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• WCF: Per-Call and Per-Session services...need convincing that Per-Call is worthwhile

  - by mrlane

  Hello all. We are currently doing a review of our WCF service design and one thing that is bothering me is the decision between Per-Call and Per-Session services. I believe I understand the concept behind both, but I am not really seeing the advantage of Per-Call services. I understand that the motivation for using Per-Call services is that a WCF services only holds a servier object for the life of a call thereby restricting the time that an expensive resource is held by the service instance, but to me its much simpler to use the more OO like Per-Session model where your proxy object instance always corrisponds to the same server object instance and just handle any expensive resources manually. For example, say I have a CRUD Service with Add, Update, Delete, Select methods on it. This could be done as a Per-Call service with database connection (the "expensive resource") instanciated in the server object constructor. Alternately it could be a Per-Session service with a database connection instanciated and closed within each CRUD method exposed. To me it is no different resource wise and it makes the programming model simpler as the client can be assured that they always have the same server object for their proxies: any in-expensive state that there may be between calls is maintained and no extra parameters are needed on methods to identify what state data must be retrieved by the service when it is instanciating a new server object again (as in the case of Per-Call). Its just like using classes and objects, where the same resource management issues apply, but we dont create new object instances for each method call we have on an object! So what am I missing with the Per-Call model? Thanks

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• Why use short-circuit code?

  - by Tim Lytle

  Related Questions: Benefits of using short-circuit evaluation, Why would a language NOT use Short-circuit evaluation?, Can someone explain this line of code please? (Logic & Assignment operators) There are questions about the benefits of a language using short-circuit code, but I'm wondering what are the benefits for a programmer? Is it just that it can make code a little more concise? Or are there performance reasons? I'm not asking about situations where two entities need to be evaluated anyway, for example: if($user->auth() AND $model->valid()){ $model->save(); } To me the reasoning there is clear - since both need to be true, you can skip the more costly model validation if the user can't save the data. This also has a (to me) obvious purpose: if(is_string($userid) AND strlen($userid) > 10){ //do something }; Because it wouldn't be wise to call strlen() with a non-string value. What I'm wondering about is the use of short-circuit code when it doesn't effect any other statements. For example, from the Zend Application default index page: defined('APPLICATION_PATH') || define('APPLICATION_PATH', realpath(dirname(__FILE__) . '/../application')); This could have been: if(!defined('APPLICATION_PATH')){ define('APPLICATION_PATH', realpath(dirname(__FILE__) . '/../application')); } Or even as a single statement: if(!defined('APPLICATION_PATH')) define('APPLICATION_PATH', realpath(dirname(__FILE__) . '/../application')); So why use the short-circuit code? Just for the 'coolness' factor of using logic operators in place of control structures? To consolidate nested if statements? Because it's faster?

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• Reinforcement learning toy project

  - by Betamoo

  My toy project to learn & apply Reinforcement Learning is: - An agent tries to reach a goal state "safely" & "quickly".... - But there are projectiles and rockets that are launched upon the agent in the way. - The agent can determine rockets position -with some noise- only if they are "near" - The agent then must learn to avoid crashing into these rockets.. - The agent has -rechargable with time- fuel which is consumed in agent motion - Continuous Actions: Accelerating forward - Turning with angle I need some hints and names of RL algorithms that suit that case.. - I think it is POMDP , but can I model it as MDP and just ignore noise? - In case POMDP, What is the recommended way for evaluating probability? - Which is better to use in this case: Value functions or Policy Iterations? - Can I use NN to model environment dynamics instead of using explicit equations? - If yes, Is there a specific type/model of NN to be recommended? - I think Actions must be discretized, right? I know it will take time and effort to learn such a topic, but I am eager to.. You may answer some of the questions if you can not answer all... Thanks

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• Ruby on Rails: How to sanitize a string for SQL when not using find?

