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  • Problem about C++ class (inheritance, variables scope and functions)

    - by Luigi Giaccari
    I have a class that contains some data: class DATA Now I would to create some functions that uses those data. I can do it easily by writing member functions like DATA::usedata(); Since there are hundreds of functions, I would to keep an order in my code, so I would like to have some "categories" (not sure of the correct name) like: DATA data; data.memory.free(); data.memory.allocate(); data.file.import(); data.whatever.foo(); where memory, file and whatever are the "categories" and free, allocate and foo are the functions. I tried the inheritance way, but I got lost since I can not declare inside DATA a memory or file object, error C2079 occurs: http://msdn.microsoft.com/en-us/library/9ekhdcxs%28VS.80%29.aspx Since I am not a programmer please don't be too complicated and if you have an easier way I am all ears.

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  • Django model class and custom property

    - by dArignac
    Howdy - today a weird problem occured to me: I have a modle class in Django and added a custom property to it that shall not be saved into the database and therefore is not represent in the models structure: class Category(models.Model): groups = models.ManyToManyField(Group) title = defaultdict() Now, when I'm within the shell or writing a test and I do the following: c1 = Category.objects.create() c1.title['de'] = 'german title' print c1.title['de'] # prints "german title" c2 = Category.objects.create() print c2.title['de'] # prints "german title" <-- WTF? It seems that 'title' is kind of global. If I change title to a simple string it works as expected, so it has to do something with the dict? I also tried setting title as a property: title = property(_title) But that did not work, too. So, how can I solve this? Thank you in advance! enter code here

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  • Basic class returns object reference instead of Array

    - by php-b-grader
    I have very basic class: class Customer { protected $id; protected $customer; public function __construct($customer_id) { $this->id = $customer_id; return $this->set_customer(); } protected function set_customer() { $query = mysql_query("SELECT * FROM customer WHERE id = '$this->id'"); $this->customer = mysql_fetch_row($query); return $this->customer; } } $customer = new Customer($order->customer->id); print_r($customer); This is not doing what I want it to but I understand why... $customer returns a reference to the Customer Object... What I want is the MySQL row array from the mysql_fetch_row() - How do I return the array? What am I missing?

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  • Using pipes inside a class in C++

    - by Paul
    I'm trying to use this tutorial to make plots with Gnuplot in C++. However I will be using the pipe to Gnuplot from within a class, but then I run into some problems: I've got a header file where I declare all variables etc. I need to declare the pipe-variable here too, but how do I do that? I've tried doing it straight away, but it doesn't work: Logger.h: class Logger { FILE pipe; } Logger.cpp: Logger::Logger() { //Constructor *pipe = popen("gnuplot -persist","w"); } Gives the error Logger.cpp:28: error: no match for ‘operator=’ in ‘*((Logger*)this)->Logger::pipe = popen(((const char*)"gnuplot -persist"), ((const char*)"w"))’ Suggestions?

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  • is counter has certain value inside a class in python

    - by mazlor
    i am learning classes in python and when i was reading the documentation i found this example that i didn't understand : class MyClass: """A simple example class""" def __init__(self): self.data = [] i = 12345 def f(self): return 'hello world' then if we assign : x = MyClass() x.counter = 1 now if we implement while loop : while x.counter < 10: x.counter = x.counter * 2 so the value of x.counter will be : 16 while for example if we have a variable y : y = 1 while y < 1 : y = y *2 then if we look for the value of y we find it 1 so i don't know how is the value of counter became 16 . thanks

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  • How to design model for multi-tiered data?

    - by Chris
    Say I have three types of object: Area, Subarea and Topic. I want to be able to display an Area, which is just a list of Subareas and the Topics contained in those Subareas. I never want to be able to display Subareas separately - they're just for breaking up the Topics. Topics can, however, appear in multiple Areas (but probably under the same Subarea). How would I design a model for this? I could use ForeignKey from Topic to Subarea and from Subarea to Area, but it seems unnecessarily complex given that I never want to interact with subareas themselves. Also, none of these objects are ever altered or added to by the user. They're just for me to represent information. Maybe there is a better way to represent it all?

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  • Comparing Design Patterns

    - by Lijo
    Hi, I am learning design patterns using C#. One of the challenges that I am facing is that they look similar. Could you please help me to distinguish them – basically when to use them? - Why not the other? Bridge and Strategy State and Strategy Façade and Strategy Composite and Strategy I understand that there are lots of resources available in the web. However they does not treat this special question. [Note: I am looking for implementation examples and rationale behind the selection; not mere explanations] It would be great if you are taking examples from any of the following 1) E-Commerce 2) Payroll system 3) Banking 4) Retailing Thanks for your understanding.. Thanks Lijo

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  • Error: cant find main class

    - by Vurb
    ok so im a newbie java dev using netbeans IDE 7.1.1 and im watching this tutorial and right off the bat i get an error in my program even after 5 retypes to make sure its exactly the same as in the video so anyways this is the error Error: Could not find or load main class javagame.JavaGame Java Result: 1 and this is the code i have written package JavaGame; import javax.swing.JFrame; public class JavaGame extends JFrame { public JavaGame(){ setTitle("java game"); setSize(500, 500); setResizable(false); setVisible(true); //setDefaultCloseOperation(); } public static void main(String[] args){ } }

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  • related categories - database design

    - by mike
    Hello! I'm looking for a little database design advice... I have a spreadsheet with a few columns in it. Column 1 being a list of categories and the rest being related categories(to the category in column 1). I'm trying to figure out what the best way to setup the tables would be... My thought so far is to have a table that just lists the categories then have a table with 2 columns that holds the id of the category and the id of a related category.... Would this be the best way to do this? Any better ideas?

