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  • Write a tree class in Java where each level has a unique object type

    - by user479576
    I need to write a tree class in Java where each level has a unique object type. The way it is written below does not take advantage of generics and causes alot of duplicate code. Is there a way to write this with Generics ? public class NodeB { private String nodeValue; //private List<NodeB> childNodes; // constructors // getters/setters } public class NodeA { private String value; private List<NodeB> childNodes; // constructors // getters/setters } public class Tree { private String value; private List<NodeA> childNodes; // constructors // tree methods }

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  • Dynamic decision on which class to use

    - by Sirupsen
    Hello, Let's say I have a class named Klass, and a class called Klass2. Depending on the user's input, I'd like to decide whether I'll call "hello_world" on Klass, or Klass2: class Klass def self.hello_world "Hello World from Klass1!" end end class Klass2 def self.hello_world "Hello World from Klass2!" end end input = gets.strip class_to_use = input puts class_to_use.send :hello_world The user inputs "Klass2" and the script should say: Hello World from Klass2! Obviously this code doesn't work, since I'm calling #hello_world on String, but I'd like to call #hello_world on Klass2. How do I "convert" the string into a referrence to Klass2 (or whatever the user might input), or how could I else would I achieve this behavior?

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  • Should I pointer-cast from a private derived class to its base class?

    - by skydoor
    I found this from C++FAQ Generally, No. From a member function or friend of a privately derived class, the relationship to the base class is known, and the upward conversion from PrivatelyDer* to Base* (or PrivatelyDer& to Base&) is safe; no cast is needed or recommended. However users of PrivatelyDer should avoid this unsafe conversion, since it is based on a private decision of PrivatelyDer, and is subject to change without notice. How to understand the above words? I don't think the explanation is correct or accurate. I have a code like this class A{ }; class B: private A{ }; int main(){ B *b = new B(); A *a = new A(); a = b; //wrong a = (A*)b; //right }

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  • How to convert a void pointer to array of classes

    - by user99545
    I am trying to convert a void pointer to an array of classes in a callback function that only supports a void pointer as a means of passing paramaters to the callback. class person { std::string name, age; }; void callback (void *val) { for (int i = 0; i < 9; i++) { std::cout << (person [])val[i].name; } } int main() { person p[10]; callback((void*)p); } My goal is to be able to pass an array of the class person to the callback which then prints out the data such as their name and age. However, the compile does not like what I am doing and complains that error: request for member 'name' in 'val', which is of non-class type 'void*' How can I go about doing this?

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  • name of class that manipulates the entities

    - by cyberguest
    hi, i have a general question regarding naming convention. if I separate the data and operations into two separate classes. one has the data elements (entity), the other class manipulates the entity class. what do we usually call that class that manipulates the entity class? (the entity I am referring to has nothing to do with any kind of entity framework) manager? controller? operator? manipulator? thanks in advance

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  • Operator & and * at function prototipe in class

    - by Puyover
    I'm having a problem with a class like this: class Sprite { ... bool checkCollision(Sprite &spr); ... }; So, if I have that clase, I can do this: ball.checkCollision(bar1); But if I change the class to this: class Sprite { ... bool checkCollision(Sprite* spr); ... }; I have to do this: ball.checkCollision(&bar1); So, what's the difference?? It's better a way instead other? Thank you.

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  • A generic Find method to search by Guid type for class implementing IDbSet interface

    - by imak
    I am implementing a FakeDataSet class by implementing IDbSet interface. As part of implementing this interface, I have to implement Find method. All my entity classes has an Guid type Id column. I am trying to implement Find method for this FakeDbSet class but having hard time to write it in a generic way. Below is my attempts for writing this method but since it does not know about Id been Guid type, I am getting compilation error on m.Id call. Any ideas on how this could be accomplished? public class FakeDataSet<T> : IDbSet<T> where T: class, new() { // Other methods for implementing IDbSet interface public T Find(params object[] keyValues) { var keyValue = (Guid)keyValues.FirstOrDefault(); return this.SingleOrDefault(m => m.Id == keyValue); // How can I write this } }

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  • Why delegate types are derived from MulticastDelegate class why not it directly derive from Delegate class?

