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  • Generics vs inheritance (when no collection classes are involved)

    - by Ram
    This is an extension of this questionand probably might even be a duplicate of some other question(If so, please forgive me). I see from MSDN that generics are usually used with collections The most common use for generic classes is with collections like linked lists, hash tables, stacks, queues, trees and so on where operations such as adding and removing items from the collection are performed in much the same way regardless of the type of data being stored. The examples I have seen also validate the above statement. Can someone give a valid use of generics in a real-life scenario which does not involve any collections ? Pedantically, I was thinking about making an example which does not involve collections public class Animal<T> { public void Speak() { Console.WriteLine("I am an Animal and my type is " + typeof(T).ToString()); } public void Eat() { //Eat food } } public class Dog { public void WhoAmI() { Console.WriteLine(this.GetType().ToString()); } } and "An Animal of type Dog" will be Animal<Dog> magic = new Animal<Dog>(); It is entirely possible to have Dog getting inherited from Animal (Assuming a non-generic version of Animal)Dog:Animal Therefore Dog is an Animal Another example I was thinking was a BankAccount. It can be BankAccount<Checking>,BankAccount<Savings>. This can very well be Checking:BankAccount and Savings:BankAccount. Are there any best practices to determine if we should go with generics or with inheritance ?

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  • Generics in return types of static methods and inheritance

    - by Axel
    Generics in return types of static methods do not seem to get along well with inheritance. Please take a look at the following code: class ClassInfo<C> { public ClassInfo(Class<C> clazz) { this(clazz,null); } public ClassInfo(Class<C> clazz, ClassInfo<? super C> superClassInfo) { } } class A { public static ClassInfo<A> getClassInfo() { return new ClassInfo<A>(A.class); } } class B extends A { // Error: The return type is incompatible with A.getClassInfo() public static ClassInfo<B> getClassInfo() { return new ClassInfo<B>(B.class, A.getClassInfo()); } } I tried to circumvent this by changing the return type for A.getClassInfo(), and now the error pops up at another location: class ClassInfo<C> { public ClassInfo(Class<C> clazz) { this(clazz,null); } public ClassInfo(Class<C> clazz, ClassInfo<? super C> superClassInfo) { } } class A { public static ClassInfo<? extends A> getClassInfo() { return new ClassInfo<A>(A.class); } } class B extends A { public static ClassInfo<? extends B> getClassInfo() { // Error: The constructor ClassInfo<B>(Class<B>, ClassInfo<capture#1-of ? extends A>) is undefined return new ClassInfo<B>(B.class, A.getClassInfo()); } } What is the reason for this strict checking on static methods? And how can I get along? Changing the method name seems awkward.

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  • c++ templates and inheritance

    - by Armen Ablak
    Hey, I'm experiencing some problems with breaking my code to reusable parts using templates and inheritance. I'd like to achieve that my tree class and avltree class use the same node class and that avltree class inherits some methods from the tree class and adds some specific ones. So I came up with the code below. Compiler throws an error in tree.h as marked below and I don't really know how to overcome this. Any help appreciated! :) node.h: #ifndef NODE_H #define NODE_H #include "tree.h" template <class T> class node { T data; ... node() ... friend class tree<T>; }; #endif tree.h #ifndef DREVO_H #define DREVO_H #include "node.h" template <class T> class tree { public: //signatures tree(); ... void insert(const T&); private: node<T> *root; //missing type specifier - int assumed. Note: C++ does not support default-int }; //implementations #endif avl.h #ifndef AVL_H #define AVL_H #include "tree.h" #include "node.h" template <class T> class avl: public tree<T> { public: //specific int findMin() const; ... protected: void rotateLeft(node<T> *)const; private: node<T> *root; }; #endif avl.cpp (I tried separating headers from implementation, it worked before I started to combine avl code with tree code) #include "drevo" #include "avl.h" #include "vozlisce.h" template class avl<int>; //I know that only avl with int can be used like this, but currently this is doesn't matter :) //implementations ...

