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• How to Inserting message into View that depends on session value. ASP.NET MVC. Best practice

  - by Andrew Florko

  User have to populate multistep questionnaire web-forms and step messages depend on the option chosen by user at the very beginning. Messages are stored in web.config file. I use asp.net mvc project, strong typed views and keep business logic separated from controller in static class. I don't want to make business logic dependency on web.config. Well, I have to insert message into view that depends on session value. There are at least 2 options how to implement this: View model has property that is populated in controller/businessLogic and rendered in view like <%: Model.HelpMessage1 %>. I have to pass web.config values from controller to businessLogic that makes business logic methods signature too complex. I don't want to make configuration source abstract (in order to let business logic read configuration values from its methods directly) also. Create static helper class that is called from view like <%: ViewHelper.HelpMessage1(Model.Option1) %>. But in this case logic what to show seems to be separated into two classes: business logic & viewHelper. What will you suggest? Thank you in advance!

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• Binding Data into a Resource

  - by Jordan

  How do you bind data from the view model into an object in the resources of the user control? Here is a very abstract example: <UserControl ... xmlns:local="clr-namespace:My.Local.Namespace" Name="userControl"> <UserControl.Resources> <local:GroupingProvider x:Key="groupingProvider" GroupValue="{Binding ???}" /> </UserControl.Resources> <Grid> <local:GroupingConsumer Name="groupingConsumer1" Provider={StaticResource groupingProvider"} /> <local:GroupingConsumer Name="groupingConsumer2" Provider={StaticResource groupingProvider"} /> </Grid> </UserControl> How do I bind GroupValue to a property in the view model behind this view. I've tried the following: <local:GroupingProvider x:Key="groupingProvider" GroupValue="{Binding ElementName=userControl, Path=DataContext.Property}"/> But this doesn't work. Edit: GroupProvider extends DependencyObject and GroupValue is the name of a DependencyProperty. I'm getting an debugging message telling me that the property to which I am binding doesn't exist.

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• Spring validation has error in XML document from ServletContext resource

  - by user1441404

  I applied spring validation in my registration page .but the follwing error are shown in my server log of my app engine server. javax.servlet.UnavailableException: org.springframework.beans.factory.xml.XmlBeanDefinitionStoreException: Line 22 in XML document from ServletContext resource [/WEB-INF/spring/appServlet/servlet-context.xml] is invalid; nested exception is org.xml.sax.SAXParseException; lineNumber: 22; columnNumber: 30; cvc-complex-type.2.4.c: The matching wildcard is strict, but no declaration can be found for element 'property'. My code is given below : <?xml version="1.0" encoding="UTF-8"?> <beans:beans xmlns="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:beans="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.0.xsd > <beans:bean name="/register" class="com.my.registration.NewUserRegistration"> <property name="validator"> <bean class="com.my.validation.UserValidator" /> </property> <beans:property name="formView" value="newuser"></beans:property> <beans:property name="successView" value="home"></beans:property> </beans:bean> <beans:bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <beans:property name="prefix" value="/WEB-INF/views/" /> <beans:property name="suffix" value=".jsp" /> </beans:bean> </beans:beans>

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• C++ destructor problem with boost::scoped_ptr

  - by bb-generation

  I have a question about the following code: #include <iostream> #include <boost/scoped_ptr.hpp> class Interface { }; class A : public Interface { public: A() { std::cout << "A()" << std::endl; } virtual ~A() { std::cout << "~A()" << std::endl; } }; Interface* get_a() { A* a = new A; return a; } int main() { { std::cout << "1" << std::endl; boost::scoped_ptr<Interface> x(get_a()); std::cout << "2" << std::endl; } std::cout << "3" << std::endl; } It creates the following output: 1 A() 2 3 As you can see, it doesn't call the destructor of A. The only way I see to get the destructor of A being called, is to add a destructor for the Interface class like this: virtual ~Interface() { } But I really want to avoid any Implementation in my Interface class and virtual ~Interface() = 0; doesn't work (produces some linker errors complaining about a non existing implementation of ~Interface(). So my question is: What do I have to change in order to make the destructor being called, but (if possible) leave the Interface as an Interface (only abstract methods).