    - by Vijay
    I have a very basic question regarding delegate types. I compared the memebers of Delegate and MulticastDelegate classes in object browser and I couldn't find any new additional member present in MulticastDelegate. I also noticed that the Delegate class has GetInvocationList virtual method. So I assume that the Delegate class should have the capability to hold references to multiple methods. If my assumption is correct I wonder why not custom delegate types directly derive from the Delegate class instead of MulticastDelegate class. Not sure what I am missing here. Please help me understand the difference.

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  • Normalized class design and code first

    - by dc7a9163d9
    There are the following two classes. public class Employee { int EmployeeId { get; set; } public string FirstName { get; set; } public string LastName { get; set; } public string Street { get; set; } public string Street2 { get; set; } public string City { get; set; } public string State { get; set; } public string Zip { get; set; } } public class Company { int CompanyId { get; set; } public string Name { get; set; } public string Street { get; set; } public string Street2 { get; set; } public string City { get; set; } public string State { get; set; } public string Zip { get; set; } } In a DDD seminar, the speaker said the better design should be, class PersonName { public string FirstName { get; set; } public string LastName { get; set; } } class Address { public string Street { get; set; } public string Street2 { get; set; } public string City { get; set; } public string State { get; set; } public string Zip { get; set; } } public class Employee { int EmployeeId { get; set; } public PersonName Name { get; set; } [ForeignKey("EmployerAddress")] public int EmployerAddressId { get; set; } public virtual Address EmployerAddress { get; set; } } public class Company { int CompanyId { get; set; } public string Name { get; set; } [ForeignKey("CompanyAddress")] public int CompanyAddressId { get; set; } public virtual Address CompanyAddress { get; set; } } Is it the optimized design? How the code first generate the PersonName table and link it to Employee?

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  • Will [WithEvents = Nothing] RemoveHandlers in the derived class?

    - by serhio
    I use to set WithEvents variables to Nothing in Destuctor, because this will "Remove" all the Handlers associated with Handles keyword. Will this have the same effect for derivated classes? Class A Protected WithEvents _Foo as Button Private Sub _Foo_Click Handles _Foo.Click ' ... some Click action ' End Sub Public Sub Dispose(disposing as Boolean) If disposing then _Foo = Nothing ' remove handler _Foo_Click ' End Sub End Class Class B Inherits A Private Sub _Foo_Move Handles _Foo.Move ' ... some Move action ' End Sub ' ????? will or NOT remove OR handler _Foo_Move the base Dispose??' Public Overrides Sub Dispose(disposing as Boolean) 'If disposing then _Foo = Nothing ' MyBase.Dispose(disposing) End Sub End Class

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  • Namespace and class conflict(?)

    - by dan gibson
    This is a bad title for the question, but I'm not quite sure of a better one. I have a namespace called Globals with a class X in it. I also have a class called Globals. When I try to access Globals.X.StaticMember it tries to access the class Globals.X and complains that X doesn't exist. How do I reference the namespace Globals - ie ::Globals.X.StaticMember (:: doesn't compile).

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  • private virtual function in derived class

    - by user1706047
    class base { public: virtual void doSomething() = 0; }; class derived : public base { **private:** virtual void doSomething(){cout<<"Derived fn"<<endl;} }; now if i do the following: base *b=new child; b->doSomething(); //it calls the derived class fn even if that is private. Question: 1.its able to call the derived class fn even if that is private.How is it possible? Now if i change the inheritance access specifier from public to protected/private then i get compilation error as "'type cast' : conversion from 'Derived *' to 'base *' exists, but is inaccessible" Notes: I am aware on the concepts of the inheritance access specifiers.So in second case as its derived private/protected, its inaccessible. But here it confuses me for the first question. Any input will be highly appreciated

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  • Member classes versus #includes

    - by ShallowThoughts
    I've recently discovered that it is bad form to have #includes in your header files because anyone who uses your code gets all those extra includes they won't necessarily want. However, for classes that have member variables defined as a type of another class, what's the alternative? For example, I was doing things the following way for the longest time: /* Header file for class myGrades */ #include <vector> //bad #include "classResult.h" //bad class myGrades { vector<classResult> grades; int average; int bestScore; } (Please excuse the fact that this is a highly artificial example) So, if I want to get rid of the #include lines, is there any way I can keep the vector or do I have to approach programming my code in an entirely different way?