  - by williamjones

  I'm trying to sanitize a string that involves user input without having to resort to manually crafting my own possibly buggy regex if possible, however, if that is the only way I would also appreciate if anyone can point me in the right direction to a regex that is unlikely to be missing anything. There are a number of methods in Rails that can allow you to enter in native SQL commands, how do people escape user input for those? The question I'm asking is a broad one, but in my particular case, I'm working with a column in my Postgres database that Rails does not natively understand as far as I know, the tsvector, which holds plain text search information. Rails is able to write and read from it as if it's a string, however, unlike a string, it doesn't seem to be automatically escaping it when I do things like vector= inside the model. For example, when I do model.name='::', where name is a string, it works fine. When I do model.vector='::' it errors out: ActiveRecord::StatementInvalid: PGError: ERROR: syntax error in tsvector: "::" "vectors" = E'::' WHERE "id" = 1 This seems to be a problem caused by lack of escaping of the semicolons, and I can manually set the vector='\:\:' fine. I also had the bright idea, maybe I can just call something like: ActiveRecord::Base.connection.execute "UPDATE medias SET vectors = ? WHERE id = 1", "::" However, this syntax doesn't work, because the raw SQL commands don't have access to find's method of escaping and inputting strings by using the ? mark. This strikes me as the same problem as calling connection.execute with any type of user input, as it all boils down to sanitizing the strings, but I can't seem to find any way to manually call Rails' SQL string sanitization methods. Can anyone provide any advice?

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• Use XMPP instead of HTTP

  - by pavel

  Hey guys. My friend and I, we are working on iPhone application. This application uses XMPP protocol to provide chat functionality. Right now we are designing architecture for the application. So my friend is working on iPhone side, and I am ruby on rails guy. My friend suggested, that we wrap every call, that is usually served via HTTP into XMPP. So, user registration, users search, profile editing, photo uploading, everything goes via XMPP. No HTTP at all. My friend wants to use XMPP, because he says, that it's much easier to implement XMPP on client-side rather HTTP. As for me, this is bullshit, but we've got a product owner, who have been working with my friend for a long time and he trusts him. So what I'm trying to do is to convince my friend and product owner that using XMPP for what HTTP can work find — is totally not the best idea. I feel, that if we implement everything on XMPP, we will have a pain in an ass till the end of lives. But how do I prove it? P.S. I'm not against chat over XMPP, I am against users search, photo uploading, rankings, nearby search and various other restful requests. Please, leave response. Any help appreciated. A little update: Yesterday we had a long discussion. And it turns out, it's quiete hard to receive response from both XMPP and HTTP in Objective-C. Because every single object and its data should be stored in Core Data model, while this model can't be securely modified from various places. Say, if you use HTTP transport, you always want to use only HTTP transport to update data in your model. And if you use XMPP, you should always use XMPP. So, you can't use both. That's what my iPhone buddy told me. It sounds weird for me, can anyone explain me that?

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• Using a4j:support 's onchange event with h:selectOneMenu

  - by user339637

  <h:selectOneMenu id="selectOneMenu" value="#{Bean1.val1}" > <f:selectItems value="#{Bean1.selectItems}"/> <a4j:support event="onchange" action="#{Bean1.onSelectOneMenuChange}" reRender="textbox1 , textbox2 , textbox3, textbox4" /> </h:selectOneMenu> <h:inputText id="textbox1" value="#{Bean1.textbox1}"> </h:inputText> <h:inputText id="textbox2" value="#{Bean1.textbox2}"> </h:inputText> <h:inputText id="textbox3" value="#{Bean1.textbox3}"> </h:inputText> <h:inputText id="textbox4" value="#{Bean1.textbox4}"> </h:inputText> Bean1.onSelectOneMenuChange() will change the value of Bean1.textbox1 , Bean1.textbox2,Bean1.textbox3 and Bean1.textbox4 depending on the value selected (Bean1.val1) .Sometimes , it will change all the textbox value and sometimes it will only changes some textbox value. When users change the value in the "selectOneMenu" drop down list control , the JSF framework will not call the update model values phase but call the Bean1.onSelectOneMenuChange() directly. After that , the all the textbox are reRender. Because the update model values phase is not called , the values entered by the user is never set the the Bean1 and the original value is shown in the textbox after reRender . So I want to ask: How can I manually call the update model values phase inside Bean1.onSelectOneMenuChange() ?How can I get the value input input by the users inside Bean1.onSelectOneMenuChange() and set it to the corresponding fields of the Bean1 ? 2.Another approach is that only reRender those textbox whose values are updated inside the Bean1.onSelectOneMenuChange() .However , there are many cases . For example , a value will change all the textbox value and a values may only change some textbox value.How can I reRender conditionally ? What method is more prefer for maintainability?