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• Is it possible to have an enum field in a class persisted with OrmLite?

  - by htf

  Hello. I'm trying to persist the following class with OrmLite: public class Field { @DatabaseField(id = true) public String name; @DatabaseField(canBeNull = false) public FieldType type; public Field() { } } The FieldType is a public enum. The field, corresponding to the type is string in SQLite (is doesn't support enums). When I try to use it, I get the following exception: INFO [main] (SingleConnectionDataSource.java:244) - Established shared JDBC Connection: org.sqlite.Conn@5224ee Exception in thread "main" org.springframework.beans.factory.BeanInitializationException: Initialization of DAO failed; nested exception is java.lang.IllegalArgumentException: Unknown field class class enums.FieldType for field FieldType:name=type,class=class orm.Field at org.springframework.dao.support.DaoSupport.afterPropertiesSet(DaoSupport.java:51) at orm.FieldDAO.getInstance(FieldDAO.java:17) at orm.Field.fromString(Field.java:23) at orm.Field.main(Field.java:38) Caused by: java.lang.IllegalArgumentException: Unknown field class class enums.FieldType for field FieldType:name=type,class=class orm.Field at com.j256.ormlite.field.FieldType.<init>(FieldType.java:54) at com.j256.ormlite.field.FieldType.createFieldType(FieldType.java:381) at com.j256.ormlite.table.DatabaseTableConfig.fromClass(DatabaseTableConfig.java:82) at com.j256.ormlite.dao.BaseJdbcDao.initDao(BaseJdbcDao.java:116) at org.springframework.dao.support.DaoSupport.afterPropertiesSet(DaoSupport.java:48) ... 3 more So how do I tell OrmLite, values on the Java side are from an enum?

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• Hibernate Transient Extends problem

  - by mrvreddy

  @MappedSuperclass public abstract class BaseAbstract implements Serializable{ private static final long serialVersionUID = 1L; protected String test = //some random value; public String getTest() { return test; } public void setTest(String test){ this.test = test; } } @Entity public class Artist extends BaseAbstract { private static final long serialVersionUID = 1L; private Integer id; @override @Transient public String getTest() { return test; } ..... } My question is... when i am trying to do any operation on the artist, along with id and name, test is also getting saved which should not be the case... if i add the same transient on the baseabstract class getTest() method, i see test column NOT getting created(ideally what it should happen) but if i try to override the method with adding annotaion in the sub class it creates the test column... I dont know why this is happening since when hibernate is creating the artist object and checks for annotations, it should see the transient annotation present on the getTest() of artist method...and should not create a column in the database... Let me know if you need any clarification.... Any response on this is greatly appreciated.... Thank you

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• Modules vs. Classes and their influence on descendants of ActiveRecord::Base

  - by Chris

  Here's a Ruby OO head scratcher for ya, brought about by this Rails scenario: class Product < ActiveRecord::Base has_many(:prices) # define private helper methods end module PrintProduct attr_accessor(:isbn) # override methods in ActiveRecord::Base end class Book < Product include PrintProduct end Product is the base class of all products. Books are kept in the products table via STI. The PrintProduct module brings some common behavior and state to descendants of Product. Book is used inside fields_for blocks in views. This works for me, but I found some odd behavior: After form submission, inside my controller, if I call a method on a book that is defined in PrintProduct, and that method calls a helper method defined in Product, which in turn calls the prices method defined by has_many, I'll get an error complaining that Book#prices is not found. Why is that? Book is a direct descendant of Product! More interesting is the following.. As I developed this hierarchy PrintProduct started to become more of an abstract ActiveRecord::Base, so I thought it prudent to redefine everything as such: class Product < ActiveRecord::Base end class PrintProduct < Product end class Book < PrintProduct end All method definitions, etc. are the same. In this case, however, my web form won't load because the attributes defined by attr_accessor (which are "virtual attributes" referenced by the form but not persisted in the DB) aren't found. I'll get an error saying that there is no method Book#isbn. Why is that?? I can't see a reason why the attr_accessor attributes are not found inside my form's fields_for block when PrintProduct is a class, but they are found when PrintProduct is a Module. Any insight would be appreciated. I'm dying to know why these errors are occurring!

