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• What are the most interesting equivalences arising from the Curry-Howard Isomorphism?

  - by Tom

  I came upon the Curry-Howard Isomorphism relatively late in my programming life, and perhaps this contributes to my being utterly fascinated by it. It implies that for every programming concept there exists a precise analogue in formal logic, and vice versa. Here's an "obvious" list of such analogies, off the top of my head: program/definition | proof type/declaration | proposition inhabited type | theorem function | implication function argument | hypothesis/antecedent function result | conclusion/consequent function application | modus ponens recursion | induction identity function | tautology non-terminating function | absurdity tuple | conjunction (and) disjoint union | exclusive disjunction (xor) parametric polymorphism | universal quantification So, to my question: what are some of the more interesting/obscure implications of this isomorphism? I'm no logician so I'm sure I've only scratched the surface with this list. For example, here are some programming notions for which I'm unaware of pithy names in logic: currying | "((a & b) => c) iff (a => (b => c))" scope | "known theory + hypotheses" And here are some logical concepts which I haven't quite pinned down in programming terms: primitive type? | axiom set of valid programs? | theory ? | disjunction (or)

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• Java - abstract class, equals(), and two subclasses

  - by msr

  Hello, I have an abstract class named Xpto and two subclasses that extend it named Person and Car. I have also a class named Test with main() and a method foo() that verifies if two persons or cars (or any object of a class that extends Xpto) are equals. Thus, I redefined equals() in both Person and Car classes. Two persons are equal when they have the same name and two cars are equal when they have the same registration. However, when I call foo() in the Test class I always get "false". I understand why: the equals() is not redefined in Xpto abstract class. So... how can I compare two persons or cars (or any object of a class that extends Xpto) in that foo() method? In summary, this is the code I have: public abstract class Xpto { } public class Person extends Xpto{ protected String name; public Person(String name){ this.name = name; } public boolean equals(Person p){ System.out.println("Person equals()?"); return this.name.compareTo(p.name) == 0 ? true : false; } } public class Car extends Xpto{ protected String registration; public Car(String registration){ this.registration = registration; } public boolean equals(Car car){ System.out.println("Car equals()?"); return this.registration.compareTo(car.registration) == 0 ? true : false; } } public class Teste { public static void foo(Xpto xpto1, Xpto xpto2){ if(xpto1.equals(xpto2)) System.out.println("xpto1.equals(xpto2) -> true"); else System.out.println("xpto1.equals(xpto2) -> false"); } public static void main(String argv[]){ Car c1 = new Car("ABC"); Car c2 = new Car("DEF"); Person p1 = new Person("Manel"); Person p2 = new Person("Manel"); foo(p1,p2); } }

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• MXML composite canvas component initialization error

  - by mkorpela

  I'm getting an odd error from my composite canvas component: An ActionScript error has occurred: Error: null at mx.core::Container/initialize()[C:\autobuild\galaga\frameworks\projects\framework\src\mx\core\Container.as:2560] at -REMOVED THIS FOR STACK OVERFLOW-.view::EditableCanvas/initialize()[.../view/EditableCanvas .... It seems to be related to the fact that my composite component has a child and I'm trying to add one in the place I'm using the component. So how can I do this correctly? Component code looks like this (EditableCanvas.mxml): <?xml version="1.0" encoding="utf-8"?> <mx:Canvas xmlns:mx="http://www.adobe.com/2006/mxml" creationComplete="{init()}"> <mx:Script> <![CDATA[ private var _editable:Boolean; public function set editable(edit:Boolean):void { _editable = edit; } private function init():void { if(_editable){ addEventListener(MouseEvent.MOUSE_OVER, showEdit); addEventListener(MouseEvent.MOUSE_OUT, hideEdit); } } private function showEdit(event:Event):void { editTextImage.visible = true; } private function hideEdit(event:Event):void { editTextImage.visible = false; } ]]> </mx:Script> <mx:Image id="editTextImage" source="@Embed('/../assets/icons/small/process.png')" click="{dispatchEvent(EditPoiEvent.text())}" visible="false"/> </mx:Canvas> The code that is using the code looks like this: <view:EditableCanvas width="290" height="120" backgroundColor="#FFFFFF" horizontalScrollPolicy="off" borderStyle="solid" cornerRadius="3" editable="{_editable}"> <mx:Text id="textContentBox" width="270" fontFamily="nautics" fontSize="12" text="{_text}"/> </view:EditableCanvas>

