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  • Design of std::ifstream class

    - by Nawaz
    Those of us who have seen the beauty of STL try to use it as much as possible, and also encourage others to use it wherever we see them using raw pointers and arrays. Scott Meyers have written a whole book on STL, with title Effective STL. Yet what happened to the developers of ifstream that they preferred char* over std::string. I wonder why the first parameter of ifstream::open() is of type const char*, instead of const std::string &. Please have a look at it's signature: void open(const char * filename, ios_base::openmode mode = ios_base::in ); Why this? Why not this: void open(const string & filename, ios_base::openmode mode = ios_base::in ); Is this a serious mistake with the design? Or this design is deliberate? What could be the reason? I don't see any reason why they have preferred char* over std::string. Note we could still pass char* to the latter function that takes std::string. That's not a problem! By the way, I'm aware that ifstream is a typedef, so no comment on my title.:P. It looks short that is why I used it. The actual class template is : template<class _Elem,class _Traits> class basic_ifstream;

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  • Class Assignment Operators

    - by Maxpm
    I made the following operator overloading test: #include <iostream> #include <string> using namespace std; class TestClass { string ClassName; public: TestClass(string Name) { ClassName = Name; cout << ClassName << " constructed." << endl; } ~TestClass() { cout << ClassName << " destructed." << endl; } void operator=(TestClass Other) { cout << ClassName << " in operator=" << endl; cout << "The address of the other class is " << &Other << "." << endl; } }; int main() { TestClass FirstInstance("FirstInstance"); TestClass SecondInstance("SecondInstance"); FirstInstance = SecondInstance; SecondInstance = FirstInstance; return 0; } The assignment operator behaves as-expected, outputting the address of the other class. Now, how would I actually assign something from the other class? For example, something like this: void operator=(TestClass Other) { ClassName = Other.ClassName; }

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  • Which frameworks (and associated languages) support class replacement?

    - by Alix
    Hi, I'm writing my master thesis, which deals with AOP in .NET, among other things, and I mention the lack of support for replacing classes at load time as an important factor in the fact that there are currently no .NET AOP frameworks that perform true dynamic weaving -- not without imposing the requirement that woven classes must extend ContextBoundObject or MarshalByRefObject or expose all their semantics on an interface. You can however do this with the JVM thanks to ClassFileTransformer: You extend ClassFileTransformer. You subscribe to the class load event. On class load, you rewrite the class and replace it. All this is very well, but my project director has asked me, quite in the last minute, to give him a list of frameworks (and associated languages) that do / do not support class replacement. I really have no time to look for this now: I wouldn't feel comfortable just doing a superficial research and potentially putting erroneous information in my thesis. So I ask you, oh almighty programming community, can you help out? Of course, I'm not asking you to research this yourselves. Simply, if you know for sure that a particular framework supports / doesn't support this, leave it as an answer. If you're not sure please don't forget to point it out. Thanks so much!

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  • Which languages support class replacement?

    - by Alix
    Hi, I'm writing my master thesis, which deals with AOP in .NET, among other things, and I mention the lack of support for replacing classes at load time as an important factor in the fact that there are currently no .NET AOP frameworks that perform true dynamic weaving -- not without imposing the requirement that woven classes must extend ContextBoundObject or MarshalByRefObject or expose all their semantics on an interface. You can however do this in Java thanks to ClassFileTransformer: You extend ClassFileTransformer. You subscribe to the class load event. On class load, you rewrite the class and replace it. All this is very well, but my project director has asked me, quite in the last minute, to give him a list of languages that do / do not support class replacement. I really have no time to look for this now: I wouldn't feel comfortable just doing a superficial research and potentially putting erroneous information in my thesis. So I ask you, oh almighty programming community, can you help out? Of course, I'm not asking you to research this yourselves. Simply, if you know for sure that a particular language supports / doesn't support this, leave it as an answer. If you're not sure please don't forget to point it out. Thanks so much!