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• Ability to switch Persistence Unit dynamically within the application (JPA)

  - by MVK

  My application data access layer is built using Spring and EclipseLink and I am currently trying to implement the following feature - Ability to switch the current/active persistence unit dynamically for a user. I tried various options and finally ended up doing the following. In the persistence.xml, declare multiple PUs. Create a class with as many EntityManagerFactory attributes as there are PUs defined. This will act as a factory and return the appropriate EntityManager based on my logic public class MyEntityManagerFactory { @PersistenceUnit(unitName="PU_1") private EntityManagerFactory emf1; @PersistenceUnit(unitName="PU_2") private EntityManagerFactory emf2; public EntityManager getEntityManager(int releaseId) { // Logic goes here to return the appropriate entityManeger } } My spring-beans xml looks like this.. <!-- First persistence unit --> <bean class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean" id="emFactory1"> <property name="persistenceUnitName" value="PU_1" /> </bean> <bean class="org.springframework.orm.jpa.JpaTransactionManager" id="transactionManager1"> <property name="entityManagerFactory" ref="emFactory1"/> </bean> <tx:annotation-driven transaction-manager="transactionManager1"/> The above section is repeated for the second PU (with names like emFactory2, transactionManager2 etc). I am a JPA newbie and I know that this is not the best solution. I appreciate any assistance in implementing this requirement in a better/elegant way! Thanks!

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• after assembling jar - No Persistence provider for EntityManager named ....

  - by alabalaa

  im developing a standalone application and it works fine when starting it from my ide(intellij idea), but after creating an uberjar and start the application from it javax.persistence.spi.PersistenceProvider is thrown saying "No Persistence provider for EntityManager named testPU" here is my persistence.xml which is placed under meta-inf directory: <persistence-unit name="testPU" transaction-type="RESOURCE_LOCAL"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <class>test.model.Configuration</class> <properties> <property name="hibernate.connection.username" value="root"/> <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/> <property name="hibernate.connection.password" value="root"/> <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/test"/> <property name="hibernate.show_sql" value="true"/> <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLInnoDBDialect"/> <property name="hibernate.c3p0.timeout" value="300"/> <property name="hibernate.hbm2ddl.auto" value="update"/> </properties> </persistence-unit> and here is how im creating the entity manager factory: emf = Persistence.createEntityManagerFactory("testPU"); im using maven and tried the assembly plug-in with the default configuration fot it, i dont have much experience with assembling jars and i dont know if im missing something, so if u have any ideas ill be glad to hear them

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• Will this web service accept both raw xml and an object?

  - by ChadNC

  We have a web service that provides auto insurance quotes and a company that provides an insurance agency management system would like to use the web service for thier client but they want to pass the web service raw xml instead of using the wsdl to create a port, the object the service expects and calling the web method. The web service has performed flawlessly by creating an object like so com.insurance.quotesvc.AgencyQuote service = new com.insurance.quotesvc.AgencyQuote(); com.insurance.quotesvc.QuotePortType port = service.getQuotePortType(); com.insurance.quotesvc.schemas.request.ACORD parameter = null; Then create initialize the request object with the other objects that make up the response. parameter = factory.createACORD(); parameter.setSignonRq(signOn); parameter.setInsurancesSvcRq(svcRq); And send the request to the web service. com.insurance.quotesvc.schemas.response.ACORD result = null; result = port.requestQuote(parameter); By doing that I am able to easily marshall the request and the result into an xml file and do with them as I wish. So if a client was to send the web service via an http post as raw xml inside of a soap envelope. Would the web service be able to handle the xml without any changes being made to the web service or would there need to be changes made to the web service in order for it to handle a request of that type? The web service is a JAX_WS and we currently have both Java and C# clients consuming the web service using the method described above but now there is another client who wants to send raw xml inside of a soap envelope instead of creating the objects. I feel pretty sure that they will be making the call to the web service using vb. I'm sure I'm missing something obvious but it is eluding me at the moment and any help is greatly appreciated.

