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  • Use Lambda in Attribute constructor to get method's parameters

    - by Anthony Shaw
    I'm not even sure if this is possible, but I've exhausted all of my ideas trying to figure this out, so I figured I'd send this out to the community and see what you thought. And, if it's not possible, maybe you'd have some ideas as well. I'm trying to make an Attribute class that I can add to a method that would allow me to use a lambda expression to get each parameter of the method public ExampleAttribute : Attribute { public object Value { get; set; } public ExampleAttribute(--something here to make the lambda work--, object value) { Value = value; } } I'd like to be able to something like this below: [Example(x=x.Id, 4)] [Example(x=x.filter, "string value")] public ActionResult Index(int Id, string filter) { return View(); } I understand that I might be completely dreaming with this idea. I'm basically trying to write a model to allow for self-documenting REST API Documentation. In a recent project here at work we wrote a dozen or so services with 5 to 15 methods on each, I figure it's easier to write something to do this, than to hand code a documentation page for each. I would plan to eventually release this as an open-source project once I have it in a place that I feel it's releasable.

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  • explicit copy constructor or implicit parameter by value

    - by R Samuel Klatchko
    I recently read (and unfortunately forgot where), that the best way to write operator= is like this: foo &operator=(foo other) { swap(*this, other); return *this; } instead of this: foo &operator=(const foo &other) { foo copy(other); swap(*this, copy); return *this; } The idea is that if operator= is called with an rvalue, the first version can optimize away construction of a copy. So when called with a rvalue, the first version is faster and when called with an lvalue the two are equivalent. I'm curious as to what other people think about this? Would people avoid the first version because of lack of explicitness? Am I correct that the first version can be better and can never be worse?

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  • Can't seem to redirect from a ViewScoped constructor.

    - by Andrew
    I'm having trouble redirecting from a view scoped bean in the case that we don't have the required info for the page in question. The log entry in the @PostContruct is visible in the log right before a NPE relating to the view trying to render itself instead of following my redirect. Why is it ignoring the redirect? Here's my code: @ManagedBean public class WelcomeView { private String sParam; private String aParam; public WelcomeView() { super(); sParam = getURL_Param("surveyName"); aParam = getURL_Param("accountName"); project = fetchProject(sParam, aParam); } @PostConstruct public void redirectWithoutProject() { if (null == project) { try { logger.warn("NO project [" + sParam + "] for account [" + aParam + "]"); FacesContext fc = FacesContext.getCurrentInstance(); fc.getExternalContext().redirect("/errors/noSurvey.jsf"); return; } catch (Exception e) { e.printStackTrace(); } } } .... public boolean getAuthenticated() { if (project.getPasswordProtected()) { return enteredPassword.equals(project.getLoginPassword()); } else return true; } } Here's the stack trace: SEVERE: Error Rendering View[/participant/welcome.xhtml] javax.el.ELException: /templates/participant/welcome.xhtml @80,70 rendered="#{welcomeView.authenticated}": Error reading 'authenticated' on type com.MYCODE.general.controllers.participant.WelcomeView at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:107) at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:190) at javax.faces.component.UIComponentBase.isRendered(UIComponentBase.java:416) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1607) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616) at javax.faces.render.Renderer.encodeChildren(Renderer.java:168) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:848) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1613) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616) at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:380) at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:126) at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:127) at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139) at javax.faces.webapp.FacesServlet.service(FacesServlet.java:313) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at com.MYCODE.general.filters.StatsFilter.doFilter(StatsFilter.java:28) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:433) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:568) at org.apache.catalina.authenticator.SingleSignOn.invoke(SingleSignOn.java:421) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447) at java.lang.Thread.run(Thread.java:637) Caused by: java.lang.NullPointerException at com.MYCODE.general.controllers.participant.WelcomeView$$M$863c205f.getAuthenticated(WelcomeView.java:127) at com.MYCODE.general.controllers.participant.WelcomeView$$A$863c205f.getAuthenticated(<generated>) at com.MYCODE.general.controllers.participant.WelcomeView.getAuthenticated(WelcomeView.java:125) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at javax.el.BeanELResolver.getValue(BeanELResolver.java:62) at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:53) at com.sun.faces.el.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:72) at org.apache.el.parser.AstValue.getValue(AstValue.java:118) at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:186) at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:102) ... 33 more

