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• 'Forward-Compatible' Program Design

  - by Jeffrey Kern

  The majority of my questions I've asked here so far on StackOverflow have been how to implement individual concepts and techniques towards developing a software-based NES clone via the XNA environment. The small samples that I've thrown together on my PC work relatively great and everything. Except I hit a brick wall. How do I merge all of these samples together. Having proof-of-concept is amazing, except when you need it to go beyond just that. I now have samples strewn about that I'm trying to merge, some of them incomplete. And now I'm stuck with the chicken-and-the-egg situation of where I would like to incorporate these samples together, to make sure they work, but I cannot without test data. And I don't have tools to create test data, because they'd need to be based off of the individual pieces that need to be put together. In my mind, I'm having nightmares with circular reference. For my sample data, I am hoping to save it in XML and write a specification - and then make sample data by hand - but I'm too paranoid of manually creating an XML file full of incorrect data and blaming it on my code, or vice-versa. It doesn't help that the end-result of my work is graphic-oriented, which makes it interseting how a graphic on the screen can be visualized in XML Nodes. I guess, my question is this: What design patterns and disciplines exist in the coding world that address this type of concern? I've always relied on brute-force coding and restarting a project with a whole new code base in attempts to further along my goals, but I doubt that would be the best way to do so. Within my college career, the majority of my programming was to work on simple projects that came out of a book, or with a given correct data set and a verifyable result. I don't have that, as my own design documents that I am going by could be terribly wrong.

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• Manage multiple UDP calls

  - by rayman

  Hi all, I would like to have an advice for this issue: I am using Jbos 5.1.0, EJB3.0 I have system, which sending requests via UDP'S to remote modems, and suppose to wait for an answer from the target modem. the remote modems support only UDP calls, therefor I o design asynchronous mechanism. (also coz I want to request X modems parallel) this is what I try to do: all calls are retrieved from Data Base, then each call will be added as a message to JMS QUE. let's say i will set X MDB'S on that que, so I can work asynchronous. now each MDB will send UDP request to the IP-address(remote modem) which will be parsed from the que message. so basicly each MDB, which takes a message is sending a udp request to the remote modem and [b]waiting [/b]for an answer from that modem. [u]now here is the BUG:[/u] could happen a scenario where MDB will get an answer, but not from the right modem( which it requested in first place). that bad scenario cause two wrong things: a. the sender which sent the message will wait forever since the message never returned to him(it got accepted by another MDB). b. the MDB which received the message is not the right one, and probablly if it was on a "listener" mode, then it supposed to wait for an answer from diffrent sender.(else it wouldnt get any messages) so ofcourse I can handle everything with a RETRY mechanisem. so both mdb's(the one who got message from the wrong sender, and the one who never got the answer) will try again, to do thire operation with a hope that next time it will success. This is the mechanism, mybe you could tell me if there is any design pattren, or any other effective solution for this problem? Thanks, ray.

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• Too many open files in one of my java routine.

  - by Irfan Zulfiqar

  I have a multithreaded code that has to generated a set of objects and write them to a file. When I run it I sometime get "Too many open files" message in Exception. I have checked the code to make sure that all the file streams are being closed properly. Here is the stack trace. When I do ulimit -a, open files allowed is set to 1024. We think increasing this number is not a viable option / solution. [java] java.io.FileNotFoundException: /export/event_1_0.dtd (Too many open files) [java] at java.io.FileInputStream.open(Native Method) [java] at java.io.FileInputStream.<init>(FileInputStream.java:106) [java] at java.io.FileInputStream.<init>(FileInputStream.java:66) [java] at sun.net.www.protocol.file.FileURLConnection.connect(FileURLConnection.java:70) [java] at sun.net.www.protocol.file.FileURLConnection.getInputStream(FileURLConnection.java:161) [java] at java.net.URL.openStream(URL.java:1010) Now what we have identified so far by looking closely at the list of open files is that the VM is opening same class file multiple times. /export/BaseEvent.class 236 /export/EventType1BaseEvent.class 60 /export/EventType2BaseEvent.class 48 /export/EventType2.class 30 /export/EventType1.class 14 Where BaseEvent is partent of all the classes and EventType1 ant EventType2 inherits EventType1BaseEvent and EventType2BaseEvent respectively. Why would a class loader load the same class file 200+ times. It seems it is opening up the base class as many time it create any child instance. Is this normal? Can it be handler any other way apart from increasing the number of open files?