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• Serialization Performance and Google Android

  - by Jomanscool2

  I'm looking for advice to speed up serialization performance, specifically when using the Google Android. For a project I am working on, I am trying to relay a couple hundred objects from a server to the Android app, and am going through various stages to get the performance I need. First I tried a terrible XML parser that I hacked together using Scanner specifically for this project, and that caused unbelievably slow performance when loading the objects (~5 minutes for a 300KB file). I then moved away from that and made my classes implement Serializable and wrote the ArrayList of objects I had to a file. Reading that file into the objects the Android, with the file already downloaded mind you, was taking ~15-30 seconds for the ~100KB serialized file. I still find this completely unacceptable for an Android app, as my app requires loading the data when starting the application. I have read briefly about Externalizable and how it can increase performance, but I am not sure as to how one implements it with nested classes. Right now, I am trying to store an ArrayList of the following class, with the nested classes below it. public class MealMenu implements Serializable{ private String commonsName; private long startMillis, endMillis, modMillis; private ArrayList<Venue> venues; private String mealName; } And the Venue class: public class Venue implements Serializable{ private String name; private ArrayList<FoodItem> foodItems; } And the FoodItem class: public class FoodItem implements Serializable{ private String name; private boolean vegan; private boolean vegetarian; } IF Externalizable is the way to go to increase performance, is there any information as to how java calls the methods in the objects when you try to write it out? I am not sure if I need to implement it in the parent class, nor how I would go about serializing the nested objects within each object.

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• How do I implement repository pattern and unit of work when dealing with multiple data stores?

  - by Jason

  I have a unique situation where I am building a DDD based system that needs to access both Active Directory and a SQL database as persistence. Initially this wasnt a problem because our design was setup where we had a unit of work that looked like this: public interface IUnitOfWork { void BeginTransaction() void Commit() } and our repositories looked like this: public interface IRepository<T> { T GetByID() void Save(T entity) void Delete(T entity) } In this setup our load and save would handle the mapping between both data stores because we wrote it ourselves. The unit of work would handle transactions and would contain the Linq To SQL data context that the repositories would use for persistence. The active directory part was handled by a domain service implemented in infrastructure and consumed by the repositories in each Save() method. Save() was responsible with interacting with the data context to do all the database operations. Now we are trying to adapt it to entity framework and take advantage of POCO. Ideally we would not need the Save() method because the domain objects are being tracked by the object context and we would just need to add a Save() method on the unit of work to have the object context save the changes, and a way to register new objects with the context. The new proposed design looks more like this: public interface IUnitOfWork { void BeginTransaction() void Save() void Commit() } public interface IRepository<T> { T GetByID() void Add(T entity) void Delete(T entity) } This solves the data access problem with entity framework, but does not solve the problem with our active directory integration. Before, it was in the Save() method on the repository, but now it has no home. The unit of work knows nothing other than the entity framework data context. Where should this logic go? I argue this design only works if you only have one data store using entity framework. Any ideas how to best approach this issue? Where should I put this logic?

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• Terminal / Panel PC - Single Server Solution: Client/Server or RDP?

  - by StillLearning

  Hi, Our current setup involves a touch screen panel pc with embedded windows, that is connected via network to a server / dedicated pc, within the same physical location. Each of our 'units' has this hardware setup. For a quick resolution we deploy our application to the dedicated pc, and have the panel pc remote desktop to an account which then activates the application. This works but seems a little clunky / rough approach. We did this because the panel pc is rather limited. Now that we have more time, I was wondering if I should separate the application into a gui / application. Deploy the gui logic on the panel pc, and the business/database logic on the dedicated pc. The app is in Java so I was wondering what technology would be best? I was thinking of using RMI, but its not really a client/server app, as there is only one client. Should I stick with RMI, or use Sockets or something else? It will be easy to implement as the application is old, and manually wraps and unwraps data which passes through one class / method call to remote services. All I would have to do is 'RMI' this one method call, and the app will do its own stuff. Cheers.