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  • Designing a database for a user/points system? (in Django)

    - by AP257
    First of all, sorry if this isn't an appropriate question for StackOverflow. I've tried to make it as generalisable as possible. I want to create a database (MySQL, site running Django) that has users, who can be allocated a certain number of points for various types of action - it's a collaborative game. My requirements are to obtain: the number of points a user has the user's ranking compared to all other users and the overall leaderboard (i.e. all users ranked in order of points) This is what I have so far, in my Django models.py file: class SiteUser(models.Model): name = models.CharField(max_length=250 ) email = models.EmailField(max_length=250 ) date_added = models.DateTimeField(auto_now_add=True) def points_total(self): points_added = PointsAdded.objects.filter(user=self) points_total = 0 for point in points_added: points_total += point.points return points_total class PointsAdded(models.Model): user = models.ForeignKey('SiteUser') action = models.ForeignKey('Action') date_added = models.DateTimeField(auto_now_add=True) def points(self): points = Action.objects.filter(action=self.action) return points class Action(models.Model): points = models.IntegerField() action = models.CharField(max_length=36) However it's rapidly becoming clear to me that it's actually quite complex (in Django query terms at least) to figure out the user's ranking and return the leaderboard of users. At least, I'm finding it tough. Is there a more elegant way to do something like this? This question seems to suggest that I shouldn't even have a separate points table - what do people think? It feels more robust to have separate tables, but I don't have much experience of database design.

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  • Inheritance concept java..help

    - by max
    Hi everyone. I'd be very grateful if someone could help me to understand the inheritance concept in Java. Is the following code an example of that? I mean the class WavPanel is actually a subclass of JPanel which acts as a superclass. Is that correct? If so it means that "what JPanel has, also WavPanel but it is more specific since through its methods you can do something else". Am I wrong? thank you. Max import javax.swing.JPanel; class WavPanel extends JPanel { List<Byte> audioBytes; List<Line2D.Double> lines; public WavPanel() { super(); setBackground(Color.black); resetWaveform(); } public void resetWaveform() { audioBytes = new ArrayList<Byte>(); lines = new ArrayList<Line2D.Double>(); repaint(); } }

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  • Inheritance not working

    - by Pendo826
    Hey im just practicing inheritance and i encountered a problem. Im getting an error in my car class(sub-class) that the variables in Vehicle(parent) are not visible. i didnt do anything to change this and i dont even know how to make it invisible. Can anyone help me with this. public class Vehicle { private String make, model, colour; private int registrationNumber; public Vehicle() { this.make = ""; this.model = ""; this.colour = ""; this.registrationNumber = 0; } public Vehicle(String make, String model, String colour, int registrationNumber) { this.make = make; this.model = model; this.colour = colour; this.registrationNumber = registrationNumber; } public String getMake() { return make; } public void setMake(String make) { this.make = make; } public String getModel() { return model; } public void setModel(String model) { this.model = model; } public String getColour() { return colour; } public void setColour(String colour) { this.colour = colour; } public int getRegistrationNumber() { return registrationNumber; } public void setRegistrationNumber(int registrationNumber) { this.registrationNumber = registrationNumber; } public String toString() { return "Vehicle [make=" + make + ", model=" + model + ", colour=" + colour + ", registrationNumber=" + registrationNumber + "]"; } } public Car() { super(); this.doors = 0; this.shape = ""; } public Car(int doors, String shape, String make, String model, String colour, int registrationNumber) { super(); this.doors = doors; this.shape = shape; this.make = make;//Error this.model = model;//Error this.colour = colour;//Error this.registrationNumber = registrationNumber;//Error } The error message: Description Resource Path Location Type The field Vehicle.make is not visible Car.java /VehicleApp/src line 19 Java Problem The field Vehicle.model is not visible Car.java /VehicleApp/src line 20 Java Problem The field Vehicle.colour is not visible Car.java /VehicleApp/src line 21 Java Problem The field Vehicle.registrationNumber is not visible Car.java /VehicleApp/src line 22 Java Problem

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  • Resolving ambiguous this pointer in C++