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  • Best practice accessing an array set within a class

    - by user350599
    I have created a basic class for a customer. I haven't done this before and want to know the best way to access the data. Should I have a get() method for every field in the customer array or should I simply pass the customer array back and access with the page. i.e. Just return the array class Customer { protected $id; protected $customer; public function __construct($customer_id) { $this->id = $customer_id; $this->set_customer(); } protected function set_customer() { $query = mysql_query("SELECT * FROM customer WHERE id = '$this->id'"); $this->customer = mysql_fetch_row($query); } public function get_customer() { return $this->customer; } } versus create a method for each item in the array class Customer { protected $id; protected $customer; public function __construct($customer_id) { $this->id = $customer_id; $this->set_customer(); } protected function set_customer() { $query = mysql_query("SELECT * FROM customer WHERE id = '$this->id'"); $this->customer = mysql_fetch_row($query); } public function get_customer_name() { return $this->customer->customer_name; } ... ... } versus option 3 based on Tobias' feedback: (not sure if syntax is correct) 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'"); return mysql_fetch_row($query); } }

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  • Execute a function to affect different template class instances

    - by Samer Afach
    I have a complicated problem, and I need help. I have a base case, class ParamBase { string paramValue; //... } and a bunch of class templates with different template parameters. template <typename T> class Param : public ParamBase { T value; //... } Now, each instance of Param has different template parameter, double, int, string... etc. To make it easier, I have a vector to their base class pointers that contains all the instances that have been created: vector<ParamBase*> allParamsObjects; The question is: How can I run a single function (global or member or anything, your choice), that converts all of those different instances' strings paramValue with different templates arguments and save the conversion result to the appropriate type in Param::value. This has to be run over all objects that are saved in the vector allParamsObjects. So if the template argument of the first Param is double, paramValue has to be converted to double and saved in value; and if the second Param's argument is int, then the paramValue of the second has to be converted to int and saved in value... etc. I feel it's almost impossible... Any help would be highly appreciated :-)

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  • Calling Base Class Functions with Inherited Type

    - by Kein Mitleid
    I can't describe exactly what I want to say but I want to use base class functions with an inherited type. Like I want to declare "Coord3D operator + (Coord3D);" in one class, but if I use it with Vector3D operands, I want it to return Vector3D type instead of Coord3D. With this line of code below, I add two Vector3D's and get a Coord3D in return, as told to me by the typeid().name() function. How do I reorganize my classes so that I get a Vector3D on return? #include <iostream> #include <typeinfo> using namespace std; class Coord3D { public: float x, y, z; Coord3D (float = 0.0f, float = 0.0f, float = 0.0f); Coord3D operator + (Coord3D &); }; Coord3D::Coord3D (float a, float b, float c) { x = a; y = b; z = c; } Coord3D Coord3D::operator+ (Coord3D &param) { Coord3D temp; temp.x = x + param.x; temp.y = y + param.y; temp.z = z + param.z; return temp; } class Vector3D: public Coord3D { public: Vector3D (float a = 0.0f, float b = 0.0f, float c = 0.0f) : Coord3D (a, b, c) {}; }; int main () { Vector3D a (3, 4, 5); Vector3D b (6, 7, 8); cout << typeid(a + b).name(); return 0; }

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  • class modifier issues in C# with "private" classes

    - by devoured elysium
    I had a class that had lots of methods: public class MyClass { public bool checkConditions() { return checkCondition1() && checkCondition2() && checkCondition3(); } ...conditions methods public void DoProcess() { FirstPartOfProcess(); SecondPartOfProcess(); ThirdPartOfProcess(); } ...process methods } I identified two "vital" work areas, and decided to extract those methods to classes of its own: public class MyClass { private readonly MyClassConditions _conditions = new ...; private readonly MyClassProcessExecution = new ...; public bool checkConditions() { return _conditions.checkConditions(); } public void DoProcess() { _process.DoProcess(); } } In Java, I'd define MyClassConditions and MyClassProcessExecution as package protected, but I can't do that in C#. How would you go about doing this in C#? Setting both classes as inner classes of MyClass? I have 2 options: I either define them inside MyClass, having everything in the same file, which looks confusing and ugly, or I can define MyClass as a partial class, having one file for MyClass, other for MyClassConditions and other for MyClassProcessExecution. Defining them as internal? I don't really like that much of the internal modifier, as I don't find these classes add any value at all for the rest of my program/assembly, and I'd like to hide them if possible. It's not like they're gonna be useful/reusable in any other part of the program. Keep them as public? I can't see why, but I've let this option here. Any other? Name it! Thanks

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  • Declaring an enum within a class

