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• Unable to specify abstract classes in TPH hierarchy in Entity Framework 4

  - by Lee Atkinson

  Hi I have a TPH heirachy along the lines of: A-B-C-D A-B-C-E A-F-G-H A-F-G-I I have A as Abstract, and all the other classes are concrete with a single discriminator column. This works fine, but I want C and G to be abstract also. If I do that, and remove their discriminators from the mapping, I get error 3034 'Two entities with different keys are mapped to the same row'. I cannot see how this statement can be correct, so I assume it's a bug in some way. Is it possible to do the above? Lee

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• Best XML Based Database

  - by monmonja

  I had been assigned to develop a system on where we would get a XML from multiple sources (millions of xml) and put them in some database like and judging from the xml i would receive, there wont be any concrete structure even if they are from the same source. With this reason i think i cannot suggest RDMS and currently looking at NoSQL databases. We need a system that could do CRUD and is fast on Read. I had been looking at MarkLogic and eXist, which are both XML based NoSQL databases, have anyone had experience with them? and any other suggestion? Thanks

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• Using implicit conversion as a substitute for multiple inheritance in .NET

  - by Daniel Plaisted

  I have a situation where I would like to have objects of a certain type be able to be used as two different types. If one of the "base" types was an interface this wouldn't be an issue, but in my case it is preferable that they both be concrete types. I am considering adding copies of the methods and properties of one of the base types to the derived type, and adding an implicit conversion from the derived type to that base type. Then users will be able treat the derived type as the base type by using the duplicated methods directly, by assigning it to a variable of the base type, or by passing it to a method that takes the base type. It seems like this solution will fit my needs well, but am I missing anything? Is there a situation where this won't work, or where it is likely to add confusion instead of simplicity when using the API?

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• Factory Method Pattern using Generics-C#

  - by nanda

  Just I am learning Generics.When i have an Abstract Method pattern like : //Abstract Product interface IPage { string pageType(); } //Concerete Product 1 class ResumePage : IPage { public string pageType() { return "Resume Page"; } } //Concrete Product 2 class SummaryPage : IPage { public string pageType() { return "SummaryPage"; } } //Fcatory Creator class FactoryCreator { public IPage CreateOnRequirement(int i) { if (i == 1) return new ResumePage(); else { return new SummaryPage(); } } } //Client/Consumer void Main() { FactoryCreator c = new FactoryCreator(); IPage p; p = c.CreateOnRequirement(1); Console.WriteLine("Page Type is {0}", p.pageType()); p = c.CreateOnRequirement(2); Console.WriteLine("Page Type is {0}", p.pageType()); Console.ReadLine(); } how to convert the code using generics?

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• Using thrift with PHP and Java

  - by Christopher McCann

  I am getting myself a bit confused about how to go about this. My plan is to use PHP to perform the final page construction and this PHP web app will contact multiple services, which i will also to develop, for the data. Lets say one of those services was done in Java. I would define a Java interface which was implemented by a concrete class. This is where I get confused - how does Thrift link the PHP web app with the java service or am I getting totally mixed up?? Thanks

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• WCF issues with KnownType for Dictionary

  - by Tom Frey

  Hi, I have a service that implements the following DataMember: [DataMember] public Dictionary<string, List<IOptionQueryResult>> QueryResultItems { get; set; } I have the class "OptionQuerySingleResult" which inherits from IOptionQueryResult. Now, I understand that I need to make the OptionQueryResult type "known" to the Service and thus tried to add the KnownType in various ways: [KnownType(typeof(Dictionary<string, OptionQuerySingleResult[]>))] [KnownType(typeof(Dictionary<string, List<OptionQuerySingleResult>>))] [KnownType(typeof(OptionQuerySingleResult)] However, none of those approaches worked and on the client side I'm either getting that deserialization failed or the server simply aborted the request, causing a connection aborted error. Does anyone have an idea on what's the proper way to get this to work? I'd like to add, the if I change the QueryResultItems definition to use the concrete type, instead of the interface, everything works just fine. Thanks, Tom