    - by Paul Tevis
    I'm trying to derive a new class from an old one. The base class declaration looks like this: class Driver : public Plugin, public CmdObject { protected: Driver(); public: static Driver* GetInstance(); virtual Engine& GetEngine(); public: // Plugin methods... virtual bool InitPlugin (Mgr* pMgr); virtual bool Open(); virtual bool Close(); // CmdObject virtual bool ExecObjCmd(uint16 cmdID, uint16 nbParams, CommandParam *pParams, CmdChannelError& error); Mgr *m_pMgr; protected: Services *m_pServices; Engine m_Engine; }; Its constructor looks like this: Driver::Driver() : YCmdObject("Driver", (CmdObjectType)100, true), m_Engine("MyEngine") { Services *m_pServices = NULL; Mgr *m_pMgr = NULL; } So when I created my derived class, I first tried to simply inherit from the base class: class NewDriver : public Driver and copy the constructor: NewDriver::NewDriver() : CmdObject("NewDriver", (EYCmdObjectType)100, true), m_Engine("MyNewEngine") { Services *m_pServices = NULL; Mgr *m_pMgr = NULL; } The compiler (VisualDSP++ 5.0 from Analog Devices) didn't like this: ".\NewDriver.cpp", line 10: cc0293: error: indirect nonvirtual base class is not allowed CmdObject("NewDriver", (EYCmdObjectType)100, true), That made sense, so I decided to directly inherit from Plugin and CmdObject. To avoid multiple inheritance ambiguity problems (so I thought), I used virtual inheritance: class NewDriver : public Driver, public virtual Plugin, public virtual CmdObject But then, in the implementation of a virtual method in NewDriver, I tried to call the Mgr::RegisterPlugin method that takes a Plugin*, and I got this: ".\NewDriver.cpp", line 89: cc0286: error: base class "Plugin" is ambiguous if (!m_pMgr->RegisterPlugin(this)) How is the this pointer ambiguous, and how do I resolve it? Thanks, --Paul

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  • Django/Mod_WSGI error: UnboundLocalError: local variable 'resolver' referenced before assignment

    - by ycseattle
    Hello, I've setup the Django with mod_wsgi and run into this error. I thought maybe the sys.path was not setup correctly but I tried everything I could think of with no luck. Any suggestions? The following is the apache2 log for the error: mod_wsgi (pid=2579): Exception occurred processing WSGI script '/home/myapp/myapp.wsgi'. Traceback (most recent call last): File "/usr/local/lib/python2.6/dist-packages/django/core/handlers/wsgi.py", line 241, in __call__ response = self.get_response(request) File "/usr/local/lib/python2.6/dist-packages/django/core/handlers/base.py", line 142, in get_response return self.handle_uncaught_exception(request, resolver, exc_info) UnboundLocalError: local variable 'resolver' referenced before assignment The following is the content in the myapp.wsgi: import os import sys # put the Django project on sys.path sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "../"))) os.environ["DJANGO_SETTINGS_MODULE"] = "photopier.settings" #os.environ["PYTHONPATH"]="/home" from django.core.handlers.wsgi import WSGIHandler application = WSGIHandler()

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  • Differences between Django ugettext and ugettext_lazy

    - by kRON
    I keep rereading the Django's internationalization documentation and still don't understand when and why should I use django.translation.ugettext_lazy as opposed to django.translation.ugettext? I understand that using ugettext_lazy means that I will deffer from translating the string until the very end. Is it because Django parses the Accept-Language request header or the request.URL for the language code very late during the execution, which would mean that I may not be targeting the user's preferred language code if I was using ugettext? Would that ultimately mean that I should only use ugettext if I want to enforce that the message gets explicitly translated to the language specified in settings.LANGUAGE_CODE, or the currently active language as per django.translation.get_language()?

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  • django + ExtJs - list of example implementations with source code

    - by Tom Tom
    Hi, I want to learn ExtJs http://www.extjs.com/ in combination with Django (I know Django already .. a bit ;-) and I'm on the search of examples I can learn from. I found already this post. Would be great if you post your links to examples here. Maybe we get a nice list of examplary implementations that help users to start with django + ExtJs. Ext js Poll Tutorial Ext js vs. Jquery "Show how you can use extjs to display a table and how to use jqgrid 3.2 to get the same as in extjs. Incluses extjs and jqgird libraries. I have had to patch jqgrid adding" RESTful Web apps with Django, Piston and Ext JS Convert your forms.Form and forms.ModelForm to extjs and handles the form submission like any django form.

