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  • How to use a object whose copy constructor and copy assignment is private?

    - by coanor
    In reading TCPL, I got a problem, as the title refered, and then 'private' class is: class Unique_handle { private: Unique_handle& operator=(const Unique_handle &rhs); Unique_handle(const Unique_handle &rhs); public: //... }; the using code is: struct Y { //... Unique_handle obj; }; and I want to execute such operations: int main() { Y y1; Y y2 = y1; } although, these code are come from TCPL, but I still can not got the solution... Can anybody help me, appreciate.

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  • Ruby on Rails with_option cannot call class method

    - by Dmitri
    I have a problem calling class method from the with_option block with validations: Model: class Model < ActiveRecord::Base attr_accessible :field with_options :if => "<not important>" do |step| ... bunch of validations step.validates :field, :inclusion => {:within => Model.field} end private self.field (1..10) end end And it returns: undefined method `field' for #Class:0x5f394a8 self.class.field also doesn't work. What is wrong with it ? How to fix it ? Big big thanks!

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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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  • How to deal with a flaw in System.Data.DataTableExtensions.CopyToDataTable()

    - by andy
    Hey guys, so I've come across something which is perhaps a flaw in the Extension method .CopyToDataTable. This method is used by Importing (in VB.NET) System.Data.DataTableExtensions and then calling the method against an IEnumerable. You would do this if you want to filter a Datatable using LINQ, and then restore the DataTable at the end. i.e: Imports System.Data.DataRowExtensions Imports System.Data.DataTableExtensions Public Class SomeClass Private Shared Function GetData() As DataTable Dim Data As DataTable Data = LegacyADO.NETDBCall Data = Data.AsEnumerable.Where(Function(dr) dr.Field(Of Integer)("SomeField") = 5).CopyToDataTable() Return Data End Function End Class In the example above, the "WHERE" filtering might return no results. If this happens CopyToDataTable throws an exception because there are no DataRows. Why? The correct behavior should be to return a DataTable with Rows.Count = 0. Can anyone think of a clean workaround to this, in such a way that whoever calls CopyToDataTable doesn't have to be aware of this issue? System.Data.DataTableExtensions is a Static Class so I can't override the behavior....any ideas? Have I missed something? cheers UPDATE: I have submitted this as an issue to Connect. I would still like some suggestions, but if you agree with me, you could vote up the issue at Connect via the link above cheers

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  • How to call another class's method from my app delegate

    - by Jared
    I have an application that utilizes UILocalNotifications to pop-up UIAlertViews. When the notification fires, the user chooses to go into the app, and this method is called from my app delegate: - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {...} Where I can handle it and where I also prompt another alertview for more information. So when the app launches, it is displaying view A, and then the alertview pops up and prompts for input. This alertview, however, is originating from my app delegate. I need to be able to reload view A when the user hits Yes/No on the alertview. How can I do that from within my app delegate? Any help is appreciated!!

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  • How do I avoid boxing/unboxing when extending System.Object?

    - by Robert H.
    I'm working on an extension method that's only applicable to reference types. I think, however, it's currently boxing and unboxing the the value. How can I avoid this? namespace System { public static class SystemExtensions { public static TResult GetOrDefaultIfNull<T, TResult>(this T obj, Func<T, TResult> getValue, TResult defaultValue) { if (obj == null) return defaultValue; return getValue(obj); } } } Example usage: public class Foo { public int Bar { get; set; } } In some method: Foo aFooObject = new Foo { Bar = 1 }; Foo nullReference = null; Console.WriteLine(aFooObject.GetOrDefaultIfNull((o) => o.Bar, 0)); // results: 1 Console.WriteLine(nullReference.GetOrDefaultIfNull((o) => o.Bar, 0)); // results: 0

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  • LINQ .Cast() extension method fails but (type)object works.

    - by Ben Robinson
    To convert between some LINQ to SQL objects and DTOs we have created explicit cast operators on the DTOs. That way we can do the following: DTOType MyDTO = (LinqToSQLType)MyLinq2SQLObj; This works well. However when you try to cast using the LINQ .Cast() extension method it trows an invalid cast exception saying cannot cast type Linq2SQLType to type DTOType. i.e. the below does not work List<DTO.Name> Names = dbContact.tNames.Cast<DTO.Name>() .ToList(); But the below works fine: DAL.tName MyDalName = new DAL.tName(); DTO.Name MyDTOName = (DTO.Name)MyDalName; and the below also works fine List<DTO.Name> Names = dbContact.tNames.Select(name => (DTO.Name)name) .ToList(); Why does the .Cast() extension method throw an invalid cast exception? I have used the .Cast() extension method in this way many times in the past and when you are casting something like a base type to a derived type it works fine, but falls over when the object has an explicit cast operator.

