Search Results

Search found 7420 results on 297 pages for 'generic collections'.

Page 51/297 | < Previous Page | 47 48 49 50 51 52 53 54 55 56 57 58  | Next Page >

  • How can the generic method called know the type of the generic return?

    - by Paulo Guedes
    I couldn't find a duplicate for this question for Java, although there are a lot of them for C#. I have this method: public <T> T getSomething() { // } According to the type of T, I will have a different return. For example: String a = getSomething(); int b = getSomething(); For a, my method will return a specific String. For b, it will return a specific int. And so on. It seems that this can be done with typeof() in C#. How can I achieve it in Java?

    Read the article

  • Serialization of generic types - GWT

    - by sarav
    I have an interface like this public interface IField<T> extends IsSerializable { public String getKey(); public void setKey(String name); public T getValue(); public void setValue(T role); } And a class like this public class FieldImpl<T> implements IField<T> { private String key; public String getKey() { return key; } public void setKey(String key) { this.key = key; } public T getValue() { return value; } public void setValue(T value) { this.value = value; } private T value; public FieldImpl() { } public FieldImpl(String key, T value) { super(); this.key = key; this.value = value; } } When I try to compile I'm getting [ERROR] In order to produce smaller client-side code, 'Object' is not allowed; please use a more specific type (reached via server.sdk.model.IField) What is the cause for this? Is there any place I can read about GWT's generics support?

    Read the article

  • Function templates for arbitrary STL containers containing arbitrary types.

    - by Chad Brewbaker
    I have an arbitrary STL container C, which contains elements of an arbitrary type T. I want to create an std::vector that has a copy of all the elements. What is the cleanest way to do this? template <typename C> void myfunction(C container){ /*Derive the type T of elements within the container*/ std::vector<T> mystack; /* Iterate over container and push_back() the elements into mystack*/ }

    Read the article

  • How do you pass a generic delegate argument to a method in .NET 2.0

    - by Seth Spearman
    Hello, I have a class with a delegate declaration as follows... Public Class MyClass Public Delegate Function Getter(Of TResult)() As TResult 'the following code works. Public Shared Sub MyMethod(ByVal g As Getter(Of Boolean)) 'do stuff End Sub End Class However, I do not want to explicitly type the Getter delegate in the Method call. Why can I not declare the parameter as follows... ... (ByVal g As Getter(Of TResult)) Is there a way to do it? My end goal was to be able to set a delegate for property setters and getters in the called class. But my reading indicates you can't do that. So I put setter and getter methods in that class and then I want the calling class to set the delegate argument and then invoke. Is there a best practice for doing this. I realize in the above example that I can set set the delegate variable from the calling class...but I am trying to create a singleton with tight encapsulation. For the record, I can't use any of the new delegate types declared in .net35. Answers in C# are welcome. Any thoughts? Seth

    Read the article

  • Control XML serialization of generic types

    - by Luca
    I'm investigating about XML serialization, and since I use lot of dictionary, I would like to serialize them as well. I found the following solution for that (I'm quite proud of it! :) ). [XmlInclude(typeof(Foo))] public class XmlDictionary<TKey, TValue> { /// <summary> /// Key/value pair. /// </summary> public struct DictionaryItem { /// <summary> /// Dictionary item key. /// </summary> public TKey Key; /// <summary> /// Dictionary item value. /// </summary> public TValue Value; } /// <summary> /// Dictionary items. /// </summary> public DictionaryItem[] Items { get { List<DictionaryItem> items = new List<DictionaryItem>(ItemsDictionary.Count); foreach (KeyValuePair<TKey, TValue> pair in ItemsDictionary) { DictionaryItem item; item.Key = pair.Key; item.Value = pair.Value; items.Add(item); } return (items.ToArray()); } set { ItemsDictionary = new Dictionary<TKey,TValue>(); foreach (DictionaryItem item in value) ItemsDictionary.Add(item.Key, item.Value); } } /// <summary> /// Indexer base on dictionary key. /// </summary> /// <param name="key"></param> /// <returns></returns> public TValue this[TKey key] { get { return (ItemsDictionary[key]); } set { Debug.Assert(value != null); ItemsDictionary[key] = value; } } /// <summary> /// Delegate for get key from a dictionary value. /// </summary> /// <param name="value"></param> /// <returns></returns> public delegate TKey GetItemKeyDelegate(TValue value); /// <summary> /// Add a range of values automatically determining the associated keys. /// </summary> /// <param name="values"></param> /// <param name="keygen"></param> public void AddRange(IEnumerable<TValue> values, GetItemKeyDelegate keygen) { foreach (TValue v in values) ItemsDictionary.Add(keygen(v), v); } /// <summary> /// Items dictionary. /// </summary> [XmlIgnore] public Dictionary<TKey, TValue> ItemsDictionary = new Dictionary<TKey,TValue>(); } The classes deriving from this class are serialized in the following way: <XmlProcessList xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <Items> <DictionaryItemOfInt32Foo> <Key/> <Value/> </DictionaryItemOfInt32XmlProcess> <Items> This give me a good solution, but: How can I control the name of the element DictionaryItemOfInt32Foo What happens if I define a Dictionary<FooInt32, Int32> and I have the classes Foo and FooInt32? Is it possible to optimize the class above? THank you very much!