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• Cant we use a Set or collection as a return type in GAE?

  - by user273422

  In my code i have used Set<Employees> as a return type to my function addEmp(). So, i m gettin an Compilation error. The Error is: Compiling module com.employeedepartmentgae.Employeedepartmentgae Refreshing module from source Validating newly compiled units Removing units with errors [ERROR] Errors in 'file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/GreetingServiceAsync.java' [ERROR] Line 6: The import com.employeedepartmentgae.server.domainobject.Employee cannot be resolved [ERROR] Line 18: Employee cannot be resolved to a type [ERROR] Errors in 'file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/GreetingService.java' [ERROR] Line 6: The import com.employeedepartmentgae.server.domainobject.Employee cannot be resolved [ERROR] Line 20: Employee cannot be resolved to a type [ERROR] Errors in 'file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/EmployeeWidget.java' [ERROR] Line 12: The import com.employeedepartmentgae.server.domainobject.Employee cannot be resolved [ERROR] Line 75: The method addEmp(String, String, String, AsyncCallback) from the type GreetingServiceAsync refers to the missing type Employee [ERROR] Line 75: The type new AsyncCallback(){} must implement the inherited abstract method AsyncCallback.onSuccess(Set) [ERROR] Line 75: Employee cannot be resolved to a type [ERROR] Line 94: The method onSuccess(Set) of type new AsyncCallback(){} must override or implement a supertype method [ERROR] Line 94: Employee cannot be resolved to a type [ERROR] Line 96: Employee cannot be resolved to a type [ERROR] Line 96: Employee cannot be resolved to a type [ERROR] Line 98: Employee cannot be resolved to a type Removing invalidated units [WARN] Compilation unit 'file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/Employeedepartmentgae.java' is removed due to invalid reference(s): [WARN] file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/EmployeeWidget.java [WARN] Compilation unit 'file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/DepartmentWidget.java' is removed due to invalid reference(s): [WARN] file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/GreetingService.java [WARN] file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/GreetingServiceAsync.java Computing all possible rebind results for 'com.employeedepartmentgae.client.Employeedepartmentgae' Rebinding com.employeedepartmentgae.client.Employeedepartmentgae Checking rule [ERROR] Unable to find type 'com.employeedepartmentgae.client.Employeedepartmentgae' [ERROR] Hint: Previous compiler errors may have made this type unavailable [ERROR] Hint: Check the inheritance chain from your module; it may not be inheriting a required module or a module may not be adding its source path entries properly So please help me.....

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• Implementing client callback functionality in WCF

  - by PoweredByOrange

  The project I'm working on is a client-server application with all services written in WCF and the client in WPF. There are cases where the server needs to push information to the client. I initially though about using WCF Duplex Services, but after doing some research online, I figured a lot of people are avoiding it for many reasons. The next thing I thought about was having the client create a host connection, so that the server could use that to make a service call to the client. The problem however, is that the application is deployed over the internet, so that approach requires configuring the firewall to allow incoming traffic and since most of the users are regular users, that might also require configuring the router to allow port forwarding, which again is a hassle for the user. My third option is that in the client, spawns a background thread which makes a call to the GetNotifications() method on server. This method on the server side then, blocks until an actual notification is created, then the thread is notified (using an AutoResetEvent object maybe?) and the information gets sent to the client. The idea is something like this: Client private void InitializeListener() { Task.Factory.StartNew(() => { while (true) { var notification = server.GetNotifications(); // Display the notification. } }, CancellationToken.None, TaskCreationOptions.LongRunning, TaskScheduler.Default); } Server public NotificationObject GetNotifications() { while (true) { notificationEvent.WaitOne(); return someNotificationObject; } } private void NotificationCreated() { // Inform the client of this event. notificationEvent.Set(); } In this case, NotificationCreated() is a callback method called when the server needs to send information to the client. What do you think about this approach? Is this scalable at all?