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• How to Write to a User.Config file through ConfigurationManager?

  - by Josh G

  I'm trying to persist user settings to a configuration file using ConfigurationManager. I want to scope these settings to the user only, because application changes can't be saved on Vista/Win 7 without admin privileges. This seems to get me the user's configuration, which appears to be saved here in Win 7 ([Drive]:\Users\[Username]\AppData\Local\[ApplicationName]\[AssemblyName][hash]\[Version\) Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.PerUserRoamingAndLocal); Whenever I try to save any changes at all to this config I get this exception: InnerException: System.InvalidOperationException Message="ConfigurationSection properties cannot be edited when locked." Source="System.Configuration" StackTrace: at System.Configuration.SectionInformation.VerifyIsEditable() at System.Configuration.MgmtConfigurationRecord.GetConfigDefinitionUpdates(Boolean requireUpdates, ConfigurationSaveMode saveMode, Boolean forceSaveAll, ConfigDefinitionUpdates& definitionUpdates, ArrayList& configSourceUpdates) I have tried adding a custom ConfigurationSection to this config. I have tried adding to the AppSettingsSection. Whenever I call config.Save() it throws the exception above. Any ideas? I tried using the ApplicationSettingsBase class through the Project-Settings designer, but it doesn't appear that you can save custom types with this. I want similar functionality with the ability to save custom types. Thanks.

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• NMock2.0 - how to stub a non interface call?

  - by dferraro

  Hello, I have a class API which has full code coverage and uses DI to mock out all the logic in the main class function (Job.Run) which does all the work. I found a bug in production where we werent doing some validation on one of the data input fields. So, I added a stub function called ValidateFoo()... Wrote a unit test against this function to Expect a JobFailedException, ran the test - it failed obviously because that function was empty. I added the validation logic, and now the test passes. Great, now we know the validation works. Problem is - how do I write the test to make sure that ValidateFoo() is actually called inside Job.Run()? ValidateFoo() is a private method of the Job class - so it's not an interface... Is there anyway to do this with NMock2.0? I know TypeMock supports fakes of non interface types. But changing mock libs right now is not an option. At this point if NMock can't support it, I will simply just add the ValidateFoo() call to the Run() method and test things manually - which obviously I'd prefer not to do considering my Job.Run() method has 100% coverage right now. Any Advice? Thanks very much it is appreciated. EDIT: the other option I have in mind is to just create an integration test for my Job.Run functionality (injecting to it true implementations of the composite objects instead of mocks). I will give it a bad input value for that field and then validate that the job failed. This works and covers my test - but it's not really a unit test but instead an integration test that tests one unit of functionality.... hmm.. EDIT2: IS there any way to do tihs? Anyone have ideas? Maybe TypeMock - or a better design?

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• Unit Testing in the real world

  - by Malfist

  I manage a rather large application (50k+ lines of code) by myself, and it manages some rather critical business actions. To describe the program simple, I would say it's a fancy UI with the ability to display and change data from the database, and it's managing around 1,000 rental units, and about 3k tenants and all the finances. When I make changes, because it's so large of a code base, I sometimes break something somewhere else. I typically test it by going though the stuff I changed at the functional level (i.e. I run the program and work through the UI), but I can't test for every situation. That is why I want to get started with unit testing. However, this isn't a true, three tier program with a database tier, a business tier, and a UI tier. A lot of the business logic is performed in the UI classes, and many things are done on events. To complicate things, everything is database driven, and I've not seen (so far) good suggestions on how to unit test database interactions. How would be a good way to get started with unit testing for this application. Keep in mind. I've never done unit testing or TDD before. Should I rewrite it to remove the business logic from the UI classes (a lot of work)? Or is there a better way?

