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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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  • 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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  • Can C++ Constructors be templates?

    - by Gokul
    Hi, I have non-template class with a templatized constructor. This code compiles for me. But i remember that somewhere i have referred that constructors cannot be templates. Can someone explain whether this is a valid usage? typedef double Vector; //enum Method {A, B, C, D, E, F}; struct A {}; class Butcher { public: template <class Method> Butcher(Method); private: Vector a, b, c; }; template <> Butcher::Butcher(struct A) : a(2), b(4), c(2) { // a = 0.5, 1; // b = -1, 1, 3, 2; // c = 0, 1; } Thanks, Gokul.

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • recursively reverse linked list.

    - by Amanda
    I am implementing a function to recursively reverse a linked-list, but getting seg-fault. typedef struct _node { int data; struct _node *next; } Node, *NodeP; NodeP recursiveReverseList(NodeP first){ if(first == NULL) return NULL; if(first->next == NULL) return head; NodeP rest = recursiveReverseList(head->next); rest->next = first; first->next = NULL; return first; } Can you please help. P.S. The iterative version is working fine though. Its not homework. Just practicing C.

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  • how to avoid temporaries when copying weakly typed object

    - by Truncheon
    Hi. I'm writing a series classes that inherit from a base class using virtual. They are INT, FLOAT and STRING objects that I want to use in a scripting language. I'm trying to implement weak typing, but I don't want STRING objects to return copies of themselves when used in the following way (instead I would prefer to have a reference returned which can be used in copying): a = "hello "; b = "world"; c = a + b; I have written the following code as a mock example: #include <iostream> #include <string> #include <cstdio> #include <cstdlib> std::string dummy("<int object cannot return string reference>"); struct BaseImpl { virtual bool is_string() = 0; virtual int get_int() = 0; virtual std::string get_string_copy() = 0; virtual std::string const& get_string_ref() = 0; }; struct INT : BaseImpl { int value; INT(int i = 0) : value(i) { std::cout << "constructor called\n"; } INT(BaseImpl& that) : value(that.get_int()) { std::cout << "copy constructor called\n"; } bool is_string() { return false; } int get_int() { return value; } std::string get_string_copy() { char buf[33]; sprintf(buf, "%i", value); return buf; } std::string const& get_string_ref() { return dummy; } }; struct STRING : BaseImpl { std::string value; STRING(std::string s = "") : value(s) { std::cout << "constructor called\n"; } STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } bool is_string() { return true; } int get_int() { return atoi(value.c_str()); } std::string get_string_copy() { return value; } std::string const& get_string_ref() { return value; } }; struct Base { BaseImpl* impl; Base(BaseImpl* p = 0) : impl(p) {} ~Base() { delete impl; } }; int main() { Base b1(new INT(1)); Base b2(new STRING("Hello world")); Base b3(new INT(*b1.impl)); Base b4(new STRING(*b2.impl)); std::cout << "\n"; std::cout << b1.impl->get_int() << "\n"; std::cout << b2.impl->get_int() << "\n"; std::cout << b3.impl->get_int() << "\n"; std::cout << b4.impl->get_int() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_ref() << "\n"; std::cout << b2.impl->get_string_ref() << "\n"; std::cout << b3.impl->get_string_ref() << "\n"; std::cout << b4.impl->get_string_ref() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_copy() << "\n"; std::cout << b2.impl->get_string_copy() << "\n"; std::cout << b3.impl->get_string_copy() << "\n"; std::cout << b4.impl->get_string_copy() << "\n"; return 0; } It was necessary to add an if check in the STRING class to determine whether its safe to request a reference instead of a copy: Script code: a = "test"; b = a; c = 1; d = "" + c; /* not safe to request reference by standard */ C++ code: STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } If was hoping there's a way of moving that if check into compile time, rather than run time.

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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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  • Hibernate Annotation for Entity existing in more than 1 catalog

    - by user286395
    I have a Person entity mapped by Hibernate to a database table in a database catalog "Active". After a period of time, records in this database table in the "Active" catalog are archived/moved to an exact copy of the table in a database Catalog "History". I have the need to retrieve from both the Active and History Catalogs. Is there a better way to model this with Hibernate annotations than making an abstract class that 2 classes extend from. This is what I have now. @MappedSuperclass public abstract class Person { @Id private Integer id; private String name; } @Entity @Table(name="Person", catalog="Active") public class PersonActive extends Person { } @Entity @Table(name="Person", catalog="History") public class PersonHistory extends Person { }

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  • Pointer to another classs as a property

    - by arjacsoh
    Why I receive an error when I try to create a property to another class through a pointer like that: #ifndef SQUARE_H #define SQUARE_H #include <string> //using namespace std; #include "Player.h" class Square { public: Square(int); void process(); protected: int ID; Player* PlayerOn; <--- }; #endif and the Player class is : #ifndef PLAYER_H #define PLAYER_H #include <string> //using namespace std; #include "Square.h" class Player { public: Player(int,int); // ~Player(void); int playDice(); private: int ID; int money; }; #endif I receive: syntax error missing ; before * (on the declaration of Player* PlayerOn;) and missing type specifier (on the same line...)