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  • apache virtual host to work with django

    - by khelll
    My project is under: /home/projects/testing and I'm adding this to the buttom of my /etc/httpd/conf/httpd.conf file on Centos machine, but that is not working, <Location "/testing/"> SetHandler python-program PythonHandler django.core.handlers.modpython SetEnv DJANGO_SETTINGS_MODULE testing.settings PythonOption django.root /testing PythonDebug On PythonPath "['/home/projects/'] + sys.path" </Location> but when requesting http://localhost/testing/jobs for example, I get: Mod_python error: "PythonHandler django.core.handlers.modpython" Traceback (most recent call last): File "/usr/lib/python2.4/site-packages/mod_python/apache.py", line 299, in HandlerDispatch result = object(req) ............. File "/usr/lib/python2.4/site-packages/Django-1.1.1-py2.4.egg/django/conf/__init__.py", line 75, in __init__ raise ImportError, "Could not import settings '%s' (Is it on sys.path? Does it have syntax errors?): %s" % (self.SETTINGS_MODULE, e) ImportError: Could not import settings 'testing.settings' (Is it on sys.path? Does it have syntax errors?): No module named testing.settings

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  • Installing Django/Python on IIS6

    - by Sohrab Hejazi
    We are currently installing the latest version of Django and Python on IIS6. We have followed the instructions on the following site: http://code.djangoproject.com/wiki/DjangoOnWindowsWithIISAndSQLServer We are receiving a 403 error when trying to access our Django application via the IIS server. We have verified the python installation on IIS6 and it is working properly. We have also verified the Django installation. Our application runs fine under the built-in Django server, but we are having difficulties getting it to run under IIS. We presume we could be getting errors from "Linking Django to PyISAPIe" section of the instructions provided on the link above. Thanks.

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  • Framework for Implementing REST web service in Django

    - by Laizer
    I'm looking to implement a RESTful interface for a Django application. It is primarily a data-service application - the interface will be (at this point) read-only. The question is which Django toolsets / frameworks make the most sense for this task. I see Django-rest and Django-piston. There's also the option of rolling my own. The question was asked here, but a good two years back. I'd like to know what the current state of play is. In this question, circa 2008, the strong majority vote was to not use any framework at all - just create Django views that reply with e.g. JSON. (The question was also addressed, crica 2008, here.) In the current landscape, what makes the most sense?

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  • Can simple javascript inheritance be simplified even further?

    - by Will
    John Resig (of jQuery fame) provides a concise and elegant way to allow simple JavaScript inheritance. It was so short and sweet, in fact, that it inspired me to try and simplify it even further (see code below). I've modified his original function such that it still passes all his tests and has the potential advantage of: readability (50% less code) simplicity (you don't have to be a ninja to understand it) performance (no extra wrappers around super/base method calls) consistency with C#'s base keyword Because this seems almost too good to be true, I want to make sure my logic doesn't have any fundamental flaws/holes/bugs, or if anyone has additional suggestions to improve or refute the code (perhaps even John Resig could chime in here!). Does anyone see anything wrong with my approach (below) vs. John Resig's original approach? if (!window.Class) { window.Class = function() {}; window.Class.extend = function(members) { var prototype = new this(); for (var i in members) prototype[i] = members[i]; prototype.base = this.prototype; function object() { if (object.caller == null && this.initialize) this.initialize.apply(this, arguments); } object.constructor = object; object.prototype = prototype; object.extend = arguments.callee; return object; }; } And the tests (below) are nearly identical to the original ones except for the syntax around base/super method calls (for the reason enumerated above): var Person = Class.extend( { initialize: function(isDancing) { this.dancing = isDancing; }, dance: function() { return this.dancing; } }); var Ninja = Person.extend( { initialize: function() { this.base.initialize(false); }, dance: function() { return this.base.dance(); }, swingSword: function() { return true; } }); var p = new Person(true); alert("true? " + p.dance()); // => true var n = new Ninja(); alert("false? " + n.dance()); // => false alert("true? " + n.swingSword()); // => true alert("true? " + (p instanceof Person && p instanceof Class && n instanceof Ninja && n instanceof Person && n instanceof Class));

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  • creating my own context processor in django

    - by dotty
    Hay, I have come to a point where i need to pass certain variables to all my views (mostly custom authentication type variables). I was told writing my own context processor was the best way to do this, but i am having some issues. My settings file looks like this TEMPLATE_CONTEXT_PROCESSORS = ( "django.contrib.auth.context_processors.auth", "django.core.context_processors.debug", "django.core.context_processors.i18n", "django.core.context_processors.media", "django.contrib.messages.context_processors.messages", "sandbox.context_processors.say_hello", ) As you can see i have a module called 'context_processors' and a function within that called 'say_hello'. This looks like def say_hello(request): return { 'say_hello':"Hello", } Am i right to assume i can now do this within my views {{ say_hello }} because it doesn't return anything.

