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  • Foolishness Check: PHP Class finds Class file but not Class in the file.

    - by Daniel Bingham
    I'm at a loss here. I've defined an abstract superclass in one file and a subclass in another. I have required the super-classes file and the stack trace reports to find an include it. However, it then returns an error when it hits the 'extends' line: Fatal error: Class 'HTMLBuilder' not found in View/Markup/HTML/HTML4.01/HTML4_01Builder.php on line 7. I had this working with another class tree that uses factories a moment ago. I just added the builder layer in between the factories and the consumer. The factory layer looked almost exactly the same in terms of includes and dependencies. So that makes me think I must have done something silly that's causes the HTMLBuilder.php file to not be included correctly or interpreted correctly or some such. Here's the full stack trace (paths slightly altered): # Time Memory Function Location 1 0.0001 53904 {main}( ) ../index.php:0 2 0.0002 67600 require_once( 'View/Page.php' ) ../index.php:3 3 0.0003 75444 require_once( 'View/Sections/SectionFactory.php' ) ../Page.php:4 4 0.0003 81152 require_once( 'View/Sections/HTML/HTMLSectionFactory.php' ) ../SectionFactory.php:3 5 0.0004 92108 require_once( 'View/Sections/HTML/HTMLTitlebarSection.php' ) ../HTMLSectionFactory.php:5 6 0.0005 99716 require_once( 'View/Markup/HTML/HTMLBuilder.php' ) ../HTMLTitlebarSection.php:3 7 0.0005 103580 require_once( 'View/Markup/MarkupBuilder.php' ) ../HTMLBuilder.php:3 8 0.0006 124120 require_once( 'View/Markup/HTML/HTML4.01/HTML4_01Builder.php' ) ../MarkupBuilder.php:3 Here's the code in question: Parent class (View/Markup/HTML/HTMLBuilder.php): <?php require_once('View/Markup/MarkupBuilder.php'); abstract class HTMLBuilder extends MarkupBuilder { public abstract function getLink($text, $href); public abstract function getImage($src, $alt); public abstract function getDivision($id, array $classes=NULL, array $children=NULL); public abstract function getParagraph($text, array $classes=NULL, $id=NULL); } ?> Child Class, (View/Markup/HTML/HTML4.01/HTML4_01Builder.php): <?php require_once('HTML4_01Factory.php'); require_once('View/Markup/HTML/HTMLBuilder.php'); class HTML4_01Builder extends HTMLBuilder { private $factory; public function __construct() { $this->factory = new HTML4_01Factory(); } public function getLink($href, $text) { $link = $this->factory->getA(); $link->addAttribute('href', $href); $link->addChild($this->factory->getText($text)); return $link; } public function getImage($src, $alt) { $image = $this->factory->getImg(); $image->addAttribute('src', $src); $image->addAttribute('alt', $alt); return $image; } public function getDivision($id, array $classes=NULL, array $children=NULL) { $div = $this->factory->getDiv(); $div->setID($id); if(!empty($classes)) { $div->addClasses($classes); } if(!empty($children)) { $div->addChildren($children); } return $div; } public function getParagraph($text, array $classes=NULL, $id=NULL) { $p = $this->factory->getP(); $p->addChild($this->factory->getText($text)); if(!empty($classes)) { $p->addClasses($classes); } if(!empty($id)) { $p->setID($id); } return $p; } } ?> I would appreciate any and all ideas. I'm at a complete loss here as to what is going wrong. I'm sure it's something stupid I just can't see...

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  • Is there a way communicate or measure levels of abstraction?

    - by hydroparadise
    I'll be the first to say that this question is a bit... out there. But here are a couple questions I bear in mind : Is abstraction continuous or discrete? Is there a single unit of abstraction? But I'm not sure those questions are truly answerable or even really makes sence. My naive answer would be something along the lines of abitrarily discrete but not necescarily having a single unit measure. Here's what I mean... Take a Black Labrador; an abstraction that could be made is that a Black Lab is a type of animal. [Animal]<--[Black Lab] A Black Lab is also a type of Dog. [Dog]<--[Black Lab] One way to establish a degree of abstraction is by comparing the two the abstractions. We could say that [Animal] is more abstract than [Dog] in respect to a Black Lab. It just so happens [Animal] can also be used as an abstraction of [Dog] So, we might end up with something like [Animal]<--[Dog]<--[Black Lab] With the model above, one might be inclined to say that there's two hops of abstraction to get from [Black Lab] to [Animal]. But you can't exactly tell somebody they need one level abstraction and reasonalby expect they will come up with [Dog] given they aren't explicity given the options above. If I needed to tell someobody in a single email that they needed an abstract class with out knowing what that abstract class is, is there a way to communaticate a degree of abstraction such that they might end up on Dog instead of Animal? As a side note, what area of study might this type of analysis fall under?

