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  • Setting custom SQL in django admin

    - by eugene y
    I'm trying to set up a proxy model in django admin. It will represent a subset of the original model. The code from models.py: class MyManager(models.Manager): def get_query_set(self): return super(MyManager, self).get_query_set().filter(some_column='value') class MyModel(OrigModel): objects = MyManager() class Meta: proxy = True Now instead of filter() I need to use a complex SELECT statement with JOINS. What's the proper way to inject it wholly to the custom manager?

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  • How do I differentiate between different descendents with the same name?

    - by zotty
    I've got some XML I'm trying to import with c#, which looks something like this: <run> <name = "bob"/> <date = "1958"/> </run> <run> <name = "alice"/> <date = "1969"/> </run> I load my xml using XElement xDoc=XElement.Load(filename); What I want to do is have a class for "run", under which I can store names and dates: public class RunDetails { public RunDetails(XElement xDoc, XNamespace xmlns) { var query = from c in xDoc.Descendants(xmlns + "run").Descendants(xmlns + "name") select c; int i=0; foreach (XElement a in query) { this.name= new NameStr(a, xmlns); // a class for names Name.Add(this.name); //Name is a List<NameStr> i++; } // Here, i=2, but what I want is a new instance of the RunDetails class for each <run> } } How can I set up my code to create a new instance of the RunDetails class for every < run, and to only select the < name and < date inside a given < run?

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  • Dynamic, reflective SignalHandler in Java

    - by pilcrow
    How do I install signal handling logic iff sun.misc.Signal is available? Background First generation of my code looked something like this: class MyApp { public static void main(String[] args) { ... Signal.handle(term_sig, new SignalHandler() { public void handle(Signal sig) { ... } }); ... } } I believe I understand how to reflectively test for and use signal handlers -- Class.forName("sun.misc.Signal"), reflectively call Signal.handle, and so forth. My impulse was simply to instantiate another anonymous inner class with the dynamically obtained SignalHandler class, but I think that's just wishful syntax.

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  • Getting list of fields back from 'use fields' pragma?

    - by makenai
    So I'm familiar with the use fields pragma in Perl that can be used to restrict the fields that are stored in a class: package Fruit; use fields qw( color shape taste ); sub new { my ( $class, $params ) = @_; my $self = fields::new( $class ) unless ref $class; foreach my $name ( keys %$params ) { $self->{ $name } = $params->{ $name }; } return $self; } My question is.. once I've declared the fields at the top, how I can get the list back.. say because I want to generate accessors dynamically? Is keys %FIELDS the only way? Secondarily, is there a more efficient way to pre-populate the fields in the constructor than looping through and assigning each parameter as I am above? Thanks!

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  • How do I avoid a race condition in my Rails app?

    - by Cathal
    Hi, I have a really simple Rails application that allows users to register their attendance on a set of courses. The ActiveRecord models are as follows: class Course < ActiveRecord::Base has_many :scheduled_runs ... end class ScheduledRun < ActiveRecord::Base belongs_to :course has_many :attendances has_many :attendees, :through => :attendances ... end class Attendance < ActiveRecord::Base belongs_to :user belongs_to :scheduled_run, :counter_cache => true ... end class User < ActiveRecord::Base has_many :attendances has_many :registered_courses, :through => :attendances, :source => :scheduled_run end A ScheduledRun instance has a finite number of places available, and once the limit is reached, no more attendances can be accepted. def full? attendances_count == capacity end attendances_count is a counter cache column holding the number of attendance associations created for a particular ScheduledRun record. My problem is that I don't fully know the correct way to ensure that a race condition doesn't occur when 1 or more people attempt to register for the last available place on a course at the same time. My Attendance controller looks like this: class AttendancesController < ApplicationController before_filter :load_scheduled_run before_filter :load_user, :only => :create def new @user = User.new end def create unless @user.valid? render :action => 'new' end @attendance = @user.attendances.build(:scheduled_run_id => params[:scheduled_run_id]) if @attendance.save flash[:notice] = "Successfully created attendance." redirect_to root_url else render :action => 'new' end end protected def load_scheduled_run @run = ScheduledRun.find(params[:scheduled_run_id]) end def load_user @user = User.create_new_or_load_existing(params[:user]) end end As you can see, it doesn't take into account where the ScheduledRun instance has already reached capacity. Any help on this would be greatly appreciated.

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  • Generics limitation, or lack of skillz ?

    - by Two Shoes
    I want to define the following class as such: public class CollectionAttribute<E extends Collection<T>> { private String name; private E value; public CollectionAttribute(String name, E value) { this.name = name; this.value = value; } public E getValue() { return value; } public void addValue(T value) { value.add(T); } } This won't compile (cannot resolve symbol T). If I replace the class declaration with the following: public class CollectionAttribute<E extends Collection<?>> Then I can't reference the parametrized type of the collection. Am I missing something or have I reached a limitation with generics in Java ?