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• C# Help: Adding a complexType to the main XmlSchema

  - by G33kKahuna

  I need to create program that creates a XML schema like below using System.Xml.XmlSchema namespace I'm using the XmlSchemaComplexType to MyString and MyInteger but I can't seem to find a way to set the extension to base string and int respectively. Any guidance is much appreciated ... thanks <?xml version="1.0" encoding="utf-8" ?> <xs:schema elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:complexType name="MyString"> <xs:simpleContent> <xs:extension base="xs:string"> <xs:attribute name="modified" type="xs:boolean" /> </xs:extension> </xs:simpleContent> </xs:complexType> <xs:complexType name="MyInteger"> <xs:simpleContent> <xs:extension base="xs:int"> <xs:attribute name="modified" type="xs:boolean" /> </xs:extension> </xs:simpleContent> </xs:complexType> <xs:element name="data"> <xs:complexType> <xs:sequence> <xs:element name="row"> <xs:complexType> <xs:sequence> <xs:element name="order_id" type="MyInteger" /> <xs:element name="order_status" type="MyString" /> </xs:sequence> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element> </xs:schema>

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• Control 'ctl00_TextBox1' of type 'TextBox' must be placed inside a form tag with runat=server.

  - by Hiru

  When a form with a run at server is added there will be two forms with runat server and another error occurs. Can some one give me an idea. Thankx in advance. The details of the error are as follows. Control 'ctl00_TextBox1' of type 'TextBox' must be placed inside a form tag with runat=server. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Web.HttpException: Control 'ctl00_TextBox1' of type 'TextBox' must be placed inside a form tag with runat=server. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [HttpException (0x80004005): Control 'ctl00_TextBox1' of type 'TextBox' must be placed inside a form tag with runat=server.] System.Web.UI.Page.VerifyRenderingInServerForm(Control control) +2052287 System.Web.UI.WebControls.TextBox.AddAttributesToRender(HtmlTextWriter writer) +49 System.Web.UI.WebControls.WebControl.RenderBeginTag(HtmlTextWriter writer) +17 System.Web.UI.WebControls.TextBox.Render(HtmlTextWriter writer) +17 System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +25 System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +121 System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +22 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +199 System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +20 System.Web.UI.Control.Render(HtmlTextWriter writer) +7 System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +25 System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +121 System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +22 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +199 System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +20 System.Web.UI.Page.Render(HtmlTextWriter writer) +26 System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +25 System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +121 System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +22 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2558 Version Information: Microsoft .NET Framework Version:2.0.50727.1873; ASP.NET Version:2.0.50727.1433

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• MVC UI with Mock Controllers?

  - by Jaimal Chohan

  I'm working with Aspnet MVC 2 (R2) and at the same time playing about with the whole alt.net stack. One of this things I would like to be able todo is basically write my Views, and be able to interact with them without having to write the controller logic. E.g. I have a view that displays a list of orders and I can click on an order which redirects to another view where I can edit it, but I don't want to get into the nitty gritty of writing the code to actually get a list of orders, or update an existing ordes. I want to do so I can write UI tests in WaitN/AOT/Selenium without having to worry about whats happening underneath, and also It would help drive my controller logic on a need basis as opposed to guess work based of of the supplied screenshots How do you guys accomplish this atm? Can you provide links ot useful blog posts/tools/framework/articles with information on how to accomplish this p.s. I primarly use Rhino Mocks & NUnit but can happliy change to other tools if they support the above better.

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• KendoUI Mobile switch and datasource

  - by OnaBai

  I'm trying to have a list of items displayed using a listview, something like: <div data-role="view" data-model="my_model"> <ul data-role="listview" data-bind="source: ds" data-template="list-tmpl"></ul> </div> Where I have a view using a model called my_model and a listview where the source is bound to ds. My model is something like: var my_model = kendo.observable({ ds: new kendo.data.DataSource({ transport: { read: readData, update: updateData, create: updateData, remove: updateData }, pageSize: 10, schema: { model: { id: "id", fields: { id: { type: "number" }, name: { type: "string" }, active: { type: "boolean" } } } } }) }); Each item includes an id, a name (that is a string) and a boolean named active. The template used to render each element is: <script id="list-tmpl" type="text/kendo-tmpl"> <span>#= name # : #= active #</span> <input data-role="switch" data-bind="checked: active"/> </script> Where I display the name and (for debugging) the value of active. In addition, I render a switch bound to active. You should see something like: The problems observed are: If you click on a switch you will see that the value of active next to the name changes its value (as expected) but if then, you pick another switch, the value (neither next to name nor in the DataSource) is not updated (despite the value of the switch is correctly updated). The update handler in the DataSource is never invoked (not even for the first chosen switch and despite the DataSource for that first toggled switch is updated). You can check it in JSFiddle: http://jsfiddle.net/OnaBai/K7wEC/ How do I make that the DataSource gets updated and update handler invoked?