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  • Extreme Optimization Numerical Libraries for .NET – Part 1 of n

    - by JoshReuben
    While many of my colleagues are fascinated in constructing the ultimate ViewModel or ServiceBus, I feel that this kind of plumbing code is re-invented far too many times – at some point in the near future, it will be out of the box standard infra. How many times have you been to a customer site and built a different variation of the same kind of code frameworks? How many times can you abstract Prism or reliable and discoverable WCF communication? As the bar is raised for whats bundled with the framework and more tasks become declarative, automated and configurable, Information Systems will expose a higher level of abstraction, forcing software engineers to focus on more advanced computer science and algorithmic tasks. I've spent the better half of the past decade building skills in .NET and expanding my mathematical horizons by working through the Schaums guides. In this series I am going to examine how these skillsets come together in the implementation provided by ExtremeOptimization. Download the trial version here: http://www.extremeoptimization.com/downloads.aspx Overview The library implements a set of algorithms for: linear algebra, complex numbers, numerical integration and differentiation, solving equations, optimization, random numbers, regression, ANOVA, statistical distributions, hypothesis tests. EONumLib combines three libraries in one - organized in a consistent namespace hierarchy. Mathematics Library - Extreme.Mathematics namespace Vector and Matrix Library - Extreme.Mathematics.LinearAlgebra namespace Statistics Library - Extreme.Statistics namespace System Requirements -.NET framework 4.0  Mathematics Library The classes are organized into the following namespace hierarchy: Extreme.Mathematics – common data types, exception types, and delegates. Extreme.Mathematics.Calculus - numerical integration and differentiation of functions. Extreme.Mathematics.Curves - points, lines and curves, including polynomials and Chebyshev approximations. curve fitting and interpolation. Extreme.Mathematics.Generic - generic arithmetic & linear algebra. Extreme.Mathematics.EquationSolvers - root finding algorithms. Extreme.Mathematics.LinearAlgebra - vectors , matrices , matrix decompositions, solvers for simultaneous linear equations and least squares. Extreme.Mathematics.Optimization – multi-d function optimization + linear programming. Extreme.Mathematics.SignalProcessing - one and two-dimensional discrete Fourier transforms. Extreme.Mathematics.SpecialFunctions

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  • Understanding Visitor Pattern

    - by Nezreli
    I have a hierarchy of classes that represents GUI controls. Something like this: Control-ContainerControl-Form I have to implement a series of algoritms that work with objects doing various stuff and I'm thinking that Visitor pattern would be the cleanest solution. Let take for example an algorithm which creates a Xml representaion of a hierarchy of objects. Using 'classic' approach I would do this: public abstract class Control { public virtual XmlElement ToXML(XmlDocument document) { XmlElement xml = document.CreateElement(this.GetType().Name); // Create element, fill it with attributes declared with control return xml; } } public abstract class ContainerControl : Control { public override XmlElement ToXML(XmlDocument document) { XmlElement xml = base.ToXML(document); // Use forech to fill XmlElement with child XmlElements return xml; } } public class Form : ContainerControl { public override XmlElement ToXML(XmlDocument document) { XmlElement xml = base.ToXML(document); // Fill remaining elements declared in Form class return xml; } } But I'm not sure how to do this with visitor pattern. This is the basic implementation: public class ToXmlVisitor : IVisitor { public void Visit(Form form) { } } Since even the abstract classes help with implementation I'm not sure how to do that properly in ToXmlVisitor. Perhaps there is a better solution to this problem. The reason that I'm considering Visitor pattern is that some algorithms will need references not available in project where the classes are implemented and there is a number of different algorithms so I'm avoiding large classes. Any thoughts are welcome.

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  • Oracle R Distribution 2-13.2 Update Available

    - by Sherry LaMonica
    Oracle has released an update to the Oracle R Distribution, an Oracle-supported distribution of open source R. Oracle R Distribution 2-13.2 now contains the ability to dynamically link the following libraries on both Windows and Linux: The Intel Math Kernel Library (MKL) on Intel chips The AMD Core Math Library (ACML) on AMD chips To take advantage of the performance enhancements provided by Intel MKL or AMD ACML in Oracle R Distribution, simply add the MKL or ACML shared library directory to the LD_LIBRARY_PATH system environment variable. This automatically enables MKL or ACML to make use of all available processors, vastly speeding up linear algebra computations and eliminating the need to recompile R.  Even on a single core, the optimized algorithms in the Intel MKL libraries are faster than using R's standard BLAS library. Open-source R is linked to NetLib's BLAS libraries, but they are not multi-threaded and only use one core. While R's internal BLAS are efficient for most computations, it's possible to recompile R to link to a different, multi-threaded BLAS library to improve performance on eligible calculations. Compiling and linking to R yourself can be involved, but for many, the significantly improved calculation speed justifies the effort. Oracle R Distribution notably simplifies the process of using external math libraries by enabling R to auto-load MKL or ACML. For R commands that don't link to BLAS code, taking advantage of database parallelism using embedded R execution in Oracle R Enterprise is the route to improved performance. For more information about rebuilding R with different BLAS libraries, see the linear algebra section in the R Installation and Administration manual. As always, the Oracle R Distribution is available as a free download to anyone. Questions and comments are welcome on the Oracle R Forum.