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  • How to get the PropertyName of a class?

    - by Mike108
    How to get the PropertyName of a class? For example, How can I get the PropertyName "StudentName" of a Student class instance. public class Student { public string StudentName{get;set;} } Student student = new Student(); //I want to get the PropertyName "StudentName" student.StudentName.GetName();

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  • Player & Level class structure in 2D python console game?

    - by Markus Meskanen
    I'm trying to create a 2D console game, where I have a player who can freely move around in a level (~map, but map is a reserved keyword) and interfere with other objects. Levels construct out of multiple Blocks, such as player(s), rocks, etc. Here's the Block class: class Block(object): def __init__(self, x=0, y=0, char=' ', solid=False): self.x = x self.y = y self.char = char self.solid = solid As you see, each block has a position (x, y) and a character to represent the block when it's printed. Each block also has a solid attribute, defining whether it can overlap with other solids or not. (Two solid blocks cannot overlap) I've now created few subclasses from Block (Rock might be useless for now) class Rock(Block): def __init__(self, x=0, y=0): super(Rock, self).__init__(x, y, 'x', True) class Player(Block): def __init__(self, x=0, y=0): super(Player, self).__init__(x, y, 'i', True) def move_left(self, x=1): ... # How do I make sure Player wont overlap with rocks? self.x -= x And here's the Level class: class Level(object): def __init__(self, name='', blocks=None): self.name = name self.blocks = blocks or [] Only way I can think of is to store a Player instance into Level's attributes (self.player=Player(), or so) and then give Level a method: def player_move_left(self): for block in self.blocks: if block.x == self.player.x - 1 and block.solid: return False But this doesn't really make any sense, why have a Player class if it can't even be moved without Level? Imo. player should be moved by a method inside Player. Am I wrong at something here, if not, how could I implement such behavior?

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  • Error Installing COM+ (Error Code: 80131501)

    - by Regina Foo
    I've written a class library that reads from an xml file and return the result as a string. But when I want to install it as a COM+ component, an error occurred (Error Code: 80131501). I checked the event log and the details of the error is: Installation of 'C:\Users\User\Documents\Visual Studio 2005\Projects\InteropSOA\InteropSOA\bin\Debug\InteropSOA.dll' into '{28E82165-AD74-4E16-90C9-0C5CE7DA97AA}' failed with an exception: System.EnterpriseServices.RegistrationException: FATAL: Could not find component 'InteropSOA.ConfigReader' we just installed. at System.EnterpriseServices.RegistrationDriver.InstallAssembly(RegistrationConfig regConfig, Object obSync) at System.EnterpriseServices.RegistrationHelper.InstallAssemblyFromConfig(RegistrationConfig& regConfig) at System.EnterpriseServices.RegistrationHelper.InstallAssembly(String assembly, String& application, String partition, String& tlb, InstallationFlags installFlags) at System.EnterpriseServices.Internal.ComManagedImportUtil.InstallAssembly(String asmpath, String parname, String appname) Below are the steps I've done while developing the class library: Added "System.EnterpriseServices" to Reference. Imported the reference to the class. Declared the class as "ServicedComponent". Set project properties ("Make assembly COM-visible" checked, "Register for COM Interop" checked, Signed the assembly with a strong key file name.) Here are my codes: using System; using System.Collections.Generic; using System.Text; using System.Xml; using System.Xml.XPath; using System.EnterpriseServices; namespace InteropSOA { public class ConfigReader : ServicedComponent { // xml file name private string strFileName; // type of request private string strRequest = ""; // response string private string strResponse = ""; // declarations for xPath private XPathDocument doc; private XPathNavigator nav; private XPathExpression expr; private XPathNodeIterator iterator; private XmlTextReader reader; private XmlDocument xmlDoc; public ConfigReader(string strFile, string request) { this.strFileName = strFile; this.strRequest = request; } public ConfigReader() { //default contructor } // reader for console program public void ReadXML() { doc = new XPathDocument(strFileName); nav = doc.CreateNavigator(); // compile xPath expression expr = nav.Compile("/Msg/" + strRequest + "/*"); iterator = nav.Select(expr); // interate on the node set try { while (iterator.MoveNext()) { XPathNavigator nav2 = iterator.Current.Clone(); strResponse += nav2.Value + "|"; } } catch (Exception ex) { Console.WriteLine(ex.Message); } strResponse = strResponse.Substring(0, strResponse.Length-1); Console.WriteLine("Response string = " + strResponse); } public void WriteXML(string strRequest, string strElement, string strValue) { reader = new XmlTextReader(strFileName); xmlDoc = new XmlDocument(); xmlDoc.Load(reader); reader.Close(); XmlNode node; XmlElement root = xmlDoc.DocumentElement; node = root.SelectSingleNode("/Msg/" + strRequest + "/" + strElement); node.InnerText = strValue; xmlDoc.Save(strFileName); } // reader for ASP.NET public string ReadXMLElement() { doc = new XPathDocument(strFileName); nav = doc.CreateNavigator(); // compile xPath expression expr = nav.Compile("/Msg/" + strRequest + "/*"); iterator = nav.Select(expr); // interate on the node set try { while (iterator.MoveNext()) { XPathNavigator nav2 = iterator.Current.Clone(); strResponse += nav2.Value + "|"; } } catch (Exception ex) { Console.WriteLine(ex.Message); } strResponse = strResponse.Substring(0, strResponse.Length - 1); return strResponse; } } }