    - by bporter
    In the following code snippet, the Color enum is declared within the Car class in order to limit the scope of the enum and to try not to "pollute" the global namespace. class Car { public: enum Color { RED, BLUE, WHITE }; void SetColor( Car::Color color ) { _color = color; } Car::Color GetColor() const { return _color; } private: Car::Color _color; }; (1) Is this a good way to limit the scope of the Color enum? Or, should I declare it outside of the Car class, but possibly within its own namespace or struct? I just came across this article today, which advocates the latter and discusses some nice points about enums: http://gamesfromwithin.com/stupid-c-tricks-2-better-enums. (2) In this example, when working within the class, is it best to code the enum as Car::Color, or would just Color suffice? (I assume the former is better, just in case there is another Color enum declared in the global namespace. That way, at least, we are explicit about the enum to we are referring.) Thanks in advance for any input on this.

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  • C++ Declaring an enum within a class

    - by bporter
    In the following code snippet, the Color enum is declared within the Car class in order to limit the scope of the enum and to try not to "pollute" the global namespace. class Car { public: enum Color { RED, BLUE, WHITE }; void SetColor( Car::Color color ) { _color = color; } Car::Color GetColor() const { return _color; } private: Car::Color _color; }; (1) Is this a good way to limit the scope of the Color enum? Or, should I declare it outside of the Car class, but possibly within its own namespace or struct? I just came across this article today, which advocates the latter and discusses some nice points about enums: http://gamesfromwithin.com/stupid-c-tricks-2-better-enums. (2) In this example, when working within the class, is it best to code the enum as Car::Color, or would just Color suffice? (I assume the former is better, just in case there is another Color enum declared in the global namespace. That way, at least, we are explicit about the enum to we are referring.) Thanks in advance for any input on this.

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  • Class lookup structure array in C++

    - by wyatt
    I'm trying to create a structure array which links input strings to classes as follows: struct {string command; CommandPath cPath;} cPathLookup[] = { {"set an alarm", AlarmCommandPath}, {"send an email", EmailCommandPath}, {"", NULL} }; which will be used as follows: CommandPath *cPath = NULL; string input; getline(cin, input); for(int i = 0; cPathLookup[i] != ""; i++) { if(cPathLookup[i].command == input) cPath = new cPathLookup[i].cPath; } Obviously, this code is meaningless, but I think my intention is apparent - depending on input, I'd like cPath to be initialized as either a new AlarmCommandPath or a new EmailCommandPath. I could handle it with a function returning an instance depending on input, but a whole sequence of ifs just seems inelegant. I should also note that, in case it's not apparent and important, that AlarmCommandPath and EmailCommandPath are derived from CommandPath, and CommandPath is an abstract class. Thanks for any help you can offer. EDIT: I just noticed that, in spite of CommandPath being abstract, I have a declaration: CommandPath *cPath = NULL; in working code. Why does that compile?

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  • Should I implement an interface directly or have the superclass do it?

    - by c_maker
    Is there a difference between public class A extends AbstractB implements C {...} versus... public class A extends AbstractB {...} AbstractB implements C {...} I understand that in both cases, class A will end up conforming to the interface. In the second case, AbstractB can provide implementation for interface methods in C. Is that the only difference? If I do NOT want to provide an implementation for any of the interface methods in AbstractB, which style should I be using? Does using one or the other have some hidden 'documentation' purpose?

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  • RPG Game loop and class structure (cocos2D for iPhone)

    - by mac_55
    I'm looking to make an RPG with Cocos2D on the iPhone. I've done a fair bit of research, and I really like the model Cocos2D uses for scenes. I can instantiate a scene, set up my characters etc. and it all works really nicely... what I have problems with is structuring a game loop and separating the code from the scenes. For example, where do I put my code that will maintain the state of the game across multiple scenes? and do I put the code for events that get fired in a scene in that scene's class? or do I have some other class that separates the init code from the logic? Also, I've read a lot of tutorials that mention changing scenes, but I've read none that talk about updating a scene - taking input from the user and updating the display based on that. Does that happen in the scene object, or in a separate display engine type class. Thanks in advance!

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  • UIComponent extended class isn't showing UIComponent extended class

    - by Arno
    I have 1 class (that is extending a UIcomponent) that is representing a component. In that component I create different instances of another class that is also a UIComponent but this class doesn't show up in de first class. I see that it is running and that it has the correct hights but I got the feeling that it doesn't show up with this hights. If I trace I see the width and height is 200 X 200 but there is still nothing visible in my component I bet there is a simple solution for this problem?