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  • An alternative to multiple inheritance when creating an abstraction layer?

    - by sebf
    In my project I am creating an abstraction layer for some APIs. The purpose of the layer is to make multi-platform easier, and also to simplify the APIs to the feature set that I need while also providing some functionality, the implementation of which will be unique to each platform. At the moment, I have implemented it by defining and abstract class, which has methods which creates objects that implement interfaces. The abstract class and these interfaces define the capabilities of my abstraction layer. The implementation of these in my layer should of course be arbitrary from the POV view of my application, but I have done it, for my first API, by creating chains of subclasses which add more specific functionality as the features of the APIs they expose become less generic. An example would probably demonstrate this better: //The interface as seen by the application interface IGenericResource { byte[] GetSomeData(); } interface ISpecificResourceOne : IGenericResource { int SomePropertyOfResourceOne {get;} } interface ISpecificResourceTwo : IGenericResource { string SomePropertyOfResourceTwo {get;} } public abstract class MyLayer { ISpecificResourceOne CreateResourceOne(); ISpecificResourceTwo CreateResourceTwo(); void UseResourceOne(ISpecificResourceOne one); void UseResourceTwo(ISpecificResourceTwo two); } //The layer as created in my library public class LowLevelResource : IGenericResource { byte[] GetSomeData() {} } public class ResourceOne : LowLevelResource, ISpecificResourceOne { int SomePropertyOfResourceOne {get{}} } public class ResourceTwo : ResourceOne, ISpecificResourceTwo { string SomePropertyOfResourceTwo {get {}} } public partial class Implementation : MyLayer { override UseResourceOne(ISpecificResourceOne one) { DoStuff((ResourceOne)one); } } As can be seen, I am essentially trying to have two inheritance chains on the same object, but of course I can't do this so I simulate the second version with interfaces. The thing is though, I don't like using interfaces for this; it seems wrong, in my mind an interface defines a contract, any class that implements that interface should be able to be used where that interface is used but here that is clearly not the case because the interfaces are being used to allow an object from the layer to masquerade as something else, without the application needing to have access to its definition. What technique would allow me to define a comprehensive, intuitive collection of objects for an abstraction layer, while their implementation remains independent? (Language is C#)

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  • Custom ASP.Net MVC 2 ModelMetadataProvider for using custom view model attributes

    - by SeanMcAlinden
    There are a number of ways of implementing a pattern for using custom view model attributes, the following is similar to something I’m using at work which works pretty well. The classes I’m going to create are really simple: 1. Abstract base attribute 2. Custom ModelMetadata provider which will derive from the DataAnnotationsModelMetadataProvider   Base Attribute MetadataAttribute using System; using System.Web.Mvc; namespace Mvc2Templates.Attributes {     /// <summary>     /// Base class for custom MetadataAttributes.     /// </summary>     public abstract class MetadataAttribute : Attribute     {         /// <summary>         /// Method for processing custom attribute data.         /// </summary>         /// <param name="modelMetaData">A ModelMetaData instance.</param>         public abstract void Process(ModelMetadata modelMetaData);     } } As you can see, the class simple has one method – Process. Process accepts the ModelMetaData which will allow any derived custom attributes to set properties on the model meta data and add items to its AdditionalValues collection.   Custom Model Metadata Provider For a quick explanation of the Model Metadata and how it fits in to the MVC 2 framework, it is basically a set of properties that are usually set via attributes placed above properties on a view model, for example the ReadOnly and HiddenInput attributes. When EditorForModel, DisplayForModel or any of the other EditorFor/DisplayFor methods are called, the ModelMetadata information is used to determine how to display the properties. All of the information available within the model metadata is also available through ViewData.ModelMetadata. The following class derives from the DataAnnotationsModelMetadataProvider built into the mvc 2 framework. I’ve overridden the CreateMetadata method in order to process any custom attributes that may have been placed above a property in a view model.   CustomModelMetadataProvider using System; using System.Collections.Generic; using System.Linq; using System.Web.Mvc; using Mvc2Templates.Attributes; namespace Mvc2Templates.Providers {     public class CustomModelMetadataProvider : DataAnnotationsModelMetadataProvider     {         protected override ModelMetadata CreateMetadata(             IEnumerable<Attribute> attributes,             Type containerType,             Func<object> modelAccessor,             Type modelType,             string propertyName)         {             var modelMetadata = base.CreateMetadata(attributes, containerType, modelAccessor, modelType, propertyName);               attributes.OfType<MetadataAttribute>().ToList().ForEach(x => x.Process(modelMetadata));               return modelMetadata;         }     } } As you can see, once the model metadata is created through the base method, a check for any attributes deriving from our new abstract base attribute MetadataAttribute is made, the Process method is then called on any existing custom attributes with the model meta data for the property passed in.   Hooking it up The last thing you need to do to hook it up is set the new CustomModelMetadataProvider as the current ModelMetadataProvider, this is done within the Global.asax Application_Start method. Global.asax protected void Application_Start()         {             AreaRegistration.RegisterAllAreas();               RegisterRoutes(RouteTable.Routes);               ModelMetadataProviders.Current = new CustomModelMetadataProvider();         }   In my next post, I’m going to demonstrate a cool custom attribute that turns a textbox into an ajax driven AutoComplete text box. Hope this is useful. Kind Regards, Sean McAlinden.

