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• save object associate to another object automatically

  - by Luca Romagnoli

  Hi i have these classes: class Core < ActiveRecord::Base belongs_to :resource, :polymorphic => true belongs_to :image, :class_name => 'Multimedia', :foreign_key => 'image_id' end class Place < ActiveRecord::Base has_one :core, :as => :resource end If i try do launch this: a = Place.find(5) a.name ="a" a.core.image_id = 24 a.save name is saved. image_id no i want save automatically all changes in records in relationship with place class at a.save command. is possible? thanks

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• Why does a Linq Cast<T> operation fail when I have an implicit cast defined?

  - by Ryan Versaw

  I've created two classes, with one of them having an implicit cast between them: public class Class1 { public int Test1; } public class Class2 { public int Test2; public static implicit operator Class1(Class2 item) { return new Class1{Test1 = item.Test2}; } } When I create a new list of one type and try to Cast<T> to the other, it fails with an InvalidCastException: List<Class2> items = new List<Class2>{new Class2{Test2 = 9}}; foreach (Class1 item in items.Cast<Class1>()) { Console.WriteLine(item.Test1); } This, however, works fine: foreach (Class1 item in items) { Console.WriteLine(item.Test1); } Why is the implicit cast not called when using Cast<T>?

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• Integer v/s int

  - by Siddhartha

  Read this on the oracle docs java.lang page: Frequently it is necessary to represent a value of primitive type as if it were an object. The wrapper classes Boolean, Character, Integer, Long, Float, and Double serve this purpose. I'm not sure I understand why these are needed. It says they have useful functions such as equals(). But if I can do (a==b), why would I ever want to declare them as Integer, use more memory and use equals()? How does the memory usage differ for the 2?

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• Difference between var and Class class in object creation

  - by Divine

  Its a silly question, however shocked to see different behaviors. Learning a lot. Lets say I have two classes below Class A { public void Display() { } } Class B : A { public void Display() { } } Class C : B { public void Display() { } } Class Final { static void Main() { var c = new C(); // B c = new C(); //My doubt is, both of the above gives different results. May I know B c = new C() creates object of B or C? What I understood is, it creates object of B. Then why we say "new C()"? I agree with C c = new C(); But I thought, B b = new C(); creates object of B. Where we use this style? Only when utilizing runtime polymorphism? (Overriding methods)? } }

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• How to map it? HasOne x References

  - by Felipe

  Hi everyones, I need to make a mapping One by One, and I have some doubts. I have this classes: public class DocumentType { public virtual int Id { get; set; } /* othes properties for documenttype */ public virtual DocumentConfiguration Configuration { get; set; } public DocumentType () { } } public class DocumentConfiguration { public virtual int Id { get; set; } /* some other properties for configuration */ public virtual DocumentType Type { get; set; } public DocumentConfiguration () { } } A DocumentType object has only one DocumentConfiguration, but it is not a inherits, it's only one by one and unique, to separate properties. How should be my mappings in this case ? Should I use References or HasOne ? Someone could give an example ? When I load a DocumentType object I'd like to auto load the property Configuration (in documentType). Thanks a lot guys! Cheers

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• .NET Micro Edition - Open Multiple Windows

  - by RM

  I've had a look through quite a few tutorials, but cant seem to find how to open multipe windows? I'm not expecting to have them layer etc, I just want to define multiple window classes and say, from a menu, launch the appropriate window class from the menu window. Then when that window is finished, call the close method on it and menu will show again. I have managed to do the same kind of functionality using panels, but think window is really what I should be using? (.NET MF 4.0) I assume you can do this? I think im missing something obvious?

