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  • Generic property- specify the type at runtime

    - by Lirik
    I was reading a question on making a generic property, but I'm a little confused at by the last example from the first answer (I've included the relevant code below): You have to know the type at compile time. If you don't know the type at compile time then you must be storing it in an object, in which case you can add the following property to the Foo class: public object ConvertedValue { get { return Convert.ChangeType(Value, Type); } } That's seems strange: it's converting the value to the specified type, but it's returning it as an object when the value was stored as an object. Doesn't the returned object still require un-boxing? If it does, then why bother with the conversion of the type? I'm also trying to make a generic property whose type will be determined at run time: public class Foo { object Value {get;set;} Type ValType{get;set;} Foo(object value, Type type) { Value = value; ValType = type; } // I need a property that is actually // returned as the specified value type... public object ConvertedValue { get { return Convert.ChangeType(Value, ValType); } } } Is it possible to make a generic property? Does the return property still require unboxing after it's accessed?

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  • Can you cast an object to one that implements an interface? (JAVA)

    - by DDP
    Can you cast an object to one that implements an interface? Right now, I'm building a GUI, and I don't want to rewrite the Confirm/Cancel code (A confirmation pop-up) over and over again. So, what I'm trying to do is write a class that gets passed the class it's used in and tells the class whether or not the user pressed Confirm or Cancel. The class always implements a certain interface. Code: class ConfirmFrame extends JFrame implements ActionListener { JButton confirm = new JButton("Confirm"); JButton cancel = new JButton("Cancel"); Object o; public ConfirmFrame(Object o) { // Irrelevant code here add(confirm); add(cancel); this.o = (/*What goes here?*/)o; } public void actionPerformed( ActionEvent evt) { o.actionPerformed(evt); } } I realize that I'm probably over-complicating things, but now that I've run across this, I really want to know if you can cast an object to another object that implements a certain interface.

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  • C# Calling Methods in Generic Classes

    - by aip.cd.aish
    I am extending the ImageBox control from EmguCV. The control's Image property can be set to anything implementing the IImage interface. All of the following implement this interface: Image<Bgr, Byte> Image<Ycc, Byte> Image<Hsv, Byte> Now I want to call the Draw method on the object of the above type (what ever it may be). The problem is when I access the Image property, the return type is IImage. IImage does not implement the Draw method, but all of the above do. I believe I can cast the object of type IImage to one of the above (the right one) and I can access the Draw method. But how do I know what the right one is? If you have a better way of doing this, please suggest that as well.

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  • Cast element in Java For Each statement

    - by Carl Summers
    Is it possible (or even advisable) to cast the element retrieved from a for each statement in the statement itself? I do know that each element in list will be of type . I.E.: List<BaseType> list = DAO.getList(); for(<SubType> element : list){ // Cannot convert from element type <BaseType> to <SubType> ... } rather than: List <BaseType> list = DAO.getList(); for(<BaseType> el : list){ <SubType> element = (<SubType>)el; ... }

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  • C# generics method invocation

    - by Firat KÜÇÜK
    Hi, i have some polymorphic methods and i want to call via using an intermediate method. Following class is the simplified version of my program. class Program { public class A { } public class B { } public class C { } public void SomeMethod(A value) { Console.WriteLine("A value"); } public void SomeMethod(B value) { Console.WriteLine("B value"); } public void SomeMethod(C value) { Console.WriteLine("C value"); } static void Main(string[] args) { Program p = new Program(); // code block p.IntermediateMethod<A>(new A()); p.IntermediateMethod<B>(new B()); p.IntermediateMethod<C>(new C()); } public void IntermediateMethod<T>(T value) { // code block SomeMethod(value); // code block } }

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  • com.sun.org.apache.xerces.internal.dom.DocumentImpl cannot be cast to org.codehaus.plexus.util.xml.X

