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  • C++ is there a difference between assignment inside a pass by value and pass by reference function?

    - by Rémy DAVID
    Is there a difference between foo and bar: class A { Object __o; void foo(Object& o) { __o = o; } void bar(Object o) { __o = o; } } As I understand it, foo performs no copy operation on object o when it is called, and one copy operation for assignment. Bar performs one copy operation on object o when it is called and another one for assignment. So I can more or less say that foo uses 2 times less memory than bar (if o is big enough). Is that correct ? Is it possible that the compiler optimises the bar function to perform only one copy operation on o ? i.e. makes __o pointing on the local copy of argument o instead of creating a new copy?

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  • Finding relative libraries when using symlinks to ruby executables

    - by dgtized
    Imagine you have an executable foo.rb, with libraries bar.rb layed out in the following manner: <root>/bin/foo.rb <root>/lib/bar.rb In the header of foo.rb you place the following require to bring in functionality in bar.rb: require File.dirname(__FILE__)+"../lib/bar.rb" This works fine so long as all calls to foo.rb are direct. If you put as say $HOME/project, and symlink foo.rb into $HOME/usr/bin, then __FILE__ resolves to $HOME/usr/bin/foo.rb, and is thus unable to locate bar.rb in relation to the dirname for foo.rb. I realize that packaging systems such as rubygems fix this by creating a namespace to search for the library, and that it is also possible to adjust the load_path using $: to include $HOME/project/lib, but it seems as if a more simple solution should exist. Has anyone had experience with this problem and found a useful solution or recipe?

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  • Initializing a char array through passed pointer segfaults

    - by Bitgarden
    Ie., why does the following work: char* char_array(size_t size){ return new char[size]; } int main(){ const char* foo = "foo"; size_t len = strlen(foo); char* bar=char_array(len); memset(bar, 0, len+1); } But the following segfaults: void char_array(char* out, size_t size){ out= new char[size]; } int main(){ const char* foo = "foo"; size_t len = strlen(foo); char* bar; char_array(bar, len); memset(bar, 0, len+1); }

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  • Binding Data Template element to property on sub-class

    - by TerrorAustralis
    Hi guys, I have a class, for experiment sake call it foo() and another class, call it bar() I have a data template for class foo() defined in my xaml, but one of foo()'s properties is a bar() object such that foo() { Public string Name {get; set;} Public int ID {get; set;} Public bar barProp {get; set;} } and bar() { Public string Description{get; set;} } I want my data template of foo to display the Description property of bar. I have tried the simple <textblock Text="{Binding Path=barProp.Description}" /> and variants to no avail Seeking wisdom, DJ

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  • What's the best way to implement a dynamic proxy in C#?

    - by gap
    Hi, I've got a need to create a dynamic proxy in C#. I want this class to wrap another class, and take on it's public interface, forwarding calls for those functions: class MyRootClass { public virtual void Foo() { Console.Out.WriteLine("Foo!"); } } interface ISecondaryInterface { void Bar(); } class Wrapper<T> : ISecondaryInterface where T: MyRootClass { public Wrapper(T otherObj) { } public void Bar() { Console.Out.WriteLine("Bar!"); } } Here's how I want to use it: Wrapper<MyRootClass> wrappedObj = new Wrapper<MyRootClass>(new MyRootClass()); wrappedObj.Bar(); wrappedObj.Foo(); to produce: Bar! Foo! Any ideas? What's the easiest way to do this? What's the best way to do this? Thanks so much.

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  • 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

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  • How to avoid "incomplete implementation" warning in partial base class

    - by garph0
    I have created a protocol that my classes need to implement, and then factored out some common functionality into a base class, so I did this: @protocol MyProtocol - (void) foo; - (void) bar; @end @interface Base <MyProtocol> @end @interface Derived_1 : Base @end @interface Derived_2 : Base @end @implementation Base - (void) foo{ //something foo } @end @implementation Derived_1 - (void) bar{ //something bar 1 } @end @implementation Derived_2 - (void) bar{ //something bar 2 } @end In this way in my code I use a generic id<MyProtocol>. The code works (as long as Base is not used directly) but the compiler chokes at the end of the implementation of Base with a warning: Incomplete implementation of class Base Is there a way to avoid this warning or, even better, a more proper way to obtain this partially implemented abstract base class behavior in Objc?

