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• Good way to identify similar images?

  - by Nick

  I've developed a simple and fast algorithm in PHP to compare images for similarity. Its fast (~40 per second for 800x600 images) to hash and a unoptimised search algorithm can go through 3,000 images in 22 mins comparing each one against the others (3/sec). The basic overview is you get a image, rescale it to 8x8 and then convert those pixels for HSV. The Hue, Saturation and Value are then truncated to 4 bits and it becomes one big hex string. Comparing images basically walks along two strings, and then adds the differences it finds. If the total number is below 64 then its the same image. Different images are usually around 600 - 800. Below 20 and extremely similar. Are there any improvements upon this model I can use? I havent looked at how relevant the different components (hue, saturation and value) are to the comparison. Hue is probably quite important but the others? To speed up searches I could probably split the 4 bits from each part in half, and put the most significant bits first so if they fail the check then the lsb doesnt need to be checked at all. I dont know a efficient way to store bits like that yet still allow them to be searched and compared easily. I've been using a dataset of 3,000 photos (mostly unique) and there havent been any false positives. Its completely immune to resizes and fairly resistant to brightness and contrast changes.

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• Testing InlineFormset clean methods

  - by Rory

  I have a Django project, with 2 models, a Structure and Bracket, the Bracket has a ForeignKey to a Structure (i.e. one-to-many, one Structure has many Brackets). I created a TabularInline for the admin site, so that there would be a table of Brackets on the Structure. I added a custom formset with some a custom clean method to do some extra validation, you can't have a Bracket that conflicts with another Bracket on the same Structure etc. The admin looks like this: class BracketInline(admin.TabularInline): model = Bracket formset = BracketInlineFormset class StructureAdmin(admin.ModelAdmin): inlines = [ BracketInline ] admin.site.register(Structure, StructureAdmin) That all works, and the validation works. However now I want to write some unittest to test my complex formset validation logic. My first attempt to validate known-good values is: data = {'form-TOTAL_FORMS': '1', 'form-INITIAL_FORMS': '0', 'form-MAX_NUM_FORMS': '', 'form-0-field1':'good-value', … } formset = BracketInlineFormset(data) self.assertTrue(formset.is_valid()) However that doesn't work and raises the exception: ====================================================================== ERROR: testValid (appname.tests.StructureTestCase) ---------------------------------------------------------------------- Traceback (most recent call last): File "/paht/to/project/tests.py", line 494, in testValid formset = BracketInlineFormset(data) File "/path/to/django/forms/models.py", line 672, in __init__ self.instance = self.fk.rel.to() AttributeError: 'BracketInlineFormset' object has no attribute 'fk' ---------------------------------------------------------------------- The Django documentation (for formset validation) implies one can do this. How come this isn't working? How do I test the custom clean()/validation for my inline formset?

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• Retrieving models from form with ModelMultipleChoiceField

  - by colinjameswebb

  I am having difficulties with forms, specifically ModelMultipleChoiceField. I've pieced together this code from various examples, but it sadly doesn't work. I would like to be able to: Search for some Works on work_search.html Display the results of the search, with checkboxes next to each result Select the Works I want, via the checkboxes After pressing Add, display which works were selected. I believe everything is okay except the last part. The page simply displays "works" :( Here is the code - sorry about the length. Models.py class Work(models.Model): title = models.CharField(max_length=200) artist = models.CharField(max_length=200) writers = models.CharField(max_length=200) def __unicode__(self): return self.title + ' - ' + self.artist forms.py class WorkSelectForm(forms.Form): def __init__(self, queryset, *args, **kwargs): super(WorkSelectForm, self).__init__(*args, **kwargs) self.fields['works'] = forms.ModelMultipleChoiceField(queryset=queryset, widget=forms.CheckboxSelectMultiple()) views.py def work_search(request): query = request.GET.get('q', '') if query: qset = ( Q(title__icontains=query) | Q(artist__icontains=query) | Q(writers__icontains=query) ) results = Work.objects.filter(qset).distinct() form = WorkSelectForm(results) return render_to_response("work_search.html", {"form": form, "query": query }) else: results = [] return render_to_response("work_search.html", {"query": query }) def add_works(request): #if request.method == POST: form = WorkSelectForm(request.POST) #if form.isvalid(): items = form.fields['works'].queryset return render_to_response("add_works.html", {"items":items}) work_search.html {% extends "base.html" %} {% block content %} <h1>Search</h1> <form action="." method="GET"> <label for="q">Search: </label> <input type="text" name="q" value="{{ query|escape }}"> <input type="submit" value="Search"> </form> {% if query %} <h2>Results for "{{ query|escape }}":</h2> <form action="add_works" method="post"> <ul> {% if form %} {{ form.as_ul }} {% endif %} </ul> <input type="submit" value="Add"> </form> {% endif %} {% endblock %} add_works.html {% extends "base.html" %} {% block content %} {% if items %} {% for item in items %} {{ item }} {% endfor %} {% else %} <p>Nothing selected</p> {% endif %} {% endblock %}