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• Problem with inheritance and List<>

  - by Jagd

  I have an abstract class called Grouping. I have a subclass called GroupingNNA. public class GroupingNNA : Grouping { // blah blah blah } I have a List that contains items of type GroupingNNA, but is actually declared to contain items of type Grouping. List<Grouping> lstGroupings = new List<Grouping>(); lstGroupings.Add( new GroupingNNA { fName = "Joe" }); lstGroupings.Add( new GroupingNNA { fName = "Jane" }); The Problem: The following LINQ query blows up on me because of the fact that lstGroupings is declared as List< Grouping and fName is a property of GroupingNNA, not Grouping. var results = from g in lstGroupings where r.fName == "Jane" select r; Oh, and this is a compiler error, not a runtime error. Thanks in advance for any help on this one! More Info: Here is the actual method that won't compile. The OfType() fixed the LINQ query, but the compiler doesn't like the fact that I'm trying to return the anonymous type as a List< Grouping. private List<Grouping> ApplyFilterSens(List<Grouping> lstGroupings, string fSens) { // This works now! Thanks @Lasse var filtered = from r in lstGroupings.OfType<GroupingNNA>() where r.QASensitivity == fSens select r; if (filtered != null) { **// Compiler doesn't like this now** return filtered.ToList<Grouping>(); } else return new List<Grouping>(); }

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• Catch a PHP Object Instantiation Error

  - by Rob Wilkerson

  It's really irking me that PHP considers the failure to instantiate an object a Fatal Error (which can't be caught) for the application as a whole. I have set of classes that aren't strictly necessary for my application to function--they're really a convenience. I have a factory object that attempts to instantiate the class variant that's indicated in a config file. This mechanism is being deployed for message storage and will support multiple store types: DatabaseMessageStore FileMessageStore MemcachedMessageStore etc. A MessageStoreFactory class will read the application's preference from a config file, instantiate and return an instance of the appropriate class. It might be easy enough to slap a conditional around the instantiation to ensure that class_exists(), but MemcachedMessageStore extends PHP's Memcached class. As a result, the class_exists() test will succeed--though instantiation will fail--if the memcached bindings for PHP aren't installed. Is there any other way to test whether a class can be instantiated properly? If it can't, all I need to do is tell the user which features won't be available to them, but let them continue one with the application. Thanks.

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• Unreleased Resource: Streams

  - by Vibhas

  Hi freinds i am getting a warning in the fortify report for the following code: if (null != serverSocket) { OutputStream socketOutPutStream = serverSocket .getOutputStream(); if (null != socketOutPutStream) { oos = new ObjectOutputStream(socketOutPutStream); if (null != oos) { int c; log.info("i am in Step 3 ooss " + oos); while ((c = mergedIS.read()) != -1) { oos.writeByte(c); } } log.info("i am in Step 4 "); } } in the catch block i have mentioned : catch (UnknownHostException e) { //catch exception Vibhas added log.info("UnknownHostException occured"); } catch (IOException e) { //catch exception Vibhas added log.info("IOException occured"); } catch (Exception e) { //catch exception //log.info("error occured in copyFile in utils-->"+e.getMessage()+"file name is-->"+destiFileName); }finally{ if (null != oos){ oos.flush(); oos.close(); } catch (Exception e) { //catch exception } } Warning which i am getting in the fortify report is: Abstract: The function copyFile() in ODCUtil.java sometimes fails to release a system resource allocated by getOutputStream() on line 61. Sink: ODCUtil.java:64 oos = new ObjectOutputStream(socketOutPutStream)() 62 if (null != socketOutPutStream) { 63 64 oos = new ObjectOutputStream(socketOutPutStream); 65 if (null != oos) { 66 int c;