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• find(:all) and then add data from another table to the object

  - by Koning Baard XIV

  I have two tables: create_table "friendships", :force => true do |t| t.integer "user1_id" t.integer "user2_id" t.boolean "hasaccepted" t.datetime "created_at" t.datetime "updated_at" end and create_table "users", :force => true do |t| t.string "email" t.string "password" t.string "phone" t.boolean "gender" t.datetime "created_at" t.datetime "updated_at" t.string "firstname" t.string "lastname" t.date "birthday" end I need to show the user a list of Friendrequests, so I use this method in my controller: def getfriendrequests respond_to do |format| case params[:id] when "to_me" @friendrequests = Friendship.find(:all, :conditions => { :user2_id => session[:user], :hasaccepted => false }) when "from_me" @friendrequests = Friendship.find(:all, :conditions => { :user1_id => session[:user], :hasaccepted => false }) end format.xml { render :xml => @friendrequests } format.json { render :json => @friendrequests } end end I do nearly everything using AJAX, so to fetch the First and Last name of the user with UID user2_id (the to_me param comes later, don't worry right now), I need a for loop which make multiple AJAX calls. This sucks and costs much bandwidth. So I'd rather like that getfriendrequests also returns the First and Last name of the corresponding users, so, e.g. the JSON response would not be: [ { "friendship": { "created_at": "2010-02-19T13:51:31Z", "user1_id": 2, "updated_at": "2010-02-19T13:51:31Z", "hasaccepted": false, "id": 11, "user2_id": 3 } }, { "friendship": { "created_at": "2010-02-19T16:31:23Z", "user1_id": 2, "updated_at": "2010-02-19T16:31:23Z", "hasaccepted": false, "id": 12, "user2_id": 4 } } ] but rather: [ { "friendship": { "created_at": "2010-02-19T13:51:31Z", "user1_id": 2, "updated_at": "2010-02-19T13:51:31Z", "hasaccepted": false, "id": 11, "user2_id": 3, "firstname": "Jon", "lastname": "Skeet" } }, { "friendship": { "created_at": "2010-02-19T16:31:23Z", "user1_id": 2, "updated_at": "2010-02-19T16:31:23Z", "hasaccepted": false, "id": 12, "user2_id": 4, "firstname": "Mark", "lastname": "Gravell" } } ] I thought of a for loop in the getfriendrequests method, but I don't know how to implement this, and maybe there is an easier way. It must also work for XML. Can anyone help me? Thanks

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• Custom Html Helper is not working in asp.net MVC 2.0

  - by chobo2

  Hey I was using this custom html helper in asp.net mvc 1.0 but now I am trying to use it in a 2.0 project and it crashes http://blog.pagedesigners.co.nz/archive/2009/07/15/asp.net-mvc-ndash-validation-summary-with-2-forms-amp-1.aspx This is the error I get. System.MissingMethodException was unhandled by user code Message=Method not found: 'System.String System.Web.Mvc.Html.ValidationExtensions.ValidationSummary(System.Web.Mvc.HtmlHelper)'. Source=CustomHtmlHelpers StackTrace: at CustomHtmlHelpers.ActionValidationSummaryHelper.ActionValidationSummary(HtmlHelper html, String action) at ASP.views_signin_signin_aspx.__RenderContent2(HtmlTextWriter __w, Control parameterContainer) in SignIn.aspx:line 23 at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) at System.Web.UI.Control.Render(HtmlTextWriter writer) at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) at ASP.views_shared_site_master.__Render__control1(HtmlTextWriter __w, Control parameterContainer) Site.Master:line 64 at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) at System.Web.UI.Control.Render(HtmlTextWriter writer) at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) at System.Web.UI.Page.Render(HtmlTextWriter writer) at System.Web.Mvc.ViewPage.Render(HtmlTextWriter writer) at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) InnerException: My other html helpers in the same library do work. I added the namespace into the webconfig.