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  • Template problems: No matching function for call

    - by Nick Sweet
    I'm trying to create a template class, and when I define a non-member template function, I get the "No matching function for call to randvec()" error. I have a template class defined as: template <class T> class Vector { T x, y, z; public: //constructors Vector(); Vector(const T& x, const T& y, const T& z); Vector(const Vector& u); //accessors T getx() const; T gety() const; T getz() const; //mutators void setx(const T& x); void sety(const T& y); void setz(const T& z); //operations void operator-(); Vector plus(const Vector& v); Vector minus(const Vector& v); Vector cross(const Vector& v); T dot(const Vector& v); void times(const T& s); T length() const; //Vector<T>& randvec(); //operators Vector& operator=(const Vector& rhs); friend std::ostream& operator<< <T>(std::ostream&, const Vector<T>&); }; and the function in question, which I've defined after all those functions above, is: //random Vector template <class T> Vector<double>& randvec() { const int min=-10, max=10; Vector<double>* r = new Vector<double>; int randx, randy, randz, temp; const int bucket_size = RAND_MAX/(max-min +1); temp = rand(); //voodoo hackery do randx = (rand()/bucket_size)+min; while (randx < min || randx > max); r->setx(randx); do randy = (rand()/bucket_size)+min; while (randy < min || randy > max); r->sety(randy); do randz = (rand()/bucket_size)+min; while (randz < min || randz > max); r->setz(randz); return *r; } Yet, every time I call it in my main function using a line like: Vector<double> a(randvec()); I get that error. However, if I remove the template and define it using 'double' instead of 'T', the call to randvec() works perfectly. Why doesn't it recognize randvec()? P.S. Don't mind the bit labeled voodoo hackery - this is just a cheap hack so that I can get around another problem I encountered.

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  • design suggestion for a message decoder in delphi