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  • Silverlight with MVVM Inheritance: ModelView and View matching the Model

    - by moonground.de
    Hello Stackoverflowers! :) Today I have a special question on Silverlight (4 RC) MVVM and inheritance concepts and looking for a best practice solution... I think that i understand the basic idea and concepts behind MVVM. My Model doesn't know anything about the ViewModel as the ViewModel itself doesn't know about the View. The ViewModel knows the Model and the Views know the ViewModels. Imagine the following basic (example) scenario (I'm trying to keep anything short and simple): My Model contains a ProductBase class with a few basic properties, a SimpleProduct : ProductBase adding a few more Properties and ExtendedProduct : ProductBase adding another properties. According to this Model I have several ViewModels, most essential SimpleProductViewModel : ViewModelBase and ExtendedProductViewModel : ViewModelBase. Last but not least, according Views SimpleProductView and ExtendedProductView. In future, I might add many product types (and matching Views + VMs). 1. How do i know which ViewModel to create when receiving a Model collection? After calling my data provider method, it will finally end up having a List<ProductBase>. It containts, for example, one SimpleProduct and two ExtendedProducts. How can I transform the results to an ObservableCollection<ViewModelBase> having the proper ViewModel types (one SimpleProductViewModel and two ExtendedProductViewModels) in it? I might check for Model type and construct the ViewModel accordingly, i.e. foreach(ProductBase currentProductBase in resultList) if (currentProductBase is SimpleProduct) viewModels.Add( new SimpleProductViewModel((SimpleProduct)currentProductBase)); else if (currentProductBase is ExtendedProduct) viewModels.Add( new ExtendedProductViewModels((ExtendedProduct)currentProductBase)); ... } ...but I consider this very bad practice as this code doesn't follow the object oriented design. The other way round, providing abstract Factory methods would reduce the code to: foreach(ProductBase currentProductBase in resultList) viewModels.Add(currentProductBase.CreateViewModel()) and would be perfectly extensible but since the Model doesn't know the ViewModels, that's not possible. I might bring interfaces into game here, but I haven't seen such approach proven yet. 2. How do i know which View to display when selecting a ViewModel? This is pretty the same problem, but on a higher level. Ended up finally having the desired ObservableCollection<ViewModelBase> collection would require the main view to choose a matching View for the ViewModel. In WPF, there is a DataTemplate concept which can supply a View upon a defined DataType. Unfortunately, this doesn't work in Silverlight and the only replacement I've found was the ResourceSelector of the SLExtensions toolkit which is buggy and not satisfying. Beside that, all problems from Question 1 apply as well. Do you have some hints or even a solution for the problems I describe, which you hopefully can understand from my explanation? Thank you in advance! Thomas

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  • Sharing Jinja2 templates between Pylons and Django applications

    - by Joe Holloway
    I'm writing a couple of Jinja2 templates that basically implement some common grid layouts. I'd like to be able to share this 'library' of templates between a Pylons app and Django app. I've hit a minor stumbling block in that Django's template context is accessible from the "top-level" of the template, whereas Pylons wraps your context inside the thread local c (or tmpl_context) variable. Here are some analogous examples that demonstrate this. Django from django.shortcuts import render_to_response ctx = {} ctx['name'] = 'John' return render_to_response('hello.html', ctx) hello.html: Hello {{ name }} Pylons from pylons import tmpl_context as c from myapp.lib.base import render c.name = 'John' return render('hello.html') hello.html: Hello {{ c.name }} What I'm trying to do is make it so that hello.html is the same across both frameworks. One way I see to do it is by wrapping the Django render_to_response and do something like this: ctx['c'] = ctx But that just doesn't feel right. Anybody see other alternatives to this? Thanks