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• In python: how to apply itertools.product to elements of a list of lists

  - by Guilherme Rocha

  I have a list of arrays and I would like to get the cartesian product of the elements in the arrays. I will use an example to make this more concrete... itertools.product seems to do the trick but I am stuck in a little detail. arrays = [(-1,+1), (-2,+2), (-3,+3)]; If I do cp = list(itertools.product(arrays)); I get cp = cp0 = [((-1, 1),), ((-2, 2),), ((-3, 3),)] But what I want to get is cp1 = [(-1,-2,-3), (-1,-2,+3), (-1,+2,-3), (-1,+2,+3), ..., (+1,+2,-3), (+1,+2,+3)]. I have tried a few different things: cp = list(itertools.product(itertools.islice(arrays, len(arrays)))); cp = list(itertools.product(iter(arrays, len(arrays)))); They all gave me cp0 instead of cp1. Any ideas? Thanks in advance.

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• Pipe implementation

  - by nunos

  I am trying to implement a linux shell that supports piping. I have already done simple commands, commands running in background, redirections, but piping is still missing. I have already read about it and seen some snippets of code, but still haven't been able to sort out a working solution. What I have so far: int fd[2]; pid_t pid = fork(); if (pid == -1) return -1; if (pid == 0) { dup2(0, fd[0]); execlp("sort", "sort", NULL); } I am a novice programmer, as you can probably tell, and when I am programming something I don't know much about, this being obviously the case, I like to start with something really easy and concrete and then build from there. So, before being able to implement three and more different commands in pipeline, I would like to be able to compute "ls names.txt | sort" or something similiar, in which names.txt is a file of names alfabetically unordered. Thanks.

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• Can't select View Content dropdown when adding view in MVC using Interfaces

  - by fearofawhackplanet

  I have my Model defined externally in two projects - a Core project and an Interface project. I am opening the Add View dialogue from my controller, and selecting Create a strongly typed view. In the drop down list, I can select the concrete types like MyProject.Model.Core.OrderDetails, but the interface types like MyProject.Model.Interface.IOrderDetails aren't there. I can type the interface class in manually and everything works, but then the View content menu that lets you select the Create, Delete, List, etc scaffolding is disabled. Is there some problem with using interfaces in MVC? Or is it something else I'm missing?

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• UITableView and keyboard scrolling problem

  - by Jonathan

  after a lot of trial and error, I'm giving up and asking the question. I've seen a lot of people with similar problems but can't get all the answers to work right. I have a UITableView which is composed of custom cells. The cells are made of 5 text fields next to each other (sort of like a grid). When I try to scroll and edit the cells at the bottom of the UITableView, I can't manage to get my cells properly positioned above the keyboard. I have seen many answers talking about changing view sizes,etc... but none of them has worked nicely so far. Could anybody clarify the "right" way to do this with a concrete code example? Thanks in advance, Jonathan

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• How do I create a reusable WF sequential workflow?

  - by djgiard

  I have two customers that have the same workflow (Create file -transport file - wait for response - send response to internal team); however the implementation of each step is different for each customer. For example, one customer requires a flat file to be sent via SFTP, while the other customer requires an XML file to be sent via FTP. I'd like to create a sequential workflow, using Microsoft Workflow Foundation (WF) and reuse this workflow for multiple vendors. Each action's call to an external module can use the same interface, but a different concrete implementation. However, I'm unfamiliar with WF and I'm not sure how to implement this. Can someone point me to the proper way to use this pattern? Will it make a difference whether I choose WF 3.5 or WF 4.0? Thank you.