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• Out of memory while iterating through rowset

  - by Phliplip

  Hi All, I have a "small" table of 60400 rows with zipcode data. I wan't to iterate through them all, update a column value, and then save it. The following is part of my Zipcodes model which extends My_Db_Table that a totalRows function that - you guessed it.. returns the total number of rows in the table (60400 rows) public function normalizeTable() { $this->getAdapter()->setProfiler(false); $totalRows = $this->totalRows(); $rowsPerQuery = 5; for($i = 0; $i < $totalRows; $i = $i + $rowsPerQuery) { $select = $this->select()->limit($i, $rowsPerQuery); $rowset = $this->fetchAll($select); foreach ($rowset as $row) { $row->{self::$normalCityColumn} = $row->normalize($row->{self::$cityColumn}); $row->save(); } unset($rowset); } } My rowClass contains a normalize function (basicly a metaphone wrapper doing some extra magic). At first i tried a plain old $this-fetchAll(), but got a out of memory (128MB) right away. Then i tried splitting the rowset into chunks, only difference is that some rows actually gets updated. Any ideas on how i can acomplish this, or should i fallback to ye'olde mysql_query()

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• Does Hibernate support one-to-one associations as pkeys?

  - by Andrzej Doyle

  Hi all, Can anyone tell me whether Hibernate supports associations as the pkey of an entity? I thought that this would be supported but I am having a lot of trouble getting any kind of mapping that represents this to work. In particular, with the straight mapping below: @Entity public class EntityBar { @Id @OneToOne(optional = false, mappedBy = "bar") EntityFoo foo // other stuff } I get an org.hibernate.MappingException: "Could not determine type for: EntityFoo, at table: ENTITY_BAR, for columns: [org.hibernate.mapping.Column(foo)]" Diving into the code it seems the ID is always considered a Value type; i.e. "anything that is persisted by value, instead of by reference. It is essentially a Hibernate Type, together with zero or more columns." I could make my EntityFoo a value type by declaring it serializable, but I wouldn't expect this would lead to the right outcome either. I would have thought that Hibernate would consider the type of the column to be integer (or whatever the actual type of the parent's ID is), just like it would with a normal one-to-one link, but this doesn't appear to kick in when I also declare it an ID. Am I going beyond what is possible by trying to combine @OneToOne with @Id? And if so, how could one model this relationship sensibly?

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• How can I have 2 ADO access methods use the same Transaction?

  - by KevinDeus

  I'm writing a test to see if my LINQ to Entity statement works.. I'll be using this for others if I can get this concept going.. my intention here is to INSERT a record with ADO, then verify it can be queried with LINQ, and then ROLLBACK the whole thing at the end. I'm using ADO to insert because I don't want to use the object or the entity model that I am testing. I figure that a plain ADO INSERT should do fine. problem is.. they both use different types of connections. is it possible to have these 2 different data access methods use the same TRANSACTION so I can roll it back?? _conn = new SqlConnection(_connectionString); _conn.Open(); _trans = _conn.BeginTransaction(); var x = new SqlCommand("INSERT INTO Table1(ID, LastName, FirstName, DateOfBirth) values('127', 'test2', 'user', '2-12-1939');", _conn); x.ExecuteNonQuery(); //So far, so good. Adding a record to the table. //at this point, we need to do **_trans.Commit()** here because our Entity code can't use the same connection. Then I have to manually delete in the TestHarness.TearDown.. I'd like to eliminate this step //(this code is in another object, I'll include it for brevity. Imagine that I passed the connection in) //check to see if it is there using (var ctx = new XEntities(_conn)) //can't do this.. _conn is not an EntityConnection! { var retVal = (from m in ctx.Table1 where m.first_name == "test2" where m.last_name == "user" where m.Date_of_Birth == "2-12-1939" where m.ID == 127 select m).FirstOrDefault(); return (retVal != null); } //Do test.. Assert.BlahBlah(); _trans.Rollback();

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• What are good strategies for organizing single class per query service layer?

