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  • In a class with no virtual methods or superclass, is it safe to assume (address of first member vari

    - by Jeremy Friesner
    Hi all, I made a private API that assumes that the address of the first member-object in the class will be the same as the class's this-pointer... that way the member-object can trivially derive a pointer to the object that it is a member of, without having to store a pointer explicitly. Given that I am willing to make sure that the container class won't inherit from any superclass, won't have any virtual methods, and that the member-object that does this trick will be the first member object declared, will that assumption hold valid for any C++ compiler, or do I need to use the offsetof() operator (or similar) to guarantee correctness? To put it another way, the code below does what I expect under g++, but will it work everywhere? class MyContainer { public: MyContainer() {} ~MyContainer() {} // non-virtual dtor private: class MyContained { public: MyContained() {} ~MyContained() {} // Given that the only place Contained objects are declared is m_contained // (below), will this work as expected on any C++ compiler? MyContainer * GetPointerToMyContainer() { return reinterpret_cast<MyContainer *>(this); } }; MyContained m_contained; // MUST BE FIRST MEMBER ITEM DECLARED IN MyContainer int m_foo; // other member items may be declared after m_contained float m_bar; };

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  • How to perform add/update of a model object that contains EntitySet

    - by David Liddle
    I have a similar concept to the SO questions/tags scenario however am trying to decide the best way of implementation. Tables Questions, QuestionTags and Tags Questions QuestionTags Tags --------- ------------ ---- QID QID TID QName TID TName When adding/updating a question I have 2 textboxes. The important part is a single textbox that allows users to enter in multiple Tags separated by spaces. I am using Linq2Sql so the Questions model has an EntitySet of QuestionTags with then link to Tags. My question is regarding the adding/updating of Questions (part 1), and also how to best show QuestionTags for a Question (part 2). Part 1 Before performing an add/update, my service layer needs to deal with 3 scenarios before passing to their respective repositories. Insert Tags that do not already exist Insert/Update Question Insert QuestionTags - when updating need to remove existing QuestionTags Here is my code below however started to get into a bit of a muddle. I've created extension methods on my repositories to get Tags WithNames etc. public void Add(Question q, string tags) { var tagList = tags.Split(new string[] { " " }, StringSplitOptions.RemoveEmptyEntries).ToList(); using (DB.TransactionScope ts = new DB.TransactionScope()) { var existingTags = TagsRepository.Get() .WithName(tagList) .ToList(); var newTags = (from t in tagList select new Tag { TName = t }).Except(existingTags, new TagsComparer()).ToList(); TagsRepository.Add(newTags); //need to insert QuestionTags QuestionsRepository.Add(q); ts.Complete(); } } Part 2 My second question is, when displaying a list of Questions how is it best to show their QuestionTags? For example, I have an Index view that shows a list of Questions in a table. One of the columns shows an image and when the user hovers over it shows the list of Tags. My current implementation is to create a custom ViewModel and show a List of QuestionIndexViewModel in the View. QuestionIndexViewModel { Question Question { get; set; } string Tags { get; set; } } However, this seems a bit clumsy and quite a few DB calls. public ViewResult Index() { var model= new List<QuestionIndexViewModel>(); //make a call to get a list of questions //foreach question make a call to get their QuestionTags, //to be able to get their Tag names and then join them //to form a single string. return View(model); } Also, just for test purposes using SQL Profiler, I decided to iterate through the QuestionTags entity set of a Question in my ViewModel however nothing was picked up in Profiler? What would be the reason for this?

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  • ActionScript 2.0 problem with the object's _visible parameter

    - by GMan
    Hey guys, I've been trying to build something simple in Flash 8, and I stumbled across something weird I cannot explain: I have an object, and at some point of the program, I want it to be visible (it is invisible at first), so I write: _root.myObj._visible = true; _root.gameOver.swapDepths(_root.getNextHighestDepth()); //so it will be on the top and this works fine, the object becomes visible and etc. What I planned to happen next is that the user presses a button on that same object, and the object will go invisible: on(release) { trace(_root.myObj._visible); _root.myObj._visible = false; trace(_root.myObj._visible); _root.gotoAndPlay("three"); } The trace returns at first true and later on false, so the command works, but oddly the object stays visible, that's what I don't understand. Thanks everybody in advance.

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  • Get a queryset of objects through an intermediary model

    - by skyl
    I want get all of the Geom objects that are related to a certain content_object (see the function I'm trying to build at the bottom, get_geoms_for_obj() class Geom(models.Model): ... class GeomRelation(models.Model): ''' For tagging many objects to a Geom object and vice-versa''' geom = models.ForeignKey(Geom) content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey() def get_geoms_for_object(obj): ''' takes an object and gets the geoms that are related ''' ct = ContentType.objects.get_for_model(obj) id = obj.id grs = GeomRelation.objects.filter( content_type=ct, object_id=id ) # how with django orm magic can I build the queryset instead of list # like below to get all of the Geom objects for a given content_object geoms = [] for gr in grs: geoms.append(gr.geom) return set(geoms) # A set makes it so that I have no redundant entries but I want the # queryset ordering too .. need to make it a queryset for so many reasons...