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  • Showing multiple elements onClick

    - by Nimbuz
    HTML: <ul id="mode"> <li><a href="#tab1">tab1</a> <div class="extra">tada</div> </li> <li><a href="#tab2">tab2</a> <div class="extra">tada</div> </li> </ul> <div id="tab1" class="tab-content" style="display: none">content 1</div> <div id="tab2" class="tab-content" style="display: none">content 2</div> ? jQuery: $(function(){ var mode = $('#mode'); var arrow = $('<span/>', {'class': 'arrow'}); $('li a', mode).bind('click.mytabs', function() { $('li', mode).removeClass('active'); $(this).parent().addClass('active').append(arrow); var a = $(this).attr('href'); $('.tab-content').hide(); $(a).show(); return false; }).filter(':first').triggerHandler('click.mytabs'); // eq(0) works as well }); JSFiddle here: http://jsfiddle.net/wwMJL/ I'd like to also show each li's 'extra' div on click and hide when the tab is inactive, what do I need to change in the code? Thanks!

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  • Django: How can I add weight/ordering to a many to many relationship?

    - by Klaas van Schelven
    I'm having Pages with TextBlocks on them. Text Blocks may appear on different pages, pages may have several text blocks on them. Every page may have these blocks in an ordering of it's own. This can be solved by using a separate through parameter. Like so: class TextBlock(models.Model): title = models.CharField(max_length=255) text = models.TextField() class Page(models.Model): textblocks = models.ManyToManyField(TextBlock, through=OrderedTextBlock) class OrderedTextBlock(models.Model): text_block = models.ForeignKey(TextBlock) product_page = models.ForeignKey(ProductPage) weight = models.IntegerField() class Meta: ordering = ('weight',) But I'm not very enthousiastic about the violations of DRY for my app. (There's a lot of ordered ManyToMany relations). Is there a recommended way to go about this?

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  • Visual Studio Default Open File Action

    - by Kleinux
    I am using Visual Studio 2008 with C#. Is there a way to set the default editor for a class file containing a DataTable derived class? Whenever I double click on one of these classes to open the file VS attempts to open a component designer. Since my class isn't compatible with that editor this is a rather useless default. I would like these files to open up in the normal code editor.

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  • ASP.Net MVC 2 is it possible to get the same instance of model(with slight changes) in HttpPost meth

    - by jjjjj
    Hi I have a complex entity User: public class User : BaseEntity { public virtual Taxi Taxi { get; set; } --> That is why i call it "complex" public virtual string Login { get; set; } public virtual string Password { get; set; } } where Taxi is a parent of User (Taxi has-many Users): public class Taxi : BaseEntity { public virtual string Name { get; set; } public virtual string ClientIp { get; set; } } BaseEntity consists of public virtual int Id { get; private set; } The problem occurs while trying to edit User [Authorize] public ActionResult ChangeAccountInfo() { var user = UserRepository.GetUser(User.Identity.Name); return View(user); } My ChangeAccountInfo.aspx <fieldset> <legend>Fields</legend> <% %> <div class="editor-label"> <%: Html.LabelFor(model => model.Login) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.Login) %> <%: Html.ValidationMessageFor(model => model.Login) %> </div> <div class="editor-label"> <%: Html.LabelFor(model => model.Password) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.Password) %> <%: Html.ValidationMessageFor(model => model.Password) %> </div> <div class="editor-field"> <%: Html.HiddenFor(model => model.Taxi.Name)%> </div> <p> <input type="submit" value="Save" /> </p> </fieldset> Post changes: [Authorize] [HttpPost] public ActionResult ChangeAccountInfo(User model) { if (ModelState.IsValid) { UserRepository.UpdateUser(model); return RedirectToAction("ChangeAccountInfoSuccess", "Account"); } return View(model); } But, the (User model) parameter has User.Id == 0 -- User entity had 5 before edit User.Login == "my new login" User.Password == "my new password" User.Taxi.Id == 0 -- User.Taxi entity had 3 before edit User.Taxi.Name == "old hidden name" User.Taxi.ClientIp == null -- User entity had 192.168.0.1 before edit Q: Is it possible not to mark all the fields of an entity (that should be in my UpdateUser) with tag "hidden" but still have them unchanged in my HttpPost method? e.g. not User.Taxi.ClientIp = null, but User.Taxi.ClientIp = 192.168.0.1 I'm using nhibernate, if it matters.