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  • Define data members within constructor

    - by bertsisterwanda
    I have got this little snippet of code, I want to be able to define each array element as a new data member. class Core_User { protected $data_memebers = array( 'id' = '%d', 'email' = '"%s"', 'password' = '"%s"', 'title' = '"%s"', 'first_name' = '"%s"', 'last_name' = '"%s"', 'time_added' = '%d' , 'time_modified' = '%d' , ); function __construct($id = 0, $data = NULL) { foreach($data_memebers as $member){ //protected new data member } }

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  • Best intro to C++ static metaprogramming?

    - by jwfearn
    Static metaprogramming (aka "template metaprogramming") is a great C++ technique that allows the execution of programs at compile-time. A light bulb went off in my head as soon as I read this canonical metaprogramming example: #include <iostream> using namespace std; template< int n > struct factorial { enum { ret = factorial< n - 1 >::ret * n }; }; template<> struct factorial< 0 > { enum { ret = 1 }; }; int main() { cout << "7! = " << factorial< 7 >::ret << endl; // 5040 return 0; } If one wants to learn more about C++ static metaprogramming, what are the best sources (books, websites, on-line courseware, whatever)?

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  • ASP.NET MVC static-asset aides/practices

    - by shannon
    I want to keep assets that are only used by one view in a view-specific folder, so my Search.aspx properly finds images/*.jpg, and helps me maintain my convention: ~/Areas/Candidate/Views/Job/Search.aspx -> ~/Assets/Candidate/Job/Search/images/*.jpg Perhaps with the ability to easily reference controller- or area-common assets manually or automatically: ~/Assets/Candidate/Job/images/*.jpg ~/Assets/Candidate/images/*.jpg If you wonder why I'm doing this, then speak up; I'm probably missing something. But here's why: I don't want stale static assets sitting in my ASP.NET MVC projects, which I expect to be an automatic outcome of the ~/Assets/Images folder: i.e. As a shared asset loses its last reference-count, who knows to delete it, especially with it being so difficult to trace content link validity in MVC projects? How do you, personally, do this? I can imagine, for example: Implement HtmlHelper extension methods for URL-generation. Extending ViewPage and ViewMasterPage with URL-generation methods. Implementing an inbound request filter to search related folders for static assets. and, are there good libraries out there for this? For example, something that also automatically appends timestamps for .JS and .CSS files, writes the / tags for me, and maybe even that allows me to inject includes in the head section from outside head code?

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  • Need some help with constructor

    - by mousey
    you have a class A, where you set ctor to be private, so a client can't call "A a;" to create obj on stack. But someday another developer add a new ctor: "A(int)" and try to call "A a(1);" inside main(). So this will create a obj on stack. How do you prevent that?

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  • Nginx for static files, Apache isn't working now...

    - by matthewsteiner
    So anything that is a "static file" that exists will just be done with nginx. Otherwise, it should pass it off to Apache. Right now, static files are working correctly. However, if something is passed to apache and it's example.com or subdomain.example.com, apache just spits out the "Apache 2 Test Page" that you get if there's nothing there. Here's my nginx.conf: location ~* ^.+.(jpg|jpeg|gif|png|ico|css|zip|tgz|gz|rar|bz2|doc|xls|exe|pdf|ppt|txt|tar|mid|midi|wav|bmp|rtf|js)$ { root /var/www/vhosts/example.com/public/; access_log off; expires 30d; } location / { proxy_pass http://127.0.0.1:8080/; proxy_redirect off; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; } Apache worked fine before, so I'm guessing it has to do with the way nginx is "asking". I'm not sure though. Any ideas?