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• How to pass a function in a function?

  - by SoulBeaver

  That's an odd title. I would greatly appreciate it if somebody could clarify what exactly I'm asking because I'm not so sure myself. I'm watching the Stanford videos on Programming Paradigms(that teacher is awesome) and I'm up to video five when he started doing this: void *lSearch( void* key, void* base, int elemSize, int n, int (*cmpFn)(void*, void*)) Naturally, I thought to myself, "Oi, I didn't know you could declare a function and define it later!". So I created my own C++ test version. int foo(int (*bar)(void*, void*)); int bar(void* a, void* b); int main(int argc, char** argv) { int *func = 0; foo(bar); cin.get(); return 0; } int foo(int (*bar)(void*, void*)) { int c(10), d(15); int *a = &c; int *b = &d; bar(a, b); return 0; } int bar(void* a, void* b) { cout << "Why hello there." << endl; return 0; } The question about the code is this: it fails if I declare function int *bar as a parameter of foo, but not int (*bar). Why!? Also, the video confuses me in the fact that his lSearch definition void* lSearch( /*params*/ , int (*cmpFn)(void*, void*)) is calling cmpFn in the definition, but when calling the lSearch function lSearch( /*params*/, intCmp ); also calls the defined function int intCmp(void* elem1, void* elem2); and I don't get how that works. Why, in lSearch, is the function called cmpFn, but defined as intCmp, which is of type int, not int* and still works? And why does the function in lSearch not have to have defined parameters?

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• How do I POST/GET from rails to API with either ActiveResource or rest-client (preferred)?

  - by Angela

  Hi, this is a pretty basic question but I'm not entirely clear how to do this. I am trying to use a third-party service that has RESTful service. The service is called Postful. But I'm not clear what exactly to do? I've looked at ActiveResource (http://api.rubyonrails.org/classes/ActiveResource/Base.html) and rest-client, but I'm still not clear exactly what steps, code, and files to create. http://www.postful.com/service/mail is one of the services (details found http://www.postful.com/developer/guide#rest ), but to upload an image I have to post the following (but I'm not sure how I actually do this?). Thanks! > http://www.postful.com/service/upload > > Be sure to include the Content-Type > and Content-Length headers and the > image itself as the body of the > request. > > POST /upload HTTP/1.0 Content-Type: > application/octet-stream > Content-Length: 301456 > > ... file content here ... > > If the upload is successful, you will > receive a response like the following: > > <?xml version="1.0" encoding="UTF-8"?> > <upload> > <id>290797321.waltershandy.2</id> > </upload>

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• Simplifying Testing through design considerations while utilizing dependency injection

  - by Adam Driscoll

  We are a few months into a green-field project to rework the Logic and Business layers of our product. By utilizing MEF (dependency injection) we have achieved high levels of code coverage and I believe that we have a pretty solid product. As we have been working through some of the more complex logic I have found it increasingly difficult to unit test. We are utilizing the CompositionContainer to query for types required by these complex algorithms. My unit tests are sometimes difficult to follow due to the lengthy mock object setup process that must take place, just right, to allow for certain circumstances to be verified. My unit tests often take me longer to write than the code that I'm trying to test. I realize this is not only an issue with dependency injection but with design as a whole. Is poor method design or lack of composition to blame for my overly complex tests? I've tried base classing tests, creating commonly used mock objects and ensuring that I utilize the container as much as possible to ease this issue but my tests always end up quite complex and hard to debug. What are some tips that you've seen to keep such tests concise, readable, and effective?

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• Why does this JavaScript not correctly update input values?

  - by dmanexe

  I have two input fields, and without changing their names (i.e., I have to use the name with the brackets), how do I make this javascript code work? <script> function calc_concreteprice(mainform) { var oprice; var ototal; oprice = (eval(mainform.'estimate[concrete][sqft]'.value) * eval(mainform.'estimate[concrete][price]'.value)); ototal = (oprice); mainform.'estimate[concrete][quick_total]'.value = ototal; } </script> Here's the HTML of the input area. <tr> <td>Concrete Base Price</td> <td><input type="text" name="concrete[concrete][price]" value="" class="item_mult" onBlur="calc_concreteprice(document.forms.mainform);" /> per SF <strong>times</strong> <input type="text" name="concrete[concrete][sqft]" value="" class="item_mult" onBlur="calc_concreteprice(document.forms.mainform);" /> SF</td> <td> = <input type="text" name="concrete[concrete][quick_total]" value="" /></td> </tr> I know I can get it working by changing_the_input_name_with_underscores but I need to have the names with the brackets (storing the form contents in an array).

