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  • How do I get a JComponent to resize after calling `setVisible(true)`?

    - by iWerner
    Our application displays a 2D view of our data (mainly maps) and then allows the user to change to a 3D view. The 2D and 3D views are generated by custom C++ code that is SWIG'ed into our Swing GUI and wrapped within a JComponent. These JComponents are then displayed within another parent JComponent. Our problem is that when we change from the 2D to the 3D view and then back to the 2D view, when we resize the window the 2D view does not get resized. The resize events don't get sent to the 2D view. Our application runs under Linux (Fedora 11). We're running Java version 1.6.0_12. Here is some sample code in which I've replaced the 2D view and 3D view with two 2 JButtons, that produces the same behaviour. Once you go to 3D and then back to 2D, resizing the window does not cause the 2D view to be resized. /* TestFrame.java * Compile with: $ javac TestFrame.java * Run with: $ java TestFrame */ import java.awt.BorderLayout; import java.awt.Container; import java.awt.event.ComponentEvent; import java.awt.event.ComponentListener; import javax.swing.JButton; public class TestFrame extends javax.swing.JFrame { private boolean mode2D = true; private JButton view2D = null; private JButton view3D = null; private Container parent = null; public TestFrame() { initComponents(); containerPanel.setLayout(new BorderLayout()); view2D = new JButton("2D View"); view2D.addComponentListener(new MyListener("2D VIEW")); containerPanel.add(view2D); } private void changerButtonActionPerformed(java.awt.event.ActionEvent evt) { if (parent == null) { parent = view2D.getParent(); } if (mode2D) { System.out.println("Going from 2D to 3D"); view2D.setVisible(false); if (view3D != null) { view3D.setVisible(true); } else { view3D = new JButton("3D View"); view3D.addComponentListener(new MyListener("3D VIEW")); parent.add(view3D); } ((JButton) evt.getSource()).setText("Change to 2D"); mode2D = false; } else { System.out.println("Going from 3D to 2D"); view3D.setVisible(false); view2D.setVisible(true); ((JButton) evt.getSource()).setText("Change to 3D"); mode2D = true; } } public static void main(String args[]) { java.awt.EventQueue.invokeLater(new Runnable() { public void run() { new TestFrame().setVisible(true); } }); } private javax.swing.JPanel containerPanel; private javax.swing.JButton changerButton; private class MyListener implements ComponentListener { private String name; public MyListener(String name) { this.name = name; } @Override public void componentHidden(ComponentEvent event) { System.out.println("@@@ [" + name + "] component Hidden"); } @Override public void componentResized(ComponentEvent event) { System.out.println("@@@ [" + name + "] component Resized"); } @Override public void componentShown(ComponentEvent event) { System.out.println("@@@ [" + name + "] component Shown"); } @Override public void componentMoved(ComponentEvent event) { System.out.println("@@@ [" + name + "] component Moved"); } }; @SuppressWarnings("unchecked") private void initComponents() { containerPanel = new javax.swing.JPanel(); changerButton = new javax.swing.JButton(); setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); containerPanel.setBorder(new javax.swing.border.MatteBorder(null)); javax.swing.GroupLayout containerPanelLayout = new javax.swing.GroupLayout(containerPanel); containerPanel.setLayout(containerPanelLayout); containerPanelLayout.setHorizontalGroup( containerPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGap(0, 374, Short.MAX_VALUE) ); containerPanelLayout.setVerticalGroup( containerPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGap(0, 239, Short.MAX_VALUE) ); changerButton.setText("Change to 3D"); changerButton.addActionListener(new java.awt.event.ActionListener() { public void actionPerformed(java.awt.event.ActionEvent evt) { changerButtonActionPerformed(evt); } }); javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane()); getContentPane().setLayout(layout); layout.setHorizontalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addContainerGap() .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addComponent(containerPanel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE) .addComponent(changerButton)) .addContainerGap()) ); layout.setVerticalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addContainerGap() .addComponent(containerPanel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE) .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED) .addComponent(changerButton) .addContainerGap()) ); pack(); } } (My apologies for the Netbeans generated GUI code) I should mention that when we call parent.remove(view2D) and parent.add(view3D) to change the views the X Windows ID of our 3D view changes and we're unable to get our 3D view back. Therefore parent.remove(view2D) and parent.add(view3D) is not really a solution and we have to call setVisible(false) and setVisible(true) on the JComponents that contain our 2D and 3D views in order to hide and show them. Any help will be greatly appreciated.