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  • Delete the first line that matches a pattern

    - by gioele
    How can I use sed to delete only the first line that contains a certain pattern? For example, I want to remove the first line matching FAA from this document: 1. foo bar quuz 2. foo FAA bar (this should go) 3. quuz quuz FAA (this should remain) 4. quuz FAA bar (this should also remain) The result should be 1. foo bar quuz 3. quuz quuz FAA (this should remain) 4. quuz FAA bar (this should also remain) A solution for POSIX sed would be greatly appreciated, GNU sed is OK.

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  • In scala can I pass repeated parameters to other methods?

    - by Fred Haslam
    Here is something I can do in java, take the results of a repeated parameter and pass it to another method: public void foo(String ... args){bar(args);} public void bar(String ... args){System.out.println("count="+args.length);} In scala it would look like this: def foo(args:String*) = bar(args) def bar(args:String*) = println("count="+args.length) But this won't compile, the bar signature expects a series of individual strings, and the args passed in is some non-string structure. For now I'm just passing around arrays. It would be very nice to use starred parameters. Is there some way to do it?

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  • C++ Generic List Assignment

    - by S73417H
    I've clearly been stuck in Java land for too long... Is it possible to do the C++ equivalent of the following Java code: // Method List<Bar> getBars() { return new LinkedList<Bar>(); } // Assignment statement. List<Foo> stuff = getBars(); Where Foo is a sub-class of Bar. So in C++.... std::list<Bar> & getBars() { std::list<Bar> bars; return bars; } std::list<Foo> stuff = getBars(); Hope that makes sense....

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  • How to serialize this Xml in .NET (array)

    - by Morri
    I need Xml that looks like this <foo> <bar ... /> <bar ... /> </foo> And currently have the following class structure : [XmlRoot("foo")] public class Foo { [XmlArrayItem("bar")] public List<Bar> myBars; } But this gives me Xml where bar items are wrapped inside a bars element. How should I define my custom XmlAttributes so I'd get the Xml structure I need?

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  • Can you have a web application project produce multiple DLLS?

    - by chris
    I have a VS 2008 web application project that is getting large. My structure looks like: - WebRoot - Common/ - Foo/ - Bar/ - Baz/ so I end up with a single Webroot.dll that contains the code for common, foo, bar, and baz. Is it possible to set it so that I end up with common/ in webroot.dll, and code in foo ends up in foo.dll, bar in bar.dll, etc? Update: A couple of suggestions to move some stuff into class libraries. We already have a dozen or so separate class library projects as part of the solution; Foo, Bar and Baz contain nothing but web forms and the associated code-behinds, so moving them into separate class library projects is not feasible.

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  • Domain Redirection While Maintaining Original URL

    - by Steve
    I have two domains ("this_site.com" and "that_site.com") that I want to point to the same place (same set of files). BUT What I really want to do is maintain the original URL in the address bar while the visitor accesses the different pages. Example: The primary domain holding the web files is "this_site.com". If I type in "that_site.com" in the address bar, I want the address bar to keep displaying "that_site.com" no matter where they go on the web site. Normal domain redirection causes the URL displayed in the address bar to change to the 'master' domain (i.e. the visitor that typed in "that_site.com" will see the address bar's URL change to "this_site.com"). Is there some sort of .htaccess trick that I can employ to do this? What I'm trying to do is NOT confuse visitors who visit one URL and find themselves on a different URL as well as avoid the additional expense and trouble of having to maintain two separate hosting accounts.