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  • Hierarchy inheritance

    - by reito
    I had faced the problem. In my C++ hierarchy tree I have two branches for entities of difference nature, but same behavior - same interface. I created such hierarchy trees (first in image below). And now I want to work with Item or Base classes independetly of their nature (first or second). Then I create one abstract branch for this use. My mind build (second in image below). But it not working. Working scheme seems (third in image below). It's bad logic, I think... Do anybody have some ideas about such hierarchy inheritance? How make it more logical? More simple for understanding? Image Sorry for my english - russian internet didn't help:) Update: You ask me to be more explicit, and I will be. In my project (plugins for Adobe Framemaker) I need to work with dialogs and GUI controls. In some places I working with WinAPI controls, and some other places with FDK (internal Framemaker) controls, but I want to work throw same interface. I can't use one base class and inherite others from it, because all needed controls - is a hierarchy tree (not one class). So I have one hierarchy tree for WinAPI controls, one for FDK and one abstract tree to use anyone control. For example, there is an Edit control (WinEdit and FdkEdit realization), a Button control (WinButton and FdkButton realization) and base entity - Control (WinControl and FdkControl realization). For now I can link my classes in realization trees (Win and Fdk) with inheritence between each of them (WinControl is base class for WinButton and WinEdit; FdkControl is base class for FdkButton and FdkEdit). And I can link to abstract classes (Control is base class for WinControl and FdkControl; Edit is base class for WinEdit and FdkEdit; Button is base class for WinButton and FdkButton). But I can't link my abstract tree - compiler swears. In fact I have two hierarchy trees, that I want to inherite from another one. Update: I have done this quest! :) I used the virtual inheritence and get such scheme (http://img12.imageshack.us/img12/7782/99614779.png). Abstract tree has only absolute abstract methods. All inheritence in abstract tree are virtual. Link from realization tree to abstract are virtual. On image shown only one realization tree for simplicity. Thanks for help!

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  • validate uniqueness amongst multiple subclasses with Single Table Inheritance

    - by irkenInvader
    I have a Card model that has many Sets and a Set model that has many Cards through a Membership model: class Card < ActiveRecord::Base has_many :memberships has_many :sets, :through => :memberships end class Membership < ActiveRecord::Base belongs_to :card belongs_to :set validates_uniqueness_of :card_id, :scope => :set_id end class Set < ActiveRecord::Base has_many :memberships has_many :cards, :through => :memberships validates_presence_of :cards end I also have some sub-classes of the above using Single Table Inheritance: class FooCard < Card end class BarCard < Card end and class Expansion < Set end class GameSet < Set validates_size_of :cards, :is => 10 end All of the above is working as I intend. What I'm trying to figure out is how to validate that a Card can only belong to a single Expansion. I want the following to be invalid: some_cards = FooCard.all( :limit => 25 ) first_expansion = Expansion.new second_expansion = Expansion.new first_expansion.cards = some_cards second_expansion.cards = some_cards first_expansion.save # Valid second_expansion.save # **Should be invalid** However, GameSets should allow this behavior: other_cards = FooCard.all( :limit => 10 ) first_set = GameSet.new second_set = GameSet.new first_set.cards = other_cards # Valid second_set.cards = other_cards # Also valid I'm guessing that a validates_uniqueness_of call is needed somewhere, but I'm not sure where to put it. Any suggestions? UPDATE 1 I modified the Expansion class as sugested: class Expansion < Set validate :validates_uniqueness_of_cards def validates_uniqueness_of_cards membership = Membership.find( :first, :include => :set, :conditions => [ "card_id IN (?) AND sets.type = ?", self.cards.map(&:id), "Expansion" ] ) errors.add_to_base("a Card can only belong to a single Expansion") unless membership.nil? end end This works when creating initial expansions to validate that no current expansions contain the cards. However, this (falsely) invalidates future updates to the expansion with new cards. In other words: old_exp = Expansion.find(1) old_exp.card_ids # returns [1,2,3,4,5] new_exp = Expansion.new new_exp.card_ids = [6,7,8,9,10] new_exp.save # returns true new_exp.card_ids << [11,12] # no other Expansion contains these cards new_exp.valid? # returns false ... SHOULD be true

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  • Conceptual inheritance implementation