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• WPF View/ViewModels using Generics- how?

  - by Investor5555

  New to WPF, so please bear with me... Suppose I have 2 tables in SQL Thing OtherThing Both have the exact same fields: ID (int) Name (string) Description (string) IsActive (bit/bool) DateModified (DateTime) So, I want to create one Model (not two) and do something like this: BaseModel<T>() { public int ID {get;set;} ... } etc. (of course, using the INotifyPropertyChanged, just trying to keep the code simple). I want to be able to create a BaseView and BaseViewModel that would work with whatever model conforms to the Thing/OtherThing. I am really at a loss as to what to do here to make this generic, so I don't have to have a ThingView/ThingViewModel and a OtherThingView/OtherThingViewModel... It seems that this should be simple, but I cannot seem to figure it out. Does anyone have a code example where they could interchange various items from a dropdown list using one view, one ViewModel, and one base datamodel (and switching out the type from a dropdown)? For example, a combobox has 3 identical table structures for Thing OtherThing SomeThing and on selection changed, I want to pull the data from whatever table was selected, to be able to do standard CRUD operations on any of these 3 tables, without having to create concrete classes for each view/viewmodel.

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• Nhibernate fires SQL commands

  - by Chris

  Hi all, when updating an entity A, NHibernate also send an SQL update command for some other entity B. A and B are not related. Just before saving entity A, the parent of entity B is loaded via a SQLQuery. Then, when accessed, B is lazy loaded (part of a collection). If I save entity A an update statement for entity B is generated as well. How can that be, that when saving an entity, another entity loaded before but is not related to the entity saved, is updated as well?! Can I somehow track where the update comes from? Btw. I am using an save event listener. Could it be that this is always triggered for entity loaded, even though they are not saved explicitly? public class EntitySaveEventListener : NHibernate.Event.Default.DefaultSaveEventListener { protected override object PerformSaveOrUpdate(SaveOrUpdateEvent e) { //auditing return base.PerformSaveOrUpdate(e); } } Update (sorry for providing not enough info): I tracked it down a bit. A select stateement on a entity called address is executed (is it lazy loaded by a parent). Then I create a new entity called Request. Right before saving this entity a session flush is called which updates the address, even though I did not call save or update on the address. Address is a collection within Request. <class name="Request" table="Request"> <bag name="addresses" access="field" cascade="all-delete-orphan" where="IsDeleted = 0"> <key column="RequestId"/> <one-to-many class="Address"/> </bag> ... // address is fetched only NHibernate.SQL: 2010-02-17 11:47:21,306 [21] DEBUG NHibernate.SQL [(null)] - SELECT addresses0_.RequestId as ServiceP8_3_, .... // session flushed here // address is updated NHibernate.SQL: 2010-02-17 11:47:34,306 [21] DEBUG NHibernate.SQL [(null)] - Batch commands: command 0:UPDATE Address SET Street = @p0, ..... Would the address be updated automatically when it is manipulated somehow even though it is not explicitly saved via it's parent (cascade)?

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• Which is the better C# class design for dealing with read+write versus readonly

  - by DanM

  I'm contemplating two different class designs for handling a situation where some repositories are read-only while others are read-write. (I don't foresee any need to a write-only repository.) Class Design 1 -- provide all functionality in a base class, then expose applicable functionality publicly in sub classes public abstract class RepositoryBase { protected virtual void SelectBase() { // implementation... } protected virtual void InsertBase() { // implementation... } protected virtual void UpdateBase() { // implementation... } protected virtual void DeleteBase() { // implementation... } } public class ReadOnlyRepository : RepositoryBase { public void Select() { SelectBase(); } } public class ReadWriteRepository : RepositoryBase { public void Select() { SelectBase(); } public void Insert() { InsertBase(); } public void Update() { UpdateBase(); } public void Delete() { DeleteBase(); } } Class Design 2 - read-write class inherits from read-only class public class ReadOnlyRepository { public void Select() { // implementation... } } public class ReadWriteRepository : ReadOnlyRepository { public void Insert() { // implementation... } public void Update() { // implementation... } public void Delete() { // implementation... } } Is one of these designs clearly stronger than the other? If so, which one and why? P.S. If this sounds like a homework question, it's not, but feel free to use it as one if you want :)