    - by stanleyxu2005
    Hi All, I want to implement a RPC module. Different requests are encoded as JSON objects. They will be decoded and then be handled by a request handler. At last a corresponding response will be returned. The demo code looks as follows: type IRequestHandler = interface function Handle(const Request: TAaaRequest): TResponse; function Handle(const Request: TBbbRequest): TResponse; end; TDecoder = class class function Decode(const Json: TJsonObject; const RequestHandler: IRequestHandler): TResponse; end; class function TDecoder.Decode(const Json: TJsonObject; const RequestHandler: IRequestHandler): TResponse; var Method: string; Request: TObject; begin Method := Json['method'].AsString; if (Method = TAaaRequest.ClassName) then begin Request := TAaaRequest.FromJSON(Json); // Casted as TObject if Request <> nil then begin Result := RequestHandler.Handle(TAaaRequest(Request)); Request.Free; end; end else if (Method = TBbbRequest.ClassName) then begin Request := TBbbRequest.FromJSON(Json); // Casted as TObject if Request <> nil then begin Result := RequestHandler.Handle(TBbbRequest(Request)); Request.Free; end; end else Result := CreateErrorResponse('Unknown method: ' + Json.ToString); end; According to the code, the handling of different request types are very similar. If I have 100 different request types, I have to copy and paste the above code block 100 times. This is not clever. I am looking for a better way to do the same logic. My imagination is as follows: TDecoder = class private FRequestTypes: TDictionary<string, TClassInfo>; // Does this work? public constructor Create; destructor Destroy; override; function Decode(const Json: TJsonObject; const RequestHandler: IRequestHandler): TResponse; end; constructor TDecoder.Create; begin FRequestTypes := TDictionary<string, TClassInfo>.Create; FRequestTypes.Add(TAaaRequest.ClassName, TAaaRequest); // Does this work? FRequestTypes.Add(TBbbRequest.ClassName, TBbbRequest); end; destructor TDecoder.Destroy; begin FRequestTypes.Free; inherited; end; function TDecoder.Decode(const Json: TJsonObject; const RequestHandler: IRequestHandler): TResponse; var Method: string; Info: TClassInfo; Request: TObject; begin Method := Json['method'].AsString; if FRequestTypes.ContainsKey(Method) then begin // An universal way Info := FRequestTypes[Method]; Request := Info.FromJSON(Json); // Casted as TObject if Request <> nil then begin Result := RequestHandler.Handle(Info(Request)); // Casted to corresponding class type (e.g. TAaaRequest or TBbbRequest) Request.Free; end; end else Result := CreateErrorResponse('Unknown method: ' + Json.ToString); end; I do not know, if I can write an universal way to handle a great number of different request types. Development environment Delphi 2010. Any hint is appreciated.

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  • Routing static IP traffic on a Comcast Business Class IP Gateway (SMCD3G-CCR)

    - by Jakobud
    We are in the process of replacing our firewall, which is currently the only thing connected to our Comcast Business Class modem. Comcast gives us 5 static IP addresses. Currently, all traffic to all 5 static IPs goes directly to the existing firewall. Eventually, obviously all traffic will goto the new firewall, once the old firewall is removed from the network. But in the meantime, as we will have two firewalls plugged into the same Comcast modem, I need to route certain traffic to the new firewall instead of the old one. The firewall switchover is going to be slow and gradual as I am testing it, so I can't simply unplug the existing firewall and plug in the new one. So my question is, how do I tell the modem to route all traffic that goes to a specific IP to goto the new firewall instead of the old one? I've logged into the web interface for the modem, but the available options aren't very clear. There is a 1-to-1 NAT option (which I can't seem to get the interface for it to work properly) but I also see a "Static Routing" section. I always understood Static Routing to refer to routing data within the LAN though, so I'm not sure if that's what I'm looking for or not. Keep in mind, I'm not looking to do simple port forwarding. I'm wanting 100% of traffic to certain public static IPs to go to the specified connected firewall (I'll deal with service policies there). The modem is an SMC SMCD3G-CCR and is labeled as a Comcast Business Class Business IP Gateway. Any help or direction would be greatly appreciated.

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  • Changing subnet-mask of class-c network host to 255.255.0.0

    - by Prashant Mandhare
    We have a existing class-c network with IP address range 11.22.33.44/24 (just for example). My domain controller has been configured within this subnet. So all servers within this subnet have subnet mask configured to 255.255.255.0. Now we have got a new subnet with IP address 11.22.88.99/24 (note that only last 2 octets have changed). I want all new hosts in this new subnet to join my existing DC. For this we have configured firewall properly so allow this. (so there is no issue with firewall). But initially I was not able to join hosts in new subnet in existing domain. Later I doubted on subnet mask used in domain controller (255.255.255.0) and for testing purpose I changed it to 255.255.0.0, it worked like charm, i was able to join subnet-2 hosts in subnet-1 domain. Now i am wondering whether it will be good practice to change subnet mask of a class-c network to 255.255.0.0? Can any issues arise due to this? Experts please provide your opinion.

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