    Read the article

  • Generic Constraints And Type Parameters Mess

    - by Dummy01
    Hi everyone, I have the following base abstract class defined as: public abstract class BaseObject<T> : IComparable, IComparable<T>, IEquatable<T> {} I also have an interface defined as: public interface ICode<T> where T : struct { T Code { get; } } Now I want to derive a class that is inherited from BaseObject<T> and includes interface ICode<T>. I tried to define it like that: public class DerivedObject<T, U> : BaseObject<T>, ICode<U> where T : DerivedObject<T, U> where U : struct { public DerivedObject(U code) { Code = code; } // From BaseObject protected override int InstanceCompareTo(T obj) { return Code.CompareTo(obj.Code); } // From BaseObject protected override bool InstanceEquals(T obj) { return Code.Equals(obj.Code); } // From ICode U _Code; public U Code { get { return _Code; } protected set { _Code = value; } } } The only error that comes from the compiler is for Code.CompareTo(obj.Code) with the message: 'U' does not contain a definition for 'CompareTo' and no extension method 'CompareTo' accepting a first argument of type 'U' could be found. But U is a value type and should know CompareTo. Have you any idea what I am doing wrong, or if I do all wrong? My final aim is to derive classes such these: public class Account : DerivedObject<Account, int> public class ItemGroup : DerivedObject<ItemGroup, string> Big Thanks In Advance!

    Read the article

  • How to bind a ComboBox to generic dictionary with xaml code

    - by MMD MNC
    I'm using the following code : private Dictionary<string, string> GetNumber { get; set; } public ReportsLetterTra() { GetMonth = new Dictionary<string, string> { {"1", "First"}, {"2", "Second"} }; InitializeComponent(); } xaml code : <ComboBox DisplayMemberPath="value" SelectedValuePath="key" ItemsSource="{Binding ElementName=reportslettra,Path=GetNumber}" SelectedIndex="0" Name="cmbFromNumber" /> Why is not bind GetNumber to cmbFromNumber?!

    Read the article

  • Adding items to a generic list (novice)

    - by Crash893
    I'm some what embarrassed to even ask this but I know there is a better way to do this I just don't know how List<int> numbers = new List<int>(22); numbers.Add(3); numbers.Add(4); numbers.Add(9); numbers.Add(14); numbers.Add(15); numbers.Add(19); numbers.Add(28); numbers.Add(37); numbers.Add(47); numbers.Add(50); numbers.Add(54); numbers.Add(56); numbers.Add(59); numbers.Add(61); numbers.Add(70); numbers.Add(73); numbers.Add(78); numbers.Add(81); numbers.Add(92); numbers.Add(95); numbers.Add(97); numbers.Add(99);

    Read the article

  • Method not being resolved for dynamic generic type

    - by kelloti
    I have these types: public class GenericDao<T> { public T Save(T t) { return t; } } public abstract class DomainObject { // Some properties protected abstract dynamic Dao { get; } public virtual void Save() { var dao = Dao; dao.Save(this); } } public class Attachment : DomainObject { protected dynamic Dao { get { return new GenericDao<Attachment>(); } } } Then when I run this code it fails with RuntimeBinderException: Best overloaded method match for 'GenericDAO<Attachment.Save(Attachment)' has some invalid arguments var obj = new Attachment() { /* set properties */ }; obj.Save(); I've verified that in DomainObject.Save() "this" is definitely Attachment, so the error doesn't really make sense. Can anyone shed some light on why the method isn't resolving? Some more information - It succeeds if I change the contents of DomainObject.Save() to use reflection: public virtual void Save() { var dao = Dao; var type = dao.GetType(); var save = ((Type)type).GetMethod("Save"); save.Invoke(dao, new []{this}); }

    Read the article

  • [VB.Net] Typecasting generic parameters.