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• WebService Stubs WSDL Axis2

  - by tt0686

  Good afternoon in my timezone. I have a wsdl file with the following snippet of code: <schema targetNamespace="http://util.cgd.pt" xmlns="http://www.w3.org/2001/XMLSchema"> <import namespace="http://schemas.xmlsoap.org/soap/encoding/" /> <complexType name="Attribute"> <sequence> <element name="fieldType" nillable="true" type="xsd:string" /> <element name="dataType" nillable="true" type="xsd:string" /> <element name="name" nillable="true" type="xsd:string" /> <element name="value" nillable="true" type="xsd:string" /> </sequence> </complexType> <complexType name="ArrayOffAttribute"> <complexContent> <restriction base="soapenc:Array"> <attribute ref="soapenc:arrayType" wsdl:arrayType="tns3:Attribute[]" /> </restriction> </complexContent> </complexType> When i use jax-rpc or Axis1 to generate the stubs the type Attribute is generated, but when i use Axis2 the type Attribute is not generated and a new type is created ArrayOffAttribute, this new type extends the axis2.databinding.types.soapencoding.Array and permits to add elements through the array.addObject(object), my question is, i am migrating one Java EE application from webservices using jax-rpc to start using Axis2, and the methods are using the Attribute type to fullfill attributes fields, now in Axis2 and do not have attribute type , what should i use in the ArrayOffAttribute.addObject(?) ? Could be something wrong with Axis2 ? i am stop here :( Thanks in advance Best regards

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• SQL, MVC, Entity Framework

  - by Anthony

  Hi Im using the above technologies and have ran into what I presume is a design issue I have made. I have an Artwork table in my DB and have been able to add art (I now think of these as Digital Products) to a shopping cart + CartLine table fine. The system I have that adds art to galleries and user accounts etc works fine. Now the client wants to sell T-shirts, Mugs and Pens etc, 'HardwareProducts' so I have created a 'HardwareProducts' table. Now I have two different product types in two tables. I use GUID's as the PK's in both the HardwareProducts table and Artwork table. When a customer adds an item to their cart I store the GUID in the ProductID column in the CartItems table. The issue is the database will not know which table to reference when I bring the LineItem object up through my ORM to the front end. In OOP I can see how you would have a base class of Product, and then a DigitalProduct class and HardwareProduct class drived from it, but how do you model this in SQL Server and the Entity Framework please, or is there another way?

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• TFS How does merging work?

  - by Johannes Rudolph

  I have a release branch (RB, starting at C5) and a changeset on trunk (C10) that I now want to merge onto RB. The file has changes at C3 (common to both), one in CS 7 on RB, and one in C9 (trunk) and one in C10). So the history for my changed file looks like this: RB: C5 -> C7 Trunk: C3 -> C9 -> C10 When I merge C10 from trunk to RB, I'd expect to see a merge window showing me C10 | C3 | C7 since C3 is the common ancestor revision and C10 and C7 are the tips of my two branches respectively. However, my merge tool shows me C10 | C9 | C7. My merge tool is configured to show %1(OriginalFile)|%3(BaseFile)|%2(Modified File), so this tells me TFS chose C9 as the base revision. This is totally unexpected and completely contrary to the way I'm used to merges working in Mercurial or Git. Did I get something wrong or is TFS trying to drive me nuts with merging? Is this the default TFS Merge behavior? If so, can you provide insight into why they chose to implement it this way? I'm using TFS 2008 with VS2010 as a Client.