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  • Java: exception-throwing class?

    - by HH
    I have classes DirReader and Search. The search uses DirReader. I want the search to know when DirReader throws exception. So how can I have class throwing exception? Currently, I use initCorrect -dummy var. Exception-style method may be more appropriate. Simplified Example Error $ javac ExceptionStatic.java ExceptionStatic.java:4: '{' expected public class ExceptionStatic throws Exception{ ^ 1 error Code import java.util.*; import java.io.*; // THIS PART NEEDS TO BE FIXED: public class ExceptionStatic throws Exception{ private static boolean initCorrect = false; public static String hello; static{ try{ hello = "hallo"; //some other conditionals in real code if( true) throw new Exception(); initCorrect=true; }catch(Exception e){ e.printStackTrace(); } } public static void main(String[] args){ if(initCorrect) System.out.println(hello); } }

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  • reference from xaml to public class in .cs class file

    - by netmajor
    I have in my WPF project file RssInfo.cs in which I have public class public class DoubleRangeRule : ValidationRule { public double Min { get; set; } public double Max { get; set; } public override System.Windows.Controls.ValidationResult Validate(object value, CultureInfo cultureInfo) { ... } } and from my XAML code in WPF window class I neet to get to this DoubleRangeRule class.. //reference to my project, all my files are in the WpfCzytanieRSS namespace xmlns:valRule="clr-namespace:WpfCzytanieRSS;assembly=WpfCzytanieRSS" <TextBox Validation.ErrorTemplate="{StaticResource TextBoxErrorTemplate}" Name="tbTitle"> <TextBox.Text> <Binding Path="Nazwa" UpdateSourceTrigger="PropertyChanged"> <Binding.ValidationRules> <valRule:DoubleRangeRule Min="0.5" Max="10"/> //error place </Binding.ValidationRules> </Binding> </TextBox.Text> </TextBox> And i get two errors: Error 1 The tag 'DoubleRangeRule' does not exist in XML namespace 'clr-namespace:WpfCzytanieRSS;assembly=WpfCzytanieRSS'. Error 2 The type 'valRule:DoubleRangeRule' was not found. Verify that you are not missing an assembly reference and that all referenced assemblies have been built. Please help to get to class DoubleRangeRule ! :)

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  • Optimizing Class Structure

    - by Derek Hammer
    I have the following class structure (abbreviated for sake of time, names changed) in my application. When I was writing the code I felt that the similarities between Action1 and Action2 should warrant some sort of generalization. I've provided the UML Class diagram with the relevant parts (except for the interfaces, which I describe in code below). I was wondering if anyone had an idea on how to make this "better" architecture / class design. Also, actions that are very similar could be implemented in a near-future iteration. Code for interfaces public IActor1 { public Property1 { get; set; } public Property2 { get; set; } } public IActor2 { public Property3 { get; set; } public Property2 { get; set; } }

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  • OSX Weak Linking - check if a class exists and use that class

    - by psychotik
    I'm trying to create a universal iPhone app, but it uses a class defined only in a newer version of the SDK. The framework exists on older systems, but a class defined in the framework doesn't. I know I want to use some kind of weak linking, but any documentation I can find talks about runtime checks for function existence - how do I check that a class exists?

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  • Python Vector Class

    - by sfjedi
    I'm coming from a C# background where this stuff is super easy—trying to translate into Python for Maya. There's gotta' be a better way to do this. Basically, I'm looking to create a Vector class that will simply have x, y and z coordinates, but it would be ideal if this class returned a tuple with all 3 coordinates and if you could edit the values of this tuple through x, y and z properties, somehow. This is what I have so far, but there must be a better way to do this than using an exec statement, right? I hate using exec statements. class Vector(object): '''Creates a Maya vector/triple, having x, y and z coordinates as float values''' def __init__(self, x=0, y=0, z=0): self.x, self.y, self.z = x, y, z def attrsetter(attr): def set_float(self, value): setattr(self, attr, float(value)) return set_float for xyz in 'xyz': exec("%s = property(fget=attrgetter('_%s'), fset=attrsetter('_%s'))" % (xyz, xyz, xyz))

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  • Unbelievable: Cannot cast from class X to its super class