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• Guice + Quartz + iBatis

  - by DroidIn.net

  I'm trying to wire together Guice (Java), Quartz scheduler and iBatis (iBaGuice) to do the following: Start command line utility-scanner using main() Periodically scan directory (provided as argument) for files containing formatted output (XML or YAML) When file is detected, parse and output result to the database The problems: I used this example to wire Guice and Quartz. However I'm missing some important details which I'm asking in the comments but the post is somewhat dated so I'm quoting it here also: It's not obvious how to set-up the scheduler. Where and how would I wire the Trigger (I can use Trigger#makeMinutelyTrigger)? I really have just one type of job I will be executing, I understand that details in the JobFactory#newJob are coming from the TriggerFiredBundle parameter but where/how do I wire that? And where/how do I create or wire concrete Job?

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• What is the best API/framework/platform you ever worked with?

  - by Yuval A

  Most programming is done on an existing framework or platform, and using various APIs which make your programming job much more convenient. It can either be a superbly designed set of APIs, or a nice framework which you managed to get really cool things done really fast. All answers should give concrete examples of why that framework is so awesome, or examples of cool stuff you did with it. What existing framework really inspired you to do some awesome work? I know this is subjective, but I think we can get some cool ideas from this question. Please be easy on the "close" link :) Also - commun-ikified in advance.

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• C#/ASP.NET MVC 4 Instantiate Object Derived From Interface In Factory Method

  - by Chris

  Currently have a Factory class that features a GetSelector function, which returns a concrete implementation of ISelector. I have several different classes that implement ISelector and based on a setting I would like to receive the appropriate ISelector back. public interface ISelector { string GetValue(string Params); } public class XmlSelector : ISelector { public string GetValue(string Params) { // open XML file and get value } } public static class SelectorFactory { public static ISelector GetSelector() { return new XmlSelector(); // Needs changing to look at settings } } My question is what is the best way to store the setting? I am aware of using AppSettings etc. but I'm not sure whether I want to have to store strings in the web.config and perform a switch on it - just seems to be really tightly coupled in that if a new implementation of ISelector is made, then the Factory would need to be changed. Is there any way of perhaps storing an assembly name and instantiating based on that? Thanks, Chris

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• Stream (.NET) handling best-practices

  - by Jader Dias

  The question is entitled with the word "Stream" because the question below is a concrete example of a more generic doubt I have about Streams: I have a problem that accepts two solutions and I want to know the best one: I download a file, save it to disk (2 min), read it and write the contents to the DB (+ 2 min). I download a file and write the contents directly to the DB (3 min). If the write to DB fails I'll have to download again in the second case, but not in the first case. Which is best? Which would you use?

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• Java Polymorphism - Selecting correct method based on subtype

  - by Marty Pitt

  Hi Given the following Class and Service layer signatures: public class PersonActionRequest { PersonVO person // ... other fields } public class MyServiceLayerClass { public void requestAction(PersonActionRequest request) { PersonVO abstractPerson = request.getPerson(); // call appropriate executeAction method based on subclass of PersonVO } private void executeAction(PersonVO person) {} private void executeAction(EmployeeVO employee) {} private void executeAction(ManagerVO manager) {} private void executeAction(UnicornWranglerVO unicornWrangler) {} } As discussed here, java will select the best method based on type info at compile time. (Ie., it will always select executeAction(PersonVO person) ). What's the most appropriate way to select the correct method? The internet tells me that using instanceof gets me slapped. However, I don't see the appropraite way to select the method without explictly casting abstractPerson to one of the other concrete types. Thanks Marty

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• groovy call private method in Java super class

  - by Jeff Storey

  I have an abstract Java class MyAbstractClass with a private method. There is a concrete implementation MyConcreteClass. public class MyAbstractClass { private void somePrivateMethod(); } public class MyConcreteClass extends MyAbstractClass { // implementation details } In my groovy test class I have class MyAbstractClassTest { void myTestMethod() { MyAbstractClass mac = new MyConcreteClass() mac.somePrivateMethod() } } I get an error that there is no such method signature for somePrivateMethod. I know groovy can call private methods but I'm guessing the problem is that the private method is in the super class, not MyConcreteClass. Is there a way to invoke a private method in the super class like this (other than using something like PrivateAccessor)? thanks Jeff

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• How do I implement a custom Brush in WPF?