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  • problem in jquery with showing pop message on submit form

    - by user1400
    hi guys in my application on php i use of 'jQuery Notify Bar' plugin for display messages, i'd like to show message when my form submit(in edit page) ,the other page(index page) is opened and notify bar be open until the other page(index page) is completely load and even some second more but the problem is that notify bar show for short Moment and when the index page begin to load , notify bar is closed, and the delay property is not effect to that $('#myForm').submit(function(){ $.notifyBar({ html: "Thank you, your settings were updated!", **delay: 20000,** animationSpeed: "normal" }); how to show notify bar in the other page too? thanks

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  • Access a static variable by $var::$reference

    - by chuckg
    I am trying to access a static variable within a class by using a variable class name. I'm aware that in order to access a function within the class, you use call_user_func(): class foo { function bar() { echo 'hi'; } } $class = "foo"; all_user_func(array($class, 'bar')); // prints hi However, this does not work when trying to access a static variable within the class: class foo { public static $bar = 'hi'; } $class = "foo"; call_user_func(array($class, 'bar')); // nothing echo $foo::$bar; // invalid How do I get at this variable? Is it even possible? I have a bad feeling this is only available in PHP 5.3 going forward and I'm running PHP 5.2.6. Thanks.

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  • Is read-only auto-imlemented property possible?

    - by abatishchev
    Hello. I found a topic on MSDN that talks that yes, this is possible. I did a test that seems to break this statement: using System; namespace Test { class Program { static void Main(string[] args) { Foo f = new Foo("1"); Console.WriteLine(f.Bar); // prints 1 f.Test("2"); Console.WriteLine(f.Bar);// successfully prints 2 } } class Foo { public Foo(string b) { this.Bar = b; } public string Bar { get; private set; } public void Test(string b) { // this would be impossible for readonly field! // next error would be occur: CS0191 or CS0191 // A readonly field cannot be assigned to (except in a constructor or a variable initializer) this.Bar = b; } } } Where am I wrong?

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  • C# Why does calling an interface member from a class generate an error?

    - by Jack
    So I have an interface: interface IFoo { int Bar(); int this[int i] {get; set;} } And a class that derives from it class Foo : IFoo { public int IFoo.Bar() { //Implementation { public int IFoo.this[int i] { //Implementation } } Now, I try to do this: var fooey = new Foo(); int i = Fooey.Bar(); or this: int i = Fooey[4]; I would expect these to work properly. However, the compiler generates an error as if such members don't exist. Why is that? I am aware I can cast Foo as IFoo, but I am also aware that casting is costly to performance, which is often the reason to use interfaces in the first place. EDIT 1: These are the errors generated 'Foo' does not contain a definition for 'Bar' and no extension method 'Bar' accepting a first argument of type 'Foo' could be found (are you missing a using directive or an assembly reference?) "Cannot apply indexing to an expression of type 'Foo'"

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  • IE9 Beta

    - by Daniel Moth
    I've been using Internet Explorer 8 since the early pre-release bits, but I never tried IE9 until today – the day the Beta is available. I downloaded it from here: http://www.beautyoftheweb.com/ The download took longer than what I expected, but I was doing other stuff, so no bother. After coming down, it asked me to reboot my computer. Really hate when apps do that, but I did it anyway. The first time I launched it, it prompted me with a list of add-ons I should disable including the start-up time that I could save fore each one. It even let me configure the prompt so, for example, it won't prompt me again unless an add-on contributes to more than 1 second of the startup time. Cool. First thing I noticed is that the search bar had gone and, as you'd expect, you have to search from the address box. I totally despise this feature. The first thing I've been doing with all versions of IE is to turn off the automatic searching from the address bar and now I have no way of searching if I do that. Ridiculous. The second thing I notice is that the tabs are next to the address bar and cannot be moved to go below it. One word for that decision: appalling (and, no, I didn't accidentally drop an 'e' and added an 'l' in the previous word). The third thing I notice to the right is the favorites button (star icon) and when I click on it, it brings up the favorites explorer under it on the right; then I pin the explorer and it jumps to the left(!). Why move the entry point to this feature to the right instead of leaving it on the left is beyond me (other than wanting to retrain me on what I've been used to for all this time), but the fact that pinning it makes it jump sides is… an "astonishing" design decision. As I browse I notice a little annoying pop up in the bottom left every time I hover over a link; there is no status bar. I correctly guessed to right click at the top and turn on the status bar (which also got rid of the popup thereafter) and while I am at it, I bring back my favorites bar which was hidden by default (and am pleased to see that all my favorites are still there). The next thing I notice, I like: IE9 is fast. No joke, I visit sites and they seem to be loading visibly much faster – try it! Beyond the speed, I am interested to find out what else is new. I searched and found a few good links: What's new in Internet Explorer 9 Internet Explorer 9 Features (check out the links under "Clean") Top Features If you are a developer, check out IE's msdn home for many articles, e.g. this section on Canvas and SVG. Either way: wherever you are, get IE9 Beta now and judge for yourself. If you don't like it, you can always uninstall (which auto-restores the previous version). Comments about this post welcome at the original blog.