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  • IIS6 compressing static files, but not JSON requests

    - by user500038
    I have IIS6 compression setup, and static content is being compressed correctly as per Coding Horror. Example of a static file: Response Headers Content-Length 55513 Content-Type application/x-javascript Content-Encoding gzip Last-Modified Mon, 20 Dec 2010 15:31:58 GMT Accept-Ranges bytes Vary Accept-Encoding Server Microsoft-IIS/6.0 X-Powered-By ASP.NET Date Wed, 29 Dec 2010 16:37:23 GMT Request Headers Accept */* Accept-Language en-us,en;q=0.5 Accept-Encoding gzip,deflate Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7 Keep-Alive 115 Connection keep-alive As you can see, the response is correctly compressed. However with a JSON call you'll see the request with the gzip parameter correctly set: Accept application/json, text/javascript, */*; q=0.01 Accept-Language en-us,en;q=0.5 Accept-Encoding gzip,deflate Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7 Keep-Alive 115 Connection keep-alive X-Requested-With XMLHttpRequest Then for the response: Cache-Control private Content-Length 6811 Content-Type application/json; charset=utf-8 Server Microsoft-IIS/6.0 X-Powered-By ASP.NET X-AspNet-Version 2.0.50727 X-AspNetMvc-Version 2.0 No gzip! I found this article by Rick Stahl, which outlines how to compress in your code, but I'd like IIS to handle this. Is this possible with IIS6?

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  • compile Boost as static Universal binary lib

    - by Albert
    I want to have a static Universal binary lib of Boost. (Preferable the latest stable version, that is 1.43.0, or newer.) I found many Google hits with similar problems and possible solutions. However, most of them seems outdated. Also none of them really worked. Right now, I am trying sudo ./bjam --toolset=darwin --link=static --threading=multi \ --architecture=combined --address-model=32_64 \ --macosx-version=10.4 --macosx-version-min=10.4 \ install That compiles and install fine. However, the produced binaries seems broken. az@ip245 47 (openlierox) %file /usr/local/lib/libboost_signals.a /usr/local/lib/libboost_signals.a: current ar archive random library az@ip245 49 (openlierox) %lipo -info /usr/local/lib/libboost_signals.a input file /usr/local/lib/libboost_signals.a is not a fat file Non-fat file: /usr/local/lib/libboost_signals.a is architecture: x86_64 az@ip245 48 (openlierox) %otool -hv /usr/local/lib/libboost_signals.a Archive : /usr/local/lib/libboost_signals.a /usr/local/lib/libboost_signals.a(trackable.o): Mach header magic cputype cpusubtype caps filetype ncmds sizeofcmds flags MH_MAGIC_64 X86_64 ALL 0x00 OBJECT 3 1536 SUBSECTIONS_VIA_SYMBOLS /usr/local/lib/libboost_signals.a(connection.o): Mach header magic cputype cpusubtype caps filetype ncmds sizeofcmds flags MH_MAGIC_64 X86_64 ALL 0x00 OBJECT 3 1776 SUBSECTIONS_VIA_SYMBOLS /usr/local/lib/libboost_signals.a(named_slot_map.o): Mach header magic cputype cpusubtype caps filetype ncmds sizeofcmds flags MH_MAGIC_64 X86_64 ALL 0x00 OBJECT 3 1856 SUBSECTIONS_VIA_SYMBOLS /usr/local/lib/libboost_signals.a(signal_base.o): Mach header magic cputype cpusubtype caps filetype ncmds sizeofcmds flags MH_MAGIC_64 X86_64 ALL 0x00 OBJECT 3 1776 SUBSECTIONS_VIA_SYMBOLS /usr/local/lib/libboost_signals.a(slot.o): Mach header magic cputype cpusubtype caps filetype ncmds sizeofcmds flags MH_MAGIC_64 X86_64 ALL 0x00 OBJECT 3 1616 SUBSECTIONS_VIA_SYMBOLS Any suggestion how to get that correct?

