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  • When to use a module, and when to use a class

    - by Matt Briggs
    I am currently working through the Gregory Brown Ruby Best Practices book. Early on, he is talking about refactoring some functionality from helper methods on a related class, to some methods on module, then had the module extend self. Hadn't seen that before, after a quick google, found out that extend self on a module lets methods defined on the module see each other, which makes sense. Now, my question is when would you do something like this module StyleParser extend self def process(text) ... end def style_tag?(text) ... end end and then refer to it in tests with @parser = Prawn::Document::Text::StyleParser as opposed to just using a class with some class methods on it? is it so that you can use it as a mixin? or are there other reasons I'm not seeing?

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  • Base class pointer vs inherited class pointer?

    - by Goose Bumper
    Suppose I have a class Dog that inherits from a class Animal. What is the difference between these two lines of code? Animal *a = new Dog(); Dog *d = new Dog(); In one, the pointer is for the base class, and in the other, the pointer is for the derived class. But when would this distinction become important? For polymorphism, either one would work exactly the same, right?

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  • Is a base class with shared fields and functions good design

    - by eych
    I've got a BaseDataClass with shared fields and functions Protected Shared dbase as SqlDatabase Protected Shared dbCommand as DBCommand ... //also have a sync object used by the derived classes for Synclock'ing Protected Shared ReadOnly syncObj As Object = New Object() Protected Shared Sub Init() //initializes fields, sets connections Protected Shared Sub CleanAll() //closes connections, disposes, etc. I have several classes that derive from this base class. The derived classes have all Shared functions that can be called directly from the BLL with no instantiation. The functions in these derived classes call the base Init(), call their specific stored procs, call the base CleanAll() and then return the results. So if I have 5 derived classes with 10 functions each, totaling 50 possible function calls, since they are all Shared, the CLR only calls one at a time, right? All calls are queued to wait until each Shared function completes. Is there a better design with having Shared functions in your DAL and still have base class functions? Or since I have a base class, is it better to move towards instance methods within the DAL?

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  • Php wrapper class for XML

    - by gms8994
    I'm working on a new class to wrap XML handling. I want my class to use simplexml if it's installed, and the built in XML functions if it's not. Can anyone give me some suggestions on a skeleton class to do this? It seems "wrong" to litter each method with a bunch of if statements, and that also seems like it would make it nearly impossible to correctly test. Any upfront suggestions would be great! EDIT: I'm talking about these built-in xml functions.

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  • Help naming a class that has a single public method called Execute()

    - by devoured elysium
    I have designed the following class that should work kind of like a method (usually the user will just run Execute()): public abstract class ??? { protected bool hasFailed = false; protected bool hasRun = false; public bool HasFailed { get { return hasFailed; } } public bool HasRun { get { return hasRun; } } private void Restart() { hasFailed = false; hasRun = false; } public bool Execute() { ExecuteImplementation(); bool returnValue = hasFailed; Restart(); return returnValue; } protected abstract void ExecuteImplementation(); } My question is: how should I name this class? Runnable? Method(sounds awkward)?

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  • C2664 when casting child class to templated parent class

    - by DC
    I have a parent class which is templated, and a child class which implements it. template< typename T1, typename T2> class ParentClass{ . . . }; class ChildClass : public ParentClass<MyT1, MyT2> { . . . }; And I want to have a pointer which I can use polymorphically: ParentClass<T1, T2>* ptr; ptr = static_cast<ParentClass<MyT1, MyT2>* >(new ChildClass() ); No matter how I cast it, I always get a C2664 which has the same expression: error C2664: cannot convert parameter 1 from 'ParentClass< T1,T2 *' to 'ParentClass< T1,T2 *' Is it not possible to cast pointer types between inherited types if the parent is templated, even if the types specified in the templates are the same?