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• Fun with "The remote server returned an error: NotFound" - Silverlight4 Out of Browser

  - by Scott Silvi

  Hey all - I'm running SL4 on VS2010. I've got an app that authenticates via a web service to SPROC in my db. Unfortunately this is not WCF/WCF RIA, as I'm inheriting the DB/services from my client. This works perfectly inside of a browser. I'm attempting to move this OOB, and it's at this point that my authentication fails. Here's the steps I took... 1) SL App Properties Enable running app Out of Browser 2) SL App Properties Out of Browser Settings Require elevated trust when running OOB If i set a breakpoint on my logon button click, I see the service call is being made. However, if I step through it (or set a breakpoint on the actual logon web service), the code never gets that far. Here's the block it fails on: public LogonSVC.LogonResponse EndLogon(System.IAsyncResult result) { object[] _args = new object[0]; LogonSVC.LogonResponse _result = ((LogonSVC.LogonResponse)(base.EndInvoke("Logon", _args, result))); return _result; } I know using Elevated Trust means the crossdomain.xml isn't necessary. I dropped one in that allows everything, just to test, and that still fails. here's the code that calls the service: private void loginButton_Click(object sender, RoutedEventArgs e) { string Username = txtUserName.Text; string Password = txtPassword.Password; Uri iSilverlightServiceUriRelative = new Uri(App.Current.Host.Source, "../Services/Logon.asmx"); EndpointAddress iSilverlightServiceEndpoint = new EndpointAddress(iSilverlightServiceUriRelative); BasicHttpBinding iSilverlightServiceBinding = new BasicHttpBinding(BasicHttpSecurityMode.Transport);// Transport if it's HTTPS:// LogonService = new LogonSVC.LogonSoapClient(iSilverlightServiceBinding, iSilverlightServiceEndpoint); LogonService.LogonCompleted += new EventHandler<LogonSVC.LogonCompletedEventArgs>(LogonService_LogonCompleted); LogonService.LogonAsync(Username, Password); } My LogonService_LogonCompleted doesn't fire either (which makes sense, just a heads up). I don't know how to fiddler this, as this is running OOB with the site served via localhost/IIS. I know this works though in browser, so I'm curious what would break it OOB. Thank you, Scott

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• How to bundle extension methods requiring configuration in a library

  - by Greg

  Hi, I would like to develop a library that I can re-use to add various methods involved in navigating/searching through a graph (nodes/relationships, or if you like vertexs/edges). The generic requirements would be: There are existing classes in the main project that already implement the equivalent of the graph class (which contains the lists of nodes / relationships), node class and relationship class (which links nodes together) - the main project likely already has persistence mechanisms for the info (e.g. these classes might be built using Entity Framework for persistance) Methods would need to be added to each of these 3 classes: (a) graph class - methods like "search all nodes", (b) node class - methods such as "find all children to depth i", c) relationship class - methods like "return relationship type", "get parent node", "get child node". I assume there would be a need to inform the library with the extending methods the class names for the graph/node/relationships table (as different project might use different names). To some extent it would need to be like how a generics collection works (where you pass the classes to the collection so it knows what they are). Need to be a way to inform the library of which node property to use for equality checks perhaps (e.g. if it were a graph of webpages the equality field to use might be the URI path) I'm assuming that using abstract base classes wouldn't really work as this would tie usage down to have to use the same persistence approach, and same class names etc. Whereas really I want to be able to, for a project that has "graph-like" characteristics, the ability to add graph searching/walking methods to it.

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• Django does not load internal .css files

  - by Rubén Jiménez

  I have created a Django project in local which runs without any kind of problem. But, after an annoying and difficult Cherokee + uWSGI installation on Amazon AWS, my project does not show Django .css internal files. http://f.cl.ly/items/2Q2W3I3R0X1n2X3v0q2P/django_error.jpg <-- /Admin/ looks like The image is a screen of my /admin/, which should have a different style, but .css files are not loaded. [pid: 23206|app: 0|req: 19/19] 83.49.10.217 () {56 vars in 1121 bytes} [Sun Apr 15 05:50:24 2012] GET /static/admin/css/base.css = generated 2896 bytes in 6 msecs (HTTP/1.1 404) 1 headers in 51 bytes (1 switches on core 0) [pid: 23206|app: 0|req: 20/20] 83.49.10.217 () {56 vars in 1125 bytes} [Sun Apr 15 05:50:24 2012] GET /static/admin/css/login.css = generated 2899 bytes in 5 msecs (HTTP/1.1 404) 1 headers in 51 bytes (1 switches on core 0) This is a log from Cherokee. I don't understand why it is looking for the .css files in that path. Cherokee should be searching the files in Django original directory so i didn't change .css files in my project. Any advice? Thanks a lot.