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  • Generic Database table design

    - by Gazeth
    Just trying to figure out the best way to design my table for the following scenario: I have several areas in my system (documents, projects, groups and clients) and each of these can have comments logged against them. My question is should I have one table like this: CommentID DocumentID ProjectID GroupID ClientID etc Where only one of the ids will have data and the rest will be NULL or should I have a seperate CommentType table and have my comments table like this: CommentID CommentTypeID ResourceID (this being the id of the project/doc/client) etc My thoughts are that option 2 would be more efficient from an indexing point of view?

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  • Customers and suppliers database design issue

    - by hectorsq
    I am developing a web application in which I will have customers and suppliers. Initially I thought on using a Customers table and a Suppliers table. Then when I was thinking on bank transactions, I noticed that each transaction needs to refer to a customer or a supplier, so I thought on using a single table named Business in which I will save both customers and suppliers. If I use Customers and Suppliers tables when I want to list the bank transactions I will have to search in both tables to get the company name. If I use a Businesses table I will have to use a business type column, and have the union of possible fields for all businesses types. Any suggestions on the design?

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  • C++ Singleton design pattern

    - by Artem Barger
    Recently I've bumped into a realization/implementation of the Singleton design pattern for C++. It has looked like this (I have adopted it from the real life example): // a lot of methods are omitted here class Singleton { public: static Singleton* getInstance( ); ~Singleton( ); private: Singleton( ); static Singleton* instance; }; From this declaration I can deduce that the instance field is initiated on the heap. That means there is a memory allocation. What is completely unclear for me is when exactly the memory is going to be deallocated? Or is there a bug and memory leak? It seems like there is a problem in the implementation. My main question is, how do I implement it in the right way?

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  • Getting all inner classes by reflection

    - by Roman
    I have the following problem. I have this pretty class and now I want to get all the classes that extend that class (inner classes ) and fill 'classList' with it. ( in an automatic way of course ) public abstract class CompoundReference { private static List<Class<? extends CompoundReference>> classList = new ArrayList<Class<? extends CompoundReference>>(); @CompoundKey(gsType = User.class, dbType = UserDetailsMappings.class) public static class CUser extends CompoundReference { } @CompoundKey(gsType = Catalog.class, dbType = CatalogDetailsMappings.class) public static class CCatalog extends CompoundReference { } @CompoundKey(gsType = Product.class, dbType = ProductDetailsMappings.class) public static class CProduct extends CompoundReference { } @CompoundKey(gsType = Category.class) public static class CCategory extends CompoundReference { } @CompoundKey(gsType = Poll.class, dbType = PollDetailsMappings.class) public static class CPoll extends CompoundReference { } // much mroe inner classes Some manual solution would be just to main such a static block , that is something that I dont want to do. static { classList.addAll(Arrays.asList(CUser.class, CCatalog.class, CProduct.class, CCategory.class, CPoll.class, CComment.class, CWebPage.class, CReview.class, CPost.class, CMessage.class, CStory.class,CPicture.class)); }

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  • Avoiding sub-type selection in view code

    - by John Donoghue
    Hi, I have some code where the model contains some classes like (vb.net pseudocode, but could be any OO language): Enum AttributeType Boolean Date String End Enum MustInherit Class Attibute Must Override Function Type As AttributeType End Class Class BooleanAttribute: Attribute Function Type As AttributeType Return AttributeType.Boolean End Function End Class And the view contains some code like: Select Case AttributeType Case Boolean //Display checkbox control Case Date //Display date picker control Case String //Display textbox control End Select I don't really like the code in the view, for the hopefully obvious reasons (what happens when I get a new attribute type etc). My question is, how should I replace it? I could easily add a method to the concrete classes, but that pollutes the model with UI stuff so that's a horrible idea. I could move the select into a factory, but that seems to be just hiding the problem. Can anybody advise a better approach?

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  • Doubt about a particular pattern of Javascript class definition

    - by fenderplayer
    Recently i saw the following code that creates a class in javascript: var Model.Foo = function(){ // private stuff var a, b; // public properties this.attr1 = ''; this.attr2 = ''; if(Model.Foo._init === 'undefined'){ Model.Foo.prototype = { func1 : function(){ //...}, func2 : function(){ //... }, //other prototype functions } } Model.Foo._init = true; } // Instantiate and use the class as follows: var foo = new Model.Foo(); foo.func1(); I guess the _init variable is used to make sure we don't define the prototypes again. Also, i feel the code is more readable since i am placing everything in a function block (so in oop-speak, all attributes and methods are in one place). Do you see any issues with the code above? Any pitfalls of using this pattern if i need to create lots of classes in a big project?