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  • noncopyable static const member class in template class

    - by Dukales
    I have a non-copyable (inherited from boost::noncopyable) class that I use as a custom namespace. Also, I have another class, that uses previous one, as shown here: #include <boost/utility.hpp> #include <cmath> template< typename F > struct custom_namespace : boost::noncopyable { F sqrt_of_half(F const & x) const { using std::sqrt; return sqrt(x / F(2.0L)); } // ... maybe others are not so dummy const/constexpr methods }; template< typename F > class custom_namespace_user { static ::custom_namespace< F > const custom_namespace_; public : F poisson() const { return custom_namespace_.sqrt_of_half(M_PI); } static F square_diagonal(F const & a) { return a * custom_namespace_.sqrt_of_half(1.0L); } }; template< typename F > ::custom_namespace< F > const custom_namespace_user< F >::custom_namespace_(); this code leads to the next error (even without instantiation): error: no 'const custom_namespace custom_namespace_user::custom_namespace_()' member function declared in class 'custom_namespace_user' The next way is not legitimate: template< typename F ::custom_namespace< F const custom_namespace_user< F ::custom_namespace_ = ::custom_namespace< F (); What should I do to declare this two classes (first as noncopyable static const member class of second)? Is this feaseble?

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  • PHP access class inside another class

    - by arxanas
    So I have two classes like this: class foo { /* code here */ } $foo = new foo(); class bar { global $foo; public function bar () { echo $foo->something(); } } I want to access the methods of foo inside all methods bar, without declaring it in each method inside bar, like this: class bar { public function bar () { global $foo; echo $foo->something(); } public function barMethod () { global $foo; echo $foo->somethingElse(); } /* etc */ } I don't want to extend it, either. I tried using the var keyword, but it didn't seem to work. What do I do in order to access the other class "foo" inside all methods of bar?

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  • Different return value of an overridden class

    - by Samer Afach
    I have a simple but confusing question here. Is it legal to have a different return value type for overridden methods than the abstact ones defined in the base class?? I did that and the compiler didn't complain... could someone please explain? class MyBaseClass { int value; public: virtual int getValue() = 0; }; class MyClass : public MyBaseClass { double value; public: virtual double getValue(); // here!!! return is double, not int }; double MyClass::getValue() { return this->value; } The compiler totally accepted something similar (MSVC und MinGW)... could anyone please exaplain to what extent this is legal?

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  • C# class in a directory without having the directory name in its namespace

    - by PaN1C_Showt1Me
    Hi ! If you add a directory in your Visual Studio project and you add a class inside it, the namespace will respect the whole path the directory inclusive. But sometimes, I prefer having the class in the main project namespace, although it lies in a directory structure, just because I don't want to have mess in my code. So often happens that I rewrite the Myproject.MyDirectory namespace to be Myproject only. Is it OK in your opinion? Or does any convention say that every class inside the directory must have it included in the namespace ? Thanks

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  • iPhone - Launching selectors from a different class

    - by David Schiefer
    Hi, I'd like to reload a table view which is in another class called "WriteIt_MobileAppDelegate" from one of my other classes which is called "Properties". I've tried to do this via the NSNotificationCenter class - the log gets called but the table is never updated. Properties.h: [[NSNotificationCenter defaultCenter] postNotificationName:@"NameChanged" object:[WriteIt_MobileAppDelegate class] userInfo:nil]; WriteIt_MobileAppDelegate.m -(void)awakeFromNib { [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reloadItProperties:) name:@"NameChanged" object:self]; } - (void) reloadItProperties: (NSNotification *)notification { NSLog(@"Reloading Data"); //this gets called [self.navigationController popToRootViewControllerAnimated:YES]; [self.tblSimpleTable reloadData]; [self.tblSimpleTable reloadSectionIndexTitles]; // but the rest doesn't } What am I doing wrong here?

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  • access property value of one class from another internal class in C#

    - by starz26
    how do i acces the property value from an internal class , see below? namespace N1 { public class ClassA { string var1 = null; private ClassB b; public ClassA() { var1 = "one"; b = new ClassB(); } //property public string Var1 { get{ return var1; } } } namespace N1 { internal class ClassB { private void method() { // I need to access the value of Var1( property) from here, how to do this? } } }

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  • generating class from hibernate mapping file

    - by Mrityunjay
    hi, i have one mapping file viz. student.hbm.xml.. i need to generate Student.java from the same. the file is below :- <?xml version="1.0" encoding="UTF-8"?> <hibernate-mapping> <class name="org.hibernate.entity.ClassRoom" table="class_room"> <id name="roomId" column="room_id" type="int"/> <property name="roomClass" column="room_class" type="string"/> <property name="floor" column="floor" type="int"/> <property name="roomMaster" column="room_mast" type="string"/> </class> </hibernate-mapping> is there any way i can create the class file from the above file.please help...