    - by Random
    Afetr using the Model library (see this) for my Maven pom.xml during this weeks I jumped on this error while attempting to write a ConfiguratonContainer into the pom.xml. The javadoc for Model says: public void setConfiguration(Object configuration) Set the configuration as DOM object. Parameters: configuration - So I made some xml with Document (org.w3c.dom.Document) and the xml parser standar javax library. You know the code (it's through all the net) but I paste it here... DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder parser = factory.newDocumentBuilder(); Document doc =parser.newDocument(); And then you fill the code with Element declaration,a lot of appendChild and such. And tried to make it work. Doesn't seem to do well. First tried using plugin.setConfiguration(doc); But it didn't work. Then I tried Obejct obj = doc; plugin.setConfiguration(obj); But it didn't work. Then I searched the net for answers, and guess... It didn't work. There are like 0 people using this library (maven.model) in all the net. So here am I again, asking the senseis for help. Where is my error? I have downloaded the source code of the library trying to see where is the error, but it seems to be ok (as should). I add the stackrace for reference java.lang.ClassCastException: com.sun.org.apache.xerces.internal.dom.DocumentImpl cannot be cast to org.codehaus.plexus.util.xml.Xpp3Dom at org.apache.maven.model.io.xpp3.MavenXpp3Writer.writePlugin(MavenXpp3Writer.java:1472) at org.apache.maven.model.io.xpp3.MavenXpp3Writer.writeBuild(MavenXpp3Writer.java:326) at org.apache.maven.model.io.xpp3.MavenXpp3Writer.writeModel(MavenXpp3Writer.java:1093) at org.apache.maven.model.io.xpp3.MavenXpp3Writer.write(MavenXpp3Writer.java:102) at com.mapfre.mutua.PDA.model.GeneratePOM.createPOM(GeneratePOM.java:28) at com.mapfre.mutua.PDA.prueba.MavenPOM.generatePOMWAR(MavenPOM.java:681) at com.mapfre.mutua.PDA.prueba.GenerarPOMMapfreAction.execute(GenerarPOMMapfreAction.java:36) at org.apache.struts.chain.commands.servlet.ExecuteAction.execute(ExecuteAction.java:58) at org.apache.struts.chain.commands.AbstractExecuteAction.execute(AbstractExecuteAction.java:67) at org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51) at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191) at org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:305) at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191) at org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283) at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913) at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462) at javax.servlet.http.HttpServlet.service(HttpServlet.java:647) at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:873) at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665) at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528) at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689) at java.lang.Thread.run(Unknown Source)

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  • How can I cast authoritatively in asp classic?

    - by Tchalvak
    In asp classic, the cint() function or procedure or whatever it is won't allow me to cast arbitrary strings, like "bob" or "null" or anything like that. Is there anything that will allow me to simply cast integers, numeric strings, and arbitrary strings to actual integers, with some sane default like 0 for strings?

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  • In a class with no virtual methods or superclass, is it safe to assume (address of first member vari

    - by Jeremy Friesner
    Hi all, I made a private API that assumes that the address of the first member-object in the class will be the same as the class's this-pointer... that way the member-object can trivially derive a pointer to the object that it is a member of, without having to store a pointer explicitly. Given that I am willing to make sure that the container class won't inherit from any superclass, won't have any virtual methods, and that the member-object that does this trick will be the first member object declared, will that assumption hold valid for any C++ compiler, or do I need to use the offsetof() operator (or similar) to guarantee correctness? To put it another way, the code below does what I expect under g++, but will it work everywhere? class MyContainer { public: MyContainer() {} ~MyContainer() {} // non-virtual dtor private: class MyContained { public: MyContained() {} ~MyContained() {} // Given that the only place Contained objects are declared is m_contained // (below), will this work as expected on any C++ compiler? MyContainer * GetPointerToMyContainer() { return reinterpret_cast<MyContainer *>(this); } }; MyContained m_contained; // MUST BE FIRST MEMBER ITEM DECLARED IN MyContainer int m_foo; // other member items may be declared after m_contained float m_bar; };

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  • Are there any C++ tools that detect misuse of static_cast, dynamic_cast, and reinterpret_cast?

    - by chrisp451
    The answers to the following question describe the recommended usage of static_cast, dynamic_cast, and reinterpret_cast in C++: http://stackoverflow.com/questions/332030/when-should-static-cast-dynamic-cast-and-reinterpret-cast-be-used Do you know of any tools that can be used to detect misuse of these kinds of cast? Would a static analysis tool like PC-Lint or Coverity Static Analysis do this? The particular case that prompted this question was the inappropriate use of static_cast to downcast a pointer, which the compiler does not warn about. I'd like to detect this case using a tool, and not assume that developers will never make this mistake.

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  • How to ANSI-C cast from unisigned int * to char *?

    - by user314290
    I want these two print functions to do the same thing: unsigned int Arraye[] = {0xffff,0xefef,65,66,67,68,69,0}; char Arrage[] = {0xffff,0xefef,65,66,67,68,69,0}; printf("%s", (char*)(2+ Arraye)); printf("%s", (char*)(2+ Arrage)); where Array is an unsigned int. Normally, I would change the type but, the problem is that most of the array is numbers, although the particular section should be printed as ASCII.

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  • Implicit Type Conversions in Reflection

    - by bradhe
    So I've written a quick bit of code to help quickly convert between business objects and view models. Not to pimp my own blog, but you can find the details here if you're interested or need to know. One issue I've run in to is that I have a custom collection type, ProductCollection, and I need to turn that in to a string[] in on my model. Obviously, since there is no default implicit cast, I'm getting an exception in my contract converter. So, I thought I would write the next little bit of code and that should solve the problem: public static implicit operator string[](ProductCollection collection) { var list = new List<string>(); foreach (var product in collection) { if (product.Id == null) { list.Add(null); } else { list.Add(product.Id.ToString()); } } return list.ToArray(); } However, it still fails with the same cast exception. I'm wondering if it has something to do with being in reflection? If so, is there anything that I can do here?? I'm open to architectural solutions, too!