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  • Extension method question. Why do I need to use someObj = someObj.somemethod();

    - by Kettenbach
    Hi All, I have a simple extension method that I would like to use to add an item to an array of items. public static T[] addElement<T>(this T[] array, T elementToAdd) { var list = new List<T>(array) {elementToAdd}; return list.ToArray(); } this works ok, but when I use it, I am having to set the array equal to the return value. I see that I am returning an Array. I likely want this method to be void, but I would like the item added. Does anyone have any ideas on what I need to do , to make this work the way I am wanting? Instead of someArray = someArray.addElement(item), I just want to do someArray.addElement(item) and then someArray be ready to go. What am I missing here? Thanks, ~ck in San Diego

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  • Why membership provider is not generic?

    - by Timmy O' Tool
    I have to confess that I hate membership provider. The default implementation is not very appropriate normally and I haven't seen so far a good implementation of a custom membership provider, probably because this is not possible :-) So the question is: In your opinion: which are the reasons for not having membership/role provider as a generic class? I mean, why Microsoft didn't selected this approach.

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  • Generic Class Vb.net

    - by KoolKabin
    hi guys, I am stuck with a problem about generic classes. I am confused how I call the constructor with parameters. My interface: Public Interface IDBObject Sub [Get](ByRef DataRow As DataRow) Property UIN() As Integer End Interface My Child Class: Public Class User Implements IDBObject Public Sub [Get](ByRef DataRow As System.Data.DataRow) Implements IDBObject.Get End Sub Public Property UIN() As Integer Implements IDBObject.UIN Get End Get Set(ByVal value As Integer) End Set End Property End Class My Next Class: Public Class Users Inherits DBLayer(Of User) #Region " Standard Methods " #End Region End Class My DBObject Class: Public Class DBLayer(Of DBObject As {New, IDBObject}) Public Shared Function GetData() As List(Of DBObject) Dim QueryString As String = "SELECT * ***;" Dim Dataset As DataSet = New DataSet() Dim DataList As List(Of DBObject) = New List(Of DBObject) Try Dataset = Query(QueryString) For Each DataRow As DataRow In Dataset.Tables(0).Rows **DataList.Add(New DBObject(DataRow))** Next Catch ex As Exception DataList = Nothing End Try Return DataList End Function End Class I get error in the starred area of the DBLayer Object. What might be the possible reason? what can I do to fix it? I even want to add New(byval someval as datatype) in IDBObject interface for overloading construction. but it also gives an error? how can i do it? Adding Sub New(ByVal DataRow As DataRow) in IDBObject producess following error 'Sub New' cannot be declared in an interface. Error Produced in DBLayer Object line: DataList.Add(New DBObject(DataRow)) Msg: Arguments cannot be passed to a 'New' used on a type parameter.

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  • how do I best create a set of list classes to match my business objects