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  • JavaScript: using constructor without operator 'new'

    - by GetFree
    Please help me to understand why the following code works: <script> var re = RegExp('\\ba\\b') ; alert(re.test('a')) ; alert(re.test('ab')) ; </script> In the first line there is no new operator. As far as I know, a contructor in JavaScript is a function that initialize objects created by the operator new and they are not meant to return anything.

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  • constructor function's object literal returns toString() method but no other method

    - by JohnMerlino
    I'm very confused with javascript methods defined in objects and the "this" keyword. In the below example, the toString() method is invoked when Mammal object instantiated: function Mammal(name){ this.name=name; this.toString = function(){ return '[Mammal "'+this.name+'"]'; } } var someAnimal = new Mammal('Mr. Biggles'); alert('someAnimal is '+someAnimal); Despite the fact that the toString() method is not invoked on the object someAnimal like this: alert('someAnimal is '+someAnimal.toString()); It still returns 'someAnimal is [Mammal "Mr. Biggles"]' . That doesn't make sense to me because the toString() function is not being called anywhere. Then to add even more confusion, if I change the toString() method to a method I make up such as random(): function Mammal(name){ this.name=name; this.random = function(){ return Math.floor(Math.random() * 15); } } var someAnimal = new Mammal('Mr. Biggles'); alert(someAnimal); It completely ignores the random method (despite the fact that it is defined the same way was the toString() method was) and returns: [object object] Another issue I'm having trouble understanding with inheritance is the value of "this". For example, in the below example function person(w,h){ width.width = w; width.height = h; } function man(w,h,s) { person.call(this, w, h); this.sex = s; } "this" keyword is being send to the person object clearly. However, does "this" refer to the subclass (man) or the super class (person) when the person object receives it? Thanks for clearing up any of the confusion I have with inheritance and object literals in javascript.

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  • Play framework does not return page and static content

    - by Anton
    I'm using play framework in production for one of my web projects. From time to time Play does not render main page or does not return some of the static content files. I have attached few screenshots below. First screenshot displays firebug console, loading of the site is stucked at the beginning, when serving home page. Second screenshot display fiddler console, when 2 static resources are not loading. This issue is hard to reproduce, it happens 1 of 15 time, I have to delete cache data and reload page. (pressing CRTL-F5 in FF). Issue can be reproduced in most of the browsers. Initially, I was thinging that there is something wrong with hosting provider. But I have changed hosting provided and issue has not gone. Version of the play is 1.2.2. Play is running as standalone server. Not sure, but probably deploying Play to Jetty/Tomcat/Resin would help. Also I'm thinging about rewriting application to another stack (well-known for me - j2ee, spring, whatever) I have no idea how to debug and resolve this issue. Any clue ? Has anyone faced same issue with Play before ?

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  • DSACryptoServiceProvider constructor throws CryptographicException

    - by Rick
    This code below thows the following error: System.Security.Cryptography.CryptographicException "The handle is invalid" CspParameters CSPParam = new System.Security.Cryptography.CspParameters(13, null, null); CSPParam.Flags = CspProviderFlags.UseMachineKeyStore; CSPParam.KeyContainerName = "MyKeys"; System.Security.Cryptography.DSACryptoServiceProvider r = new System.Security.Cryptography.DSACryptoServiceProvider(CSPParam); //Error occurs here This code had been working with no issues then it started throwing this error. I can't think of anything that I have changed that relates to this. Has nayone seen this error? Any ideas of what to try?