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  • Comparing objects and inheritance

    - by ereOn
    Hi, In my program I have the following class hierarchy: class Base // Base is an abstract class { }; class A : public Base { }; class B : public Base { }; I would like to do the following: foo(const Base& one, const Base& two) { if (one == two) { // Do something } else { // Do something else } } I have issues regarding the operator==() here. Of course comparing an instance A and an instance of B makes no sense but comparing two instances of Base should be possible. (You can't compare a Dog and a Cat however you can compare two Animals) I would like the following results: A == B = false A == A = true or false, depending on the effective value of the two instances B == B = true or false, depending on the effective value of the two instances My question is: is this a good design/idea ? Is this even possible ? What functions should I write/overload ? My apologies if the question is obviously stupid or easy, I have some serious fever right now and my thinking abilities are somewhat limited :/ Thank you.

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  • Putting a thread to sleep until event X occurs

    - by tipu
    I'm writing to many files in a threaded app and I'm creating one handler per file. I have HandlerFactory class that manages the distribution of these handlers. What I'd like to do is that thread A requests and gets foo.txt's file handle from the HandlerFactory class thread B requests foo.txt's file handler handler class recognizes that this file handle has been checked out handler class puts thread A to sleep thread B closes file handle using a wrapper method from HandlerFactory HandlerFactory notifies sleeping threads thread B wakes and successfully gets foo.txt's file handle This is what I have so far, def get_handler(self, file_path, type): self.lock.acquire() if file_path not in self.handlers: self.handlers[file_path] = open(file_path, type) elif not self.handlers[file_path].closed: time.sleep(1) self.lock.release() return self.handlers[file_path][type] I believe this covers the sleeping and handler retrieval successfully, but I am unsure how to wake up all threads, or even better wake up a specific thread.

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  • Is there a way to know if std::chrono::monotonic_clock is defined?

    - by Vicente Botet Escriba
    C++0X N3092 states that monotonic_clock is optional. 20.10.5.2 Class monotonic_clock [time.clock.monotonic] 1 Objects of class monotonic_clock represent clocks for which values of time_point never decrease as physical time advances. monotonic_clock may be a synonym for system_clock if system_clock::is_monotonic is true. ** 2 The class monotonic_clock is conditionally supported.** Is there a way using SFINAE or another technique to define a traits class that states if monotonic_clock is defined? struct is_monotonic_clock_defined; If yes, how? If not, shouldn't the standard define macro that gives this information at preprocessing time?

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  • Why do I get the error "X is not a member of Y" even though X is a friend of Y?

    - by user1232138
    I am trying to write a binary tree. Why does the following code report error C2039, "'<<' : is not a member of 'btree<T'" even though the << operator has been declared as a friend function in the btree class? #include<iostream> using namespace std; template<class T> class btree { public: friend ostream& operator<<(ostream &,T); }; template<class T> ostream& btree<T>::operator<<(ostream &o,T s) { o<<s.i<<'\t'<<s.n; return o; }

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  • Qt: any way to automatically generate QSharedData-based structures?

    - by Eye of Hell
    Hello. Qt has a build-in supprt for creating objects with integrated reference counting via QSharedData and QSharedDataPointer. All wordks great, but for each such object i need to write a lot of code: QSharedData-based implementation class with constructor and copy constructor, object class itsef with accessor methods for each filed. For a simple structures with 5-10 fields this requires really lot of near same code. Is it some ways to automate such classes generation? Maybe it's some generators exists that take a short description and automatically generates implementation class and object class with all accessors?

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  • Is it an example of decorator pattern?

    - by Supereme
    Hi, I've an example please tell me whether it is Decorator pattern or not? public abstract class ComputerComponent { String description ="Unknown Type"; public String getDescription() { return description; } public abstract double getCost(); } public abstract class AccessoryDecorator { ComputerComponent comp; public abstract String getDescription(); } public class PIIIConcreteComp extends ComputerComponent { public PIIIConcreteComp() { description=“Pentium III”; } public double getCost() { return 19950.00; } public class floppyConcreteDeco extends AccessoryDecorator { public floppyConcreteDeco(ComputerComponent comp) this.comp=comp; } public String getDescription() { return comp.getDescription() +”, floppy 1.44 mb”; } public double getCost() { return 250+comp.getCost(); } } public class ComponentAssembly { public static void createComponent() { ComputerComponent comp = new PIIConcreteComp(); // create a PIII computer object ComputerComponent deco1= new floppyConcreteDeco(comp); // decorate it with a floppy //ComputerComponent deco2= newCDRomConcreteDeco(deco1); ComputerComponent deco2= new floppyConcreteDeco(deco1); // decorate with a CDRom or with one more floppy System.out.println( deco2.getdescription() +” “+ deco2.getCost(); } } Thank you.