  - by MojoFilter

  Where can I find out enough info about how Brushes work to implement my own System.Windows.Media.Brush? I can handle all of the freezable baggage, but it's not really obvious what I need to override to get it to work. Yeah, so I didn't mean that I want to use a predefined brush. I want to extend System.Windows.Media.Brush, which is an abstract class. This is all purely for my own edification. I'm not even sure what kind of brush I could make. I was just trying to learn how brushes work. As in: public AwesomeBrush : Brush { protected override Freezable CreateInstanceCore() { return new AwesomeBrush(); } ... // concrete brush stuff }

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• It's possible to don't pass in GET some fields of a form?

  - by avastreg

  I have a form with some input texts passed in GET, and i don't want to have in GET all the fields; i want to avoid empty fields. So, a concrete example for: <form method="GET" action="an_url"> <input type="text" name="field1"/> <input type="text" name="field2"/> <input type="text" name="field3"/> <input type="submit" value="submit"/> </form> I supposed that fields disabled by html attribute "disabled" shouldn't be passed to GET. So i have done a js (based on jquery) to disable empty fields on submit, something like this: $("form").submit(function() { $(this).find("input[type=text]").each( function () { if (!$.trim($(this).val())) { $(this).attr("disabled", "true"); } }); }); However, this doesn't work. Any ideas?

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• how to debug SIGSEGV in jvm GCTaskThread

  - by ekeren

  Hi, My application is experiencing cashes in production. The crash dump indicates a SIGSEGV has occurred in GCTaskThread It uses JNI, so there might be some source for memory corruption, although I can't be sure. How can I debug this problem - I though of doing -XX:OnError... but i am not sure what will help me debug this. Also, can some of you give a concrete example on how JNI code can crash GC with SIGSEGV EDIT: OS:SUSE Linux Enterprise Server 10 (x86_64) vm_info: Java HotSpot(TM) 64-Bit Server VM (11.0-b15) for linux-amd64 JRE (1.6.0_10-b33), built on Sep 26 2008 01:10:29 by "java_re" with gcc 3.2.2 (SuSE Linux)

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• Struts2 dynamic form elements

  - by bozo

  Hi, I would like to create little higer-level framework on top of Stuts2 which can take form element description from Action and render a complete form, in order to avoid having a separate JSP files with hardcoded form elements for every form in a large web application (so if I manage to do this I will have just a few generic JSPs for data form and few for layout). Application is extremely data-driven. My idea is to create form description using custom objects in the Action (i.e. Button, TextInput etc.) and then to create a single JSP page that will render eveything out. What is the best way of doing this? Can you propose some concrete way to do this? I don't want to write something if I can reuse the existing code with some effort. Any ideas are appreciated. Kind regards, Bozo

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• Java - binary compatibility of abstract class & subclasses

  - by thSoft

  In Java, I define an abstract class with both concrete and abstract methods in it, and it has to be subclassed independently by third-party developers. Just to be sure: are there any changes I could make to the abstract class that are source compatible with their classes but not binary compatible? In other words: after they have compiled their subclasses, could I change the abstract class - apart from e.g. adding an abstract method to it or removing a protected method from it that is called by subclasses, which are of course source incompatible - in a way that could force them to recompile their subclasses?

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• Specification, modeling and programming are principially the same, right?

  - by Gabriel Šcerbák

  In formal specifications based on abstract algebraic types and equational theory you use formulas of equational theory to specify theory. System which will satisfy those constraints is called in formal logic a model. Modeling is process of creating a model, which abstracts of some aspects, which are unnecessary details for a specific case. So concrete system has to adhere to created model in observed aspects. Programming is a process of creating a program which will have specific behaviour - will perform specific algorithms - and programming languages through different paradigms enable us to think in a certain specific way, which abstracts of some details, usually machine specific ones. So could we be doing all those things at the same time, because they are principially the same? Is declarative programming the nearest attempt to do that? Could we use some sort f programming languages which will be good for programming as well as for modeling and specification?