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  • Passing a class ("Country.class") as an argument in Java

    - by Coronatus
    I'm trying to make a method that takes an argument of Country.class, User.class etc, and returns argument.count(). All the possible classes that I would give to this method extend from Model and have the method count(). My code: private static long <T> countModel(Model<T> clazz) { return clazz.count(); } Called by: renderArgs.put("countryCount", countModel(Country.class)); However this just doesn't work at all. How do I do this, please?

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  • Do Portable Class Libraries work with .net 3.5?

    - by Eric
    I am running Windows 8 and have both Visual Studio 2010 Ultimate w/sp1 and Visual Studio 2012 Ultimate and I am trying to create a Portable Class Library that supports .net 3.5 and greater. When I first try to create a PCL I get a screen like this: I noticed that .net 3.5 is not in the list so I clicked on "Install additional frameworks" and found a Targeting Pack for version 3.5. But when I download and run "dotnetfx35setup.exe" nothing happens. And when I go back into VS and try to create a new Portable Class Library, it lists the same target frameworks as before. I have also turned on the Windows Features for .NET Framework 3.5 and am now out of ideas. Here is a screen shot in case I missed something else. Thanks,

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  • Python: Give a class its own `self` at instantiation time

    - by SuperDisk
    I've got a button class that you can instantiate like so: engine.createElement((0, 0), Button(code=print, args=("Stuff!",))) And when it is clicked it will print "Stuff!". However, I need the button to destroy itself whenever it is clicked. Something like this: engine.createElement((0, 0), Button(code=engine.killElement, args=(self,))) However, that would just kill the caller, because self refers to the caller at that moment. What I need to do is give the class its own 'self' in advance... I thought of just making the string 'self' refer to the self variable upon click, but what if I wanted to use the string 'self' in the arguments? What is the way to do this? Is my architecture all wrong or something? Thanks.

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  • Converting C# class to JavaScript

    - by AgileMeansDoAsLittleAsPossible
    Take a look at this basic class: namespace AcmeWeb { public string FirstName { get; set; } public class Person { public Person(string firstName, string lastName) { if (String.IsNullOrEmpty(firstName)) { throw new ArgumentNullException(firstName); } this.FirstName = firstName; } } } What's the best translation of this into JavaScript? This is what I'm thinking: (function(namespace) { namespace.Person = function(firstName, lastName) { // Constructor (function() { if (!firstName) { throw "'firstName' argument cannot be null or empty"; } })(); // Private memberts var _ = { firstName: firstName }; // Public members this.firstName = function(value) { if (typeof(value) === "undefined") { return _.firstName; } else { _.firstName = value; return this; } }; }; })(AcmeWeb);

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  • Why does this basic class not work?

    - by kalaba2003
    I could not understand why my class does no t work. Returns nothing. Is there any mistake? class User { public $first_name; public $last_name; public function full_name() { if(isset($this->first_name) && isset($this->last_name)) { return $this->first_name . " " . $this->last_name; } else { return "No name!"; } } public function assign () { $this->first_name = "Name"; $this->last_name = "Surname"; } } $user = new User(); $user->assign(); $user->full_name(); ?>

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  • Load custom class properly

    - by LinusAn
    I have a custom class which I want to "load" inside the firstViewController and then access it from other classes by segues. My Problem is, I can't even access and change the instance variable inside the firstViewController. Somehow I'm "loading" it wrong. Here is the code I used until now: inside viewController.h @property (strong, nonatomic) myClass *newClass; inside viewController.m @synthesize newClass; I then try to access it by: self.newClass.string = @"myString"; if(newClass.string == @"myString"){ NSLog(@"didn't work"); } Well, I get "didn't work". Why is that? When I write myClass *newClass = [myClass new]; It does work. But the class and its properties gets overwritten every time the ViewController loads again. What would you recommend? Thank you very much.

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  • Is there a pattern or best practice for passing a reference type to multiple classes vs a static class?

    - by Dave
    My .NET application creates HTML files, and as such, the structure looks like variable myData BuildHomePage() variable graph = new BuildGraphPage(myData) variable table = BuildTablePage(myData) BuildGraphPage and BuildTablePage both require access data, the myData object. In the above example, I've passed the myData object to 2 constructors. This is what I'm doing now, in my current project. The myData object, and it's properties are all readonly. The problem is, the number of pages which will require this object has grown. In the real project, there are currently 4, but the new spec is to have about 20. Passing this object to the constructor of each new object and assigning it to a field is a little time consuming, but not a hardship! This poses the question whether it's better practice to continue as I have, or to refactor and create a new static class for myData which can be referenced from any where in my project. I guess my abilities to use Google are poor, because I did try and find an appropriate pattern as I am sure this type of design must be common place but my results returned nothing. Is there a pattern which is suited, or do best practices lean towards one implementation over another.

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