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• java.lang.NoClassDefFoundError when the file is there

  - by tsOverflow

  I've tried to look around for postings that might help me, cant find any. I am deploying an ear to JBoss4 server, and I started having this problem since I added a new project. this new project is defined as Java project in eclipse, and the EAR project has an EJB project that has the new Java project as one of the projects as its dependent upon - if deployed on JBoss locally through eclipse, there's no problem and everything goes smoothly But when being deployed to JBoss in test environment (outside eclipse), kept getting java.lang.NoClassDefFoundError on one of the classes that are defined in the new Java project. I looked inside the EAR file to get to the jar (EJB project), and then inside the jar, I can see the directory structure and all the class files from the new Java project - ie. The class that it complains about is right there inside the EAR-JAR and matching the exact structure that it's looking for. I am at lost to what else I can look at. Any pointers are greatly appreciated! Thanks

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• how to display "complex" widgets in a list in pyqt?

  - by Giorgio Gelardi

  I'm quite new to QT and I have to display a list of "panels" like this: My datamodel handles different classes' instances, so having more than one panel layout would be great - but it's not a requirement. Btw I have to catch mouse clicks on the images to execute related actions. I'm thinking about use some html capable widget (QWebPage?) to render the items in a QListView or QListWidget, but as I said, I don't know QTs so much and need a direction (delegates? stylesheets?). Any help will be appreciated.

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• Best practice in Rails when editing scaffold made pages

  - by abegbg

  I have a best practice question. I have two classes, company and category. They have a many-to-many relationship. When clicking a category I shall go to a page showing all companies with the chosen category. Pretty straight forward. My question is: Should I list all the companies on the companies/index.html.erb after filtering the companies in the controller? or Should I list all the companies on the categories/show.html.erb page? or Should I do a completely new page, since it doesn't really fit into any of the two above? Do you generally make a new page when your goal doesn't fit the scaffold made pages or do you use them quite freely? I am working/learning alone with rails, so there are a lot of best practice questions popping up all the time. Cheers Carl

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• Get all descendants types of base class

  - by user1260827

  I have a base class called BaseEvent and several descendants classes: public class BaseEvent { // the some properties ... } [MapInheritance(MapInheritanceType.ParentTable)] public class Film : BaseEvent { // the some properties ... } [MapInheritance(MapInheritanceType.ParentTable)] public class Concert : BaseEvent { // the some properties ... } I have a code which create the BaseEvent instance at runtime: BaseEvent event = new BaseEvent(); //assign values for a properties ... baseEvent.XPObjectType = Database.XPObjectTypes.SingleOrDefault(t => t.TypeName == "MyApp.Module.BO.Events.BaseEvent"); Now, this event will be shows in BaseEvent list view. I want to do the following: when a user click Edit button then show in list view lookup field with all descendants types. And when user saves record change ObjectType to selected value. How can I do this? Thanks. PS. this is asp.net app.

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• Scraping html WITHOUT uniquie identifiers using python

  - by Nicholas Law

  I would like to design an algorithm using python that scrapes thousands of pages like this one and this one, gathers all the data and inserts it into a MySQL database. The script will be run on a weekly or bi-weekly basis to update the database of any new information added to each individual page. Ideally I would like a scraper that is easy to work with for table structured data but also data that does not have unique identifiers (ie. id and classes attributes). Which scraper add-on should I use? BeautifulSoup, Scrapy or Mechanize? Are there any particular tutorials/books I should be looking at for this desired result? In the long-run I will be implementing a mobile app that works with all this data through querying the database.

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• How to convert objects in reflection (Linq to XML)