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  • ActionLink sending a model of a complex type

    - by Xenph Yan
    I'm trying to paginate the results of a "advanced search", I have a complex model that represents the search options; int ZipCode int MinAge int MaxAge Availability bool Monday bool Tuesday ... bool Friday Requirements bool FirstAid bool DriversLicense I'm using; <%: Html.ActionLink("Next »", "Save", "Notification", Model.options)%> Which correctly sends all the data at the first level, but anything that is a sub-object (Availability or requirements) isn't expanded in the URL, all I get is the class name and so I lose most of the search options when I click the link to change to a different page. Any thoughts?

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  • Ext.app.application object is erased after initialization

    - by Queequeg
    I am trying to organize an existing extjs code in a more standard order (extjs wise). extjs version: extjs-4.0.2a. I've worked through the Extjs tutorial example and every thing went well. When I started working on the company's code I've notice there is no use of the application object there for I've added the Ext.application({...}); call. Ext.application({ name: 'FOO', appFolder: 'appFolderName', launch: function() { console.log('application was created'); } }); Upon loading the page I see the console.log output that is included in the "launch" function property - meaning the application object is created but when I look for it ("FOO" object) under the "window" object it is not there. Compering to the tutorial code the application object exist as a property of window. I encounter a few loading problems but I'm guessing the source of it all is this issue. What am I doing wrong? thanks.

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  • Passing values from action class to model class in symfony

    - by THOmas
    I have a action class for saving some data to a database.In action class iam getting a id through url.I have to save the id in table. I am getting the id by $request-getParameter('id') I used this code for saving $this-form-bind($request-getParameter('question_answers')); if ($this-form-isValid()) { $this-form-save(); $this-redirect('@homepage'); } in model class i used a override save method to save extra field public function save(Doctrine_Connection $conn = null) { if ($this-isNew()) { $now=date('Y-m-d H:i:s', time()); $this->setPostedAt($now); } return parent::save($conn); so i want to get the id value here . So how can i pass id value from action class to model class is any-other way to save the id in action class itself Thanks in advance

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  • Query for model by key

    - by Jason Hall
    What I'm trying to do is query the datastore for a model where the key is not the key of an object I already have. Here's some code: class User(db.Model): partner = db.SelfReferenceProperty() def text_message(self, msg): user = User.get_or_insert(msg.sender) if not user.partner: # user doesn't have a partner, find them one # BUG: this line returns 'user' himself... :( other = db.Query(User).filter('partner =', None).get() if other: # connect users else: # no one to connect to! The idea is to find another User who doesn't have a partner, that isn't the User we already know. I've tried filter('key !=, user.key()), filter('__key__ !=, user.key()) and a couple others, and nothing returns another User who doesn't have a partner. filter('foo !=, user.key()) also returns nothing, for the record.

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  • ASP.NET MVC: View does not get rendered with updated model value

    - by Newton
    I'm experiencing the a challenge in populating the child records. My previous code was like - <%= Html.TextBox("DyeOrder.Summary[" + i + "].Ratio", Model.DyeOrder.Summary[i].Ratio.ToString("#0.00"), ratioProperties) %> This code does not render the updated values after post back. To resolve this issue my work around was like - <%= "<input id='DyeOrder_Summary_" + i + "__Ratio' name='DyeOrder.Summary[" + i + "].Ratio' value='" + Model.DyeOrder.Summary[i].Ratio.ToString("#0.00") + "' " + ratioCss + " type='text' />"%> This is very clumsy to me. Is there any better ideas...

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  • Not loading the object caused EF4 (code first) to remove the relationship

    - by Lavinski
    Firstly this is a EF4: Code First - Property Loading question. I'm loading an object like so var item = Context.Table.Find( update.Identifier ); This object has a property Relationship so a table has a Relationship object. Now i'm updating my item but my Relationship object is not toched (and therefore not lazy loaded). Now here's the problem .. I save my item and my relationship to the Relationship object is deleted, apparently the model thinks i set it to null. However it all works if I look at the property before saving. So I'm looking into LoadProperty or doing a query and using Include. Has anyone else come across this issue and how did you get around it?

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  • Static member object of a class in the same class

    - by Luv
    Suppose we have a class as class Egg { static Egg e; int i; Egg(int ii):i(ii) {} Egg(const Egg &); //Prevents copy-constructor to be called public: static Egg* instance() {return &e} }; Egg Egg::e(47); This code guarantees that we cannot create any object, but could use only the static object. But how could we declare static object of the same class in the class. And also one thing more since e is a static object, and static objects can call only static member functions, so how could the constructor been called here for static object e, also its constructors are private.