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• WCF: Serializing and Deserializing generic collections

  - by Fabiano

  I have a class Team that holds a generic list: [DataContract(Name = "TeamDTO", IsReference = true)] public class Team { [DataMember] private IList<Person> members = new List<Person>(); public Team() { Init(); } private void Init() { members = new List<Person>(); } [System.Runtime.Serialization.OnDeserializing] protected void OnDeserializing(StreamingContext ctx) { Log("OnDeserializing of Team called"); Init(); if (members != null) Log(members.ToString()); } [System.Runtime.Serialization.OnSerializing] private void OnSerializing(StreamingContext ctx) { Log("OnSerializing of Team called"); if (members != null) Log(members.ToString()); } [System.Runtime.Serialization.OnDeserialized] protected void OnDeserialized(StreamingContext ctx) { Log("OnDeserialized of Team called"); if (members != null) Log(members.ToString()); } [System.Runtime.Serialization.OnSerialized] private void OnSerialized(StreamingContext ctx) { Log("OnSerialized of Team called"); Log(members.ToString()); } When I use this class in a WCF service, I get following log output OnSerializing of Team called System.Collections.Generic.List 1[Person] OnSerialized of Team called System.Collections.Generic.List 1[Person] OnDeserializing of Team called System.Collections.Generic.List 1[ENetLogic.ENetPerson.Model.FirstPartyPerson] OnDeserialized of Team called ENetLogic.ENetPerson.Model.Person[] After the deserialization members is an Array and no longer a generic list although the field type is IList< (?!) When I try to send this object back over the WCF service I get the log output OnSerializing of Team called ENetLogic.ENetPerson.Model.FirstPartyPerson[] After this my unit test crashes with a System.ExecutionEngineException, which means the WCF service is not able to serialize the array. (maybe because it expected a IList<) So, my question is: Does anybody know why the type of my IList< is an array after deserializing and why I can't serialize my Team object any longer after that? Thanks

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• Linq, Left Join and Dates...

  - by BitFiddler

  So my situation is that I have a linq-to-sql model that does not allow dates to be null in one of my tables. This is intended, because the database does not allow nulls in that field. My problem, is that when I try to write a Linq query with this model, I cannot do a left join with that table anymore because the date is not a 'nullable' field and so I can't compare it to "Nothing". Example: There is a Movie table, {ID,MovieTitle}, and a Showings table, {ID,MovieID,ShowingTime,Location} Now I am trying to write a statement that will return all those movies that have no showings. In T.SQL this would look like: Select m.* From Movies m Left Join Showings s On m.ID = s.MovieID Where s.ShowingTime is Null Now in this situation I could test for Null on the 'Location' field but this is not what I have in reality (just a simplified example). All I have are non-null dates. I am trying to write in Linq: From m In dbContext.Movies _ Group Join s In Showings on m.ID Equals s.MovieID into MovieShowings = Group _ From ms In MovieShowings.DefaultIfEmpty _ Where ms.ShowingTime is Nothing _ Select ms However I am getting an error saying 'Is' operator does not accept operands of type 'Date'. Operands must be reference or nullable types. Is there any way around this? The model is correct, there should never be a null in the Showings:ShowTime table. But if you do a left join, and there are no show times for a particular movie, then ShowTime SHOULD be Nothing for that movie... Thanks everyone for your help.

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• Which pattern should be used for editing properties with modal view controller on iPhone?

  - by Matthew Daugherty

  I am looking for a good pattern for performing basic property editing via a modal view on the iPhone. Assume I am putting together an application that works like the Contacts application. The "detail" view controller displays all of the contact's properties in a UITableView. When the UITableView goes into edit mode a disclosure icon is displayed in the cells. Clicking a cell causes a modal "editor" view controller to display a view that allows the user to modify the selected property. This view will often contain only a single text box or picker. The user clicks Cancel/Save and the "editor" view is dismissed and the "detail" view is updated. In this scenario, which view is responsible for updating the model? The "editor" view could update the property directly using Key-Value Coding. This appears in the CoreDataBooks example. This makes sense to me on some level because it treats the property as the model for the editor view controller. However, this is not the pattern suggested by the View Controller Programming Guide. It suggests that the "editor" view controller should define a protocol that the "detail" controller adopts. When the user indicates they are done with the edit, the "detail" view controller is called back with the entered value and it dismisses the "editor" view. Using this approach the "detail" controller updates the model. This approach seems problematic if you are using the same "editor" view for multiple properties since there is only a single call-back method. Would love to get some feedback on what approach works best.