    - by CFP
    Hello world! Using the following code: Function GetSetting(Of T)(ByVal SettingName As String, ByRef DefaultVal As T) As T Return If(Configuration.ContainsKey(SettingName), CType(Configuration(SettingName), T), DefaultVal) End Function Yields the following error: Value of type 'String' cannot be converted to 'T'. Any way I could specify that in all cases, the conversion will indeed be possible (I'm basically getting integers, booleans, doubles and strings). Thanks!

    Read the article

  • How to specify generic method type parameters partly

    - by DNNX
    I have an extension method like below: public static T GetValueAs<T, R>(this IDictionary<string, R> dictionary, string fieldName) where T : R { R value; if (!dictionary.TryGetValue(fieldName, out value)) return default(T); return (T)value; } Currently, I can use it in the following way: var dictionary = new Dictionary<string, object(); //... var list = dictionary.GetValueAs<List<int, object("A"); // this may throw ClassCastException - this is expected behavior; It works pretty fine, but the second type parameter is really annoying. Is it possible in C# 4.0 rewrite GetValueAs is such a way that the method will still be applicable to different types of string-keyed dictionaries AND there will be no need to specify second type parameter in the calling code, i.e. use var list = dictionary.GetValueAs<List<int("A"); or at least something like var list = dictionary.GetValueAs<List<int, ?("A"); instead of var list = dictionary.GetValueAs<List<int, object("A");

    Read the article

  • Iterating over member typed collection fails when using untyped reference to generic object

    - by Alexander Pavlov
    Could someone clarify why iterate1() is not accepted by compiler (Java 1.6)? I do not see why iterate2() and iterate3() are much better. This paragraph is added to avoid silly "Your post does not have much context to explain the code sections; please explain your scenario more clearly." protection. import java.util.Collection; import java.util.HashSet; public class Test<T> { public Collection<String> getCollection() { return new HashSet<String>(); } public void iterate1(Test test) { for (String s : test.getCollection()) { // ... } } public void iterate2(Test test) { Collection<String> c = test.getCollection(); for (String s : c) { // ... } } public void iterate3(Test<?> test) { for (String s : test.getCollection()) { // ... } } } Compiler output: $ javac Test.java Test.java:11: incompatible types found : java.lang.Object required: java.lang.String for (String s : test.getCollection()) { ^ Note: Test.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. 1 error

    Read the article

  • Generic applet style system for publishing mathematics demonstrations?

    - by Alex
    Anyone who's tried to study mathematics using online resources will have come across these Java applets that demonstrate a particular mathematical idea. Examples: http://www.math.ucla.edu/~tao/java/Mobius.html http://www.mathcs.org/java/programs/FFT/index.html I love the idea of this interactive approach because I believe it is very helpful in conveying mathematical principles. I'd like to create a system for visually designing and publishing these 'mathlets' such that they can be created by teachers with little programming experience. So in order to create this app, i'll need a GUI and a 'math engine'. I'll probably be working with .NET because thats what I know best and i'd like to start experimenting with F#. Silverlight appeals to me as a presentation framework for this project (im not worried about interoperability right now). So my questions are: does anything like this exist already in full form? are there any GUI frameworks for displaying mathematical objects such as graphs & equations? are there decent open source libraries that exposes a mathematical framework (Math.NET looks good, just wondering if there is anything else out there) is there any existing work on taking mathematical models/demos built with maple/matlab/octave/mathematica etc and publishing them to the web?

    Read the article

  • C#. Saving information about events and event handlers and removing handlers using this information