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  • How do i free objects in C#

    - by assassin
    Hi, Can anyone please tell me how I can free objects in C#? For example, I have an object: Object obj1 = new Object(); //Some code using obj1 //Here I would like to free obj1, after it is no longer required and also more importantly its scope is the full run time of the program. Thanks for all your help

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  • R: including model specifications in xtable(anova(...))

    - by HamiltonUlmer
    Hello R comrades: I have a bunch of loglinear models, which, for our purposes will just be glm() objects called mx, my, mz. I want to get a nicely-formatted xtable of the analysis of deviance, so naturally I would want to perform xtable(anova(mx, my, mz, test = "Chisq")). The vanilla output of xtable, however, doesn't include the model specifications. I'd like to include those for all the ANOVA tests I'm running, so if there is not a param I'm missing that does this I'll probably just have to hack up my own solution. But looking over the help page, there doesn't seem to be an easy way to include the model specifications. Any thoughts? Alternatives? If it helps this was done in 2.9.1 with xtable 1.5-5.

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  • Django: request object to template context transparancy

    - by anars
    Hi! I want to include an initialized data structure in my request object, making it accessible in the context object from my templates. What I'm doing right now is passing it manually and tiresome within all my views: render_to_response(...., ( {'menu': RequestContext(request)})) The request object contains the key,value pair which is injected using a custom context processor. While this works, I had hoped there was a more generic way of passing selected parts of the request object to the template context. I've tried passing it by generic views, but as it turns out the request object isn't instantiated when parsing the urlpatterns list.

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  • How to handle this type of model validation in Ruby on Rails

    - by randombits
    I have a controller/model hypothetically named Pets. Pets has the following declarations: :belongs_to owner :has_many dogs :has_many cats Not the best example, but again, it demonstrates what I'm trying to solve. Now when a request comes in as an HTTP POST to http://127.0.0.1/pets, I want to create an instance of Pets. The restriction here is, if the user doesn't submit at least one dog or one cat, it should fail validation. It can have both, but it can't be missing both. How does one handle this in Ruby on Rails? Dogs don't care if cats exists and the inverse is also true. Can anyone show some example code of what the Pets model would look like to ensure that one or the other exists, or fail otherwise? errors.add also takes an attribute, in this case, there is no particular attribute that's failing. It's almost a 'virtual' combination that's missing.

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  • Backbone JS central model where all views can use

    - by chchrist
    I am new to backbone js and require js. I use requirejS to organize my backbone code into modules. I don't know if this has any importance to what I want though. I want to have a central model where all my views will have access to. They should be able to get and set values. I don't want to use it as each view model though. I need to keep in memory search options, user status (logged in/out) etc. Any ideas? EDIT Maybe the answer is here? Share resources across different amd modules

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  • How did My Object Get into ASP.NET Page State?

    - by Paul Knopf
    I know what this error is, how to fix it, etc. My question is that I don't know why my current page I am developing is throwing this error when I am not using the foo class directly in any way, nor am I setting anything to the viewstate. I am using postbacks alot, but like I said, I am not storing anything in the viewstate etc one integer. I am using nhibernate if that is relevant. Any idea why I need to mark this classes as serializable that arent being used? Where should I start investigating? [SerializationException: Type 'FlexiCommerce.Persistence.NH.ContentPersister' in Assembly 'FlexiCommerce.Persistence.NH, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' is not marked as serializable.] System.Runtime.Serialization.FormatterServices.InternalGetSerializableMembers(RuntimeType type) +9434541 System.Runtime.Serialization.FormatterServices.GetSerializableMembers(Type type, StreamingContext context) +247 System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitMemberInfo() +160 System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitSerialize(Object obj, ISurrogateSelector surrogateSelector, StreamingContext context, SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter, ObjectWriter objectWriter, SerializationBinder binder) +218 System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Write(WriteObjectInfo objectInfo, NameInfo memberNameInfo, NameInfo typeNameInfo) +388 System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Serialize(Object graph, Header[] inHeaders, __BinaryWriter serWriter, Boolean fCheck) +444 System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph, Header[] headers, Boolean fCheck) +133 System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph) +13 System.Web.UI.ObjectStateFormatter.SerializeValue(SerializerBinaryWriter writer, Object value) +2937 [ArgumentException: Error serializing value 'Music#2' of type 'FlexiCommerce.Components.Category.'] System.Web.UI.ObjectStateFormatter.SerializeValue(SerializerBinaryWriter writer, Object value) +3252 System.Web.UI.ObjectStateFormatter.SerializeValue(SerializerBinaryWriter writer, Object value) +2276 [ArgumentException: Error serializing value 'System.Object[]' of type 'System.Object[].'] System.Web.UI.ObjectStateFormatter.SerializeValue(SerializerBinaryWriter writer, Object value) +3252 System.Web.UI.ObjectStateFormatter.Serialize(Stream outputStream, Object stateGraph) +116 System.Web.UI.ObjectStateFormatter.Serialize(Object stateGraph) +57 System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Serialize(Object state) +4 System.Web.UI.Util.SerializeWithAssert(IStateFormatter formatter, Object stateGraph) +37 System.Web.UI.HiddenFieldPageStatePersister.Save() +79 System.Web.UI.Page.SavePageStateToPersistenceMedium(Object state) +108 System.Web.UI.Page.SaveAllState() +315 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2492