  - by KallDrexx

  Right now my Asp.net MVC application is structured as Controller - Services - Repositories. The services consist of aggregate root classes that contain methods. Each method is a specific operation that gets performed, such as retrieving a list of projects, adding a new project, or searching for a project etc. The problem with this is that my service classes are becoming really fat with a lot of methods. As of right now I am separating methods out into categories separated by #region tags, but this is quickly becoming out of control. I can definitely see it becoming hard to determine what functionality already exists and where modifications need to go. Since each method in the service classes are isolated and don't really interact with each other, they really could be more stand alone. After reading some articles, such as this, I am thinking of following the single query per class model, as it seems like a more organized solution. Instead of trying to figure out what class and method you need to call to perform an operation, you just have to figure out the class. My only reservation with the single query per class method is that I need some way to organize the 50+ classes I will end up with. Does anyone have any suggestions for strategies to best organize this type of pattern?

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• Tab bar application with UINavigation Controller MOC not being retained.

  - by iamsmug

  I created a tab bar application from the template and added a navigation controller to one of the tabs. I have already created this app from the navigation app template already and is working. The reason I am doing it this way is because I need to add a tab bar and thought it would be easier starting by using the tab bar project template and adding the nav controller to it rather than the other way round. I have copied the data model over from the other project and added the relevant code to where it should be. The problem I am having is passing the moc from the app delegate to the tab with the nav controller on. Here is a snippet from my applicationDidFinishLaunching method in my app delegate: - (void)applicationDidFinishLaunching:(UIApplication *)application { [self createEditableCopyOfDatabaseIfNeeded]; Top_BananaTableViewController *top_BananaTableViewController = (Top_BananaTableViewController *)[navigationController topViewController]; top_BananaTableViewController.managedObjectContext = self.managedObjectContext; // Add the tab bar controller's current view as a subview of the window [window addSubview:tabBarController.view]; [window makeKeyAndVisible]; } Everything seems fine here but when it comes to the fetchedResultsController on my nav controller view it bombs out with: '+entityForName: could not locate an NSManagedObjectModel for entity name 'cards'' When I checked what was set to my managedObjectContext on that view it was null. I don't know why or where it is loosing it's setting. Please help.

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• Abstract factory pattern on top of IoC?

  - by Sergei

  I have decided to use IoC principles on a bigger project. However, i would like to get something straight that's been bothering me for a long time. The conclusion that i have come up with is that an IoC container is an architectural pattern, not a design pattern. In other words, no class should be aware of its presence and the container itself should be used at the application layer to stitch up all components. Essentially, it becomes an option, on top of a well designed object-oriented model. Having said that, how is it possible to access resolved types without sprinkling IoC containers all over the place (regardless of whether they are abstracted or not)? The only option i see here is to utilize abstract factories which use an IoC container to resolve concrete types. This should be easy enough to swap out for a set of standard factories. Is this a good approach? Has anyone on here used it and how well did it work for you? Is there anything else available? Thanks!

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• App crashes every second time a tableview row is selected in navigation controller setup

  - by Thaurin

  Disclaimer first: I'm pretty new to Objective-C and the retain model. I've been developing in a garbage collected .NET environment for the last five years, so I've been spoiled. I'm still learning. I'm having my iPhone app crash with EXC_BAD_ACCESS. It happens in a navigtation controller/tableview setup. When I select a row the first time, no problems. It switches in the child controller without problems. I go back and select the same row again. Program then proceeds to crash. Every other row works fine, but every second time a row is accessed, it's a crash. I've pinpointed the location where this happens. The child controller (which is a class that I reuse for every row of the same type) that's being switched into has an array of NSString's representing the rows that will be displayed. I set it before pushing the child viewcontroller. It's there where this apparently happens. I'm having a hard time debugging this problem, still wrestling with xcode and all. I fear there may be some vital information missing here, but maybe there is something you recognize here.