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  • Trouble with an depreciated constructor visual basic visual studio 2010

    - by VBPRIML
    My goal is to print labels with barcodes and a date stamp from an entry to a zebra TLP 2844 when the user clicks the ok button/hits enter. i found what i think might be the code for this from zebras site and have been integrating it into my program but part of it is depreciated and i cant quite figure out how to update it. below is what i have so far. The printer is attached via USB and the program will also store the entered numbers in a database but i have that part done. any help would be greatly Appreciated.   Public Class ScanForm      Inherits System.Windows.Forms.Form    Public Const GENERIC_WRITE = &H40000000    Public Const OPEN_EXISTING = 3    Public Const FILE_SHARE_WRITE = &H2      Dim LPTPORT As String    Dim hPort As Integer      Public Declare Function CreateFile Lib "kernel32" Alias "CreateFileA" (ByVal lpFileName As String,                                                                           ByVal dwDesiredAccess As Integer,                                                                           ByVal dwShareMode As Integer, <MarshalAs(UnmanagedType.Struct)> ByRef lpSecurityAttributes As SECURITY_ATTRIBUTES,                                                                           ByVal dwCreationDisposition As Integer, ByVal dwFlagsAndAttributes As Integer,                                                                           ByVal hTemplateFile As Integer) As Integer          Public Declare Function CloseHandle Lib "kernel32" Alias "CloseHandle" (ByVal hObject As Integer) As Integer      Dim retval As Integer           <StructLayout(LayoutKind.Sequential)> Public Structure SECURITY_ATTRIBUTES          Private nLength As Integer        Private lpSecurityDescriptor As Integer        Private bInheritHandle As Integer      End Structure            Private Sub OKButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OKButton.Click          Dim TrNum        Dim TrDate        Dim SA As SECURITY_ATTRIBUTES        Dim outFile As FileStream, hPortP As IntPtr          LPTPORT = "USB001"        TrNum = Me.ScannedBarcodeText.Text()        TrDate = Now()          hPort = CreateFile(LPTPORT, GENERIC_WRITE, FILE_SHARE_WRITE, SA, OPEN_EXISTING, 0, 0)          hPortP = New IntPtr(hPort) 'convert Integer to IntPtr          outFile = New FileStream(hPortP, FileAccess.Write) 'Create FileStream using Handle        Dim fileWriter As New StreamWriter(outFile)          fileWriter.WriteLine(" ")        fileWriter.WriteLine("N")        fileWriter.Write("A50,50,0,4,1,1,N,")        fileWriter.Write(Chr(34))        fileWriter.Write(TrNum) 'prints the tracking number variable        fileWriter.Write(Chr(34))        fileWriter.Write(Chr(13))        fileWriter.Write(Chr(10))        fileWriter.Write("A50,100,0,4,1,1,N,")        fileWriter.Write(Chr(34))        fileWriter.Write(TrDate) 'prints the date variable        fileWriter.Write(Chr(34))        fileWriter.Write(Chr(13))        fileWriter.Write(Chr(10))        fileWriter.WriteLine("P1")        fileWriter.Flush()        fileWriter.Close()        outFile.Close()        retval = CloseHandle(hPort)          'Add entry to database        Using connection As New SqlClient.SqlConnection("Data Source=MNGD-LABS-APP02;Initial Catalog=ScannedDB;Integrated Security=True;Pooling=False;Encrypt=False"), _        cmd As New SqlClient.SqlCommand("INSERT INTO [ScannedDBTable] (TrackingNumber, Date) VALUES (@TrackingNumber, @Date)", connection)            cmd.Parameters.Add("@TrackingNumber", SqlDbType.VarChar, 50).Value = TrNum            cmd.Parameters.Add("@Date", SqlDbType.DateTime, 8).Value = TrDate            connection.Open()            cmd.ExecuteNonQuery()            connection.Close()        End Using          'Prepare data for next entry        ScannedBarcodeText.Clear()        Me.ScannedBarcodeText.Focus()      End Sub

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  • Why can't you call abstract functions from abstract classes in PHP?