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  • Best way to load application settings

    - by enzom83
    A simple way to keep the settings of a Java application is represented by a text file with ".properties" extension containing the identifier of each setting associated with a specific value (this value may be a number, string, date, etc..). C# uses a similar approach, but the text file must be named "App.config". In both cases, in source code you must initialize a specific class for reading settings: this class has a method that returns the value (as string) associated with the specified setting identifier. // Java example Properties config = new Properties(); config.load(...); String valueStr = config.getProperty("listening-port"); // ... // C# example NameValueCollection setting = ConfigurationManager.AppSettings; string valueStr = setting["listening-port"]; // ... In both cases we should parse strings loaded from the configuration file and assign the ??converted values to the related typed objects (parsing errors could occur during this phase). After the parsing step, we must check that the setting values ??belong to a specific domain of validity: for example, the maximum size of a queue should be a positive value, some values ??may be related (example: min < max), and so on. Suppose that the application should load the settings as soon as it starts: in other words, the first operation performed by the application is to load the settings. Any invalid values for the settings ??must be replaced automatically with default values??: if this happens to a group of related settings, those settings are all set with default values. The easiest way to perform these operations is to create a method that first parses all the settings, then checks the loaded values ??and finally sets any default values??. However maintenance is difficult if you use this approach: as the number of settings increases while developing the application, it becomes increasingly difficult to update the code. In order to solve this problem, I had thought of using the Template Method pattern, as follows. public abstract class Setting { protected abstract bool TryParseValues(); protected abstract bool CheckValues(); public abstract void SetDefaultValues(); /// <summary> /// Template Method /// </summary> public bool TrySetValuesOrDefault() { if (!TryParseValues() || !CheckValues()) { // parsing error or domain error SetDefaultValues(); return false; } return true; } } public class RangeSetting : Setting { private string minStr, maxStr; private byte min, max; public RangeSetting(string minStr, maxStr) { this.minStr = minStr; this.maxStr = maxStr; } protected override bool TryParseValues() { return (byte.TryParse(minStr, out min) && byte.TryParse(maxStr, out max)); } protected override bool CheckValues() { return (0 < min && min < max); } public override void SetDefaultValues() { min = 5; max = 10; } } The problem is that in this way we need to create a new class for each setting, even for a single value. Are there other solutions to this kind of problem? In summary: Easy maintenance: for example, the addition of one or more parameters. Extensibility: a first version of the application could read a single configuration file, but later versions may give the possibility of a multi-user setup (admin sets up a basic configuration, users can set only certain settings, etc..). Object oriented design.

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  • How to avoid OCIError in rails application?

    - by qichunren
    OCIError (ORA-12541: TNS:no listener): oci8.c:270:in oci8lib.so /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connection_adapters/oracle_enhanced_oci_connection.rb:223:in new' /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connection_adapters/oracle_enhanced_oci_connection.rb:223:innew_connection' /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connection_adapters/oracle_enhanced_oci_connection.rb:328:in initialize' /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connection_adapters/oracle_enhanced_oci_connection.rb:24:innew' /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connection_adapters/oracle_enhanced_oci_connection.rb:24:in initialize' /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connection_adapters/oracle_enhanced_connection.rb:9:innew' /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connection_adapters/oracle_enhanced_connection.rb:9:in create' /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connection_adapters/oracle_enhanced_adapter.rb:50:inoracle_enhanced_connection' /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/connection_adapters/abstract/connection_specification.rb:291:in send' /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/connection_adapters/abstract/connection_specification.rb:291:inconnection=' /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/connection_adapters/abstract/connection_specification.rb:259:in retrieve_connection' /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/connection_adapters/abstract/connection_specification.rb:78:inconnection' /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1063:in table_exists?' /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1153:ininspect' /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activesupport-2.0.2/lib/active_support/core_ext/class/inheritable_attributes.rb:131:in to_proc' /usr/local/ruby-1.8.7-p248/lib/ruby/gems/1.8/gems/activesupport-2.0.2/lib/active_support/dependencies.rb:426:incollect' It seems that rails app lost oracle connection,how to avoid this in application controller: def rescue_action_in_public(exception) I use def rescue_action_in_public(exception) case exception.class.to_s when "OCIError" # my solution end It still throw me 500.html