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  • cocoa - referencing a method on the parent

    - by Mike
    I had a method on my main view controller named "calculateThis". This method was run, obviously, as int newValue = [self calculateThis:myVariable]; when I run it from inside the view controller. Then I created a static class and I need to run this method from there. How do I reference this method from that class using just relative references, as super, superview, delegate, etc. I cannot use the class name defined on the delegate because this static class is used in several apps of mine.

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  • Getting a Type variable knowing the name of type C#

    - by StuffHappens
    Hello! I'm developing a TypeTranslator class which has a method Type TranslateType(Type type). This method gets a type of an interface and if there's a class of interface name without leading I it creates it, otherwise an exception is raised. Here's some code to clearify what's written before: class Program { interface IAnimal { } class Animal : IAnimal { } void Function() { TypeTranslator typeTranslator = new TypeTranslator(); Assert(typeTranslator.TranslateType(typeof(IAnimal) == typeof(Animal))); } } Is it possible to get what I want? Thank you for your help!

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  • How can I specify dependencies in the manifest file and then to include it into my .jar file?

    - by Roman
    I generated .class files by the following command: javac -cp \directoryName\external.jar myPackageDirectory\First.java myPackageDirectory\Second.java I needed to use -cp during compilation and name of .jar file of an "external" library (external.jar) to be able to use this library from my code. Using my .class files I have generated my .jar file in the following way: jar cfm app.jar manifest.txt myPackageDirectory\*.class manifest.txt contains just one line: Main-Class: myPackageName.First My problem is that I am not sure that I will be able to run my .jar file on other computers. I think so because during the compilation I specified the location of the .jar file of the external library. So, my .class files (included into the .jar file will try to find the .jar file of the external library in a specific directory and there is no guaranty that that the .jar file of the external library will be in the same directory as on the my computer. I heard that the above problem can be solved by a usage of a MANIFEST file that I include in my own jar, and which will list dependency locations but I do not understand how it works. I do need to specify location of the "external.jar" at the compilation stage (otherwise the compiler complains).

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  • Use different Solr Similarity algo for every search

    - by snickernet
    Hi Guys, Is possible in Solr 1.4 to specify which similarity class to use for every search within a single index? Let's say, I got 2 type of search (keyword and brand). For keyword search, I want to use the DefaultSimilarity class. But, for brand search, I want to use my CustomSimilarity class. I've been modifying the schema.xml to specify a single similarity class to use. But, I came to this requirement that I have to use 2 different similarity classes. I'll be glad to here your thoughts on this. Thanks in advance.

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  • Loop results executing twice

    - by ozzysmith
    I creating a simple site with PHP where the users can submit blogs and other users (who are logged in) can post comments on them. I have made a link called "comments" below each blog that when clicked will show / hide all the comments relevant to the specific blog (also if the user is logged in, it will show a form field in which they can submit new comments). So basically each blog will have multiple comments. I have done two different codes for this but they both have the same problem that each comment appears twice (everything else works fine). Could anyone point out why? mysql_select_db ("ooze"); $result = mysql_query ("select * from blog") or die(mysql_error()); $i = 1; while($row = mysql_fetch_array($result)) { echo "<h1>$row[title]</h1>"; echo "<p class ='second'>$row[blog_content]</p> "; echo "<p class='meta'>Posted by .... &nbsp;&bull;&nbsp; $row[date] &nbsp;&bull;&nbsp; <a href='#' onclick=\"toggle_visibility('something$i'); return false\">Comments</a><div id='something$i' style='display: none;'>"; $i++; $a = $row["ID"]; $result2 = mysql_query ("select * from blog, blogcomment where $a=blogID") or die(mysql_error()); while($sub = mysql_fetch_array($result2)) { echo "<p class='third' >$sub[commentdate] &nbsp;&bull;&nbsp; $sub[username]</p><p>said:</p> <p>$sub[comment]</p>"; } if ( isset ($_SESSION["gatekeeper"])) { echo '<form method="post" name="result_'.$row["ID"].'" action="postcomment.php"><input name="ID" type = "hidden" value = "'.$row["ID"].'" /><input name="comment" id="comment" type="text" style="margin-left:20px;"/><input type="submit" value="Add comment" /></form>'; } else { echo '<p class="third"><a href="register.html">Signup </a>to post a comment</p>'; } echo "</div>"; } mysql_close($conn); //second version of inner loop:// if ( isset ($_SESSION["gatekeeper"])) { while($sub = mysql_fetch_array($result2)) { echo "<p class='third' >$sub[commentdate] &nbsp;&bull;&nbsp; $sub[username] said:</p> <p>$sub[comment]</p>"; } echo '<form method="post" name="result_'.$row["ID"].'" action="postcomment.php"><input name="ID" type = "hidden" value = "'.$row["ID"].'" /><input name="comment" id="comment" type="text" style="margin-left:20px;"/><input type="submit" value="Add comment" /></form>'; } else { while($sub = mysql_fetch_array($result2)) { echo "<p class='third' >$sub[commentdate] &nbsp;&bull;&nbsp; $sub[username] said:</p> <p>$sub[comment]</p>"; } echo '<p class="third"><a href="register.html">Signup </a>to post a comment</p>'; } echo "</div>"; } mysql_close($conn);

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