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• python packaging causes importerror

  - by Absolute0

  I am getting an annoying import error when I try to import a variable in an init.py file. I have attached the files involved and my directory structure: #/home/me/app/app/__init__.py from flaskext.sqlalchemy import SQLAlchemy db = SQLAlchemy(app) #/home/me/app/app/models/__init__.py from datetime import datetime from app import db #shell [me@archlinux app]$ pwd /home/me/app [me@archlinux app]$ ./manage.py /home/me/app/app/__init__.pyc Traceback (most recent call last): File "./manage.py", line 7, in <module> from app import app File "/home/me/app/app/__init__.py", line 3, in <module> from app.views.post import post File "/home/me/app/app/views/post.py", line 4, in <module> from app.models import Post File "/home/me/app/app/models/__init__.py", line 5, in <module> from app import db ImportError: cannot import name db [me@archlinux app]$ tree . +-- apikey.txt +-- manage.py +-- app ¦   +-- forms ¦   ¦   +-- __init__.py ¦   ¦   +-- __init__.py~ ¦   +-- __init__.py ¦   +-- __init__.py~ ¦   +-- __init__.pyc ¦   +-- models ¦   ¦   +-- __init__.py ¦   ¦   +-- __init__.py~ ¦   ¦   +-- __init__.pyc ¦   +-- static ¦   ¦   +-- css ¦   ¦   ¦   +-- style.css ¦   ¦   +-- images ¦   ¦   ¦   +-- favicon.png ¦   ¦   ¦   +-- logo.png ¦   ¦   ¦   +-- text_logo.png ¦   ¦   ¦   +-- thumb_down_active.png ¦   ¦   ¦   +-- thumb_down_inactive.png ¦   ¦   ¦   +-- thumb_up_active.png ¦   ¦   ¦   +-- thumb_up_inactive.png ¦   ¦   +-- js ¦   ¦   ¦   +-- index.js ¦   ¦   +-- sitemap.xml ¦   +-- templates ¦   ¦   +-- 404.html ¦   ¦   +-- 500.html ¦   ¦   +-- about.html ¦   ¦   +-- base.html ¦   ¦   +-- feedback ¦   ¦   ¦   +-- feedback_form.html ¦   ¦   +-- form.html ¦   ¦   +-- posts ¦   ¦   ¦   +-- comment.html ¦   ¦   ¦   +-- post.html ¦   ¦   ¦   +-- posts.html ¦   ¦   +-- spam.html ¦   ¦   +-- terms.html ¦   ¦   +-- users ¦   ¦   +-- login_form.html ¦   ¦   +-- sign_up_form.html ¦   +-- util ¦   ¦   +-- forms.py ¦   ¦   +-- honeypot.py ¦   ¦   +-- __init__.py ¦   ¦   +-- __init__.py~ ¦   ¦   +-- json_http.py ¦   ¦   +-- models.py ¦   ¦   +-- spam.py ¦   +-- views ¦   +-- feedback.py ¦   +-- __init__.py ¦   +-- __init__.pyc ¦   +-- post.py ¦   +-- post.pyc ¦   +-- user.py +-- settings.py +-- settings.pyc +-- TiddlyWiki.html 13 directories, 49 files What might be the problem?

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• Saving Abstract and Sub classes to database

  - by bretddog

  Hi, I have an abstract class "StrategyBase", and a set of sub classes, StrategyA/B/C etc. The sub classes use some of the properties of the base class, and have some individual properties. My question is how to save this to a database. I'm currently using SqlCE, and Linq-To-Sql by creating entity classes automatically with SqlMetal.exe. I've seen there are three solutions shown in this question, but I'm not able to see how these solutions will work or not with SqlMetal/entity classes. Though it seems to me the "concrete table inheritance" would probably work without any manual modifying. What about the other two, would they be problematic? For "Single Table Inheritance" wouldn't all classes get all variables, even though they don't need them? And for the "Class table inheritance" solution I can't really see at all how that will map into the entity-classes for a useful purpose. I may note that I extend these partial entity classes for making the classes of my business objects. I may also consider moving to EntityFramework instead of SqlMetal/Linq2Sql, so would be nice also to know if that makes any difference to what schema is easy to implement. One likely important thing to note is that I will constantly be develop new strategies, which makes me have to modify the program code, and probably the database shcema; when adding a new strategy. Sorry the question is a bit "all over the place", but hopefully it's some clear advantages/disadvantages here that you may be able to advice. ? Cheers!