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• entity framework POCO template in a n-tiers design question

  - by bryan

  HI all I was trying to follow the POCO Template walkthrough . And now I am having problems using it in n-tiers design. By following the article, I put my edmx model, and the template generated context.tt in my DAL project, and moved the generated model.tt entity classes to my Business Logic layer (BLL) project. By doing this, I could use those entities inside my BLL without referencing the DAL, I guess that is the idea of PI; without knowing anything about the data source. Now, I want to extend the entities (inside the model.tt) to perform some CUD action in the BLL project,so I added a new partial class same name as the one generated from template, public partial class Company { public static IEnumerable AllCompanies() { using(var context = new Entities()){ var q = from p in context.Companies select p; return q.ToList(); } } } however visual studio won't let me do that, and I think it was because the context.tt is in the DAL project, and the BLL project could not add a reference to the DAL project as DAL has already reference to the BLL. So I tried to added this class to the DAL and it compiled, but intelisense won't show up the BLL.Company.AllCompanies() in my web service method from my webservice project which has reference to my BLL project. What should I do now? I want to add CUD methods to the template generated entities in my BLL project, and call them in my web services from another project. I have been looking for this answer a few days already, and I really need some guides from here please. Bryan

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• Get paperclip to crop the image without validating

  - by Micke

  Hello fellow stackoverflow members. I have been following this guide to enable users to have their own avatar. But i have bumped in to a litle problem. When the user is cropping the image the model tries to validate all my validations. My user model looks like this: class User < ActiveRecord::Base has_attached_file :avatar, :styles => { :small => "100x100>", :large => "500x500>" }, :processors => [:cropper] attr_accessor :password, :crop_x, :crop_y, :crop_w, :crop_h attr_accessible :crop_x, :crop_y, :crop_w, :crop_h validates_confirmation_of :password validates_presence_of :password And when the user runs the crop updating script the user model tries to validate the password. But because i have no password field on the cropping page it can't validate it. Here is the updating of the crop: @user = User.find(current_user.id) if @user.update_attributes(params[:user]) flash[:notice] = "Successfully updated user." end How can i bypass this in a easy and clean way?

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• I am getting null pointer exception while publishing dynamic web project on jboss using eclipse

  - by Rozer

  I am getting null pointer exception while publishing dynamic web project on jboss using eclipse Environment details Version: 3.3.2 Build id: M20080221-1800 Jboss: 3.2.3 JDK 1.5 I have checked with google, but nothing work, can anyone suggest me what is the root cause for that Following is the log trace may be help to understance the situation !ENTRY org.eclipse.wst.server.core 4 0 2010-06-13 19:03:44.568 !MESSAGE Error calling delegate restart() JBOSS 4.0 !ENTRY org.eclipse.wst.server.core 4 0 2010-06-13 19:39:34.365 !MESSAGE Could not publish to the server. !STACK 0 java.lang.NullPointerException at org.eclipse.wst.common.componentcore.internal.util.ComponentUtilities.getDeployUriOfComponent(ComponentUtilities.java:327) at org.eclipse.jst.j2ee.internal.deployables.J2EEFlexProjDeployable.getURI(J2EEFlexProjDeployable.java:429) at org.eclipse.jst.server.generic.core.internal.publishers.AntPublisher.guessModuleName(AntPublisher.java:259) at org.eclipse.jst.server.generic.core.internal.publishers.AntPublisher.getPublishProperties(AntPublisher.java:224) at org.eclipse.jst.server.generic.core.internal.publishers.AntPublisher.publish(AntPublisher.java:110) at org.eclipse.jst.server.generic.core.internal.GenericServerBehaviour.publishModule(GenericServerBehaviour.java:84) at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.publishModule(ServerBehaviourDelegate.java:749) at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.publishModules(ServerBehaviourDelegate.java:835) at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.publish(ServerBehaviourDelegate.java:669) at org.eclipse.wst.server.core.internal.Server.doPublish(Server.java:887) at org.eclipse.wst.server.core.internal.Server.publish(Server.java:874) at org.eclipse.wst.server.core.internal.PublishServerJob.run(PublishServerJob.java:72) at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

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• MVC Html.textbox/dropdown/whatever won't refresh on postback

  - by Cynthia

  OK, let's start with the Html.Textbox. It is supposed to contain text read from a file. The file read is based on what the user picks from a dropdown list. The first time it is fine. The user picks a value from the dropdown list. The controller uses that value to read some text from a file, and returns that text to the view via the view model. Everything is fine. THen the user picks another value from the dropdown list. The controller reads a new value from a file and returns it via the view model. Debugging to the LINE BEFORE THE HTML.TEXTBOX is set in the view shows that the model contains the correct value. However, the textbox itself still shows the PREVIOUS value when the page displays! If I switch from Html.Textbox to a plain input, type="text" html control, everything works fine. That's not so hard, but the same thing happens with my dropdown list -- I can't set the selected value in code. It always reverts to whatever was chosen last. Rendering a "select" tag with a dynamically-generated option list is a pain. I would love to be able to use Html.Dropdown. What am I missing here?? This is such a simple thing in webforms!