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  • Circular database relationships. Good, Bad, Exceptions?

    - by jim
    I have been putting off developing this part of my app for sometime purely because I want to do this in a circular way but get the feeling its a bad idea from what I remember my lecturers telling me back in school. I have a design for an order system, ignoring the everything that doesn't pertain to this example I'm left with: CreditCard Customer Order I want it so that, Customers can have credit cards (0-n) Customers have orders (1-n) Orders have one customer(1-1) Orders have one credit card(1-1) Credit cards can have one customer(1-1) (unique ids so we can ignore uniqueness of cc number, husband/wife may share cc instances ect) Basically the last part is where the issue shows up, sometimes credit cards are declined and they wish to use a different one, this needs to update which their 'current' card is but this can only change the current card used for that order, not the other orders the customer may have on disk. Effectively this creates a circular design between the three tables. Possible solutions: Either Create the circular design, give references: cc ref to order, customer ref to cc customer ref to order or customer ref to cc customer ref to order create new table that references all three table ids and put unique on the order so that only one cc may be current to that order at any time Essentially both model the same design but translate differently, I am liking the latter option best at this point in time because it seems less circular and more central. (If that even makes sense) My questions are, What if any are the pros and cons of each? What is the pitfalls of circular relationships/dependancies? Is this a valid exception to the rule? Is there any reason I should pick the former over the latter? Thanks and let me know if there is anything you need clarified/explained. --Update/Edit-- I have noticed an error in the requirements I stated. Basically dropped the ball when trying to simplify things for SO. There is another table there for Payments which adds another layer. The catch, Orders can have multiple payments, with the possibility of using different credit cards. (if you really want to know even other forms of payment). Stating this here because I think the underlying issue is still the same and this only really adds another layer of complexity.

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  • Model Django Poll

    - by MacPython
    I followed the django tutorial here: http://docs.djangoproject.com/en/dev/intro/tutorial01/ and now I am at creating a poll. The code below works fine until I want to create choices, where for some reason I always get this error message: line 22, in unicode return self.question AttributeError: 'Choice' object has no attribute 'question' Unfortunatley, I dont understand where I made an error. Any help would be greatly appreciated. Thanks for the time! CODE: import datetime from django.db import models class Poll(models.Model): question = models.CharField(max_length=200) pub_date = models.DateTimeField('date published') def __unicode__(self): return self.question def was_published_today(self): return self.pub_date.date() == datetime.date.today() class Choice(models.Model): poll = models.ForeignKey(Poll) choice = models.CharField(max_length=200) votes = models.IntegerField() def __unicode__(self): return self.question

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  • a completely decoupled OO system ?

    - by shrini1000
    To make an OO system as decoupled as possible, I'm thinking of the following approach: 1) we run an RMI/directory like service where objects can register and discover each other. They talk to this service through an interface 2) we run a messaging service to which objects can publish messages, and register subscription callbacks. Again, this happens through interfaces 3) when object A wants to invoke a method on object B, it discovers the target object's unique identity through #1 above, and publishes a message on the message service for object B 4) message services invokes B's callback to give it the message 5) B processes the request and sends the response for A on message service 6) A's callback is called and it gets the response. I feel this system is as decoupled as practically possible, but it has the following problems: 1) communication is typically asynchronous 2) hence it's non real time 3) the system as a whole is less efficient. Are there any other practical problems where this design obviously won't be applicable ? What are your thoughts on this design in general ?

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  • CakePHP: Using two tables for a single model

    - by mwaterous
    I'm just picking up development in CakePHP right now so forgive me if this seems obvious; it did to me when I first read about has, belongsTo, hasMany, etc. The problem is I would like to associate two tables with a single model, and was wondering if there was a way to configure this so that when CakePHP did it's queries it automatically performed a join on the two tables. I don't want to create a separate model for the second table as it is merely a meta information table - the master table will contain the primary information required, the meta table will be populated with secondary information that is not required and therefore may or may not be set for every row of the master table.

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