    - by ken-forslund
    I'm a bit fuzzy on the best way to solve the problem of needing a list for each of my business objects that implements some overridden functions. Here's the setup: I have a baseObject that sets up database, and has its proper Dispose() method All my other business objects inherit from it, and if necessary, override Dispose() Some of these classes also contain arrays (lists) of other objects. So I create a class that holds a List of these. I'm aware I could just use the generic List, but that doesn't let me add extra features like Dispose() so it will loop through and clean up. So if I had objects called User, Project and Schedule, I would create UserList, ProjectList, ScheduleList. In the past, I have simply had these inherit from List< with the appropriate class named and then written the pile of common functions I wanted it to have, like Dispose(). this meant I would verify by hand, that each of these List classes had the same set of methods. Some of these classes had pretty simple versions of these methods that could have been inherited from a base list class. I could write an interface, to force me to ensure that each of my List classes has the same functions, but interfaces don't let me write common base functions that SOME of the lists might override. I had tried to write a baseObjectList that inherited from List, and then make my other Lists inherit from that, but there are issues with that (which is really why I came here). One of which was trying to use the Find() method with a predicate. I've simplified the problem down to just a discussion of Dispose() method on the list that loops through and disposes its contents, but in reality, I have several other common functions that I want all my lists to have. What's the best practice to solve this organizational matter?

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  • Is converting this ArrayList to a Generic List efficient?

    - by Greg
    The code I'm writing receives an ArrayList from unmanaged code, and this ArrayList will always contain one or more objects of type Grid_Heading_Blk. I've considered changing this ArrayList to a generic List, but I'm unsure if the conversion operation will be so expensive as to nullify the benefits of working with the generic list. Currently, I'm just running a foreach (Grid_Heading_Blk in myArrayList) operation to work with the ArrayList contents after passing the ArrayList to the class that will use it. Should I convert the ArrayList to a generic typed list? And if so, what is the most efficient way of doing so?

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  • C# Get Keys from a Dictionary<string, Stream>

    - by alex
    Suppose I have a Dictionary like so: Dictionary<string, Stream> How can I get a list (or IEnumerable or whatever) of JUST the Keys from this dictionary? Is this possible? I could enumerate the dictionary, and extract the keys one by one, but I was hoping to avoid this. In my instance, the Dictionary contains a list of filenames (file1.doc, filex.bmp etc...) and the stream content of the file from another part of the application.

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  • C# - implementing GetEnumerator() for a collection inherited from List<string>

    - by Vojtech
    Hi, I am trying to implement FilePathCollection. Its items would be simple file names (without a path - such as "image.jpg"). Once the collection is used via foreach cycle, it should return the full path created by concatenating with "baseDirectory". How can I do that? public class FilePathCollection : List<string> { string baseDirectory; public FileCollection(string baseDirectory) { this.baseDirectory = baseDirectory; } new public System.Collections.IEnumerator GetEnumerator() { foreach (string value in this._list) //this does not work because _list is private yield return baseDirectory + value; } } Thanks in advance! :-)

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  • StaX: Content not allowed in prolog

    - by RalfB
    I have the following (test) XML file below and Java code that uses StaX. I want to apply this code to a file that is about 30 GB large but with fairly small elements, so I thought StaX is a good choice. I am getting the following error: Exception in thread "main" javax.xml.stream.XMLStreamException: ParseError at [row,col]:[1,1] Message: Content is not allowed in prolog at com.sun.org.apache.xerces.internal.impl.XMLStreamReaderImpl.next(XMLStreamReaderImpl.java:598) at at.tuwien.mucke.util.xml.staxtest.StaXTest.main(StaXTest.java:18) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120) <?xml version='1.0' encoding='utf-8'?> <catalog> <book id="bk101"> <author>Gambardella, Matthew</author> <title>XML Developer's Guide</title> <price>44.95</price> <description>An in-depth look at creating applications with XML.</description> </book> <book id="bk102"> <author>Ralls, Kim</author> <title>Midnight Rain</title> <price>5.95</price> <description>A former architect battles corporate zombies, an evil sorceress, and her own childhood to become queen of the world.</description> </book> </catalog> Here the code: package xml.staxtest; import java.io.*; import javax.xml.stream.*; public class StaXTest { public static void main(String[] args) throws Exception { XMLInputFactory xif = XMLInputFactory.newInstance(); XMLStreamReader streamReader = xif.createXMLStreamReader(new FileReader("D:/Data/testFile.xml")); while(streamReader.hasNext()){ int eventType = streamReader.next(); if(eventType == XMLStreamReader.START_ELEMENT){ System.out.println(streamReader.getLocalName()); } //... more to come here later ... } } }

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  • How can an object not be compared to null?