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• KO3: How to deal with stylesheets and scriptfiles

  - by Svish

  I'm using Kohana 3 and it's template controller. My main site template controller currently looks something like this: <?php defined('SYSPATH') or die('No direct script access.'); abstract class Controller_SiteTemplate extends Controller_Template { public function before() { parent::before(); // Initialize default template variables $this->template->styles = Kohana::config('site.styles'); $this->template->scripts = Kohana::config('site.scripts'); $this->template->title = ''; $this->template->content = ''; } } And then in my template view I do: <?php # Styles foreach($styles as $file => $media) echo HTML::style($file, array('media' => $media)).PHP_EOL ?> <?php # Scripts foreach($scripts as $file) echo HTML::script($file).PHP_EOL ?> This works alright. The problem is that it requires the style- and script files to be added in the controller, which shouldn't really have to care about those. It also makes it a hassle if the views are done by someone else than me since they would have to fool around with the controller just to add a new stylesheet or a new script file. How can this be done in a better way? Just to clearify, what I am wondering is how to deal with page specific stylesheets and scripts. The default and site-wide ones I have no problem with fetching from a config file or just put directly in the template view. My issue is how to add custom ones for specific pages in a good way.

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• Kohana 3, problem with m2m data adding

  - by Marek

  Hello I posted this on official forum but with no result. I am getting :Undefined index: enrollment error when trying to save data. My pivot model: class Model_Enrollment extends ORM { protected $_belongs_to = array('page' => array(), 'menugroup' => array()); } Model_Page protected $_has_many = array('templates' => array(), 'menugroups' => array('through' => 'enrollment')); Model_Menugroup protected $_has_many = array('menuitems' => array(), 'pages' => array('through' => 'enrollment')); //Overriden save() method in Model_Menugroup: public function save() { if (empty($this->created)) { $this->created = time(); } parent::save(); $this->reload(); if (! $this->is_global) { if (! empty($this->groupOwnerPagesId) { $page = ORM::factory('page'); foreach($this->groupOwnerPagesId as $id) { $this->add('enrollment', $page->find($id)); } } } } I did: I corrected table names in pivot model by changing them to singular I even now using the same name for pivot table / model = enrollment. The same as in tutorial. Just in case So the pivot table has name 'enrollment' and has 2 columns: page_id , menugroup_id I tried to add pk in pivot table, but it changed nothing I tried to add/remove db relation between pages/menugroups and pivot table (InnoDB) but with no luck I tried save all data in controller, but with the same bad result:( I am still getting the same error: Undefined index: enrollment in ORM line: $columns = array($this-_has_many[$alias]['foreign_key'], $this-_has_many[$alias]['far_key']); Could somebody tell me, what can be else wrong? I have no other ideas:( Kind regards

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• Need help with a custom Spinner/ArrayAdapter setup

  - by MisterSquonk

  I have a WeatherSpinner class which extends Spinner. The class shows region names which I originally did using an ArrayAdapter<String> but I now want to use ArrayAdapter<Locale>(Locale is an abstract 'empty' class of my own). I'm getting a ClassCastException when trying to populate my ArrayAdapter with the following... protected ArrayList<?> theList; protected ArrayAdapter<Locale> aa = null; ... protected void updateContents(ArrayList<?> list, int selectedItem) { theList = list; // Exception thrown on next line aa = new ArrayAdapter<Locale>(theContext, android.R.layout.simple_spinner_item, (Locale[]) theList.toArray()); ... } I'm passing a RegionList object into updateContents() as the 'list' parameter and RegionList extends ArrayList<Region>, and Region extends Locale. I've also overriden Region's toString() method to return a valid String. What am I not seeing here? Am I wrong about the way ArrayList<?>.toArray() works?

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• How can I refactor this to work without breaking the pattern horribly?