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  • Passing ActionListeners in Java, pack()

    - by Crystal
    Two questions. First question is I'm trying to create a simple form that when you press a button, it adds a Person object to the ArrayList. However, since I am not used to GUIs, I tried creating one and am first just trying to get the user input from the JTextField, create an ActionListener object of the appropriate type, so once that works, then I can pass in all the JTextField inputs to create my Person object. Unfortunately, I am not getting any data when I type in something to the firstName JTextField and was wondering if someone could look at my code below. import java.awt.*; import java.awt.event.*; import javax.swing.*; import java.util.List; import java.util.ArrayList; public class AddressBook { public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { public void run() { AddressBookFrame frame = new AddressBookFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); JMenuBar menuBar = new JMenuBar(); frame.setJMenuBar(menuBar); JMenu fileMenu = new JMenu("File"); JMenuItem openItem = new JMenuItem("Open"); JMenuItem saveItem = new JMenuItem("Save"); JMenuItem saveAsItem = new JMenuItem("Save As"); JMenuItem printItem = new JMenuItem("Print"); JMenuItem exitItem = new JMenuItem("Exit"); fileMenu.add(openItem); fileMenu.add(saveItem); fileMenu.add(saveAsItem); fileMenu.add(printItem); fileMenu.add(exitItem); menuBar.add(fileMenu); JMenu editMenu = new JMenu("Edit"); JMenuItem newItem = new JMenuItem("New"); JMenuItem editItem = new JMenuItem("Edit"); JMenuItem deleteItem = new JMenuItem("Delete"); JMenuItem findItem = new JMenuItem("Find"); JMenuItem firstItem = new JMenuItem("First"); JMenuItem previousItem = new JMenuItem("Previous"); JMenuItem nextItem = new JMenuItem("Next"); JMenuItem lastItem = new JMenuItem("Last"); editMenu.add(newItem); editMenu.add(editItem); editMenu.add(deleteItem); editMenu.add(findItem); editMenu.add(firstItem); editMenu.add(previousItem); editMenu.add(nextItem); editMenu.add(lastItem); menuBar.add(editMenu); JMenu helpMenu = new JMenu("Help"); JMenuItem documentationItem = new JMenuItem("Documentation"); JMenuItem aboutItem = new JMenuItem("About"); helpMenu.add(documentationItem); helpMenu.add(aboutItem); menuBar.add(helpMenu); frame.setVisible(true); } }); } } class AddressBookFrame extends JFrame { public AddressBookFrame() { setLayout(new BorderLayout()); setTitle("Address Book"); setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT); AddressBookToolBar toolBar = new AddressBookToolBar(); add(toolBar, BorderLayout.NORTH); AddressBookStatusBar aStatusBar = new AddressBookStatusBar("5"); add(aStatusBar, BorderLayout.SOUTH); AddressBookForm form = new AddressBookForm(); add(form, BorderLayout.CENTER); } public static final int DEFAULT_WIDTH = 500; public static final int DEFAULT_HEIGHT = 500; } /* Create toolbar buttons and add buttons to toolbar */ class AddressBookToolBar extends JPanel { public AddressBookToolBar() { setLayout(new FlowLayout(FlowLayout.LEFT)); JToolBar bar = new JToolBar(); JButton newButton = new JButton("New"); JButton editButton = new JButton("Edit"); JButton deleteButton = new JButton("Delete"); JButton findButton = new JButton("Find"); JButton firstButton = new JButton("First"); JButton previousButton = new JButton("Previous"); JButton nextButton = new JButton("Next"); JButton lastButton = new JButton("Last"); bar.add(newButton); bar.add(editButton); bar.add(deleteButton); bar.add(findButton); bar.add(firstButton); bar.add(previousButton); bar.add(nextButton); bar.add(lastButton); add(bar); } } /* Creates the status bar string */ class AddressBookStatusBar extends JPanel { public AddressBookStatusBar(String statusBarString) { setLayout(new FlowLayout(FlowLayout.LEFT)); this.statusBarString = new JLabel("Total number of people: " + statusBarString); add(this.statusBarString); } private JLabel statusBarString; private int totalContacts; } class AddressBookForm extends JPanel { public AddressBookForm() { this.setLayout(new GridLayout(2, 1)); JPanel formPanel = new JPanel(); formPanel.setLayout(new GridLayout(4, 2)); JTextField firstName = new JTextField(20); JTextField lastName = new JTextField(20); JTextField telephone = new JTextField(20); JTextField email = new JTextField(20); JLabel firstNameLabel = new JLabel("First Name: ", JLabel.LEFT); formPanel.add(firstNameLabel); formPanel.add(firstName); JLabel lastNameLabel = new JLabel("Last Name: ", JLabel.LEFT); formPanel.add(lastNameLabel); formPanel.add(lastName); JLabel telephoneLabel = new JLabel("Telephone: ", JLabel.LEFT); formPanel.add(telephoneLabel); formPanel.add(telephone); JLabel emailLabel = new JLabel("Email: ", JLabel.LEFT); formPanel.add(emailLabel); formPanel.add(email); add(formPanel); JPanel buttonPanel = new JPanel(); JButton insertButton = new JButton("Insert"); JButton displayButton = new JButton("Display"); // create button actions AddressBookManager insertAction = new AddressBookManager(firstName.getText()); insertButton.addActionListener(insertAction); buttonPanel.add(insertButton); buttonPanel.add(displayButton); add(buttonPanel); } private List<Person> addressList = new ArrayList<Person>(); private class AddressBookManager implements ActionListener { public AddressBookManager(String text) { // addressList.add( setName(text); System.out.println("Test" + text); } public void actionPerformed(ActionEvent e) { System.out.println("Hello" + name); } public void setName(String name) { this.name = name; } private String name; } } Second question is, how do I make my form not take up the whole center space. I don't like the stretch look and was hoping the JTextFields could be just one line long, not a big box. Same thing with the buttons. Any thoughts? Thanks.

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  • Store comparison in variable (or execute comparison when it's given as an string)

    - by BorrajaX
    Hello everyone. I'd like to know if the super-powerful python allows to store a comparison in a variable or, if not, if it's possible calling/executing a comparison when given as an string ("==" or "!=") I want to allow the users of my program the chance of giving a comparison in an string. For instance, let's say I have a list of... "products" and the user wants to select the products whose manufacturer is "foo". He could would input something like: Product.manufacturer == "foo" and if the user wants the products whose manufacturer is not "bar" he would input Product.manufacturer != "bar" If the user inputs that line as an string, I create a tree with an structure like: != / \ manufacturer bar I'd like to allow that comparison to run properly, but I don't know how to make it happen if != is an string. The "manufacturer" field is a property, so I can properly get it from the Product class and store it (as a property) in the leaf, and well... "bar" is just an string. I'd like to know if I can something similar to what I do with "manufacturer": storing it with a 'callable" (kind of) thing: the property with the comparator: != I have tried with "eval" and it may work, but the comparisons are going to be actually used to query a MySQL database (using sqlalchemy) and I'm a bit concerned about the security of that... Any idea will be deeply appreciated. Thank you! PS: The idea of all this is being able to generate a sqlalchemy query, so if the user inputs the string: Product.manufacturer != "foo" || Product.manufacturer != "bar" ... my tree thing can generate the following: sqlalchemy.or_(Product.manufacturer !="foo", Product.manufacturer !="bar") Since sqlalchemy.or_ is callable, I can also store it in one of the leaves... I only see a problem with the "!="