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  • Dynamic swappable Data Access Layer

    - by Andy
    I'm writing a data driven WPF client. The client will typically pull data from a WCF service, which queries a SQL db, but I'd like the option to pull the data directly from SQL or other arbitrary data sources. I've come up with this design and would like to hear your opinion on whether it is the best design. First, we have some data object we'd like to extract from SQL. // The Data Object with a single property public class Customer { private string m_Name = string.Empty; public string Name { get { return m_Name; } set { m_Name = value;} } } Then I plan on using an interface which all data access layers should implement. Suppose one could also use an abstract class. Thoughts? // The interface with a single method interface ICustomerFacade { List<Customer> GetAll(); } One can create a SQL implementation. // Sql Implementation public class SqlCustomrFacade : ICustomerFacade { public List<Customer> GetAll() { // Query SQL db and return something useful // ... return new List<Customer>(); } } We can also create a WCF implementation. The problem with WCF is is that it doesn't use the same data object. It creates its own local version, so we would have to copy the details over somehow. I suppose one could use reflection to copy the values of similar fields across. Thoughts? // Wcf Implementation public class WcfCustomrFacade : ICustomerFacade { public List<Customer> GetAll() { // Get date from the Wcf Service (not defined here) List<WcfService.Customer> wcfCustomers = wcfService.GetAllCustomers(); // The list we're going to return List<Customer> customers = new List<Customer>(); // This is horrible foreach(WcfService.Customer wcfCustomer in wcfCustomers) { Customer customer = new Customer(); customer.Name = wcfCustomer.Name; customers.Add(customer); } return customers; } } I also plan on using a factory to decide which facade to use. // Factory pattern public class FacadeFactory() { public static ICustomerFacade CreateCustomerFacade() { // Determine the facade to use if (ConfigurationManager.AppSettings["DAL"] == "Sql") return new SqlCustomrFacade(); else return new WcfCustomrFacade(); } } This is how the DAL would typically be used. // Test application public class MyApp { public static void Main() { ICustomerFacade cf = FacadeFactory.CreateCustomerFacade(); cf.GetAll(); } } I appreciate your thoughts and time.

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  • ASP.NET MVC - Appending data onto a file download

    - by aschepis
    what is the best way to append data onto a file download? I figure that i can make my own class that implements InputStream and just consolidates two input streams (the file first, my additional data to append second.) but is there an existing view class that i can use to just return an InputStream or will i have to roll my own view class as well?

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  • Fluent NHibernate Mappings ClassMap<Entities>....

    - by Pandiya Chendur
    I was going through fluent hibernate getting started tutorial.... In my asp.net mvc web application i have created Entities and Mapping folder as they stated... I created an entity class and i tried to map it my mapping class using this, using System; using System.Collections.Generic; using System.Linq; using System.Web; using FluentNhibernateMVC.Entities; namespace FluentNhibernateMVC.Mappings { public class ClientMap : ClassMap<Client> { } } I cant able to find a ClassMap keyword in my autosuggest list why? This is my entity class using System; using System.Collections.Generic; using System.Linq; using System.Web; namespace FluentNhibernateMVC.Entities { public class Client { public int ClientId { get; set; } public string ClientName { get; set; } public string ClientMobNo { get; set; } public string ClientAddress { get; set; } public DateTime CreatedDate { get; set; } public byte IsDeleted { get; set; } public int CreatedBy { get; set; } } } I have added all references to my project...Am i missing some thing...

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  • C++ constant reference lifetime

    - by aaa
    hello I have code that looks like this: class T {}; class container { const T &first, T &second; container(const T&first, const T & second); }; class adapter : T {}; container(adapter(), adapter()); I thought lifetime of constant reference would be lifetime of container. However, it appears otherwise, adapter object is destroyed after container is created, leading dangling reference. What is the correct lifetime? how to correctly implement binding temporary object to class member reference? Thanks

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  • Accessing the "super of this" in Java

    - by gerdemb
    This is what I'm doing now. Is there a better way to access the super class? public class SearchWidget { private void addWishlistButton() { final SearchWidget thisWidget = this; button.addClickHandler(new ClickHandler() { public void onClick(ClickEvent event) { // A better way to access the super class? // something like "this.super" ...? workWithWidget(thisWidget); } } } } I'm programming with Google Web Toolkit, but I think this is really a generic Java question.

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  • C++ Multiple Inheritance Question

    - by John
    The scenario generating this is quite complex so I'll strip out a few pieces and give an accurate representation of the classes involved. /* This is inherited using SI by many classes, as normal */ class IBase { virtual string toString()=0; }; /* Base2 can't inherit IBase due to other methods on IBase which aren't appropriate */ class Base2 { string toString() { ... } }; /* a special class, is this valid? */ class Class1 : public IBase, public Base2 { }; So, is this valid? Will there be conflicts on the toString? Or can Class1 use Base2::toString to satisfy IBase? Like I say there are lots of other things not shown, so suggestions for major design changes on this example are probably not that helpful... though any general suggestions/advice are welcome.

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