  - by SnOrfus

  I've got a base class object that is used for filtering. It's a template method object that looks something like this. public class Filter { public void Process(User u, GeoRegion r, int countNeeded) { List<account> selected = this.Select(u, r, countNeeded); // 1 List<account> filtered = this.Filter(selected, u, r, countNeeded); // 2 if (filtered.Count > 0) { /* do businessy stuff */ } // 3 if (filtered.Count < countNeeded) this.SendToSuccessor(u, r, countNeeded - filtered) // 4 } } Select(...), Filter(...) are protected abstract methods and implemented by the derived classes. Select(...) finds objects in the based on x criteria, Filter(...) filters those selected further. If the remaining filtered collection has more than 1 object in it, we do some business stuff with it (unimportant to the problem here). SendToSuccessor(...) is called if there weren't enough objects found after filtering (it's a composite where the next class in succession will also be derived from Filter but have different filtering criteria) All has been ok, but now I'm building another set of filters, which I was going to subclass from this. The filters I'm building however would require different params and I don't want to just implement those methods and not use the params or just add to the param list the ones I need and have them not used in the existing filters. They still perform the same logical process though. I also don't want to complicated the consumer code for this (which looks like this) Filter f = new Filter1(); Filter f2 = new Filter2(); Filter f3 = new Filter3(); f.Sucessor = f2; f2.Sucessor = f3; /* and so on adding filters as successors to previous ones */ foreach (User u in users) { foreach (GeoRegion r in regions) { f.Process(u, r, ##); } } How should I go about it?

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• How do I organize C# classes that inherit from one another, but also have properties that inherit from one another?

  - by Chris

  I have an application that has a concept of a Venue, a place where events happen. A Venue is owned by a Company and has many VenueParts. So, it looks like this: public abstract class Venue { public int Id { get; set; } public string Name { get; set; } public virtual Company Company { get; set; } public virtual ICollection<VenuePart> VenueParts { get; set; } } A Venue can be a GolfCourseVenue, which is a Venue that has a Slope and a specific kind of VenuePart called a HoleVenuePart: public class GolfCourseVenue { public string Slope { get; set; } public virtual ICollection<HoleVenuePart> Holes { get; set; } } In the future, there may also be other kinds of Venues that all inherit from Venue. They might add their own fields, and will always have VenueParts of their own specific type. My declarations above seem wrong, because now I have a GolfCourseVenue with two collections, when really it should just have the one. I can't override it, because the type is different, right? When I run reports, I would like to refer to the classes generically, where I just spit out Venues and VenueParts. But, when I render forms and such, I would like to be specific. I have a lot of relationships like this and am wondering what I am doing wrong. For example, I have an Order that has OrderItems, but also specific kinds of Orders that have specific kinds of OrderItems.

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• What's the proper approach for writing multi-path "story" flows?

  - by Basiclife

  Hi, I wonder if you can help me. I'm writing a game (2d) which allows players to take multiple routes, some of which branch/merge - perhaps even loop. Each section of the game will decide which section is loaded next. I'm calling each section an IStoryElement - And I'm wondering how best to link these elements up in a way that is easily changed/configured and at the same time, graphable I'm going to have an engine/factory assembly which will load the appropriate StoryElement(s) based on various config options. I initially planned to give each StoryElement a NextElement() As IStoryElement property and a Completed() event. When the vent fires, the engine reads the NextElement property to find the next StoryElement. The downside to this is that if I ever wanted to graph all the routes through the game, I would be unable to - I couldn't determine all possible targets for each StoryElement. I considered a couple of other solutions but they all feel a little clunky - eg Do I need an additional layer of abstraction? ie StoryElementPlayers or similar - Each one would be responsible for stringing together multiple StoryElement perhaps a Series and a ChoicePlayer with each responsible for graphing its own StoryElement - But this will just move the problem up a layer. In short, I need some way of emulating a simple but dynamic workflow (but I'd rather not actually use WWF). Is there a pattern for something this simple? All the ones I've managed to find relate to more advanced control flow (parallel processing, etc.)