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  • Access inner function variables in Javascript

    - by Elazar Leibovich
    In many frameworks, internal function variables are used as private variables, for example Raphael = (function(){ var private = function(a,b) {return a+b;}; var public = function(a) {return private(a,a);} var object = {mult2:public}; return object; })(); here, we cannot access from the global namespace the variable named private, as it is an inner variable of the anonymous function in the first line. Sometimes this function is contains a big Javascript framework, so that it wouldn't pollute the global namespace. I need to unit tests some object Raphael uses internally (in the above example, I wish to run unit tests on the object private). How can I test them?

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  • Java Method declaration

    - by user1701604
    I'm trying to declare a method for my program that takes only a 5 digit integer and for each digit of the integer, reads a value from the program and prints it out. I understand this isn't very clear but im having trouble relaying what I mean. I understand it will be some sort of for loop to read each digit of the integer individually until something reaches 5. Something like the charAt() string method but works for digits.

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  • Anonymous method as function result

    - by iamjoosy
    What I want to do is to assign an anonymous method which I get as a function result to a variable of the same type. Delphi complains about not beeing able to do the assignement. Obviously Delphi things I want to assign the "GetListener" function instead of the result of that same function. Any help with this is very much appreciated. type TPropertyChangedListener = reference to procedure (Sender: TStimulus); TMyClass = class function GetListener:TPropertyChangedListener end; .... var MyClass: TMyClass; Listener: TPropertyChangedListener; begin MyClass:= TMyClass.create; Listener:= MyClass.GetListener; // Delphi compile error: E2010 Incompatible types: TPropertyChangedListener' and 'Procedure of object' end;

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  • Why can't you call a non-static method from a static method?

    - by VoodooChild
    I have a static method [Method1] in my class, which calls another method [Method2] in the same class and is not a static method. But this is a no-no. I get this error: An object reference is required for the non-static field, method, or property "ClassName.MethodName()" Can someone please briefly describe why? including other things that might be related to this.

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  • Extension method not working if I set controller property in Action, works in OnExecuting

    - by Blankman
    I have a class MyController that inherits from Controller, so all my controllers inherit from MyController. I have a property in MyController: public class MyController : Controller { public string SomeProperty {get;set;} } if I set this property in MyController's OnExecuting method, my HtmlHelper extension method works fine: public static string SomeExtension(this HtmlHelper htmlHelper) { StringBuilder sb = new StringBuilder(); string result = ""; var controller = htmlHelper.ViewContext.Controller as MyController; if (controller != null) { result = controller.SomeProperty; } return result; } it doesn't work if I set 'SomeProperty' in my controllers action method. I guess because I am doing 'as MyController' in the extension method? is there a way for it to work in both situations? I am using the value of SomeProperty to be outputted on my view pages.

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  • Using ms: xpath functions inside XPathExpression

    - by Filini
    I am trying to use Microsoft XPath Extension Functions (such as ms:string-compare http://msdn.microsoft.com/en-us/library/ms256114.aspx) inside an XPathExpression object. These functions are extensions inside the MSXML library, and if I use them in an XslCompiledTransform (simply adding the "ms" namespace) they work like a charm: var xsl = @" <?xml version=""1.0"" encoding=""UTF-8""?> <xsl:stylesheet version=""2.0"" xmlns:xsl=""http://www.w3.org/1999/XSL/Transform"" xmlns:xs=""http://www.w3.org/2001/XMLSchema"" xmlns:fn=""http://www.w3.org/2005/xpath-functions"" xmlns:ms=""urn:schemas-microsoft-com:xslt""> <xsl:output method=""xml"" version=""1.0"" encoding=""UTF-8"" indent=""yes""/> <xsl:template match=""/Data""> <xsl:element name=""Result""> <xsl:value-of select=""ms:string-compare(@timeout1, @timeout2)""/> </xsl:element> </xsl:template> </xsl:stylesheet>"; var xslDocument = new XmlDocument(); xslDocument.LoadXml(xsl); var transform = new XslCompiledTransform(); transform.Load(xslDocument); Then I tried using them in an XPathExpression: XPathNavigator nav = document.DocumentElement.CreateNavigator(); XPathExpression expr = nav.Compile("ms:string-compare(/Data/@timeout1, /Data/@timeout2)"); XmlNamespaceManager manager = new XmlNamespaceManager(document.NameTable); manager.AddNamespace("ms", "urn:schemas-microsoft-com:xslt"); expr.SetContext(manager); nav.Evaluate(expr); But I get an exception "XsltContext is needed for this query because of an unknown function". XsltContext is a specific XmlNamespaceManager, but I don't know if it's possible to instantiate it without an actual XslCompiledTransform (it's abstract) and use it as my expression context. Is there any way to do this (or any other way to use ms: extensions inside an XPathExpression)?