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• Design patter to keep track UITableView rows correspondance to underlying data in constant time.

  - by DenNukem

  When my model changes I want to animate changes in UITableView by inserting/deleting rows. For that I need to know the ordinal of the given row (so I can construct NSIndexPath), which I find hard to do in better-than-linear time. For example, consider that I have a list of addressbook entries which are manualy sorted by the user, i.e. there is no ordering "key" that represents the sort order. There is also a corresponding UITableView that shows one row per addressbook entry. When UITableView queries the datasource I query the NSMUtableArray populated with my entries and return required data in constant time for each row. However, if there is a change in underlying model I am getting a notification "Joe Smith, id#123 has been removed". Now I have a dilemma. A naive approach would be to scan the array, determine the index at which Joe Smith is and then ask UITableView to remove that precise row from the view, also removing it form the array. However, the scan will take linear time to finish. Now I could have an NSDictionary which allows me to find Joe Smith in constant time, but that doesn't do me a lot of good because I still need to find his ordinal index within the array in order to instruct UITableView to remove that row, which is again a linear search. I could further decide to store each object's ordinal inside the object itself to make it constant, but it will become outdated after first such update as all subsequent index values will have changed due to removal of an object. So what is the correct design pattern to accurately reflect model changes in the UITableView in costant (or at least logarithmic) time?

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• WPF TabBarControl Setting Focus to element when tab changes

  - by Aran Mulholland

  I have a TabControl that is bound to a view model <TabControl ItemsSource="{Binding Path=ViewModelCollection}" > <TabControl.ItemContainerStyle> <Style TargetType="TabItem" BasedOn="{StaticResource {x:Type TabItem}}"> <Setter Property="Header" Value="{Binding Title}" /> <Setter Property="Content" Value="{Binding}" /> </Style> </TabControl.ItemContainerStyle> </TabControl> Each Tab simply contains a View Model Item. I use a data template to display this. <!-- View Model Template --> <DataTemplate DataType="{x:Type local:ViewModelItem}"> <DockPanel> <TextBox Text="I want this to have the focus"/> </DockPanel> </DataTemplate> When the current tab is changed i want the focus to be on the textbox (this is a simple example, in my production code i have a datagrid) in the data template. how do i accomplish this?

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• how to show avg of employees salary in a NSTextField using NSArrayController and cocoa bindings

  - by Miraaj

  Hi all, I am new to cocoa bindings so I tried to make a simple application which will simply calculate avg of employees salary and display it in a text field, using cocoa bindings. I followed these steps: Made the model class : Person with one property for now - @property (readwrite, assign) int salary; In the application delegate class I initialized a mutable array : personArray with certain objects like this: Person *person1 = [[Person alloc] init]; person1.salary = 5000; Person *person2 = [[Person alloc] init]; person2.salary = 15000; Person *person3 = [[Person alloc] init]; person3.salary = 7000; Person *person4 = [[Person alloc] init]; person4.salary = 9000; Person *person5 = [[Person alloc] init]; person5.salary = 11000; personArray= [[NSMutableArray alloc] initWithObjects:person1, person2, person3, person4, person5,nil]; In IB I dropped a NSArrayController object, set its mode as Class - Person, added key salary in attribute pane. Then in bindings pane, binded contents array to ApplicationDelegate class with model key path set to self.personArray. Dropped a NSTextField on window. Binded its value to ArrayController object. Assigned controller key as - arrangedObjects. Assigned Model key path to @avg.salary When I executed the application I found no value being displayed in the text field. Can anyone suggest me where I may be wrong? Thanks, Miraaj

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• Business Logic Layer Pattern on Rails? MVCL