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• Circular Reference exception with JSON Serialisation with MVC3 and EF4 CTP5w

  - by nakchak

  Hi I'm having problems with a circular reference when i try and serialise an object returned via EF4 CTP5. Im using the code first approach and simple poco's for my model. I have added [ScriptIgnore] attributes to any properties that provide a back references to an object and annoyingly every seems to work fine if i manually instantiate the poco's, i.e. they serialise to JSON fine, and the scriptignore attribute is acknowledged. However when i try and serialise an object returned from the DAL i get the circular reference exception "A circular reference was detected while serializing an object of type 'System.Data.Entity.DynamicProxies.xxxx'" I have tried several ways of retreiving the data but they all get stuck with this error: public JsonResult GetTimeSlot(int id) { TimeSlotDao tsDao = new TimeSlotDao(); TimeSlot ts = tsDao.GetById(id); return Json(ts); } The method below works slightly better as rather than the timeslot dynamic proxied object causing the circular refference its the appointment object. public JsonResult GetTimeSlot(int id) { TimeSlotDao tsDao = new TimeSlotDao(); var ts = from t in tsDao.GetQueryable() where t.Id == id select new {t.Id, t.StartTime, t.Available, t.Appointment}; return Json(ts); } Any ideas or solutions to this problem? Update I would prefer to use the out of the box serialiser if possible although Json.Net via nuget is ok as an alternative i would hope its possible to use it as I intended as well...

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• odd nullreference error at foreach when rendering view

  - by giddy

  This error is so weird I Just can't really figure out what is really wrong! In UserController I have public virtual ActionResult Index() { var usersmdl = from u in RepositoryFactory.GetUserRepo().GetAll() select new UserViewModel { ID = u.ID, UserName = u.Username, UserGroupName = u.UserGroupMain.GroupName, BranchName = u.Branch.BranchName, Password = u.Password, Ace = u.ACE, CIF = u.CIF, PF = u.PF }; if (usersmdl != null) { return View(usersmdl.AsEnumerable()); } return View(); } My view is of type @model IEnumerable<UserViewModel> on the top. This is what happens: Where and what exactly IS null!? I create the users from a fake repository with moq. I also wrote unit tests, which pass, to ensure the right amount of mocked users are returned. Maybe someone can point me in the right direction here? Top of the stack trace is : at lambda_method(Closure , User ) at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext() at ASP.Index_cshtml.Execute() Is it something to do with linq here? Tell me If I should include the full stack trace.

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• Java Play Mustache NPE Error

  - by zanedev

  We are getting a mustache play error in production (amazon linux EC2 AMI) but not in development (MACs) and we have tried upgrading the jvm, using the jdk instead, and changing from a tomcat deploy model to match our development environments as much as possible but nothing is working. Please any help would be greatly appreciated. We have lots of shared code in java and javascript using mustache and it would be a big deal to rewrite everything if we had to ditch mustache on the java side. 20:48:52,403 ERROR ~ @6al2dd0po Internal Server Error (500) for request GET /mystuff/people Execution exception (In {module:mustache-0.2}/app/play/modules/mustache/MustacheTags.java around line 32) NullPointerException occured : null play.exceptions.JavaExecutionException at play.templates.BaseTemplate.throwException(BaseTemplate.java:90) at play.templates.GroovyTemplate.internalRender(GroovyTemplate.java:257) at play.templates.Template.render(Template.java:26) at play.templates.GroovyTemplate.render(GroovyTemplate.java:187) at play.mvc.results.RenderTemplate.<init>(RenderTemplate.java:24) at play.mvc.Controller.renderTemplate(Controller.java:660) at play.mvc.Controller.renderTemplate(Controller.java:640) at play.mvc.Controller.render(Controller.java:695) at controllers.MyStuff.people(MyStuff.java:183) at play.mvc.ActionInvoker.invokeWithContinuation(ActionInvoker.java:548) at play.mvc.ActionInvoker.invoke(ActionInvoker.java:502) at play.mvc.ActionInvoker.invokeControllerMethod(ActionInvoker.java:478) at play.mvc.ActionInvoker.invokeControllerMethod(ActionInvoker.java:473) at play.mvc.ActionInvoker.invoke(ActionInvoker.java:161) at Invocation.HTTP Request(Play!) Caused by: java.lang.NullPointerException at play.modules.mustache.MustacheTags._template(MustacheTags.java:32) at play.modules.mustache.MustacheTags$_template.call(Unknown Source) at /app/views/User/people.html.(line:22) at play.templates.GroovyTemplate.internalRender(GroovyTemplate.java:232) ... 13 more

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• How do I keep my DataService up to date with ObservableCollection?