    - by incrediman
    I've set up an abstract parent class, and a concrete class which extends it. Why can the parent class not call the abstract function? //foo.php <?php abstract class AbstractFoo{ abstract public static function foo(); public static function getFoo(){ return self::foo();//line 5 } } class ConcreteFoo extends AbstractFoo{ public static function foo(){ return "bar"; } } echo ConcreteFoo::getFoo(); ?> Error: Fatal error: Cannot call abstract method AbstractFoo::foo() in foo.php on line 5

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  • const object and const constructor

    - by Muhammad alaa
    Is there any way to know if an object is a const object or regular object, for instance consider the following class class String { String(const char* str); }; if user create a const object from String then there is no reason to copy the passed native string and that because he will not make any manipulation on it, the only thing he will do is get string size, string search and other functions that will not change the string.

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  • Nested class with hidden constructor impossible in c#?

    - by luckyluke
    I' ve been doing some programming lately and faced an issue which i found weird in c#. (at least for me) public class Foo { //whatever public class FooSpecificCollection : List<Bar> { //implementation details } public FooSpecificCollection GetFoosStuff() { //return the collection } } I want the consumer of Foo to be able to obtain a reference to FooSpecificCollection, even perform some operations on it. Maybe even set it to some other property of Foo or smth like that, but not To be able to CREATE an instance of this class. (the only class that should be able to instatiate this collection should be Foo. Is my request really that far-fetched? I know that people way smarter defined c# but shouldn't there be such an option that a parent class can create a nested class instance but nobody else can't. So far I created a solution to make an abstract class, or interface available through the property and implement a concrete private class that is not available anywhere else. Is this a correct way to handle such a situation.?

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  • Why do not C++11's move constructor/assignment operator act as expected

    - by xmllmx
    #include <iostream> using namespace std; struct A { A() { cout << "A()" << endl; } ~A() { cout << "~A()" << endl; } A(A&&) { cout << "A(A&&)" << endl; } A& operator =(A&&) { cout << "A& operator =(A&&)" << endl; return *this; } }; struct B { // According to the C++11, the move ctor/assignment operator // should be implicitly declared and defined. The move ctor // /assignment operator should implicitly call class A's move // ctor/assignment operator to move member a. A a; }; B f() { B b; // The compiler knows b is a temporary object, so implicitly // defined move ctor/assignment operator of class B should be // called here. Which will cause A's move ctor is called. return b; } int main() { f(); return 0; } My expected output should be: A() A(A&&) ~A() ~A() However, the actual output is: (The C++ compiler is: Visual Studio 2012) A() ~A() ~A() Is this a bug of VC++? or just my misunderstanding?

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  • Using a constructor for return.

    - by Fecal Brunch
    Hi, Just a quick question. I've written some code that returns a custom class Command, and the code I've written seems to work fine. I was wondering if there are any reasons that I shouldn't be doing it this way. It's something like this: Command Behavior::getCommand () { char input = 'x'; return Command (input, -1, -1); } Anyway, I read that constructors aren't meant to have a return value, but this works in g++. Thanks for any advice, Rhys

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  • What is the advantage to hosting static resources on a separate domain?

    - by Michael Ekstrand
    I notice a lot of sites host their resources on a separate domain from the main site, e.g. StackExchange using sstatic.net, Barnes & Noble using imagesbn.com, etc. I understand that there are benefits to putting your static resources on a separate host, possibly with an efficient static-file web server like nginx, freeing up the main server to focus on serving dynamic content. Similarly, outsourcing to a shared CDN like cloudfront Akamai is logical. What is the benefit to using a separate domain otherwise, though? Why sstatic.net instead of static.stackexchange.com? Update: Several answers miss the core question. I understand that there is benefit to splitting between multiple hosts — parallel downloads, slimmer web server, etc. But what is more elusive is why multiple domains. Why sstatic.net rather than static.stackexchange.com as the host for shared resources? So far, only one answer has addressed that.

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  • How to run Jquery constructor from own function?