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  • Python: Hack to call a method on an object that isn't of its class

    - by cool-RR
    Assume you define a class, which has a method which does some complicated processing: class A(object): def my_method(self): # Some complicated processing is done here return self And now you want to use that method on some object from another class entirely. Like, you want to do A.my_method(7). This is what you'd get: TypeError: unbound method my_method() must be called with A instance as first argument (got int instance instead). Now, is there any possibility to hack things so you could call that method on 7? I'd want to avoid moving the function or rewriting it. (Note that the method's logic does depend on self.) One note: I know that some people will want to say, "You're doing it wrong! You're abusing Python! You shouldn't do it!" So yes, I know, this is a terrible terrible thing I want to do. I'm asking if someone knows how to do it, not how to preach to me that I shouldn't do it.

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  • C++: Create abstract class with abstract method and override the method in a subclass

    - by Martijn Courteaux
    Hi, How to create in C++ an abstract class with some abstract methods that I want to override in a subclass? How should the .h file look? Is there a .cpp, if so how should it look? In Java it would look like this: abstract class GameObject { public abstract void update(); public abstract void paint(Graphics g); } class Player extends GameObject { @Override public void update() { // ... } @Override public void paint(Graphics g) { // ... } } // In my game loop: for (int i = 0; i < objects.size(); i++) { objects.get(i).update(); } for (int i = 0; i < objects.size(); i++) { objects.get(i).paint(g); } Translating this code to C++ is enough for me.

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  • Trouble Copying custom class initialization

    - by Parad0x13
    I have a custom class of type NSObject that contains a single NSMutableArray. This class is called Mutable2DArray and is designed to emulate a 2 dimensional array of type NSMutableArray. There is a custom init method - (id)initWithX:(int)x Y:(int)y that asks for the dimensions for the array and allocates the required arrays within the only array the class owns. My issue is when I try to copy an instance of Mutable2DArray I get an error saying the copyWithZone is an unrecognized selector. I thought copy was a base method of NSObject so I'm confused why I cant create a copy of the instance like this: Mutable2DArray *Array1 = [[Mutable2DArray alloc] initWithX:10 Y:10]; Mutable2DArray *Array2 = [Array1 copy]; Am I missing something so obvious here?

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  • Confused about Base class libary and Framework Class Library

    - by n0vic3c0d3r
    Is ADO.NET and ASP.NET a part of Base Class Library? The information given in wikipedia looks ambiguous to me. In the figure, it is shown as a separate block. What is the difference between Base Class Library(BCL) and Framework Class Library(FCL)? Is FCL as a part of .NET Framework? If so why is FCL not shown in the figure as part of .NET framework? Got confused!!

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  • Using control from a separate class in C#

    - by DazSlayer
    I have a program that dynamically creates controls when it starts, it works just fine when the code to do this is in the class of the actual form. I tried moving the code to a separate class and found that I could not use Controls.Add(). How can I add controls to the Form from a separate class? This is what I have so far: TextBox txtbx = new TextBox(); txtbx.Text = "asd" + x.ToString(); txtbx.Name = "txtbx" + x.ToString(); txtbx.Location = new Point(10, (20 * x)); txtbx.Height = 20; txtbx.Width = 50; Controls.Add(txtbx); Error 1 The name 'Controls' does not exist in the current context

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  • Defining private static class member

    - by mnn
    class B { /* ... */ }; class A { public: A() { obj = NULL; } private: static B* obj; }; However this produces huge mass of linker errors that symbol obj is unresolved. What's the "correct" way to have such private static class member without these linker errors? Edit: I tried this: B *A::obj = NULL; but I got about same amount of linker errors however this time about already defining A::obj. (LNK2005). Also I get LNK4006 warnings, also about A::obj

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  • C# cross class enum visibility - Possible?

    - by 537mfb
    so i have a class ClassA that contains an enum MyEnum, and a class ClassB that references that class (different Projects) and so in ClassB i have a using ClassA; clause and i can access that enum using something like MyEnum value = MyEnum.EnumValue; Now on a third project i have my Windows form and it has a clause like using ClassB; Now what can i add in ClassB to acess that enum on my windows Form? Is it even Possible? i would like to avoid having to add ClassA to my form just to access an enum. The idea is that ClassB is sort of a manager between my form and the functionality in ClassA - but i would like to get access to that enum as it makes a lot of tasks easier

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