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  • Multiple database connection in Rails

    - by Sanal
    I'm using active_delegate for multiple connection in Rails. Here I'm using mysql as master_database for some models,and postgresql for some other models. Problem is that when I try to access the mysql models, I'm getting the error below! Stack trace shows that, it is still using the postgresql adapter to access my mysql models! RuntimeError: ERROR C42P01 Mrelation "categories" does not exist P15 F.\src\backend\parser\parse_relation.c L886 RparserOpenTable: SELECT * FROM "categories" STACKTRACE =========== d:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/connection_adapters/abstract_adapter.rb:212:in `log' d:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/connection_adapters/postgresql_adapter.rb:507:in `execute' d:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/connection_adapters/postgresql_adapter.rb:985:in `select_raw' d:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/connection_adapters/postgresql_adapter.rb:972:in `select' d:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/connection_adapters/abstract/database_statements.rb:7:in `select_all_without_query_cache' d:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/connection_adapters/abstract/query_cache.rb:60:in `select_all' d:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/connection_adapters/abstract/query_cache.rb:81:in `cache_sql' d:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/connection_adapters/abstract/query_cache.rb:60:in `select_all' d:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/base.rb:661:in `find_by_sql' d:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/base.rb:1553:in `find_every' d:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/base.rb:615:in `find' D:/ROR/Aptana/dedomenon/app/models/category.rb:50:in `get_all_with_exclusive_scope' D:/ROR/Aptana/dedomenon/app/models/category.rb:50:in `get_all_with_exclusive_scope' D:/ROR/Aptana/dedomenon/app/controllers/categories_controller.rb:48:in `index' here is my database.yml file postgre: &postgre adapter: postgresql database: codex host: localhost username: postgres password: root port: 5432 mysql: &mysql adapter: mysql database: project host: localhost username: root password: root port: 3306 development: <<: *postgre test: <<: *postgre production: <<: *postgre master_database: <<: *mysql and my master_databse model is like this class Category < ActiveRecord::Base delegates_connection_to :master_database, :on => [:create, :save, :destroy] end Anyone has any solution??

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  • Is this a good way to expose generic base class methods through an interface?

    - by Nate Heinrich
    I am trying to provide an interface to an abstract generic base class. I want to have a method exposed on the interface that consumes the generic type, but whose implementation is ultimately handled by the classes that inherit from my abstract generic base. However I don't want the subclasses to have to downcast to work with the generic type (as they already know what the type should be). Here is a simple version of the only way I can see to get it to work at the moment. public interface IFoo { void Process(Bar_base bar); } public abstract class FooBase<T> : IFoo where T : Bar_base { abstract void Process(T bar); // Explicit IFoo Implementation void IFoo.Process(Bar_base bar) { if (bar == null) throw new ArgumentNullException(); // Downcast here in base class (less for subclasses to worry about) T downcasted_bar = bar as T; if (downcasted_bar == null) { throw new InvalidOperationException( string.Format("Expected type '{0}', not type '{1}'", T.ToString(), bar.GetType().ToString()); } //Process downcasted object. Process(downcasted_bar); } } Then subclasses of FooBase would look like this... public class Foo_impl1 : FooBase<Bar_impl1> { void override Process(Bar_impl1 bar) { //No need to downcast here! } } Obviously this won't provide me compile time Type Checking, but I think it will get the job done... Questions: 1. Will this function as I think it will? 2. Is this the best way to do this? 3. What are the issues with doing it this way? 4. Can you suggest a different approach? Thanks!

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  • Factory Pattern: Determining concrete factory class instantiation?