    - by ProfK
    I have an 'optional' parameter on a method that is a KeyValuePair. I wanted an overload that passes null to the core method for this parameter, but in the core method, when I want to check if the KeyValuePair is null, I get the following error: Operator '!=' cannot be applied to operands of type System.Collections.Generic.KeyValuePair<string,object>' and '<null>. How can I not be allowed to check if an object is null?

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  • Casting Type array to Generic array?

    - by George R
    The short version of the question - why can't I do this? I'm restricted to .NET 3.5. T[] genericArray; // Obviously T should be float! genericArray = new T[3]{ 1.0f, 2.0f, 0.0f }; // Can't do this either, why the hell not genericArray = new float[3]{ 1.0f, 2.0f, 0.0f }; Longer version - I'm working with the Unity engine here, although that's not important. What is - I'm trying to throw conversion between its fixed Vector2 (2 floats) and Vector3 (3 floats) and my generic Vector< class. I can't cast types directly to a generic array. using UnityEngine; public struct Vector { private readonly T[] _axes; #region Constructors public Vector(int axisCount) { this._axes = new T[axisCount]; } public Vector(T x, T y) { this._axes = new T[2] { x, y }; } public Vector(T x, T y, T z) { this._axes = new T[3]{x, y, z}; } public Vector(Vector2 vector2) { // This doesn't work this._axes = new T[2] { vector2.x, vector2.y }; } public Vector(Vector3 vector3) { // Nor does this this._axes = new T[3] { vector3.x, vector3.y, vector3.z }; } #endregion #region Properties public T this[int i] { get { return _axes[i]; } set { _axes[i] = value; } } public T X { get { return _axes[0];} set { _axes[0] = value; } } public T Y { get { return _axes[1]; } set { _axes[1] = value; } } public T Z { get { return this._axes.Length (Vector2 vector2) { Vector vector = new Vector(vector2); return vector; } public static explicit operator Vector(Vector3 vector3) { Vector vector = new Vector(vector3); return vector; } #endregion }

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  • Is there a way to define a List<> of two elements string array?

    - by Alexander Prokofyev
    I want to build two-dimentional array of strings where length of one dimention is 2. Similar to this string[,] array = new string[,] { {"a", "b"}, {"c", "d"}, {"e", "f"}, {"g", "h"} } Doing List<string[]> list = new List<string[]>(); list.Add(new string[2] {"a", "b"}); list.Add(new string[2] {"c", "d"}); list.Add(new string[2] {"e", "f"}); list.Add(new string[2] {"g", "h"}); list.ToArray(); gives me string[][] but not string[,] array. Just curious, is there some trick to build dynamically string[,] array somehow?

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  • VB.NET Two different approaches to generic cross-threaded operations; which is better?

    - by BASnappl
    VB.NET 2010, .NET 4 Hello, I recently read about using SynchronizationContext objects to control the execution thread for some code. I have been using a generic subroutine to handle (possibly) cross-thread calls for things like updating UI controls that utilizes Invoke. I'm an amateur and have a hard time understanding the pros and cons of any particular approach. I am looking for some insight on which approach might be preferable and why. Update: This question is motivated, in part, by statements such as the following from the MSDN page on Control.InvokeRequired. An even better solution is to use the SynchronizationContext returned by SynchronizationContext rather than a control for cross-thread marshaling. Method 1: Public Sub InvokeControl(Of T As Control)(ByVal Control As T, ByVal Action As Action(Of T)) If Control.InvokeRequired Then Control.Invoke(New Action(Of T, Action(Of T))(AddressOf InvokeControl), New Object() {Control, Action}) Else Action(Control) End If End Sub Method 2: Public Sub UIAction(Of T As Control)(ByVal Control As T, ByVal Action As Action(Of Control)) SyncContext.Send(New Threading.SendOrPostCallback(Sub() Action(Control)), Nothing) End Sub Where SyncContext is a Threading.SynchronizationContext object defined in the constructor of my UI form: Public Sub New() InitializeComponent() SyncContext = WindowsFormsSynchronizationContext.Current End Sub Then, if I wanted to update a control (e.g., Label1) on the UI form, I would do: InvokeControl(Label1, Sub(x) x.Text = "hello") or UIAction(Label1, Sub(x) x.Text = "hello") So, what do y'all think? Is one way preferred or does it depend on the context? If you have the time, verbosity would be appreciated! Thanks in advance, Brian