    - by Philipp
    I have an object which is creating several event handlers using lambda expressions, and I need to remove all handlers created in that object in one time. I'm trying to create some unified static object which will 'know' which handler relates to which object and event if event handler was created through this static object. I tried something like code below, but I don't understand how to save events and event handlers objects, to be able remove handlers in one time. class Program { static void Main(string[] args) { var EventSender = new EventSender(); var EventReceiver = new EventReceiver(EventSender); EventSender.Invoke(" some var "); LinkSaver.RemoveEvent(EventReceiver); // ?? Console.ReadKey(); } } public class ObjLink{ public object Event; public object Action; } public static class LinkSaver { public static void SetEvent<T>(object obj, Action<T> Event, T Action) { Event(Action); var objLink = new ObjLink{Event = Event, Action = Action}; if (!Links.ContainsKey(obj)) Links.Add(obj, new List<ObjLink>{objLink}); else Links[obj].Add(objLink); } static Dictionary<object,List<ObjLink>> Links = new Dictionary<object, List<ObjLink>>(); public static void RemoveEvent(object obj){ foreach(var objLink in Links[obj]){ // objLink.Event -= objLink.Action; ??? } } } public class EventReceiver { public EventReceiver(EventSender obj) { LinkSaver.SetEvent<EventSender.TestDelegate>(this, obj.SetEvent, str => Console.WriteLine(str + " test event!")); } } public class EventSender { public void Invoke(string var) { if (eventTest != null) eventTest(var); } public void SetEvent(TestDelegate Action) { eventTest += Action; } public delegate void TestDelegate(string var); private event TestDelegate eventTest; // by the way public void RemoveFromEvent() { foreach (var handler in eventTest.GetInvocationList()) eventTest -= (TestDelegate)handler; } }

    Read the article

  • removing items from a generic List<t>

    - by frosty
    I have the following method, I wish to remove items from my collection that match the product Id. Seems fairly straight forward, but i get an exception. Basically my collection is getting out of sync. So what is the best way to remove an item from a collection. public void RemoveOrderItem(Model.Order currentOrder, int productId) { foreach (var orderItem in currentOrder.OrderItems) { if (orderItem.Product.Id == productId) { currentOrder.OrderItems.Remove(orderItem); } } } Exception Details: System.InvalidOperationException: Collection was modified; enumeration operation may not execute

    Read the article

  • Map inheritance from generic class in Linq To SQL

    - by Ksenia Mukhortova
    Hi everyone, I'm trying to map my inheritance hierarchy to DB using Linq to SQL: Inheritance is like this, classes are POCO, without any LINQ to SQL attributes: public interface IStage { ... } public abstract class SimpleStage<T> : IStage where T : Process { ... } public class ConcreteStage : SimpleStage<ConcreteProcess> { ... } Here is the mapping: <Database Name="NNN" xmlns="http://schemas.microsoft.com/linqtosql/mapping/2007"> <Table Name="dbo.Stage" Member="Stage"> <Type Name="BusinessLogic.Domain.IStage"> <Column Name="ID" Member="ID" DbType="Int NOT NULL IDENTITY" IsPrimaryKey="true" IsDbGenerated="true" AutoSync="OnInsert" /> <Column Name="StageType" Member="StageType" IsDiscriminator="true" /> <Type Name="BusinessLogic.Domain.SimpleStage" IsInheritanceDefault="true"> <Type Name="BusinessLogic.Domain.ConcreteStage" IsInheritanceDefault="true" InheritanceCode="1"/> </Type> </Type> </Table> </Database> In the runtime I get error: System.InvalidOperationException was unhandled Message="Mapping Problem: Cannot find runtime type for type mapping 'BusinessLogic.Domain.SimpleStage'." Neither specifying SimpleStage, nor SimpleStage<T> in mapping file helps - runtime keeps producing different types of errors. DC is created like this: StreamReader sr = new StreamReader(@"MappingFile.map"); XmlMappingSource mapping = XmlMappingSource.FromStream(sr.BaseStream); DataContext dc = new DataContext(@"connection string", mapping); If Linq to SQL doesn't support this, could you, please, advise some other ORM, which does. Thanks in advance, Regards! Ksenia

    Read the article

  • C++ creating generic template function specialisations

    - by Fire Lancer
    I know how to specialise a template function, however what I want to do here is specialise a function for all types which have a given method, eg: template<typename T> void foo(){...} template<typename T, if_exists(T::bar)>void foo(){...}//always use this one if the method T::bar exists T::bar in my classes is static and has different return types. I tried doing this by having an empty base class ("class HasBar{};") for my classes to derive from and using boost::enable_if with boost::is_base_of on my "specialised" version. However the problem then is that for classes that do have bar, the compiler cant resolve which one to use :(. template<typename T> typename boost::enable_if<boost::is_base_of(HasBar, T>, void>::type f() {...} I know that I could use boost::disable_if on the "normal" version, however I do not control the normal version (its provided by a third party library and its expected for specialisations to be made, I just don't really want to make explicit specialisations for my 20 or so classes), nor do I have that much control over the code using these functions, just the classes implementing T::bar and the function that uses it. Is there some way to tell the compiler to "always use this version if possible no matter what" without altering the other versions?