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  • Whats wrong with this method?

    - by David
    Here's the method: public static String CPUcolor () { System.out.println ("What color am I?") ; String s = getIns() ; System.out.println ("are you sure I'm "+s+"? (Y/N)") ; String a = getIns() ; while (!((a.equals ("y")) || (a.equals ("Y")) || (a.equals ("n")) || (a.equals ("N")))) { System.out.println ("try again") ; a = getIns () ; } if (a.equals ("n") || a.equals("N")) {CPUcolor() ;} System.out.println ("I am "+s) ; return s ; } here is a possible output of this method (y's and n's are user inputs): What color am I? red are you sure I'm red? (Y/N) N What color am I? blue are you sure I'm blue? (Y/N) N What color am I? Yellow are you sure I'm Yellow? (Y/N) y I am Yellow I am blue I am red Why is it that the line's "I am blue" and "I am Blue" printed? Why are they printed in reverse order with red, the first entered, printed last?

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  • Method in RootViewController not Storing Array

    - by Antonio
    I have an array initialized in my RootViewController and a method that addsObjects to an array. I created a RootViewController object in my SecondViewController. The method runs (outputs a message) but it doesn't add anything to the array, and the array seems empty. Code is below, any suggestions? RootViewController.h #import "RootViewController.h" #import "SecondViewController.h" @implementation RootViewController - (void)viewDidLoad { [super viewDidLoad]; myArray2 = [[NSMutableArray alloc] init]; NSLog(@"View was loaded"); } -(void)addToArray2{ NSLog(@"Array triggered from SecondViewController"); [myArray2 addObject:@"Test"]; [self showArray2]; } -(void)showArray2{ NSLog(@"Array Count: %d", [myArray2 count]); } -(IBAction)switchViews{ SecondViewController *screen = [[SecondViewController alloc] initWithNibName:nil bundle:nil]; screen.modalTransitionStyle = UIModalTransitionStyleCoverVertical; [self presentModalViewController:screen animated:YES]; [screen release]; } SecondViewController.m #import "SecondViewController.h" #import "RootViewController.h" @implementation SecondViewController -(IBAction)addToArray{ RootViewController *object = [[RootViewController alloc] init]; [object addToArray2]; } -(IBAction)switchBack{ [self dismissModalViewControllerAnimated:YES]; } EDIT***** With Matt's code I got the following error: " expected specifier-qualifier-list before 'RootViewController' "

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  • Does iPhone SDK Objective C support functions inside of functions?

    - by Moshe
    I know that javascript, for example supports functions inside of functions, like so: function doSomething(){ function doAnothingThing(){ //this function is redefined every time doSomething() is called and only exists inside doSomething() } //you can also stick it inside of conditions if(yes){ function doSomethingElse(){ //this function only exists if yes is true } } } Does objective-c support this? Theoretical example: -(void) doSomething:(id) sender{ -(void) respondToEvent: (id) sender{ //theoretically? ... please? } } BONUS: What is the proper term for a "local" function?