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• Variable alpha blending in pylab

  - by Hooked

  How does one control the transparency over a 2D image in pylab? I'd like to give two sets of values (X,Y,Z,T) where X,Y are arrays of positions, Z is the color value, and T is the transparency to a function like imshow but it seems that the function only takes alpha as a scalar. As a concrete example, consider the code below that attempts to display two Gaussians. The closer the value is to zero, the more transparent I'd like the plot to be. from pylab import * side = linspace(-1,1,100) X,Y = meshgrid(side,side) extent = (-1,1,-1,1) Z1 = exp(-((X+.5)**2+Y**2)) Z2 = exp(-((X-.5)**2+(Y+.2)**2)) imshow(Z1, cmap=cm.hsv, alpha=.6, extent=extent) imshow(Z2, cmap=cm.hsv, alpha=.6, extent=extent) show() Note: I am not looking for a plot of Z1+Z2 (that would be trivial) but for a general way to specify the alpha blending across an image.

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• C++: Declaration of template class member specialization (+ Doxygen bonus question!)

  - by Ziv

  When I specialize a (static) member function/constant in a template class, I'm confused as to where the declaration is meant to go. Here's an example of what I what to do - yoinked directly from IBM's reference on template specialization: template<class T> class X { public: static T v; static void f(T); }; template<class T> T X<T>::v = 0; template<class T> void X<T>::f(T arg) { v = arg; } template<> char* X<char*>::v = "Hello"; template<> void X<float>::f(float arg) { v = arg * 2; } int main() { X<char*> a, b; X<float> c; c.f(10); // X<float>::v now set to 20 } The question is, how do I divide this into header/cpp files? The generic implementation is obviously in the header, but what about the specialization? It can't go in the header file, because it's concrete, leading to multiple definition. But if it goes into the .cpp file, is code which calls X::f() aware of the specialization, or might it rely on the generic X::f()? So far I've got the specialization in the .cpp only, with no declaration in the header. I'm not having trouble compiling or even running my code (on gcc, don't remember the version at the moment), and it behaves as expected - recognizing the specialization. But A) I'm not sure this is correct, and I'd like to know what is, and B) my Doxygen documentation comes out wonky and very misleading (more on that in a moment). What seems most natural to me would be something like this, declaring the specialization in the header and defining it in the .cpp: ===XClass.hpp=== #ifndef XCLASS_HPP #define XCLASS_HPP template<class T> class X { public: static T v; static void f(T); }; template<class T> T X<T>::v = 0; template<class T> void X<T>::f(T arg) { v = arg; } /* declaration of specialized functions */ template<> char* X<char*>::v; template<> void X<float>::f(float arg); #endif ===XClass.cpp=== #include <XClass.hpp> /* concrete implementation of specialized functions */ template<> char* X<char*>::v = "Hello"; template<> void X<float>::f(float arg) { v = arg * 2; } ...but I have no idea if this is correct. The most immediate consequence of this issue, as I mentioned, is my Doxygen documentation, which doesn't seem to warm to the idea of member specialization, at least the way I'm defining it at the moment. It will always present only the first definition it finds of a function/constant, and I really need to be able to present the specializations as well. If I go so far as to re-declare the entire class, i.e. in the header: /* template declaration */ template<class T> class X { public: static T v; static void f(T); }; /* template member definition */ template<class T> T X<T>::v = 0; template<class T> void X<T>::f(T arg) { v = arg; } /* declaration of specialized CLASS (with definitions in .cpp) */ template<> class X<float> { public: static float v; static void f(float); }; then it will display the different variations of X as different classes (which is fine by me), but I don't know how to get the same effect when specializing only a few select members of the class. I don't know if this is a mistake of mine, or a limitation of Doxygen - any ideas? Thanks much, Ziv

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