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• Tricky MySQL Query for messaging system in Rails - Please Help

  - by ole_berlin

  Hi, I'm writing a facebook style messaging system for a Rails App and I'm having trouble selecting the Messages for the inbox (with will_paginate). The messages are organized in threads, in the inbox the most recent message of a thread will appear with a link to it's thread. The thread is organized via a parent_id 1-n relationship with itself. So far I'm using something like this: class Message < ActiveRecord::Base belongs_to :sender, :class_name => 'User', :foreign_key => "sender_id" belongs_to :recipient, :class_name => 'User', :foreign_key => "recipient_id" has_many :children, :class_name => "Message", :foreign_key => "parent_id" belongs_to :thread, :class_name => "Message", :foreign_key => "parent_id" end class MessagesController < ApplicationController def inbox @messages = current_user.received_messages.paginate :page => params[:page], :per_page => 10, :order => "created_at DESC" end end That gives me all the messages, but for one thread the thread itself and the most recent message will appear (and not only the most recent message). I can also not use the GROUP BY clause, because for the thread itself (the parent so to say) the parent_id = nil of course. Anyone got an idea on how to solve this in an elegant way? I already thought about adding the parent_id to the parent itself and then group by parent_id, but I'm not sure if that works. Thanks

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• Should a setter return immediately if assigned the same value?

  - by Andrei Rinea

  In classes that implement INotifyPropertyChanged I often see this pattern : public string FirstName { get { return _customer.FirstName; } set { if (value == _customer.FirstName) return; _customer.FirstName = value; base.OnPropertyChanged("FirstName"); } } Precisely the lines if (value == _customer.FirstName) return; are bothering me. I've often did this but I am not that sure it's needed nor good. After all if a caller assigns the very same value I don't want to reassign the field and, especially, notify my subscribers that the property has changed when, semantically it didn't. Except saving some CPU/RAM/etc by freeing the UI from updating something that will probably look the same on the screen/whatever_medium what do we obtain? Could some people force a refresh by reassigning the same value on a property (NOT THAT THIS WOULD BE A GOOD PRACTICE HOWEVER)? 1. Should we do it or shouldn't we? 2. Why?

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• steps to fix a project that won't compile

  - by eco_bach

  Hi Pulling my hair out in trying to get a simple window based project to compile. I am running both 3.2.2 and 3.2.3 versions of Xcode. The latter is set up in a separate folder. Originally I used the latter to create and compile my project against the new 4.0 sdk. It compiled fine. Then I made the mistake of deleting some sdks I thought I no longer needed. Ever since I can no longer compile. Right now I get a dozen or so errors similar to the following "_OBJC_CLASS_$_CATransition", referenced from: objc-class-ref-to-CATransition in ViewTransitionsAppDelegate.o My active executable is the iphone simulator 4 and Base SDK is iPhone device 3.0. I tried reinstalling the xcode3.2.3 installer, no difference. I'm totally stymied, as my project WAS working and compiling fine, both to the simulator and external device. Are there any best practices or recommended steps in fixing or rebuilding a project when it won't compile? Any help welcome!

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• ASP.NET MVC2 and Browser Caching

  - by Dan

  Hi I have a web application that fetches a lot of content via ajax. For example when a user edits some data, the browser will send the changes using an ajax post and then do an ajax get to get fresh content and replace an existing div on the page with that content. This was working just find with MVC1, but in MVC2 I would get inconsistent results. I've found that MVC1 by default included an Expires item in the response headers set to the current time, but in MVC2 the Expires header is missing. This is a problem with some browsers (IE8) actually using the cached version of the ajax get instead of the fresh version. To deal with the problem I created a simple ActionFilterAttribute that sets the reponse cache to NoCache (see below), which works, but it seems kind of sillly to decorate every controller with this attribute. Is there a global way to set this for every controller? Is this a bug in MVC2 and it really should be setting the expires on every ActionResult/view/page? Don't most MVC programs deal with data entry where stale data is a very bad thing? Thanks Dan public class ResponseNoCachingAttribute : ActionFilterAttribute { public override void OnResultExecuted(ResultExecutedContext filterContext) { base.OnResultExecuted(filterContext); filterContext.HttpContext.Response.Cache.SetCacheability(System.Web.HttpCacheability.NoCache); } }

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• Java OO design confusion: how to handle actions modified by states modified by actions...