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  • C# How to check if a class implements generic interface ?

    - by PaN1C_Showt1Me
    How to get generic interface type for an instance ? Suppose this code: interface IMyInterface<T> { T MyProperty { get; set; } } class MyClass : IMyInterface<int> { #region IMyInterface<T> Members public int MyProperty { get; set; } #endregion } MyClass myClass = new MyClass(); /* returns the interface */ Type[] myinterfaces = myClass.GetType().GetInterfaces(); /* returns null */ Type myinterface = myClass.GetType().GetInterface(typeof(IMyInterface<int>).FullName);

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  • How to create a generic method in C# that's all applicable to many types - ints, strings, doubles et

    - by satyajit
    Let's I have a method to remove duplicates in an integer Array public int[] RemoveDuplicates(int[] elems) { HashSet<int> uniques = new HashSet<int>(); foreach (int item in elems) uniques.Add(item); elems = new int[uniques.Count]; int cnt = 0; foreach (var item in uniques) elems[cnt++] = item; return elems; } How can I make this generic such that now it accepts a string array and remove duplicates in it? How about a double array? I know I am probably mixing things here in between primitive and value types. For your reference the following code won't compile public List<T> RemoveDuplicates(List<T> elems) { HashSet<T> uniques = new HashSet<T>(); foreach (var item in elems) uniques.Add(item); elems = new List<T>(); int cnt = 0; foreach (var item in uniques) elems[cnt++] = item; return elems; } The reason is that all generic types should be closed at run time. Thanks for you comments

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  • Initialize generic object from a System.Type

    - by CaptnCraig
    I need to create a generic type, but I do not know the type at compile time. I would like to do this: Type t = typeof(whatever); var list = new List<t> this won't compile, because t is not a valid type. But it does know all about a valid type. Is there a way to dynamically create the generic list from a System.Type like this? I may need reflection, and that's ok, I am just a bit lost here.

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  • How to infer the type of a derived class in base class?

    - by enzi
    I want to create a method that allows me to change arbitrary properties of classes that derive from my base class, the result should look like this: SetPropertyValue("size.height", 50); – where size is a property of my derived class and height is a property of size. I'm almost done with my implementation but there's one final obstacle that I want to solve before moving on, to describe this I will first have to explain my implementation a bit: Properties that can be modified are decorated with an attribute There's a method in my base class that searches for all derived classes and their decorated properties For each property I generate a "property modifier", a class that contains 2 delegates: one to set and one to get the value of the property. Property Modifiers are stored in a dictionary, with the name of the property as key In my base class, there is another dictionary that contains all property-modifier-dictionaries, with the Type of the respective class as key. What the SetPropertyValue method does is this: Get the correct property-modifier-dictionary, using the concrete type of the derived class (<- yet to solve) Get the property modifier of the property to change (e.g. of the property size) Use the get or set delegate to modify the property's value Some example code to clarify further: private static Dictionary<RuntimeTypeHandle, object> EditableTypes; //property-modifier-dictionary protected void SetPropertyValue<T>(EditablePropertyMap<T> map, string property, object value) { var property = map[property]; // get the property modifier property.Set((T)this, value); // use the set delegate (encapsulated in a method) } In the above code, T is the Type of the actual (derived) class. I need this type for the get/set delegates. The problem is how to get the EditablePropertyMap<T> when I don't know what T is. My current (ugly) solution is to pass the map in an overriden virtual method in the derived class: public override void SetPropertyValue(string property, object value) { base.SetPropertyValue((EditablePropertyMap<ExampleType>)EditableTypes[typeof(ExampleType)], property, value); } What this does is: get the correct dictionary containing the property modifiers of this class using the class's type, cast it to the appropiate type and pass it to the SetPropertyValue method. I want to get rid of the SetPropertyValue method in my derived class (since there are a lot of derived classes), but don't know yet how to accomplish that. I cannot just make a virtual GetEditablePropertyMap<T> method because I cannot infer a concrete type for T then. I also cannot acces my dictionary directly with a type and retrieve an EditablePropertyMap<T> from it because I cannot cast to it from object in the base class, since again I do not know T. I found some neat tricks to infere types (e.g. by adding a dummy T parameter), but cannot apply them to my specific problem. I'd highly appreciate any suggestions you may have for me.