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  • Can I select 0 columns in SQL Server?

    - by Woody Zenfell III
    I am hoping this question fares a little better than the similar Create a table without columns. Yes, I am asking about something that will strike most as pointlessly academic. It is easy to produce a SELECT result with 0 rows (but with columns), e.g. SELECT a = 1 WHERE 1 = 0. Is it possible to produce a SELECT result with 0 columns (but with rows)? e.g. something like SELECT NO COLUMNS FROM Foo. (This is not valid T-SQL.) I came across this because I wanted to insert several rows without specifying any column data for any of them. e.g. (SQL Server 2005) CREATE TABLE Bar (id INT NOT NULL IDENTITY PRIMARY KEY) INSERT INTO Bar SELECT NO COLUMNS FROM Foo -- Invalid column name 'NO'. -- An explicit value for the identity column in table 'Bar' can only be specified when a column list is used and IDENTITY_INSERT is ON. One can insert a single row without specifying any column data, e.g. INSERT INTO Foo DEFAULT VALUES. One can query for a count of rows (without retrieving actual column data from the table), e.g. SELECT COUNT(*) FROM Foo. (But that result set, of course, has a column.) I tried things like INSERT INTO Bar () SELECT * FROM Foo -- Parameters supplied for object 'Bar' which is not a function. -- If the parameters are intended as a table hint, a WITH keyword is required. and INSERT INTO Bar DEFAULT VALUES SELECT * FROM Foo -- which is a standalone INSERT statement followed by a standalone SELECT statement. I can do what I need to do a different way, but the apparent lack of consistency in support for degenerate cases surprises me. I read through the relevant sections of BOL and didn't see anything. I was surprised to come up with nothing via Google either.

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  • Why can't I use WCF DataContract and ISerializable on the same class?

    - by Dave
    Hi all, I have a class that I need to be able to serialize to a SQLServer session variable and be available over a WCF Service. I have declared it as follows namespace MyNM { [Serializable] [DataContract(Name = "Foo", Namespace = "http://www.mydomain.co.uk")] public class Foo : IEntity, ISafeCopy<Foo> { [DataMember(Order = 0)] public virtual Guid Id { get; set; } [DataMember(Order = 1)] public virtual string a { get; set; } DataMember(Order = 2)] public virtual Bar c { get; set; } /* ISafeCopy implementation */ } [Serializable] [DataContract(Name = "Bar ", Namespace = "http://www.mydomain.co.uk")] public class Bar : IEntity, ISafeCopy<Bar> { #region Implementation of IEntity DataMember(Order = 0)] public virtual Guid Id { get; set; } [DataMember(Order = 1)] public virtual Baz y { get; set; } #endregion /* ISafeCopy implementation*/ } [Serializable] [DataContract] public enum Baz { [EnumMember(Value = "one")] one, [EnumMember(Value = "two")] two, [EnumMember(Value = "three")] three } But when I try and call this service, I get the following error in the trace log. "System.Runtime.Serialization.InvalidDataContractException: Type 'BarProxybcb100e8617f40ceaa832fe4bb94533c' cannot be ISerializable and have DataContractAttribute attribute." If I take out the Serializable attribute, the WCF service works, but when the object can't be serialized to session. If I remove the DataContract attribute from class Bar, the WCF service fails saying Type 'BarProxy3bb05a31167f4ba492909ec941a54533' with data contract name 'BarProxy3bb05a31167f4ba492909ec941a54533:http://schemas.datacontract.org/2004/07/' is not expected. Add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer I've tried adding a KnownType attribute to the foo class [KnownType(typeof(Bar))] But I still get the same error. Can anyone help me out with this? Many thanks Dave

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  • LinqKit System.InvalidCastException When Invoking method-provided expression on member property.