  - by joebeazelman

  I have a class called CustomerService which simply reads a collection of customers from a file or creates one and passes it back to the Main Model View where it is turned into an ObservableCollection. What the best practice for making sure the items in the CustomerService and ObservableCollection are in sync. I'm guessing I could hookup the CustomerService object to respond to RaisePropertyChanged, but isn't this only for use with WPF controls? Is there a better way? using System; public class MainModelView { public MainModelView() { _customers = new ObservableCollection<CustomerViewModel>(new CustomerService().GetCustomers()); } public const string CustomersPropertyName = "Customers" private ObservableCollection<CustomerViewModel> _customers; public ObservableCollection<CustomerViewModel> Customers { get { return _customers; } set { if (_customers == value) { return; } var oldValue = _customers; _customers = value; // Update bindings and broadcast change using GalaSoft.MvvmLight.Messenging RaisePropertyChanged(CustomersPropertyName, oldValue, value, true); } } } public class CustomerService { /// <summary> /// Load all persons from file on disk. /// </summary> _customers = new List<CustomerViewModel> { new CustomerViewModel(new Customer("Bob", "" )), new CustomerViewModel(new Customer("Bob 2", "" )), new CustomerViewModel(new Customer("Bob 3", "" )), }; public IEnumerable<LinkViewModel> GetCustomers() { return _customers; } }

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• Rails - any fancy ways to handle 404s?

  - by jyoseph

  I have a rails app I built for an old site I converted from another cms (in a non-rails language, hehe). Most of the old pages are mapped to the new pages using routes.rb. But there are still a few 404s. I am a rails newb so I'm asking if there are any advanced ways to handle 404s. For example, if I was programming in my old language I'd do this: Get the URL (script_name) that was being accessed and parse it. Do a lookup in the database for any keywords, ids, etc found in the new URL. If found, redirect to the page (or if multiple records are found, show them all on a results page and let user choose). With rails I'd probably want to do :status = :moved_permanently I'm guessing? If not found, show a 404. Are there any gems/plugins or tutorials you know of that would handle such a thing, if it's even possible. Or can you explain on a high level how that can be done? I don't need a full code sample, just a push in the right direction. PS. It's a simple rails 3 app that uses a single Content model.

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• What makes an effective UI for displaying versioning of structured hierarchical data

  - by Fadrian Sudaman

  Traditional version control system are displaying versioning information by grouping Projects-Folders-Files with Tree view on the left and details view on the right, then you will click on each item to look at revision history for that configuration history. Assuming that I have all the historical versioning information available for a project from Object-oriented model perspective (e.g. classes - methods - parameters and etc), what do you think will be the most effective way to present such information in UI so that you can easily navigate and access the snapshot view of the project and also the historical versioning information? Put yourself in the position that you are using a tool like this everyday in your job like you are currently using SVN, SS, Perforce or any VCS system, what will contribute to the usability, productivity and effectiveness of the tool. I personally find the classical way for display folders and files like above are very restrictive and less effective for displaying deep nested logical models. Assuming that this is a greenfield project and not restricted by specific technology, how do you think I should best approach this? I am looking for idea and input here to add values to my research project. Feel free to make any suggestions that you think is valuable. Thanks again for anyone that shares their thoughts.

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• How to check for a null object reference when validating forms in MVC

  - by quakkels

  Hello SO, I'm experimenting with validating forms in the asp.net MVC framework. I'm focusing on server side validation for the time being. I've come across an error that I'm not sure how to rectify. System.NullReferenceException: Object reference not set to an instance of an object. The code that throws the error is: [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create([Bind(Exclude="ID")] MembersCreate mc ) { mc.Modules = ModuleListDataContext.GetModuleList(); ViewData.Model = mc; //Validation using ModelState // // //line below errors when form field is empty // if ((string)mc.Member.Username.Trim() == "") ModelState.AddModelError("Member.Username", "Username is required."); if (!ModelState.IsValid) return View(); try { // TODO: Add insert logic here return RedirectToAction("Index","Home"); } catch { return View(); } } When I put spaces in the field it performs exactly as i want, but if I leave the field blank and press submit I get the error. What's the best way to avoid this error and still validate blank form fields? Thanks all -

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• Dynamically generate client-side HTML form control using JavaScript and server-side Python code in Google App Engine