  - by Fabiano PS

  That is a broad question, and I appreciate no short/dumb asnwers like: "Oh that is the model job, this quest is retarded (period)" PROBLEM Where I work at people created a system over 2 years for managing the manufacture process over demand in the most simplified still broad as possible, involving selling, buying, assemble, The system is coded over Ruby On Rails. The app has been changed lots of times and the result is a mess on callbacks (some are called several times), 200+ models, and fat controllers: Total bad. The QUESTION is, if there is a gem, or pattern designed to handle Rails large app logic? The logic whould be able to fully talk to models (whose only concern would be data format handling and validation) What I EXPECT is to reduce complexity from various controllers, and hard to track callbacks into files with the responsibility to handle a business operation logic. In some cases there is the need to wait for a response, in others, only validation of the input is enough and a bg process would take place. ie: -- Sell some products (need to wait the operation to finish) 1. Set a View able to get the products input 2. Controller gets the product list inputed by employee and call the logic Logic::ExecuteWithResponse('sell', 'products', :prods => @product_list_with_qtt, :when => @date, :employee => current_user() ) This Logic would handle buying order, assemble order, machine schedule, warehouse reservation, and others. Have in mind that a callback on SalesOrder is not enough, since it depends on where it is called (no field for that), depends on the class of the user, among other stuff not visible for the model, or in some cases it would take long for the model to process.

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• Manditory read-only fields in django

  - by jamida

  I'm writing a test "grade book" application. The models.py file is shown below. class Student(models.Model): name = models.CharField(max_length=50) parent = models.CharField(max_length=50) def __unicode__(self): return self.name class Grade(models.Model): studentId = models.ForeignKey(Student) finalGrade = models.CharField(max_length=3) I'd like to be able to change the final grade for several students in a modelformset but for now I'm just trying one student at a time. I'm also trying to create a form for it that shows the student name as a field that can not be changed, the only thing that can be changed here is the finalGrade. So I used this trick to make the studentId read-only. class GradeROForm(ModelForm): studentId = forms.ModelChoiceField(queryset=Student.objects.all()) def __init__(self, *args, **kwargs): super(GradeROForm,self).__init__(*args, **kwargs) instance = getattr(self, 'instance', None) if instance and instance.id: self.fields['studentId'].widget.attrs['disabled']='disabled' def clean_studentId(self): instance = getattr(self,'instance',None) if instance: return instance.studentId else: return self.cleaned_data.get('studentId',None) class Meta: model=Grade And here is my view: def modifyGrade(request,student): student = Student.objects.get(name=student) mygrade = Grade.objects.get(studentId=student) if request.method == "POST": myform = GradeROForm(data=request.POST, instance=mygrade) if myform.is_valid(): grade = myform.save() info = "successfully updated %s" % grade.studentId else: myform=GradeROForm(instance=mygrade) return render_to_response('grades/modifyGrade.html',locals()) This displays the form like I expect, but when I hit "submit" I get a form validation error for the student field telling me this field is required. I'm guessing that, since the field is "disabled", the value is not being reported in the POST and for reasons unknown to me the instance isn't being used in its place. I'm a new Django/Python programmer, but quite experienced in other languages. I can't believe I've stumbled upon such a difficult to solve problem in my first significant django app. I figure I must be missing something. Any ideas?

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• mvvm - prismv2 - INotifyPropertyChanged

  - by depictureboy

  Since this is so long and prolapsed and really doesnt ask a coherent question: 1: what is the proper way to implement subproperties of a primary object in a viewmodel? 2: Has anyone found a way to fix the delegatecommand.RaiseCanExecuteChanged issue? or do I need to fix it myself until MS does? For the rest of the story...continue on. In my viewmodel i have a doctor object property that is tied to my Model.Doctor, which is an EF POCO object. I have onPropertyChanged("Doctor") in the setter as such: Private Property Doctor() As Model.Doctor Get Return _objDoctor End Get Set(ByVal Value As Model.Doctor) _objDoctor = Value OnPropertyChanged("Doctor") End Set End Property The only time OnPropertyChanged fires if the WHOLE object changes. This wouldnt be a problem except that I need to know when the properties of doctor changes, so that I can enable other controls on my form(save button for example). I have tried to implement it in this way: Public Property FirstName() As String Get Return _objDoctor.FirstName End Get Set(ByVal Value As String) _objDoctor.FirstName = Value OnPropertyChanged("Doctor") End Set End Property this is taken from the XAMLPowerToys controls from Karl Shifflet, so i have to assume that its correct. But for the life of me I cant get it to work. I have included PRISM in here because I am using a unity container to instantiate my view and it IS a singleton. I am getting change notification to the viewmodel via eventaggregator that then populates Doctor with the new value. The reason I am doing all this is because of PRISM's DelegateCommand. So maybe that is my real issue. It appears that there is a bug in DelegateCommand that does not fire the RaiseCanExecuteChanged method on the commands that implement it and therefore needs to be fired manually. I have the code for that in my onPropertyChangedEventHandler. Of course this isnt implemented through the ICommand interface either so I have to break and make my properties DelegateCommand(of X) so that I have access to RaiseCanExecuteChanged of each command.