  - by user829174

  I have the following code which is working fine, the code creates plugins in reflection via run time: using System; using System.Collections.Generic; using System.Linq; using System.IO; using System.Xml.Linq; using System.Reflection; using System.Text; namespace WindowsFormsApplication1 { public abstract class Plugin { public string Type { get; set; } public string Message { get; set; } } public class FilePlugin : Plugin { public string Path { get; set; } } public class RegsitryPlugin : Plugin { public string Key { get; set; } public string Name { get; set; } public string Value { get; set; } } static class MyProgram { [STAThread] static void Main(string[] args) { string xmlstr =@" <Client> <Plugin Type=""FilePlugin""> <Message>i am a file plugin</Message> <Path>c:\</Path> </Plugin> <Plugin Type=""RegsitryPlugin""> <Message>i am a registry plugin</Message> <Key>HKLM\Software\Microsoft</Key> <Name>Version</Name> <Value>3.5</Value> </Plugin> </Client> "; Assembly asm = Assembly.GetExecutingAssembly(); XDocument xDoc = XDocument.Load(new StringReader(xmlstr)); Plugin[] plugins = xDoc.Descendants("Plugin") .Select(plugin => { string typeName = plugin.Attribute("Type").Value; var type = asm.GetTypes().Where(t => t.Name == typeName).First(); Plugin p = Activator.CreateInstance(type) as Plugin; p.Type = typeName; foreach (var prop in plugin.Descendants()) { var pi = type.GetProperty(prop.Name.LocalName); object newVal = Convert.ChangeType(prop.Value, pi.PropertyType); pi.SetValue(p, newVal, null); } return p; }).ToArray(); // //"plugins" ready to use // } } } I am trying to modify the code and adding new class named DetailedPlugin so it will be able to read the following xml: string newXml = @" <Client> <Plugin Type=""FilePlugin""> <Message>i am a file plugin</Message> <Path>c:\</Path> <DetailedPlugin Type=""DetailedFilePlugin""> <Message>I am a detailed file plugin</Message> </DetailedPlugin> </Plugin> <Plugin Type=""RegsitryPlugin""> <Message>i am a registry plugin</Message> <Key>HKLM\Software\Microsoft</Key> <Name>Version</Name> <Value>3.5</Value> <DetailedPlugin Type=""DetailedRegsitryPlugin""> <Message>I am a detailed registry plugin</Message> </DetailedPlugin> </Plugin> </Client> "; for this i modified my classes to the following: public abstract class Plugin { public string Type { get; set; } public string Message { get; set; } public DetailedPlugin DetailedPlugin { get; set; } // new } public class FilePlugin : Plugin { public string Path { get; set; } } public class RegsitryPlugin : Plugin { public string Key { get; set; } public string Name { get; set; } public string Value { get; set; } } // new classes: public abstract class DetailedPlugin { public string Type { get; set; } public string Message { get; set; } } public class DetailedFilePlugin : Plugin { public string ExtraField1 { get; set; } } public class DetailedRegsitryPlugin : Plugin { public string ExtraField2{ get; set; } } from here i need some help to accomplish reading the xml and create the plugins with the nested DetailedPlugin

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• C# private (hidden) base class

  - by Loadmaster

  It is possible to make a C# base class accessible only within the library assembly it's compiled into, while making other subclasses that inherit from it public? For example: using System.IO; class BaseOutput: Stream // Hidden base class { protected BaseOutput(Stream o) { ... } ...lots of common methods... } public class MyOutput: BaseOutput // Public subclass { public BaseOutput(Stream o): base(o) { ... } public override int Write(int b) { ... } } Here I'd like the BaseOutput class to be inaccessible to clients of my library, but allow the subclass MyOutput to be completely public. I know that C# does not allow base classes to have more restrictive access than subclasses, but is there some other legal way of achieving the same effect?

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• Hibernate Annotation for Entity existing in more than 1 catalog

  - by user286395

  I have a Person entity mapped by Hibernate to a database table in a database catalog "Active". After a period of time, records in this database table in the "Active" catalog are archived/moved to an exact copy of the table in a database Catalog "History". I have the need to retrieve from both the Active and History Catalogs. Is there a better way to model this with Hibernate annotations than making an abstract class that 2 classes extend from. This is what I have now. @MappedSuperclass public abstract class Person { @Id private Integer id; private String name; } @Entity @Table(name="Person", catalog="Active") public class PersonActive extends Person { } @Entity @Table(name="Person", catalog="History") public class PersonHistory extends Person { }

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• Subsonic foreign key returning collection?

  - by Shaul

  I'm just writing my first "Hello World" program using Subsonic, for which I've thrown together a simple little Customer/Invoice/InvoiceItem/Product database. The connection was successfully made to the DB, and it generated all the right ActiveRecord classes. But for some reason, the Invoice class has a property called Customers, which returns a collection of Customer objects, even though the Invoice table has a CustomerID field which has a foreign key to the Customer table. I would have expected a Customer property returning a single Customer object. I must be doing something wrong - but what?

