And this is where the problem is... when I deploy to the Android I get deployment errors saying that the Android project can't resolve references to DevExpress assemblies.
I'm sure that if I were to remove the "[HighlightedClass]" attribute from the Entities project then everyting would deploy fine. But then I would not be able to create new reports in the WPF project.
Possible Solution
One idea I have is to create local models in the WPF project for reporting. My UI project could call back into the back end, get back a list of data as LIST<t>, them map them to local models which would use the attribute. This way the attribute only appears in the WPF project where the reporting happens. The Entities project would no longer know about DevExpress. And the Android app would no longer complain about it.
But this is a lot of work and could create maintenance headaches as I would have local Models that are exact duplicates of the Entity classes in the Entites project. I would have to make changes in two places.
I'm open to suggestion here.
Thanks
If it's not broken, fix it until it is.
Everything makes sense in someone's mind.
Ya can't fix stupid.
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Have you considered creating your own [HighlightedClass] stub attribute in the correct namespace that could be used as a stand-in reference in the other project?
It would just need to be compile compatible with the real class.
Or possibly even it is compiled as a source only attribute in one context…
This leads to a scenario where you might want the same source to be shared across two different projects so it can be compiled two different ways?
Or use it as a binary dependency? You have 2 versions of a DLL?
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Like a Halo ring, or a Dyson Sphere? Just want your thoughts on megastructures.
And if you are not a Halo fan, go by Larry Niven's Ringworld.
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Tagged you as a troll for posting OBVIOUS off-topic, bullshit questions in the programming forums.
modified 29-Dec-21 9:49am.
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To be fair if they are new to technology/programming they might not know what "Design and Architecture" means.
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To be fair, you just have to look at all the other posts to figure out this isn't the forum for Halo and megastructures.
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Experienced people might be expected to look at that. I would not expect someone with no experience to know to do that. Same as I would not be able to expect them to craft specific enough google queries to return relevant results to many programming problems.
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Really? It's in the name of the site!
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Circular? As I said in the first post....
"they might not know what "Design and Architecture" means."
Architecture for someone new to programming would mean 'the art or practice of designing and constructing buildings.'
So yes in that context this would be exactly the forum to ask that question.
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jschell wrote: So yes in that context this would be exactly the forum to ask that question.
Well, yeah, IF you completely ignore the larger context of "Code Project".
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Also already stated in my original post....
"To be fair if they are new to technology/programming"
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I know what design is, but not software architecture. My bad, won't happen again.
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And it's he. not they or it. I understand you can't assume, so I am clarifying.
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