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• Rails: keeping DRY with ActiveRecord models that share similar complex attributes

  - by Greg

  This seems like it should have a straightforward answer, but after much time on Google and SO I can't find it. It might be a case of missing the right keywords. In my RoR application I have several models that share a specific kind of string attribute that has special validation and other functionality. The closest similar example I can think of is a string that represents a URL. This leads to a lot of duplication in the models (and even more duplication in the unit tests), but I'm not sure how to make it more DRY. I can think of several possible directions... create a plugin along the lines of the "validates_url_format_of" plugin, but that would only make the validations DRY give this special string its own model, but this seems like a very heavy solution create a ruby class for this special string, but how do I get ActiveRecord to associate this class with the model attribute that is a string in the db Number 3 seems the most reasonable, but I can't figure out how to extend ActiveRecord to handle anything other than the base data types. Any pointers? Finally, if there is a way to do this, where in the folder hierarchy would you put the new class that is not a model? Many thanks.

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• Asp.Net MVC Tutorial Unit Tests

  - by Nicholas

  I am working through Steve Sanderson's book Pro ASP.NET MVC Framework and I having some issues with two unit tests which produce errors. In the example below it tests the CheckOut ViewResult: [AcceptVerbs(HttpVerbs.Post)] public ViewResult CheckOut(Cart cart, FormCollection form) { // Empty carts can't be checked out if (cart.Lines.Count == 0) { ModelState.AddModelError("Cart", "Sorry, your cart is empty!"); return View(); } // Invoke model binding manually if (TryUpdateModel(cart.ShippingDetails, form.ToValueProvider())) { orderSubmitter.SubmitOrder(cart); cart.Clear(); return View("Completed"); } else // Something was invalid return View(); } with the following unit test [Test] public void Submitting_Empty_Shipping_Details_Displays_Default_View_With_Error() { // Arrange CartController controller = new CartController(null, null); Cart cart = new Cart(); cart.AddItem(new Product(), 1); // Act var result = controller.CheckOut(cart, new FormCollection { { "Name", "" } }); // Assert Assert.IsEmpty(result.ViewName); Assert.IsFalse(result.ViewData.ModelState.IsValid); } I have resolved any issues surrounding 'TryUpdateModel' by upgrading to ASP.NET MVC 2 (Release Candidate 2) and the website runs as expected. The associated error messages are: *Tests.CartControllerTests.Submitting_Empty_Shipping_Details_Displays_Default_View_With_Error: System.ArgumentNullException : Value cannot be null. Parameter name: controllerContext* and the more detailed at System.Web.Mvc.ModelValidator..ctor(ModelMetadata metadata, ControllerContext controllerContext) at System.Web.Mvc.DefaultModelBinder.OnModelUpdated(ControllerContext controllerContext, ModelBindingContext bindingContext) at System.Web.Mvc.DefaultModelBinder.BindComplexModel(ControllerContext controllerContext, ModelBindingContext bindingContext) at System.Web.Mvc.Controller.TryUpdateModel[TModel](TModel model, String prefix, String[] includeProperties, String[] excludeProperties, IValueProvider valueProvider) at System.Web.Mvc.Controller.TryUpdateModel[TModel](TModel model, IValueProvider valueProvider) at WebUI.Controllers.CartController.CheckOut(Cart cart, FormCollection form) Has anyone run into a similar issue or indeed got the test to pass?

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• Using ComplexType with ToList causes InvalidOperationException

  - by Chris Paynter

  I have this model namespace ProjectTimer.Models { public class TimerContext : DbContext { public TimerContext() : base("DefaultConnection") { } public DbSet<Project> Projects { get; set; } public DbSet<ProjectTimeSpan> TimeSpans { get; set; } } public class DomainBase { [Key] public int Id { get; set; } } public class Project : DomainBase { public UserProfile User { get; set; } public string Name { get; set; } public string Description { get; set; } public IList<ProjectTimeSpan> TimeSpans { get; set; } } [ComplexType] public class ProjectTimeSpan { public DateTime TimeStart { get; set; } public DateTime TimeEnd { get; set; } public bool Active { get; set; } } } When I try to use this action I get the exception The type 'ProjectTimer.Models.ProjectTimeSpan' has already been configured as an entity type. It cannot be reconfigured as a complex type. public ActionResult Index() { using (var db = new TimerContext()) { return View(db.Projects.ToList); } } The view is using the model @model IList<ProjectTimer.Models.Project> Can any one shine some light as to why this would be happening?