  - by Arvanem

  Hi folks, Given an entity, whose action is potentially modified by states (of the entity and other entities) in turn potentially modified by other actions (of the entity and other entities) , what is the best way to code or design to handle the potential existence of the modifiers? Speaking metaphorically, I am coding a Java application representing a piano. As you know a piano has keys (which, when pressed, emit sound) and pedals (which, when pressed, modify the keys' sounds). My base class structure is as follows: Entity (for keys and pedals) State (this holds each entity's states, e.g. name such as "soft pedal", and boolean "Pressed"), Action (this holds each entity's actions, e.g. play sound when pressed, or modify others sounds). By composition, the Entity class has a copy of each of State and Action inside it. e.g.: public class Entity { State entityState = new State(); Action entityAction = new Action(); Thus I have coded a "C-Sharp" key Entity. When I "press" that entity (set its "Pressed" state to true), its action plays a "C-Sharp" sound and then sets its "Pressed" state to false. At the same time, if the "C-Sharp" key entity is not "tuned", its sound deviates from "C-Sharp". Meanwhile I have coded a "soft pedal" Entity. When that entity is "pressed", no sound plays but its action is to make softer the sound of the "C-Sharp" and other key entities. I have also coded a "sustain pedal" Entity. When that entity is "pressed", no sound plays but its action is to enable reverberation of the sound of the "C-Sharp" and other key entities. Both the "soft" and "sustain pedals" can be pressed at the same time with the result that keys entities become both softened and reverberating. In short, I do not understand how to make this simultaneous series of states and actions modify each other in a sensible OO way. I am wary of coding a massive series of "if" statements or "switches". Thanks in advance for any help or links you can offer.

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• C++ Problems with #import of .NET out-of-proc server.

  - by jm

  In C++ program, I am trying to #import TLB of .NET out of proc server. I get errors like: z:\server.tlh(111) : error C2146: syntax error : missing ';' before identifier 'GetType' z:\server.tlh(111) : error C2501: 'TypePtr' : missing storage-class or type specifiers z:\server.tli(74) : error C2143: syntax error : missing ';' before 'tag::id' z:\server.tli(74) : error C2433: 'TypePtr' : 'inline' not permitted on data declarations z:\server.tli(74) : error C2501: '_TypePtr' : missing storage-class or type specifiers z:\server.tli(74) : fatal error C1004: unexpected end of file found The TLH looks like: ... _bstr_t GetToString ( ); VARIANT_BOOL Equals ( const _variant_t & obj ); long GetHashCode ( ); _TypePtr GetType ( ); long Open ( ); ... I am not really interested in the having the base object .NET object methods like GetType(), Equals(), etc. But GetType() seems to be causing problems. Some google research indicates I could #import MSCORLIB.TLB (or put it in path), but I can't get that to compile either. Any tips?

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• PHP/MySQL - Working with two databases, one shared and one local to an instance of application

  - by Extrakun

  The situation: Using a off-the-shelf PHP application, I have to add in a new module for extra functionality. Today, it is made known that eventually four different instances of the application are to be deployed, but the data from the new functionality is to be shared among those 4 instances. Each instance should still have their own database for users, content and etc. So the data for the new functionality goes into a 'shared' database. The data for the application (user login, content, uploads) go into a 'local' database To make things more complex, the new module I am writing will fetch data from the local DB and the shared DB at the same time. A re-write of the base application will take too long. I only have control over the new module which I am writing. The ideal solution: Is there a way to encapsulate 2 databases into one name using MySQL? I do not wish to switch DB connections or specifically name the DB to query from inside my SQL statements. The application uses a DB wrapper, so I am able to change it somehow so I can invisibly attempt to read/write to two different DB. What is the best way to handle this problem?

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