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• Deserializing XML to Objects in C#

  - by Justin Bozonier

  So I have xml that looks like this: <todo-list> <id type="integer">#{id}</id> <name>#{name}</name> <description>#{description}</description> <project-id type="integer">#{project_id}</project-id> <milestone-id type="integer">#{milestone_id}</milestone-id> <position type="integer">#{position}</position> <!-- if user can see private lists --> <private type="boolean">#{private}</private> <!-- if the account supports time tracking --> <tracked type="boolean">#{tracked}</tracked> <!-- if todo-items are included in the response --> <todo-items type="array"> <todo-item> ... </todo-item> <todo-item> ... </todo-item> ... </todo-items> </todo-list> How would I go about using .NET's serialization library to deserialize this into C# objects? Currently I'm using reflection and I map between the xml and my objects using the naming conventions.

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• TypeError: Error #1009 - (Null reference error) With Flash.

  - by Wind Chimez

  I am not an expert in flash, but i do work with AS and tweak Flash projects , though not having deep expertise in it. Currently i need to revamp a flash website done by one another guy, and the code base given to me, upon execution is throwing the following error. "--- TypeError: Error #1009: Cannot access a property or method of a null object reference. at NewSite_fla::MainTimeline/__setProp_ContactOutP1_ContactOut_Contents_0() at NewSite_fla::MainTimeline/frame1() --" The structure of the project is like, it has the different sections split into different movie clips. There is no single main timeline, but click actions on different areas of seperate movie clips will take them between one another. All the AS logic of event handling are written inline in FLA , no seperate Document class exists. Preloader Movie clip is the first one getting loaded. As i understood the error is getting thrown initially itself, and it is not happening due to any Action script logic written inline, because it is throwing error even before hitting the first inline AS code. I am not able to figure Out what exactly it causing the problem, or where to resolve it. I setup the stuff online, for reference if anybody want to take a look at it, and here is the link.You need to have flash debugger turned ON in your browser, if need to see the exception getting triggered. http://tinyurl.com/2alvlfx I really got stuck at this point. Any help will be great.I had not seen the particular solution i am looking for anywhere yet, though Error #1009 is common.

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• Retactoring advanced has_many example

  - by atmorell

  Hello, My user model has three relations for the same message model, and is using raw SQL :/ Is there a better more rails way to achieve the same result? Could the foreign key be changed dynamically? e.g User.messages.sent (foreign key = author_id) and User.messages.received (foreign key = recipient ) I have been trying to move some of the logic into scopes in the message model, but the user.id is not available from the message model... Any thoughts? Table layout: create_table "messages", :force => true do |t| t.string "subject" t.text "body" t.datetime "created_at" t.datetime "updated_at" t.integer "author_id" t.integer "recipient_id" t.boolean "author_deleted", :default => false t.boolean "recipient_deleted", :default => false end This is my relations for my user model: has_many :messages_received, :foreign_key => "recipient_id", :class_name => "Message", :conditions => ['recipient_deleted = ?', false] has_many :messages_sent, :foreign_key => "author_id", :class_name => "Message", :conditions => ['author_deleted = ?', false] has_many :messages_deleted, :class_name => "Message", :finder_sql => 'SELECT * FROM Messages WHERE author_id = #{self.id} AND author_deleted = true OR recipient_id = #{self.id} AND recipient_deleted = true' Best regards. Asbjørn Morell

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• When *not* to use prepared statements?

  - by Ben Blank

  I'm re-engineering a PHP-driven web site which uses a minimal database. The original version used "pseudo-prepared-statements" (PHP functions which did quoting and parameter replacement) to prevent injection attacks and to separate database logic from page logic. It seemed natural to replace these ad-hoc functions with an object which uses PDO and real prepared statements, but after doing my reading on them, I'm not so sure. PDO still seems like a great idea, but one of the primary selling points of prepared statements is being able to reuse them… which I never will. Here's my setup: The statements are all trivially simple. Most are in the form SELECT foo,bar FROM baz WHERE quux = ? ORDER BY bar LIMIT 1. The most complex statement in the lot is simply three such selects joined together with UNION ALLs. Each page hit executes at most one statement and executes it only once. I'm in a hosted environment and therefore leery of slamming their servers by doing any "stress tests" personally. Given that using prepared statements will, at minimum, double the number of database round-trips I'm making, am I better off avoiding them? Can I use PDO::MYSQL_ATTR_DIRECT_QUERY to avoid the overhead of multiple database trips while retaining the benefit of parametrization and injection defense? Or do the binary calls used by the prepared statement API perform well enough compared to executing non-prepared queries that I shouldn't worry about it? EDIT: Thanks for all the good advice, folks. This is one where I wish I could mark more than one answer as "accepted" — lots of different perspectives. Ultimately, though, I have to give rick his due… without his answer I would have blissfully gone off and done the completely Wrong Thing even after following everyone's advice. :-) Emulated prepared statements it is!