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• Querying a self referencing join with NHibernate Linq

  - by Ben

  In my application I have a Category domain object. Category has a property Parent (of type category). So in my NHibernate mapping I have: <many-to-one name="Parent" column="ParentID"/> Before I switched to NHibernate I had the ParentId property on my domain model (mapped to the corresponding database column). This made it easy to query for say all top level categories (ParentID = 0): where(c => c.ParentId == 0) However, I have since removed the ParentId property from my domain model (because of NHibernate) so I now have to do the same query (using NHibernate.Linq) like so: public IList<Category> GetCategories(int parentId) { if (parentId == 0) return _catalogRepository.Categories.Where(x => x.Parent == null).ToList(); else return _catalogRepository.Categories.Where(x => x.Parent.Id == parentId).ToList(); } The real impact that I can see, is the sql generated. Instead of a simple 'select x,y,z from categories where parentid = 0' NHibernate generates a left outer join: SELECT this_.CategoryId as CategoryId4_1_, this_.ParentID as ParentID4_1_, this_.Name as Name4_1_, this_.Slug as Slug4_1_, parent1_.CategoryId as CategoryId4_0_, parent1_.ParentID as ParentID4_0_, parent1_.Name as Name4_0_, parent1_.Slug as Slug4_0_ FROM Categories this_ left outer join Categories parent1_ on this_.ParentID = parent1_.CategoryId WHERE this_.ParentID is null Which doesn't seems much less efficient that what I had before. Is there a better way of querying these self referencing joins as it's very tempting to drop the ParentID back onto my domain model for this reason. Thanks, Ben

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• Unit Testing - Validation of ViewModel ASP.NET MVC 2

  - by dean nolan

  I am currently unit testing a service that adds users to a repository. I am using dependency injection to test using a fake repository. The repository has a method CreateUser(User user) which just adds it to the database or in this case a List of Users. The logic for the creation is in the UserServices class. The application has a form for creating a user that requires some properties such as name and address. This is an MVC 2 app and I will be using the new validation using data annotations. This makes me wonder about a few things: 1) Should I annotate a POCO object that will map to the database? Or should I create a specific View Model that has these annotations and pass this data to the UserServices class? 2)Should the UserServicesClass also check this data? Would I best be constructing a Usr out of the ViewModel and passing this into the Service as a parameter? 3) The actual unit testing would depend on 2), I either populate a User object and pass that in, or I pass a large list of strings to the method CreateUser. Writing this out I get a basic idea that I should probably annotate the view model only, pass in a user (constructed by the view model if the data is valid) and also just construct the user in the unit test also. Is this the best way to go?

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• ASP.Net MVC Object Reference in Edit View when using DropDownListFor()

  - by hermiod

  This question is related to another I ask recently, it can be found here for some background information. Here is the code in the Edit ActionResult: public virtual ActionResult Edit(int id) { ///Set data for DropDownLists. ViewData["MethodList"] = tr.ListMethods(); ViewData["GenderList"] = tr.ListGenders(); ViewData["FocusAreaList"] = tr.ListFocusAreas(); ViewData["SiteList"] = tr.ListSites(); ViewData["TypeList"] = tr.ListTalkbackTypes(); ViewData["CategoryList"] = tr.ListCategories(); return View(tr.GetTalkback(id)); } I add lists to the ViewData to use in the dropdownlists, these are all IEnumerable and are all returning values. GetTalkback() returns an Entity framework object of type Talkback which is generated from the Talkback table. The DropDownListFor code is: <%: Html.DropDownListFor(model=>model.method_id,new SelectList(ViewData["MethodList"] as IEnumerable<SelectListItem>,"Value","Text",Model.method_id)) %> The record I am viewing has values in all fields. When I click submit on the View, I get an Object reference not set to an instance of an object. error on the above line. There are a number of standard fields in the form prior to this, so the error is only occurring on dropdown lists, and it is occurring on all of them. Any ideas? This is my first foray in to MVC, C#, and Entity so I am completely lost!

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