    - by Chris
    I'm trying to learn patterns and I'm stuck on determining how or where a Factory Pattern determines what class to instanciate. If I have a Application that calls the factory and sends it, say, an xml config file to determine what type of action to take, where does that logic for interpreting the config file happen? THE FACTORY using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace myNamespace { public abstract class SourceFactory { abstract public UploadSource getUploadSource(); } public class TextSourceFactory : SourceFactory { public override UploadSource getUploadSource() { return new TextUploadSource(); } } public class XmlSourceFacotry : SourceFactory { public override UploadSource getUploadSource() { return new XmlUploadSource(); } } public class SqlSourceFactory : SourceFactory { public override UploadSource getUploadSource() { return new SqlUploadSource(); } } } THE CLASSES using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace myNamespace { public abstract class UploadSource { abstract public void Execute(); } public class TextUploadSource : UploadSource { public override void Execute() { Console.WriteLine("You executed a text upload source"); } } public class XmlUploadSource : UploadSource { public override void Execute() { Console.WriteLine("You executed an XML upload source"); } } public class SqlUploadSource : UploadSource { public override void Execute() { Console.WriteLine("You executed a SQL upload source"); } } }

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  • Polymorphic Numerics on .Net and In C#

    - by Bent Rasmussen
    It's a real shame that in .Net there is no polymorphism for numbers, i.e. no INumeric interface that unifies the different kinds of numerical types such as bool, byte, uint, int, etc. In the extreme one would like a complete package of abstract algebra types. Joe Duffy has an article about the issue: http://www.bluebytesoftware.com/blog/CommentView,guid,14b37ade-3110-4596-9d6e-bacdcd75baa8.aspx How would you express this in C#, in order to retrofit it, without having influence over .Net or C#? I have one idea that involves first defining one or more abstract types (interfaces such as INumeric - or more abstract than that) and then defining structs that implement these and wrap types such as int while providing operations that return the new type (e.g. Integer32 : INumeric; where addition would be defined as public Integer32 Add(Integer32 other) { return Return(Value + other.Value); } I am somewhat afraid of the execution speed of this code but at least it is abstract. No operator overloading goodness... Any other ideas? .Net doesn't look like a viable long-term platform if it cannot have this kind of abstraction I think - and be efficient about it. Abstraction is reuse.

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  • Multiple IntenseDebate Comment Counts

    - by Aristotle
    I just setup IntenseDebate on my blog this evening and am, for the most part, pleased with it. One thing I did see is that they offered me a small snippet to show the current number of comments: <script> var idcomments_acct = 'abcdefgef12345678mykey8675309acdc'; var idcomments_post_id; var idcomments_post_url; </script> <script type="text/javascript" src="http://www.intensedebate.com/js/genericLinkWrapperV2.js"></script> This is nice, but what I would like to do is have something similar on my archives page where many posts are listed - not just one. Presently the page looks like this: Some Post TitleAuthor NameShort abstract from this post... Some Post TitleAuthor NameShort abstract from this post... I would like it to look like this: Some Post TitleAuthor NameShort abstract from this post...7 Comments Some Post TitleAuthor NameShort abstract from this post...3 Comments But I'm not exactly sure how I can do this with IntenseDebate. Do they offer any sort of method to gather the total number of comments for multiple pages from a single page?

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  • Java RMI Proxy issue

    - by Antony Lewis
    i am getting this error : java.lang.ClassCastException: $Proxy0 cannot be cast to rmi.engine.Call at Main.main(Main.java:39) my abstract and call class both extend remote. call: public class Call extends UnicastRemoteObject implements rmi.engine.Abstract { public Call() throws Exception { super(Store.PORT, new RClient(), new RServer()); } public String getHello() { System.out.println("CONN"); return "HEY"; } } abstract: public interface Abstract extends Remote { String getHello() throws RemoteException; } this is my main: public static void main(String[] args) { if (args.length == 0) { try { System.out.println("We are slave "); InetAddress ip = InetAddress.getLocalHost(); Registry rr = LocateRegistry.getRegistry(ip.getHostAddress(), Store.PORT, new RClient()); Object ss = rr.lookup("FILLER"); System.out.println(ss.getClass().getCanonicalName()); System.out.println(((Call)ss).getHello()); } catch (Exception e) { e.printStackTrace(); } } else { if (args[0].equals("master")) { // Start Master try { RMIServer.start(); } catch (Exception e) { e.printStackTrace(); } } Netbeans says the problem is on line 39 which is System.out.println(((Call)ss).getHello()); the output looks like this: run: We are slave Connecting 10.0.0.212:5225 $Proxy0 java.lang.ClassCastException: $Proxy0 cannot be cast to rmi.engine.Call at Main.main(Main.java:39) BUILD SUCCESSFUL (total time: 1 second) i am running a master in cmd listening on port 5225.

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  • Where in the standard is forwarding to a base class required in these situations?