    - by Phuong Nguyen de ManCity fan
    I'm encountering a very weird problem with Spring (3.0.1.RELEASE), TestNG (5.11) and Maven Surefire (2.5). I have a test class that extends a Spring helper class for testNG so that test context can be loaded from an xml file (that contains some bean definitions). My project was imported into eclipse using m2eclipse (using Import Maven Project) The class run fine in Eclipse TestNG runner. However, it throws this exception with Maven Surefire Caused by: java.lang.ClassCastException: com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl cannot be cast to javax.xml.parsers.DocumentBuilderFactory at javax.xml.parsers.DocumentBuilderFactory.newInstance(DocumentBuilderFactory.java:123) at org.springframework.beans.factory.xml.DefaultDocumentLoader.createDocumentBuilderFactory(DefaultDocumentLoader.java:89) at org.springframework.beans.factory.xml.DefaultDocumentLoader.loadDocument(DefaultDocumentLoader.java:70) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:388) I have eliminated all involved dependencies in my pom so that the two classes com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl and javax.xml.parsers.DocumentBuilderFactory are coming from JRE only (the rt.jar). So, it looks so unbelievable to me. I wonder if there is any mechanism in loading class that can explain for this behavior? Thanks.

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  • Change select's class based on selected option's class

    - by Alasdair
    I have a page that contains numerous <select> elements. What I'm trying to achieve is to ensure that if a <select>'s selected <option> has a class called italic, then the <select> then has the italic class added (i.e. jQuery.addClass('italic')). If it doesn't, then the italic class is removed from the <select> to ensure other <option> elements are displayed correctly (i.e. jQuery.removeClass('italic')). What I'm noticing with most of my attempts is that either all the <select> have the italic class or that the italic class isn't being removed accordingly. Since I'm unsure my choice in selectors and callback logic are particularly sound or good practice in this instance (as I've been frustratingly trying to make it work) I've decided not to include the code I used in previous attempts. Instead, refer to this small HTML & CSS example: .italic { font-style: italic; } <select id="foo" name="foo" size="1" <option value="NA" selected="selected" - Select - </option <option value="1"Bar</option <option value="2"Fu</option <option value="3"Baz</option </select Also, I am aware that not all browsers support CSS styling of <select> and <option>. The related J2EE web application will only ever be accessed via Firefox under a controlled environment.

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  • F#: Define an abstract class that inherits an infterface, but does not implement it

    - by akaphenom
    I owuld like to define an abstract class that inerhits from UserControl and my own Interface IUriProvider, but doesn't implement it. The goal is to be able to define pages (for silverlight) that implement UserControl but also provide their own Uri's (and then stick them in a list / array and deal with them as a set: type IUriProvider = interface abstract member uriString: String ; abstract member Uri : unit -> System.Uri ; end type UriUserControl() as this = inherit IUriProvider with abstract member uriString: String ; inherit UserControl() Also the Uri in the definition - I would like to implement as a property getter - and am having issues with that as well. this does not compile type IUriProvider = interface abstract member uriString: String with get; end Thank you...

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  • Dotnet website - class in one file can't access class in a different file

    - by bmutch
    I've inherited a web site I'm editing in dotnet and it won't compile because the class in one file (say class1.vb) refers to a class in another file (say class2) (like Dim m_c As class2) , but the compiler says "Type Class2 is not defined". when I look in the object browswer the classes are listed separately (i.e. not all grouped under the same namespace) and appear as: Public Class Class1 Inherits System.Object Member of C:...\mywebsite\ Help!, thanks.

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  • Inside a decorator-class, access instance of the class which contains the decorated method

    - by ifischer
    I have the following decorator, which saves a configuration file after a method decorated with @saveconfig is called: class saveconfig(object): def __init__(self, f): self.f = f def __call__(self, *args): self.f(object, *args) # Here i want to access "cfg" defined in pbtools print "Saving configuration" I'm using this decorator inside the following class. After the method createkvm is called, the configuration object self.cfg should be saved inside the decorator: class pbtools() def __init__(self): self.configfile = open("pbt.properties", 'r+') # This variable should be available inside my decorator self.cfg = ConfigObj(infile = self.configfile) @saveconfig def createkvm(self): print "creating kvm" My problem is that i need to access the object variable self.cfg inside the decorator saveconfig. A first naive approach was to add a parameter to the decorator which holds the object, like @saveconfig(self), but this doesn't work. How can I access object variables of the method host inside the decorator? Do i have to define the decorator inside the same class to get access?

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