    - by mdworkin
    Given a simple parent/child class structure. I want to use linqkit to apply a child lambda expression on the parent. I also want the Lambda expression to be provided by a utility method. public class Foo { public Bar Bar { get; set; } } public class Bar { public string Value { get; set; } public static Expression<Func<Bar, bool>> GetLambdaX() { return c => c.Value == "A"; } } ... Expression<Func<Foo, bool>> lx = c => Bar.GetLambdaX().Invoke(c.Bar); Console.WriteLine(lx.Expand()); The above code throws System.InvalidCastException: Unable to cast object of type 'System.Linq.Expressions.MethodCallExpression' to type 'System.Linq.Expressions.LambdaExpression'. at LinqKit.ExpressionExpander.VisitMethodCall(MethodCallExpression m) at LinqKit.ExpressionVisitor.Visit(Expression exp) at LinqKit.ExpressionVisitor.VisitLambda(LambdaExpression lambda) at LinqKit.ExpressionVisitor.Visit(Expression exp) at LinqKit.Extensions.Expand<TDelegate>(Expression`1 expr) .... Please help!

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  • Django model operating on a queryset

    - by jmoz
    I'm new to Django and somewhat to Python as well. I'm trying to find the idiomatic way to loop over a queryset and set a variable on each model. Basically my model depends on a value from an api, and a model method must multiply one of it's attribs by this api value to get an up-to-date correct value. At the moment I am doing it in the view and it works, but I'm not sure it's the correct way to achieve what I want. I have to replicate this looping elsewhere. Is there a way I can encapsulate the looping logic into a queryset method so it can be used in multiple places? I have this atm (I am using django-rest-framework): class FooViewSet(viewsets.ModelViewSet): model = Foo serializer_class = FooSerializer bar = # some call to an api def get_queryset(self): # Dynamically set the bar variable on each instance! foos = Foo.objects.filter(baz__pk=1).order_by('date') for item in foos: item.needs_bar = self.bar return items I would think something like so would be better: def get_queryset(self): bar = # some call to an api # Dynamically set the bar variable on each instance! return Foo.objects.filter(baz__pk=1).order_by('date').set_bar(bar) I'm thinking the api hit should be in the controller and then injected to instances of the model, but I'm not sure how you do this. I've been looking around querysets and managers but still can't figure it out nor decided if it's the best method to achieve what I want. Can anyone suggest the correct way to model this with django? Thanks.

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  • How to get forkpty to handle redirection and other bash-isms?

    - by Jeremy Friesner
    Hi all, I've got a GUI C++ program that takes a shell command from the user, calls forkpty() and execvp() to execute that command in a child process, while the parent (GUI) process reads the child process's stdout/stderr output and displays it in the GUI. This all works nicely (under Linux and MacOS/X). For example, if the user enters "ls -l /foo", the GUI will display the contents of the /foo folder. However, bash niceties like output redirection aren't handled. For example, if the user enters "echo bar /foo/bar.txt", the child process will output the text "bar /foo/bar.txt", instead of writing the text "bar" to the file "/foo/bar.txt". Presumably this is because execvp() is running the executable command "echo" directly, instead of running /bin/bash and handing it the user's command to massage/preprocess. My question is, what is the correct child process invocation to use, in order to make the system behave exactly as if the user had typed in his string at the bash prompt? I tried wrapping the user's command with a /bin/bash invocation, like this: /bin/bash -c the_string_the_user_entered, but that didn't seem to work. Any hints?

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