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• Data Access Layer, Best Practices

  - by labratmatt

  I'm looking for input on the best way to refactor the data access layer (DAL) in my PHP based web app. I follow an MVC pattern: PHP/HTML/CSS/etc. views on the front end, PHP controllers/services in the middle, and a PHP DAL sitting on top of a relational database in the model. Pretty standard stuff. Things are working fine, but my DAL is getting large (codesmell?) and becoming a bit unwieldy. My DAL contains almost all of the logic to interface with my database and is full of functions that look like this: function getUser($user_id) { $statement = "select id, name from users where user_id=:user_id"; PDO builds statement and fetchs results as an array return $array_of_results_generated_by_PDO_fetch_method; } Notes: The logic in my controller only interacts with the model using functions like the above in the DAL I am not using a framework (I'm of the opinion that PHP is a templating language and there's no need to inject complexity via a framework) I generally use PHP as a procedural language and tend to shy away from its OOP approach (I enjoy OOP development but prefer to keep that complexity out of PHP) What approaches have you taken when your DAL has reached this point? Do I have a fundamental design problem? Do I simply need to chop my DAL into a number of smaller files (logically divide it)? Thanks.

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• Can I compare a template variable to an integer in App Engine templates?

  - by matt b

  Using Django templates in Google App Engine (on Python), is it possible to compare a template variable to an integer in an {% if %} block? views.py: class MyHandler(webapp.RequestHandler): def get(self): foo_list = db.GqlQuery(...) ... template_values['foos'] = foo_list template_values['foo_count'] = len(foo_list) handler.response.out.write(template.render(...)) My template: {% if foo_count == 1 %} There is one foo. {% endif %} This blows up with 'if' statement improperly formatted. What I was attempting to do in my template was build a simple if/elif/else tree to be grammatically correct to be able to state #foo_count == 0: There are no foos. #foo_count == 1: There is one foo. #else: There are {{ foos|length }} foos. Browsing the Django template documents (this link provided in the GAE documentation appears to be for versions of Django far newer than what is supported on GAE), it appears as if I can only actually use boolean operators (if in fact boolean operators are supported in this older version of Django) with strings or other template variables. Is it not possible to compare variables to integers or non-strings with Django templates? I'm sure there is an easy way to workaround this - built up the message string on the Python side rather than within the template - but this seems like such a simple operation you ought to be able to handle in a template. It sounds like I should be switching to a more advanced templating engine, but as I am new to Django (templates or any part of it), I'd just like some confirmation first.

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• How to build Graceful Degradation AJAX web page?

  - by Morgan Cheng

  I want to build web page with "Graceful Degradation". That is, the web page functions even javascript is disabled. Now I have to make design decision on the format of AJAX response. If javascript is disabled, each HTTP request to server will generate HTML as response. The browser refreshes with the returned HTML. That's fine. If javascript is enabled, each AJAX HTTP request to server will generate ... well, JSON or HTML. If it is HTML, it is easy to implement. Just have javascript to replace part of page with the returned HTML. And, in server side, not much code change is needed. If it is JSON, then I have to implement JSON-to-html logic in javascript again which is almost duplicate of server side logic. Duplication is evil. I really don't like it. The benefit is that the bandwidth usage is better than HTML, which brings better performance. So, what's the best solution to Graceful Degradation? AJAX request better to return JSON or HTML?