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• SQL Design Question regarding schema and if Name value pair is the best solution

  - by Aur

  I am having a small problem trying to decide on database schema for a current project. I am by no means a DBA. The application parses through a file based on user input and enters that data in the database. The number of fields that can be parsed is between 1 and 42 at the current moment. The current design of the database is entirely flat with there being 42 columns; some have repeated columns such as address1, address2, address3, etc... This says that I should normalize the data. However, data integrity is not needed at this moment and the way the data is shaped I'm looking at several joins. Not a bad thing but the data is still in a 1 to 1 relationship and I still see a lot of empty fields per row. So my concerns are that this does not allow the database or the application to be very extendable. If they want to add more fields to be parsed (which they do) than I'd need to create another table and add another foreign key to the linking table. The third option is I have a table where the fields are defined and a table for each record. So what I was thinking is to make a table that stores the value and then links to those two tables. The problem is I can picture the size of that table growing large depending on the input size. If someone gives me a file with 300,000 records than 300,000 x 40 = 12 million so I have some reservations. However I think if I get to that point than I should be happy it is being used. This option also allows for more custom displaying of information albeit a bit more work but little rework even if you add more fields. So the problem boils down to: 1. Current design is a flat file which makes extending it hard and it is not normalized. 2. Normalize the tables although no real benefits for the moment but requirements change. 3. Normalize it down into the name value pair and hope size doesn't hurt. There are a large number of inserts, updates, and selects against that table. So performance is a worry but I believe the saying is design now, performance testing later? I'm probably just missing something practical so any comments would be appreciated even if it’s a quick sanity check. Thank you for your time.

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• how to call a function to refresh GUI

  - by SWKK

  Hi Guys, I am refactoring some code to decouple GUI from some state. #include <StateObject> Class GUI{ ... StateObject A; void doSomething() { A->hullaballoo();} **void ReFreshMyGui() { //take state A and redraw }** }; State object is being shared by multiple classes to update the state but this Gui Object specializes in displaying the state. So I would like to call the Refresh function via StateObject whenever its modified. I am not sure how or if signals will provide the solution. Any hints?

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• Should the include guards be unique even between namespaces?

  - by Arun

  I am using same class name in two namespaces, say A and B. Should the include guards be unique while declaring the classes with different namespaces too? I mean can't there be two files names AFile.h (in different directories) with same include guards and declaring different namespaces? File 1: #ifndef AFILE_H #define AFILE_H namespace A { class CAFile {... }; }; #endif File 2: #ifndef AFILE_H #define AFILE_H namespace B { class CAFile {... }; }; #endif

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• What features of Scala cannot be translated to Java?

  - by Paul

  The Scala compiler compiles direct to Java byte code (or .NET CIL). Some of the features of Scala could be re-done in Java straightforwardly (e.g. simple for comprehensions, classes, translating anonymous/inner functionc etc). What are the features that cannot be translated that way? That is presumably mostly of academic interest. More usefully, perhaps, what are the key features or idioms of Scala that YOU use that cannot be easily represented in Java? Are there any the other way about? Things that can be done straightforwardly in Java that have no straightforward equivalent in Scala? Idioms in Java that don't translate?

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• In Ruby, is there are better way of selecting a constant (or avoiding the constant altogether) based

  - by Vertis

  Not sure the title fully describes the problem/question I'm trying to ask, sorry. I'm One of my fellow developers has created classes as such: class Widget attr_accessor :model_type ... end and: class ModelType MODEL1 = "model1" MODEL2 = "model2" MODEL3 = "model3" end Now he wants me to convert a retrieved string "MODEL1" to the constant. So that when he is referencing that model elsewhere he can use ModelType::MODEL1. Obviously I've got to convert from the string I'm being given with something like the following: case model_type when 'MODEL1' @model_type = ModelType::MODEL1 ... end I feel like this is clunky, so I'd like to know if there is a better DRYer way of providing this kind of functionality.