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  • How do I create a generic method with a generic in the where clause? (Man that's clear as mud!)

    - by Jordan
    Is there a way of doing this: protected void SubscribeToEvent<TEvent, TPayload>(Action<TPayload> a_action) where TEvent : CompositePresentationEvent<TPayload> { TEvent newEvent = _eventAggregator.GetEvent<TEvent>(); SubscriptionToken eventToken = newEvent.Subscribe(a_action); _lstEventSubscriptions.Add(new KeyValuePair<EventBase, SubscriptionToken>(newEvent, eventToken)); } without requiring the user to specify a TPayload parameter?

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  • Nested for loop error with !null checking an element that doesn't exist

    - by Programatt
    I am currently using nested for loops in a 2D array of size 4,2. When I run my program, I get index out of bounds Exception on the following line else if (state[i][j+1] != null && state[i][j].getFlash() <= state[i][j].getCycleLength() && state[i][j+1].getCycleLength() == state[i][j].getCycleLength()){ } It says the index out of bounds is 2. I would understand the error if I wasn't checking to see if [i][j+1] wasn't null, but I don't understand the exception with the check? I tried moving around the !null check but the program still fails on this line. Any help would be greatly appreciated. Stack trace: Exception in thread "Timer-0" java.lang.ArrayIndexOutOfBoundsException: 2 at NatComp.data$1.run(data.java:67) at java.util.TimerThread.mainLoop(Timer.java:512) at java.util.TimerThread.run(Timer.java:462)

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  • Accessing generic lists with delegate notation

    - by n0vic3c0d3r
    I see some people write: //wordList is List<string> wordList.ForEach(delegate(string word){ Console.WriteLine(word);}); instead of: foreach(string word in wordList) { Console.WriteLine(word); } What is the advantage in doing so. Also I couldn't fathom the Action delegate syntax given above though I have used delegates in C# 2.0. Basically I am not able to relate the syntax with the concept of delegates I am familiar with. Can you please help me understand the syntax. Is it some shorthand?

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  • Generic TypeIdenitifier convertion.How?

    - by John
    How do I convert the TypeIdenitifier to a class type? I need to use implicit convertion. type TMyChildArray<T>=class(TMyArray<T>) private FData:Array of T; procedure AddEnd(); end; TTypeIdenitifierParentClass=class(TAnotherParentClass) protected TestField:Cardinal; end; procedure TMyChildArray<T>.AddEnd(); var elem:T; begin for elem in Fdata do TTypeIdenitifierParentClass(elem).TestField:=0; end; I get "Invalid typecast" on the implicit convertion "TTypeIdenitifierParentClass(elem).TestField:=0;". The principle I want to use is that the TypeIdenitifier will represent a class that descends from TTypeIdenitifierParentClass.There are many class types,but all of them descend that class. How do I do this?