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  • Converting 'x' value of a CGPoint ivar to NSTimeInterval?

    - by eco_bach
    Hi I have a velocity ivar defined as a CGPoint. I need to somehow extract just the 'x' value of velocity, and then use this to call-send a message to the following method signature -(void) adjustTimer:(NSTimeInterval*)newInterval How do I obtain just the 'x' value of a CGPoint? Do I then need to convert or cast this result before calling my adjustTimer method?

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  • C two functions in one with casts

    - by Favolas
    I have two functions that do the exact same thing but in two different types of struct and this two types of struct are very similar. Imagine I have this two structs. typedef struct nodeOne{ Date *date; struct nodeOne *next; struct nodeOne *prev; }NodeOne; typedef struct nodeTwo{ Date *date; struct nodeTwo *next; struct nodeTwo *prev; }NodeTwo; Since my function to destroy each of the list is almost the same (Just the type of the arguments are different) I would like to make just one function to make the two thins. I have this two functions void destroyListOne(NodeOne **head, NodeOne **tail){ NodeOne *aux; while (*head != NULL){ aux = *head; *head = (*head)->next; free(aux); } *tail = NULL; } and this one: void destroyListTwo(NodeTwo **head, NodeTwo **tail){ NodeTwo *aux; while (*head != NULL){ aux = *head; *head = (*head)->next; free(aux); } *tail = NULL; } Since they are very similar I thought making something like this: void destroyList(void **ini, void **end, int listType){ if (listType == 0) { NodeOne *aux; NodeOne head = (NodeOne) ini; NodeOne tail = (NodeOne) ed; } else { NodeTwo *aux; NodeTwo head = (NodeTwo) ini; NodeTwo tail = (NodeTwo) ed; } while (*head != NULL){ aux = *head; *head = (*head)->next; free(aux); } *tail = NULL; } As you may now this is not working but I want to know if this is possible to achieve. I must maintain both of the structs as they are.

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  • Data loss between conversion

    - by Alex Brooks
    Why is it that I loose data between the conversions below even though both types take up the same amount of space? If the conversion was done bitwise, it should be true that x = z unless data is being stripped during the conversion, right? Is there a way to do the two conversions without losing data (i.e. so that x = z)? main.cpp: #include <stdio.h> #include <stdint.h> int main() { double x = 5.5; uint64_t y = static_cast<uint64_t>(x); double z = static_cast<double>(y) // Desire : z = 5.5; printf("Size of double: %lu\nSize of uint64_t: %lu\n", sizeof(double), sizeof(uint64_t)); printf("%f\n%lu\n%f\n", x, y, z); } Results: Size of double: 8 Size of uint64_t: 8 5.500000 5 5.000000

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  • boost::shared_ptr<const T> to boost::shared_ptr<T>

    - by Flevine
    I want to cast the const-ness out of a boost::shared_ptr, but I boost::const_pointer_cast is not the answer. boost::const_pointer_cast wants a const boost::shared_ptr, not a boost::shared_ptr. Let's forego the obligitory 'you shouldn't be doing that'. I know... but I need to do it... so what's the best/easiest way to do it? For clarity sake: boost::shared_ptr<const T> orig_ptr( new T() ); boost::shared_ptr<T> new_ptr = magic_incantation(orig_ptr); I need to know the magic_incantation() Thanks!

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  • Need to cast to an object without knowing what type the object is

    - by jle
    I am trying to dynamically load my authentication server type based on a setting. I am hung up on how to cast to a type when I don't know the type. Type t = Type.GetType(WebConfigurationManager.AppSettings.Get("AuthenticationSvcImpl")); IAuthenticationService authCli = Activator.CreateInstance(t); return authCli.AuthenticateUser(login); I know there is Convert.ChangeType(), but that just converts to an object...

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  • Upcasting without any added data fields.

    - by Benjamin Manns
    In my project I have a generic Packet class. I would like to be able to upcast to other classes (like LoginPacket or MovePacket). The base class contains a command and arguments (greatly simplified): public class Packet { public String Command; public String[] Arguments; } I would like to have be able to convert from Packet to LoginPacket (or any other) based on a check if Packet.Command == "LOGIN". The login packet would not contain any new data members, but only methods for accessing specific arguments. For example: public class LoginPacket : Packet { public String Username { get { return Arguments[0]; } set { Arguments[0] == value; } } public String Password { get { return Arguments[1]; } set { Arguments[1] == value; } } } It would be great if I could run a simple code that would cast from Packet to LoginPacket with something like LoginPacket _Login = (LoginPacket)_Packet;, but that throws a System.InvalidCastException. It seems like this would be an easy task, as no new data is included, but I can't figure out any other way than copying everything from the Packet class to a new LoginPacket class.

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