    - by pgast
    Maybe even better is: Why does the standard require forwarding to a base class in these situations? (yeah yeah yeah - Why? - Because.) class B1 { public: virtual void f()=0; }; class B2 { public: virtual void f(){} }; class D : public B1,public B2{ }; class D2 : public B1,public B2{ public: using B2::f; }; class D3 : public B1,public B2{ public: void f(){ B2::f(); } }; D d; D2 d2; D3 d3; EDG gives: sourceFile.cpp sourceFile.cpp(24) : error C2259: 'D' : cannot instantiate abstract class due to following members: 'void B1::f(void)' : is abstract sourceFile.cpp(6) : see declaration of 'B1::f' sourceFile.cpp(25) : error C2259: 'D2' : cannot instantiate abstract class due to following members: 'void B1::f(void)' : is abstract sourceFile.cpp(6) : see declaration of 'B and similarly for the MS compiler. I might buy the first case,D. But in D2 - f is unambiguously defined by the using declaration, why is that not enough for the compiler to be required to fill out the vtable? Where in the standard is this situation defined?

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  • Is it an example of decorator pattern?

    - by Supereme
    Hi, I've an example please tell me whether it is Decorator pattern or not? public abstract class ComputerComponent { String description ="Unknown Type"; public String getDescription() { return description; } public abstract double getCost(); } public abstract class AccessoryDecorator { ComputerComponent comp; public abstract String getDescription(); } public class PIIIConcreteComp extends ComputerComponent { public PIIIConcreteComp() { description=“Pentium III”; } public double getCost() { return 19950.00; } public class floppyConcreteDeco extends AccessoryDecorator { public floppyConcreteDeco(ComputerComponent comp) this.comp=comp; } public String getDescription() { return comp.getDescription() +”, floppy 1.44 mb”; } public double getCost() { return 250+comp.getCost(); } } public class ComponentAssembly { public static void createComponent() { ComputerComponent comp = new PIIConcreteComp(); // create a PIII computer object ComputerComponent deco1= new floppyConcreteDeco(comp); // decorate it with a floppy //ComputerComponent deco2= newCDRomConcreteDeco(deco1); ComputerComponent deco2= new floppyConcreteDeco(deco1); // decorate with a CDRom or with one more floppy System.out.println( deco2.getdescription() +” “+ deco2.getCost(); } } Thank you.

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  • C# WCF and Object Inheritence

    - by Michael Edwards
    I have the following setup of two classes: [SerializableAttribute] public class ParentData{ [DataMember] public string Title{get;set;} } [DataContract] public class ChildData : ParentData{ [DataMember] public string Abstract{get;set;} } These two classes are served through a WCF service. However I only want the service to expose the ChildData class to the end user but pull the marked up DataMember properties from the parent. E.g. The consuming client would have a stub class that looked like: public class ChildData{ public string Title{get;set;} public string Abstract{get;set;} } If I uses the parent and child classes as above the stub class only contains the Abstract property. I have looked at using the KnownType attribute on the ChildData class like so: [DataContract] [KnownType(typeOf(ParentData)] public class ChildData : ParentData{ [DataMember] public string Abstract{get;set;} } However this didn't work. I then applied the DataContract attribute to the ParentData class, however this then creates two stub classes in the client application which I don't want. Is there any way to tell the serializer that it should flatten the inheritance to that of the sub-class i.e. ChildData

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  • Is it good practise to blank out inherited functionality that will not be used?

    - by Timo Kosig
    I'm wondering if I should change the software architecture of one of my projects. I'm developing software for a project where two sides (in fact a host and a device) use shared code. That helps because shared data, e.g. enums can be stored in one central place. I'm working with what we call a "channel" to transfer data between device and host. Each channel has to be implemented on device and host side. We have different kinds of channels, ordinary ones and special channels which transfer measurement data. My current solution has the shared code in an abstract base class. From there on code is split between the two sides. As it has turned out there are a few cases when we would have shared code but we can't share it, we have to implement it on each side. The principle of DRY (don't repeat yourself) says that you shouldn't have code twice. My thought was now to concatenate the functionality of e.g. the abstract measurement channel on the device side and the host side in an abstract class with shared code. That means though that once we create an actual class for either the device or the host side for that channel we have to hide the functionality that is used by the other side. Is this an acceptable thing to do: public abstract class MeasurementChannelAbstract { protected void MethodUsedByDeviceSide() { } protected void MethodUsedByHostSide() { } } public class DeviceMeasurementChannel : MeasurementChannelAbstract { public new void MethodUsedByDeviceSide() { base.MethodUsedByDeviceSide(); } } Now, DeviceMeasurementChannel is only using the functionality for the device side from MeasurementChannelAbstract. By declaring all methods/members of MeasurementChannelAbstract protected you have to use the new keyword to enable that functionality to be accessed from the outside. Is that acceptable or are there any pitfalls, caveats, etc. that could arise later when using the code?

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  • Java: Why is this Subclass valid?