  - by gisc

  I have the following client-side front-end HTML using Jinja2 template engine: {% for record in result %} <textarea name="remark">{{ record.remark }}</textarea> <input type="submit" name="approve" value="Approve" /> {% endfor %} Thus the HTML may show more than 1 set of textarea and submit button. The back-end Python code retrieves a variable number of records from a gql query using the model, and pass this to the Jinja2 template in result. When a submit button is clicked, it triggers the post method to update the record: def post(self): if self.request.get('approve'): updated_remark = self.request.get('remark') record.remark = db.Text(updated_remark) record.put() However, in some instances, the record updated is NOT the one that correspond to the submit button clicked (eg if a user clicks on record 1 submit, record 2 remark gets updated, but not record 1). I gather that this is due to the duplicate attribute name remark. I can possibly use JavaScript/jQuery to generate different attribute names. The question is, how do I code the back-end Python to get the (variable number of) names generated by the JavaScript? Thanks.

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• Enum exeeding the 65535 bytes limit of static initializer... what's best to do?

  - by Daniel Bleisteiner

  I've started a rather large Enum of so called Descriptors that I've wanted to use as a reference list in my model. But now I've come across a compiler/VM limit the first time and so I'm looking for the best solution to handle this. Here is my error : The code for the static initializer is exceeding the 65535 bytes limit It is clear where this comes from - my Enum simply has far to much elements. But I need those elements - there is no way to reduce that set. Initialy I've planed to use a single Enum because I want to make sure that all elements within the Enum are unique. It is used in a Hibernate persistence context where the reference to the Enum is stored as String value in the database. So this must be unique! The content of my Enum can be devided into several groups of elements belonging together. But splitting the Enum would remove the unique safety I get during compile time. Or can this be achieved with multiple Enums in some way? My only current idea is to define some Interface called Descriptor and code several Enums implementing it. This way I hope to be able to use the Hibernate Enum mapping as if it were a single Enum. But I'm not even sure if this will work. And I loose unique safety. Any ideas how to handle that case?

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• XForms relation of 'constraint' and 'required' properties

  - by Danny

  As a reference, the most similar question already asked is: http://stackoverflow.com/questions/8667849/making-xforms-enforce-the-constraint-and-type-model-item-properties-only-when-fi The difference is that I cannot use the relevant properties since I do want the field to be visible and accessible. I'm attempting to make a XForms form that has the following properties: It displays a text field named 'information'. (for the example) This field must not be required, since it may not be necessary to enter data. (Or this data will be entered at a later time.) However, if data is entered in this field, it must adhere to the specified constraint. I cannot mark the field as not relevant since this would hide the field and some data may need to be entered in it. The trouble now is that even though the field has no data in it, the constraint is still enforced (i.e. even though it is not marked as 'required'). I have taken a look at the XForms 1.1 specification, however it does not seem to describe how the properties 'required' and 'constraint' should interact. The only option I see, is to add a part to the constraint such that an empty value is allowed. e.g.: . = '' or <actual-constraint However, I don't like this. It feels like a workaround to add this to every such field. Is there any other way to express that non-required fields should not need to match the constraint for that field? (Am I missing something?)

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• Why doesn't the Java Collections API include a Graph implementation?

  - by dvanaria

  I’m currently learning the Java Collections API and feel I have a good understanding of the basics, but I’ve never understood why this standard API doesn’t include a Graph implementation. The three base classes are easily understandable (List, Set, and Map) and all their implementations in the API are mostly straightforward and consistent. Considering how often graphs come up as a potential way to model a given problem, this just doesn’t make sense to me (it’s possible it does exist in the API and I’m not looking in the right place of course). Steve Yegge suggests in one of his blog posts that a programmer should consider graphs first when attacking a problem, and if the problem domain doesn’t fit naturally into this data structure, only then consider the alternative structures. My first guess is that there is no universal way to represent graphs, or that their interfaces may not be generic enough for an API implementation to be useful? But if you strip down a graph to its basic components (vertices and a set of edges that connect some or all of the vertices) and consider the ways that graphs are commonly constructed (methods like addVertex(v) and insertEdge(v1, v2)) it seems that a generic Graph implementation would be possible and useful. Thanks for helping me understand this better.

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• How do I secure a .NET Web Service for use by an iPhone application?