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• Use DataContext to create schema in an existing blank database file?

  - by jdk

  With a DataContext and a blank file-based database that already exists, is it possible to write the Data Context classes (i.e. the ones I added to the designer) to create the db schema? With a data context I only see the abilities to either: create a new database file and have its structure created at the same time, or to populate data into an existing database having preexisting schema. I'm looking for a hybrid solution between those two worlds. Update 1: My proof that a preexisting db is not compatible with the Data Context CreateDatabase() operation is this error Database 'C:...\App_Data\IntermediateData.mdf' already exists. Choose a different database name. based on this code using (IntermediateClassesDataContext intermediateContext = new IntermediateClassesDataContext(_getIntermediateConn())) { intermediateContext.CreateDatabase(); }

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• how to implement this observer pattern?

  - by lethal

  Hello. I have 4 classes, that describe state diagram. Node, Edge, ComponentOfNode, ComponentOfEdge. ComponentOfEdge compounds from ComponentsOfNode. Node can have 0..n outgoing edges. Edge can have only 2 nodes. Edge should be able to offer ComponentOfNode, but only from nodes that Edge has, in form ComponentOfEdge. The user can change ComponentsOfNode. I need this change spreads to all Edge. Hw to do it? I expect the observer should be used. Can you give me example in pseudocode please?

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• How to add Ads for my android app using eclipse?

  - by user3896367

  I am trying to add ads to my app but I don't know how I followed the instructions from this site: https://developer.android.com/google/play-services/ads.html I did step 1 and 2 in the getting started column, I imported the google-play-services_libs to my workspace then I referenced it in my app and I added this code in my mainfest: <meta-data android:name="com.google.android.gms.version" android:value="@integer/google_play_services_version" /> I opened the sample ad and copied this code to my xml: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:ads="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent" android:layout_height="match_parent" android:background="@android:color/black" android:gravity="center" android:orientation="vertical" > <com.google.android.gms.ads.AdView android:id="@+id/adView" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_alignParentBottom="true" android:layout_alignParentLeft="true" ads:adUnitId="@string/ad_unit_id"/> but I am getting this error: The following classes could not be instantiated: - com.google.android.gms.ads.AdView so do you know how to fix this problem and can you tell me what should i write in the java to make in work thanks

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• Should downcasting be avoided while using a class hierarchy in C++?

  - by neuviemeporte

  Let's say I'm writing an application which works with projects, and exposes different functionality depending on the type of the project. I have a hierarchy of classes for the different types of projects: class AbstractProject { }; class ProjectA : public AbstractProject { }; class ProjectB : public AbstractProject { }; class ProjectC : public AbstractProject { }; Now, I was planning to have an AbstractProject *_currentProject pointer as a member in the application's main class, pop up a dialog box on startup and based on the selection, do: _currentProject = new ProjectB(); // e.g. Later, I'll have to downcast the pointer to the specific type to utilize the functionality specific to different Project-s. Somehow this makes me feel uneasy. Is there a Better Way of doing this?

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• Real-world examples of populating a GWT CellTable using a clean MVP pattern?

  - by piehole

  We are using the GWT-Presenter framework and attempting to use CellTable to put together an updateable grid. It seems as though several of the GWT constructs for CellTable don't lend themselves to easily breaking up the logic into clean view and presenter code. Examples: 1) Within the View's constructor, the CellTable is defined and each column is created by anonymous inner classes that extend the Column class to provide the onValue() method. 2) The FieldUpdater interface must be implemented to provide logic to execute when a user alters data in a cell. This seems like it would best fit in the Presenter's onBind() method, but FieldUpdaters often need access to the Cell or Column which belong in the view. CellTable does not have accessor methods to get hold of the Columns or Cells, so it seems the only way for the Presenter to get them is for me to create a multitude of member variables on the View and accessors on my Display interface. Can anyone provide good examples for dealing with CellTable in GWT-Presenter or a comparable MVP

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