    - by Invidian
    I need to create a function which will returning jQuery.Color object and i have no idea how to do it. Here is code example function newcolor () { var obj = new $.Color( 'rgb(0,0,0)' ); return obj;} var foo = newcolor(); foo.red(); Edit: My full code: function my (element,a,b,c){ //class my this.target = $(elem); this.new_color = function (a,b,c) { return new $.Color( 'rgb('+a+','+b+','+c+')'); } this.base_color = new_color (a,b,c); this.colorize = function () ( this.target.css({ background-color: new_color }); } var div = new My($('foo'),0,0,0); div.new_color(255,255,255); div.colorize(); My goal is to create class which can hold jquery element and operate on it. Now I'm stuck on returning $.Color().

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  • How should platform specific lib files be named?

    - by Scott Langham
    Hello, I'm working on a C++ project that produces a lib that other teams use. It's being produced in a few different flavours: Win32 Debug Win32 Debug Static Win32 Release Win32 Release Static x64 Debug x64 Debug Static x64 Release x64 Release Static I'm wondering what the best wisdom is on how to name the dlls and what arguments are for different naming conventions. Do I output the libs into different directories, or do I append some letters on the end of the lib to differentiate them, or something else? One concern is that if I use directories, but don't give all the libs different names, users of the library will have problems where they accidentally use the wrong lib. Are these concerns valid? Thanks very much.

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  • C++ Virtual Constructor, without clone()

    - by Julien L.
    I want to perform "deep copies" of an STL container of pointers to polymorphic classes. I know about the Prototype design pattern, implemented by means of the Virtual Ctor Idiom, as explained in the C++ FAQ Lite, Item 20.8. It is simple and straightforward: struct ABC // Abstract Base Class { virtual ~ABC() {} virtual ABC * clone() = 0; }; struct D1 : public ABC { virtual D1 * clone() { return new D1( *this ); } // Covariant Return Type }; A deep copy is then: for( i = 0; i < oldVector.size(); ++i ) newVector.push_back( oldVector[i]->clone() ); Drawbacks As Andrei Alexandrescu states it: The clone() implementation must follow the same pattern in all derived classes; in spite of its repetitive structure, there is no reasonable way to automate defining the clone() member function (beyond macros, that is). Moreover, clients of ABC can possibly do something bad. (I mean, nothing prevents clients to do something bad, so, it will happen.) Better design? My question is: is there another way to make an abstract base class clonable without requiring derived classes to write clone-related code? (Helper class? Templates?) Following is my context. Hopefully, it will help understanding my question. I am designing a class hierarchy to perform operations on a class Image: struct ImgOp { virtual ~ImgOp() {} bool run( Image & ) = 0; }; Image operations are user-defined: clients of the class hierarchy will implement their own classes derived from ImgOp: struct CheckImageSize : public ImgOp { std::size_t w, h; bool run( Image &i ) { return w==i.width() && h==i.height(); } }; struct CheckImageResolution; struct RotateImage; ... Multiple operations can be performed sequentially on an image: bool do_operations( std::vector< ImgOp* > v, Image &i ) { std::for_each( v.begin(), v.end(), /* bind2nd(mem_fun(&ImgOp::run), i ...) don't remember syntax */ ); } int main( ... ) { std::vector< ImgOp* > v; v.push_back( new CheckImageSize ); v.push_back( new CheckImageResolution ); v.push_back( new RotateImage ); Image i; do_operations( v, i ); } If there are multiple images, the set can be split and shared over several threads. To ensure "thread-safety", each thread must have its own copy of all operation objects contained in v -- v becomes a prototype to be deep copied in each thread.

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  • C++ explicit template specialization of templated constructor of templated class

    - by Victor Liu
    I have a class like template <class T> struct A{ template <class U> A(U u); }; I would like to write an explicit specialization of this for a declaration like A<int>::A(float); In the following test code, if I comment out the specialization, it compiles with g++. Otherwise, it says I have the wrong number of template parameters: #include <iostream> template <class T> struct A{ template <class U> A(T t, U *u){ *u += U(t); } }; template <> template <> A<int>::A<int,float>(int t, float *u){ *u += U(2*t); } int main(){ float f = 0; int i = 1; A<int>(i, &f); std::cout << f << std::endl; return 0; }

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