    - by incrediman
    Here, I have an abstract class: abstract class A<E extends A> { abstract void foo(E x); } Here's a class that extends A: class B extends A<B>{ void foo(B x){} } And here's another (E is B here on purpose): class C extends A<B>{ void foo(B x){} } Both of those classes are valid, and the reasoning for that makes sense to me. However what confuses me is how this could possibly be valid: class D extends A{ void foo(A x){} } Since when are generics optional like that? I thought the extending class (subclass) of A would be required to specify an E?

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  • Extracting pure content / text from HTML Pages by excluding navigation and chrome content

    - by Ankur Gupta
    Hi, I am crawling news websites and want to extract News Title, News Abstract (First Paragraph), etc I plugged into the webkit parser code to easily navigate webpage as a tree. To eliminate navigation and other non news content I take the text version of the article (minus the html tags, webkit provides api for the same). Then I run the diff algorithm comparing various article's text from same website this results in similar text being eliminated. This gives me content minus the common navigation content etc. Despite the above approach I am still getting quite some junk in my final text. This results in incorrect News Abstract being extracted. The error rate is 5 in 10 article i.e. 50%. Error as in Can you Suggest an alternative strategy for extraction of pure content, Would/Can learning Natural Language rocessing help in extracting correct abstract from these articles ? How would you approach the above problem ?. Are these any research papers on the same ?. Regards Ankur Gupta

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  • Address calling class [Java]

    - by Samuel
    Hello! [I am rather new to Java and Object Oriented programming] I have an abstract class Moveable with the method abstract void move() which is extended by the class Bullet and the abstract class Character, and Character is extended by the class Survivor and the class Zombie. In Survivor and Bullet the move() method doesnt require any parameters while in the class Zombie the move() method depends on the actual position of the survivor. The survivor and multiple zombies are created in the class Gui. I wanted to access the survivor in Zombie - what's the best way of doing this? In Gui i wrote a method getSurvivor() but i don't see how to access this method in Zombie? I am aware that as a workaround i could just pass a [Survivor survivor] as parameter in move() and ignore it in Bullet and Survivor, but that feels so ... bad practice. Thank you for your time! Samuel [I am not sure what tags to set here, please correct me if i'm wrong]

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  • subclassing and data contracts

    - by Sergio Romero
    I'm playing with the following code: [ServiceContract] public interface IUserAccountService { [OperationContract] UserAccountResponse CreateNewUserAccount(UserAccountRequest userAccountRequest); } public abstract class BaseResponse { public bool Success { get; set; } public string Message { get; set; } } public class UserAccountResponse : BaseResponse { public int NewUserId { get; set; } } My questions are: Do I need to add the DataContract attribute to both the abstract class and the subclass? If the abstract class does not need the DataContract attribute, can I add the DataMember attribure to its properties?

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  • Is there a general concrete implementation of a KeyedCollection?

    - by CodeSavvyGeek
    The System.Collections.ObjectModel.KeyedCollection class is a very useful alternative to System.Collections.Generic.Dictionary, especially when the key data is part of the object being stored or you want to be able to enumerate the items in order. Unfortunately, the class is abstract, and I am unable to find a general concrete implementation in the core .NET framework. The Framework Design Guidlines book indicates that a concrete implementation should be provided for abstract types (section 4.4 Abstract Class Design). Why would the framework designers leave out a general concrete implementation of such a useful class, especially when it could be provided by simply exposing a constructor that accepts and stores a Converter from the item to its key: public class ConcreteKeyedCollection : KeyedCollection { private Converter getKeyForItem = null; public GenericKeyedCollection(Converter getKeyForItem) { if (getKeyForItem == null) { throw new ArgumentNullException("getKeyForItem"); } this.getKeyForItem = getKeyForItem; } protected override TKey GetKeyForItem(TItem item) { return this.getKeyForItem(item); } }

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  • Using injected EntityManager in class hierarchies

    - by Emre Sahin
    The following code works: @Stateless @LocalBean public class MyClass { @PersistenceContext(name = "MyPU") EntityManager em; public void myBusinessMethod(MyEntity e) { em.persist(e); } } But the following hierarchy gives a TransactionRequiredException in Glassfish 3.0 (and standard JPA annotations with EclipseLink.) at the line of persist. @Stateless @LocalBean public class MyClass extends MyBaseClass { public void myBusinessMethod(MyEntity e) { super.update(e); } } public abstract class MyBaseClass { @PersistenceContext(name = "MyPU") EntityManager em; public void update(Object e) { em.persist(e); } } For my EJB's I collected common code in an abstract class for cleaner code. (update also saves who did the operation and when, all my entities implement an interface.) This problem is not fatal, I can simply copy update and sister methods to subclasses but I would like to keep all of them together in a single place. I didn't try but this may be because my base class is abstract, but I would like to learn a proper method for such a (IMHO common) use case.

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