    - by TheSENDER
    Hi there, I'm writing a spatial data structure and I have a doubt about what's the best NODE implementation. According to my design I have an abstract node entity and three classes which inherit from it: EMPTYNODE, FULLNODE, INTERNALNODE. The first one has no particular data. The second one has 1 reference to a generic element. The third one has 2 references to other nodes. I have found several ways to implement this situation (that I have already coded) but I can't decide what's the best. The first solution that I have found is to use a single class Node that potentially performs all the operation in this way: private static class Node { private Elem elem = null; private Node left = null, right = null; public Elem getElem() { assert isFull(); return elem; } public boolean isEmpty() { return elem == null && left == null; } public boolean isFull() { return elem != null; } public boolean isInternal() { return elem == null && left != null; } } The second solution is to write an explicit division by classes where every class offers only its methods. Obviously in this way we are obliged to perform several casts to the node objects. private static abstract class Node { public abstract boolean isEmpty(); public abstract boolean isFull(); public abstract boolean isInternal(); } private static class FullNode extends Node{ private ITriangle elem; @Override public boolean isEmpty() { return false; } @Override public final boolean isFull() { return true; } @Override public final boolean isInternal() { return false; } public Elem getElem() { return elem; } } The third one solution is to use the inheritance allowing every classes to offer all the methods, but the object type should by check by "isEmpty()" and similar methods. In case of wrong call we'll throw an exception. private static abstract class Node { public abstract boolean isEmpty(); public abstract boolean isFull(); public abstract boolean isInternal(); public abstract Elem getElem(); } private static class Empty extends Node{ @Override public boolean isEmpty() { return true; } @Override public final boolean isFull() { return false; } @Override public final boolean isInternal() { return false; } @Override public Elem getElem() { throw new AssertionError(); } } What do you think about these three solutions? Which one would you use? Any other ideas? Thanks for your help. Every idea will be appreciated.

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  • Nginx and Django on Dotcloud

    - by jmetz
    I currently have a dotcloud app that uses django to serve everything. It works great, however, we recently had our site redone in angular.js, and I don't want to use django to serve the actual html pages (I want to just use nginx for that), but I want django to serve some links for the API we built for the angular code to use. Is it possible for me, in the same app, to configure nginx to serve some static files for particular urls, and have it send other urls for django to serve? I want nginx to serve my index.html page is a request comes in to wwww.example.com, but if a request for example.com/api/login/ comes in, I want that to be handled by django. Is this possible?

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  • Is there a 'hello world' website for django? OR (I've installed django, now what) ?

    - by morpheous
    I'm learning Python and decided to start familiarizing myself with the (defacto?) Python web framework - django. I have successfully installed the latest release of django. I want a simple 'hello world' website that will get me up and running quickly. I am already familiar with web frameworks (albeit for different languages) - so I just need a simple 'hello world' example website to help me get going. Ideally, I don't want to mess up with my Apache server settings (as I am still experimenting), so I want to use the lightweight web server that django bundles. I cant seem to find how to do this on the django website though - no doubt someone will post a link and shame me ... So, does anyone know of a link that shows how to get a simple 'hello world' django website up and running with minimal fuss?

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  • Check something before django server starts

    - by Vijay Shankar Kalyanaraman
    I am running my api behind a django server and say I have a one time token that is needed by the django application and used through out its existence until the process quits. To check if I can proceed and serve requests (using the django server) I need to validate this token against a database entry. Now, I can have a script that hits the db, then issues the run server command if the token is valid. But if the db used by the django applications change, I will have to change the script also to point to the same db. Is there a way I can pass this token into the runserver command as an additional parameter (along with hostname:port) and validate this before django serves any requests? How can I access this parameter that is sent into ./manage.py runserver. Thanks.

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  • How to transition from PHP to Python Django?

    - by ggfan
    Here's my background: Decent experience with PHP/MySql. Beginner's experience with OOP Why I want to learn Python Django? I gave in, based on many searches on SO and reading over some of the answers, Python is a great, clean, and structured language to learn. And with the framework Django, it's easier to write codes that are shorter than with PHP Questions Can i do everything in Django as in PHP? Is Django a "big" hit in web development as PHP? I know Python is a great general-purpose language but I'm focused on web development and would like to know how Django ranks in terms of web development.

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  • Can I use Visual studio for Python and Django development?

    - by Pankaj Upadhyay
    I have been using Visual Studio for quite some time now, in fact from the VS 2005 version. Right now, I am not only comfortable but addict to using it(VS 2010) for all my development needs. Recently I have been learning Python and Django. In that getting the tutorial tasks up and running with IDLE seems very lame and outdated(I am following the Django Book). Therefore, I downloaded and configured Eclipse & PyDev. Eclipse seems good and fine but needs a bit of learning curve for itself. So, I am looking for a way to configure Visual Studio 2010 for Python and Django development if possible. Please tell me if that's possible and How ?

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