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  • .NET 4.0 Generic Invariant, Covariant, Contravariant

    - by Sameer Shariff
    Here's the scenario i am faced with: public abstract class Record { } public abstract class TableRecord : Record { } public abstract class LookupTableRecord : TableRecord { } public sealed class UserRecord : LookupTableRecord { } public interface IDataAccessLayer<TRecord> where TRecord : Record { } public interface ITableDataAccessLayer<TTableRecord> : IDataAccessLayer<TTableRecord> where TTableRecord : TableRecord { } public interface ILookupTableDataAccessLayer<TLookupTableRecord> : ITableDataAccessLayer<TLookupTableRecord> where TLookupTableRecord : LookupTableRecord { } public abstract class DataAccessLayer<TRecord> : IDataAccessLayer<TRecord> where TRecord : Record, new() { } public abstract class TableDataAccessLayer<TTableRecord> : DataAccessLayer<TTableRecord>, ITableDataAccessLayer<TTableRecord> where TTableRecord : TableRecord, new() { } public abstract class LookupTableDataAccessLayer<TLookupTableRecord> : TableDataAccessLayer<TLookupTableRecord>, ILookupTableDataAccessLayer<TLookupTableRecord> where TLookupTableRecord : LookupTableRecord, new() { } public sealed class UserDataAccessLayer : LookupTableDataAccessLayer<UserRecord> { } Now when i try to cast UserDataAccessLayer to it's generic base type ITableDataAccessLayer<TableRecord>, the compiler complains that it cannot implicitly convert the type.

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  • Multiple generic types in one container

    - by Lirik
    I was looking at the answer of this question regarding multiple generic types in one container and I can't really get it to work: the properties of the Metadata class are not visible, since the abstract class doesn't have them. Here is a slightly modified version of the code in the original question: public abstract class Metadata { } public class Metadata<T> : Metadata { // ... some other meta data public T Function{ get; set; } } List<Metadata> metadataObjects; metadataObjects.Add(new Metadata<Func<double,double>>()); metadataObjects.Add(new Metadata<Func<int,double>>()); metadataObjects.Add(new Metadata<Func<double,int>>()); foreach( Metadata md in metadataObjects) { var tmp = md.Function; // <-- Error: does not contain a definition for Function } The exact error is: error CS1061: 'Metadata' does not contain a definition for 'Function' and no extension method 'Function' accepting a first argument of type 'Metadata' could be found (are you missing a using directive or an assembly reference?) I believe it's because the abstract class does not define the property Function, thus the whole effort is completely useless. Is there a way that we can get the properties?

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  • Where are the function literals c++?

    - by academicRobot
    First of all, maybe literals is not the right term for this concept, but its the closest I could think of (not literals in the sense of functions as first class citizens). The idea is that when you make a conventional function call, it compiles to something like this: callq <immediate address> But if you make a function call using a function pointer, it compiles to something like this: mov <memory location>,%rax callq *%rax Which is all well and good. However, what if I'm writing a template library that requires a callback of some sort with a specified argument list and the user of the library is expected to know what function they want to call at compile time? Then I would like to write my template to accept a function literal as a template parameter. So, similar to template <int int_literal> struct my_template {...};` I'd like to write template <func_literal_t func_literal> struct my_template {...}; and have calls to func_literal within my_template compile to callq <immediate address>. Is there a facility in C++ for this, or a work around to achieve the same effect? If not, why not (e.g. some cataclysmic side effects)? How about C++0x or another language? Solutions that are not portable are fine. Solutions that include the use of member function pointers would be ideal. I'm not particularly interested in being told "You are a <socially unacceptable term for a person of low IQ>, just use function pointers/functors." This is a curiosity based question, and it seems that it might be useful in some (albeit limited) applications. It seems like this should be possible since function names are just placeholders for a (relative) memory address, so why not allow more liberal use (e.g. aliasing) of this placeholder. p.s. I use function pointers and functions objects all the the time and they are great. But this post got me thinking about the don't pay for what you don't use principle in relation to function calls, and it seems like forcing the use of function pointers or similar facility when the function is known at compile time is a violation of this principle, though a small one.

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