  - by David A Gibson

  Hello, The title says it all, I have a Web Service written in .NET that provides data for an iPhone application. It will also allow the application make a "reservation." Currently it's all internal to the corporate network but obviously when the iPhone application is published I will need ensure the Web Service is available externally. How would I go about securing the Web Service? There are two aspects I'm looking into: Authentication for accessing the web service Protection for the data being transferred I'm no so bothered about the data being passed back and forth as it will be viewable in the application anyway (which will be free). The key issue for me is preventing users from accessing the Web Service and making reservations themselves. At the moment I am considering encrypting any strings in the XML data passed back and forth so only the client can effectively use the web service sidestepping the need for authentication and providing protection for the data. This is the only model I have seen but I think the overheads on the iPhone and even for the web service make for a poor user experience. Any solutions at all would be most welcome? Thanks

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• Lost Array After Validation Error

  - by Georges Kmeid

  I'm working on a CakePHP project and I have User, Post and Location models among others. User hasMany Location and Post belongsTo User so Location is not directly related to Post. This is my code in the Post controller: public function add() { if ($this->request->is('get')) { $this->loadModel('Location'); $this->set('locations', $this->Location->find('all', array('conditions' => array('user_id' => $this->Auth->user('id'))))); } ... } And this is my code in the posts/add view: <?php $i = 0; $j = 0; foreach ($locations as $location): $location_names[$i] = $location['Location']['name']; $i++; endforeach; echo "<select name=\"location\" onchange=\"select(this.value)\">"; echo "<option value=\"\">Select a saved location</option>"; foreach ($locations as $location): echo "<option value=\"" . $location['Location']['latitude'] . "," . $location['Location']['longitude'] . "\">" . $location_names[$j] . "</option>"; $j++; endforeach; ?> </select> If I enter a wrong value in one of the post inputs that has a validation rule in Post model, it redirects to the current add view, shows what is the validation error, but then the $locations array passed from controller to view disappears and can't use it in view and I get this error: Notice (8): Undefined variable: locations [APP\View\Posts\add.ctp, line 68]

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• Capture and handling the tab/Textchanged event in a textbox in asp.net MVC

  - by Icerman

  I have the following code th handle a user name validation on the server side. But the event seems not firing since break points in js or C# code didn't hit. Can anyone point out where I did wrong? Here is the user control which has a user name textbox: <%: Html.TextBox("UserName", Model.Username, new { maxlength = "40", size = "20", tabindex = "1", @onchange = "CheckAvailability()" })% CheckAvailability() is defined in the User.Validation.js and included in the above user control: $(document).ready(function () { function CheckAvailability() { $.post("/Home/Survey/CheckAvailability", { Username: $("#UserName").val() }, function (data) { var myObject = eval('(' + data + ')'); var newid = myObject; if (newid == 0) { $("#usernamelookupresult").html("<font color='green'>Available :-D</font>") } else { $("#usernamelookupresult").html("<font color='red'>Taken :-(</font>") } }); } }); Here is the survey controller function which will have server side validation: [HttpPost] public ActionResult CheckAvailability(string Username) { int Taken = 0; // This is where you add your database lookup if (Username == "abc") { Taken = 1; } return Json(Taken); }

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• Asp MVC - "The Id field is required" validation message on Create; Id not set to [Required]

  - by Dann

  This is happening when I try to create the entity using a Create style action in Asp.Net MVC 2. The POCO has the following properties: public int Id {get;set;} [Required] public string Message {get; set} On the creation of the entity, the Id is set automatically, so there is no need for it on the Create action. The ModelState says that "The Id field is required", but I haven't set that to be so. Is there something automatic going on here? EDIT - Reason Revealed The reason for the issue is answered by Brad Wilson via Paul Speranza in one of the comments below where he says (cheers Paul): You're providing a value for ID, you just didn't know you were. It's in the route data of the default route ("{controller}/{action}/{id}"), and its default value is the empty string, which isn't valid for an int. Use the [Bind] attribute on your action parameter to exclude ID. My default route was: new { controller = "Customer", action = "Edit", id = " " } // Parameter defaults EDIT - Update Model technique I actually changed the way I did this again by using TryUpdateModel and the exclude parameter array asscoiated with that. [HttpPost] public ActionResult Add(Venue collection) { Venue venue = new Venue(); if (TryUpdateModel(venue, null, null, new[] { "Id" })) { _service.Add(venue); return RedirectToAction("Index", "Manage"); } return View(collection); }

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