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• Random String Generator creates same string on multiple calls

  - by rockinthesixstring

  Hi there. I've build a random string generator but I'm having a problem whereby if I call the function multiple times say in a Page_Load method, the function returns the same string twice. here's the code ''' <summary>' ''' Generates a Random String' ''' </summary>' ''' <param name="n">number of characters the method should generate</param>' ''' <param name="UseSpecial">should the method include special characters? IE: # ,$, !, etc.</param>' ''' <param name="SpecialOnly">should the method include only the special characters and excludes alpha numeric</param>' ''' <returns>a random string n characters long</returns>' Public Function GenerateRandom(ByVal n As Integer, Optional ByVal UseSpecial As Boolean = True, Optional ByVal SpecialOnly As Boolean = False) As String Dim chars As String() ' a character array to use when generating a random string' Dim ichars As Integer = 74 'number of characters to use out of the chars string' Dim schars As Integer = 0 ' number of characters to skip out of the characters string' chars = { _ "A", "B", "C", "D", "E", "F", _ "G", "H", "I", "J", "K", "L", _ "M", "N", "O", "P", "Q", "R", _ "S", "T", "U", "V", "W", "X", _ "Y", "Z", "0", "1", "2", "3", _ "4", "5", "6", "7", "8", "9", _ "a", "b", "c", "d", "e", "f", _ "g", "h", "i", "j", "k", "l", _ "m", "n", "o", "p", "q", "r", _ "s", "t", "u", "v", "w", "x", _ "y", "z", "!", "@", "#", "$", _ "%", "^", "&", "*", "(", ")", _ "-", "+"} If Not UseSpecial Then ichars = 62 ' only use the alpha numeric characters out of "char"' If SpecialOnly Then schars = 62 : ichars = 74 ' skip the alpha numeric characters out of "char"' Dim rnd As New Random() Dim random As String = String.Empty Dim i As Integer = 0 While i < n random += chars(rnd.[Next](schars, ichars)) System.Math.Max(System.Threading.Interlocked.Increment(i), i - 1) End While rnd = Nothing Return random End Function but if I call something like this Dim str1 As String = GenerateRandom(5) Dim str2 As String = GenerateRandom(5) the response will be something like this g*3Jq g*3Jq and the second time I call it, it will be 3QM0$ 3QM0$ What am I missing? I'd like every random string to be generated as unique.

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• Business Objects - Containers or functional?

  - by Walter

  Where I work, we've gone back and forth on this subject a number of times and are looking for a sanity check. Here's the question: Should Business Objects be data containers (more like DTOs) or should they also contain logic that can perform some functionality on that object. Example - Take a customer object, it probably contains some common properties (Name, Id, etc), should that customer object also include functions (Save, Calc, etc.)? One line of reasoning says separate the object from the functionality (single responsibility principal) and put the functionality in a Business Logic layer or object. The other line of reasoning says, no, if I have a customer object I just want to call Customer.Save and be done with it. Why do I need to know about how to save a customer if I'm consuming the object? Our last two projects have had the objects separated from the functionality, but the debate has been raised again on a new project. Which makes more sense? EDIT These results are very similar to our debates. One vote to one side or another completely changes the direction. Does anyone else want to add their 2 cents? EDIT Eventhough the answer sampling is small, it appears that the majority believe that functionality in a business object is acceptable as long as it is simple but persistence is best placed in a separate class/layer. We'll give this a try. Thanks for everyone's input...

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• Bind SQLiteDataReader to GridView in ASP.NET

  - by Charles Gargent

  Hi, this is all rather new to me, but I have searched for a good while and cant find any idea why I cant get this to work, dr looks like it is populated but I get this nullreferenceexeception when I try to bind to the gridview Thanks code SQLiteConnection cnn = new SQLiteConnection(@"Data Source=c:\log.db"); cnn.Open(); SQLiteCommand cmd = new SQLiteCommand(@"SELECT * FROM evtlog", cnn); SQLiteDataReader dr = cmd.ExecuteReader(); GridView1.DataSource = dr; GridView1.DataBind(); dr.Close(); cnn.Close(); Codebehind <asp:ContentPlaceHolder ID="MainContent" runat="server"> <asp:GridView ID="GridView1" runat="server"> </asp:GridView> </asp:ContentPlaceHolder> error Object reference not set to an instance of an object. at WPKG_Report.SiteMaster.Button1_Click(Object sender, EventArgs e) in C:\Projects\Report\Site.Master.cs:line 32 at System.Web.UI.WebControls.Button.OnClick(EventArgs e) at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

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