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• initialise a var in scala

  - by user unknown

  I have a class where I like to initialize my var by reading a configfile, which produces intermediate objects/vals, which I would like to group and hide in a method. Here is the bare minimum of the problem - I call the ctor with a param i, in reality a File to parse, and the init-method generates the String s, in reality more complicated than here, with a lot of intermediate objects being created: class Foo (val i: Int) { var s : String; def init () { s = "" + i } init () } This will produce the error: class Foo needs to be abstract, since variable s is not defined. In this example it is easy to solve by setting the String to "": var s = "";, but in reality the object is more complex than String, without an apropriate Null-implementation. I know, I can use an Option, which works for more complicated things than String too: var s : Option [String] = None def init () { s = Some ("" + i) } or I can dispense with my methodcall. Using an Option will force me to write Some over and over again, without much benefit, since there is no need for a None else than to initialize it that way I thought I could. Is there another way to achieve my goal?

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• Inheritance of TCollectionItem

  - by JamesB

  I'm planning to have collection of items stored in a TCollection. Each item will derive from TBaseItem which in turn derives from TCollectionItem, With this in mind the Collection will return TBaseItem when an item is requested. Now each TBaseItem will have a Calculate function, in the the TBaseItem this will just return an internal variable, but in each of the derivations of TBaseItem the Calculate function requires a different set of parameters. The Collection will have a Calculate All function which iterates through the collection items and calls each Calculate function, obviously it would need to pass the correct parameters to each function I can think of three ways of doing this: Create a virtual/abstract method for each calculate function in the base class and override it in the derrived class, This would mean no type casting was required when using the object but it would also mean I have to create lots of virtual methods and have a large if...else statement detecting the type and calling the correct "calculate" method, it also means that calling the calculate method is prone to error as you would have to know when writing the code which one to call for which type with the correct parameters to avoid an Error/EAbstractError. Create a record structure with all the possible parameters in and use this as the parameter for the "calculate" function. This has the added benefit of passing this to the "calculate all" function as it can contain all the parameters required and avoid a potentially very long parameter list. Just type casting the TBaseItem to access the correct calculate method. This would tidy up the TBaseItem quite alot compared to the first method. What would be the best way to handle this collection?

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• Checking if a function has C-linkage at compile-time

  - by scjohnno

  Is there any way to check if a given function is declared with C-linkage (that is, with extern "C") at compile-time? I am developing a plugin system. Each plugin can supply factory functions to the plugin-loading code. However, this has to be done via name (and subsequent use of GetProcAddress or dlsym). This requires that the functions be declared with C-linkage so as to prevent name-mangling. It would be nice to be able to throw a compiler error if the referred-to function is declared with C++-linkage (as opposed to finding out at runtime when a function with that name does not exist). Here's a simplified example of what I mean: extern "C" void my_func() { } void my_other_func() { } // Replace this struct with one that actually works template<typename T> struct is_c_linkage { static const bool value = true; }; template<typename T> void assertCLinkage(T *func) { static_assert(is_c_linkage<T>::value, "Supplied function does not have C-linkage"); } int main() { assertCLinkage(my_func); // Should compile assertCLinkage(my_other_func); // Should NOT compile } Thanks.

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• Casting pointer to object to void * in C++

  - by JB

  I've been reading StackOverflow too much and started doubting all the code I've ever written, I keep thinking "Is that undefined behavour?" even in code that has been working for ages. So my question - Is it safe and well defined behavour to cast a pointer to an object (In this case abstract interface classes) to a void* and then later on cast them back to the original class and call method using them? I'm fully aware that the code that does this is probably awful. I wouldn't even consider writing it like this now (this is old code which I don't really want to change), so I'm not looking for a discussion of better ways to do this. I already know how to write it better if I ever did this again. But if it's actually broken to rely on this in C++ then I'll have to look at changing the code, if it's merely awful code then changing it won't be a priority. I would have had no doubts about something this simple a year or two ago but as my understanding of C++ increases I actually find I have more and more worries about code being safe under the standards even if it works perfectly well. Perhaps reading too much stack overflow is a bad thing for productivity sometimes :P

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