    Read the article

  • Compile time error: cannot convert from specific type to a generic type

    - by Water Cooler v2
    I get a compile time error with the following relevant code snippet at the line that calls NotifyObservers in the if construct. public class ExternalSystem<TEmployee, TEventArgs> : ISubject<TEventArgs> where TEmployee : Employee where TEventArgs : EmployeeEventArgs { protected List<IObserver<TEventArgs>> _observers = null; protected List<TEmployee> _employees = null; public virtual void AddNewEmployee(TEmployee employee) { if (_employees.Contains(employee) == false) { _employees.Add(employee); string message = FormatMessage("New {0} hired.", employee); if (employee is Executive) NotifyObservers(new ExecutiveEventArgs { e = employee, msg = message }); else if (employee is BuildingSecurity) NotifyObservers(new BuildingSecurityEventArgs { e = employee, msg = message }); } } public void NotifyObservers(TEventArgs args) { foreach (IObserver<TEventArgs> observer in _observers) observer.EmployeeEventHandler(this, args); } } The error I receive is: The best overloaded method match for 'ExternalSystem.NotifyObservers(TEventArgs)' has some invalid arguments. Cannot convert from 'ExecutiveEventArgs' to 'TEventArgs'. I am compiling this in C# 3.0 using Visual Studio 2008 Express Edition.

    Read the article

  • Find the class of the generic object

    - by Mgccl
    Suppose I have the following class. public class gen<T> { public gen(){ } Class<T> class(){ //something that figures out what T is. } } How can I implement the class() function without pass any additional information? What I did is here, but I have to pass a object of T into the object gen. public class gen<T> { public gen(){ } Class<T> class(T var){ return (Class<T>) var.getClass(); } }

    Read the article

  • How to bind a List<DateTime> to a DataGridView/ListBox .NET C#

    - by nat
    Hi there I have a List that I want to bind to a DataGridView in a windows forms app. however, I cannot for the life of me find the DataPropertyName I need to show what I want. I have had similar problems with binding this list to a listbox. what i really want is to show .ToString("dddd, dd MMMM yyyy HH:mm"), or certainly more than the standard 'date' part of the datetime - do i need to add a property of my own? public partial class DateTime{ public string myFormat{ get{return this.ToString("dddd dd MMM yyyy HH:mm");} } } or some such? thanks nat

    Read the article

  • Logic: Best way to sample & count bytes of a 100MB+ file

    - by Jami
    Let's say I have this 170mb file (roughly 180 million bytes). What I need to do is to create a table that lists: all 4096 byte combinations found [column 'bytes'], and the number of times each byte combination appeared in it [column 'occurrences'] Assume two things: I can save data very fast, but I can update my saved data very slow. How should I sample the file and save the needed information? Here're some suggestions that are (extremely) slow: Go through each 4096 byte combinations in the file, save each data, but search the table first for existing combinations and update it's values. this is unbelievably slow Go through each 4096 byte combinations in the file, save until 1 million rows of data in a temporary table. Go through that table and fix the entries (combine repeating byte combinations), then copy to the big table. Repeat going through another 1 million rows of data and repeat the process. this is faster by a bit, but still unbelievably slow This is kind of like taking the statistics of the file. NOTE: I know that sampling the file can generate tons of data (around 22Gb from experience), and I know that any solution posted would take a bit of time to finish. I need the most efficient saving process

    Read the article

  • Why can I derived from a templated/generic class based on that type in C# / C++

    - by stusmith
    Title probably doesn't make a lot of sense, so I'll start with some code: class Foo : public std::vector<Foo> { }; ... Foo f; f.push_back( Foo() ); Why is this allowed by the compiler? My brain is melting at this stage, so can anyone explain whether there are any reasons you would want to do this? Unfortunately I've just seen a similar pattern in some production C# code and wondered why anyone would use this pattern.

    Read the article

  • C#, Generic Lists and Inheritance

    - by Andy
    I have a class called Foo that defines a list of objects of type A: class Foo { List<A> Items = new List<A>(); } I have a class called Bar that can save and load lists of objects of type B: class Bar { void Save(List<B> ComplexItems); List<B> Load(); } B is a child of A. Foo, Bar, A and B are in a library and the user can create children of any of the classes. What I would like to do is something like the following: Foo MyFoo = new Foo(); Bar MyBar = new Bar(); MyFoo.Items = MyBar.Load(); MyBar.Save(MyFoo.Items); Obviously this won't work. Is there a clever way to do this that avoids creating intermediate lists? thanks, Andy

    Read the article

< Previous Page | 47 48 49 50 51 52 53 54 55 56 57 58  | Next Page >