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  • No Method Error Undefined method 'save' for nil:NilClass

    - by BennyB
    I'm getting this error when i try to create a "Lecture" via my Lecture controller's create method. This used to work but i went on to work on other parts of the app & then of course i come back & something is now throwing this error when a user tries to create a Lecture in my app. I'm sure its something small i'm just overlooking (been at it a while & probably need to take a break)...but I'd appreciate if someone could let me know why this is happening...let me know if i need to post anything else...thx! The error I get NoMethodError in LecturesController#create undefined method `save' for nil:NilClass Rails.root: /Users/name/Sites/rails_projects/app_name Application Trace | Framework Trace | Full Trace app/controllers/lectures_controller.rb:13:in `create' My view to create a new Lecture views/lectures/new.html.erb <% provide(:title, 'Start a Lecture') %> <div class="container"> <div class="content-wrapper"> <h1>Create a Lecture</h1> <div class="row"> <div class="span 6 offset3"> <%= form_for(@lecture) do |f| %> <%= render 'shared/error_messages', :object => f.object %> <div class="field"> <%= f.text_field :title, :placeholder => "What will this Lecture be named?" %> <%= f.text_area :content, :placeholder => "Describe this Lecture & what will be learned..." %> </div> <%= f.submit "Create this Lecture", :class => "btn btn-large btn-primary" %> <% end %> </div> </div> </div> </div> Then my controller where its saying the error is coming from controllers/lectures_controller.rb class LecturesController < ApplicationController before_filter :signed_in_user, :only => [:create, :destroy] before_filter :correct_user, :only => :destroy def index end def new @lecture = current_user.lectures.build if signed_in? end def create if @lecture.save flash[:success] = "Lecture created!" redirect_to @lecture else @activity_items = [ ] render 'new' end end def show @lecture = Lecture.find(params[:id]) end def destroy @lecture.destroy redirect_to root_path end private def correct_user @lecture = current_user.lectures.find_by_id(params[:id]) redirect_to root_path if @lecture.nil? end

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  • Can fields of the class and arguments of the method interfere?

    - by Roman
    I have a class with a fields called "a". In the class I have a method and in the list of arguments of this method I also have "a". So, which "a" I will see inside of the method? Will it be the field or it will be the argument of the method? public class myClass { private String a; // Method which sets the value of the field "a". public void setA(String a) { a = a; } } By the way, there is a similar situation. A method has some local (for method) variables whose names coincide with the names of the fields. What will the "see" the method if I refer to such a method-local variable inside the method (the field or the local variable)?

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  • Calling gwt static method from parent of iframe

    - by Richard Wallis
    I'd like to know how to call a GWT static method from the parent of the iframe in which the gwt module is loaded. As a simple example suppose I have the following gwt class: public class Simple { public static void showWindow() { Window.alert("Hello from the iframe"); } } I create an html host page called "iFrameHost.html" that can run the function above. Then in an unrelated GWT module on a different page I call: Frame iFrame = new Frame("iFrameHost.html"); RootPanel.get().add(iFrame); How do I now call the showWindow() method from the parent page?

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  • How to pass a class method as an argument for another function in C++ and openGL?

    - by tsubasa
    I know this thing works: void myDisplay() { ... } int main() { ... glutDisplayFunc(myDisplay) ... } so I tried to include myDisplay() function to a class that I made. Because I want to overload it in the future with a different class. However, the compiler complains that argument of type 'void (ClassBlah::)()' does not match 'void(*)()' . Here is the what I try to make: class ClassBlah { .... void myDisplay() .... } ...... int main() { ... ClassBlah blah glutDisplayFunc(blah.myDisplay) ... } Does anybody knows how to fix this problem? Many thanks.

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  • How should I deal with floating numbers that numbers that can get so small that the become zero

    - by Tristan Havelick
    So I just fixed an interesting bug in the following code, but I'm not sure the approach I took it the best: p = 1 probabilities = [ ... ] # a (possibly) long list of numbers between 0 and 1 for wp in probabilities: if (wp > 0): p *= wp # Take the natural log, this crashes when 'probabilites' is long enough that p ends up # being zero try: result = math.log(p) Because the result doesn't need to be exact, I solved this by simply keeping the smallest non-zero value, and using that if p ever becomes 0. p = 1 probabilities = [ ... ] # a long list of numbers between 0 and 1 for wp in probabilities: if (wp > 0): old_p = p p *= wp if p == 0: # we've gotten so small, its just 0, so go back to the smallest # non-zero we had p = old_p break # Take the natural log, this crashes when 'probabilites' is long enough that p ends up # being zero try: result = math.log(p) This works, but it seems a bit kludgy to me. I don't do a ton of this kind of numerical programming, and I'm not sure if this is the kind of fix people use, or if there is something better I can go for.

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