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• How effective are technical test(s) and is it necessary?

  - by The Elite Gentleman

  Hi everyone, I recently took a Java technical test (for a company who wanted are looking for senior java developers) and, funny enough, I only realised the technical terms of what I've been doing all along after I've written the test. I'm not too IT jargon when it comes to development but I can pretty much code and create solutions unaware that I'm using design pattern (or the specifics of that design pattern) or technology. I learned things such as JMS, Frameworks, etc. while programming at home and having to google stuff online to problems I have. Others e.g. IoC, Surrogates in Databases, etc., I have used extensively without knowing that it had a name for it. Do you think that these technical test are effective and why? What interesting questions did you find that boggled your brains out while the clock kept ticking? Seeing that IT is vastly evolving at a rapid rate, do we have to constantly be updated with new terms that comes out? Some questions I was asked : What object oriented principle is violated by this architectural mechanism for dot notation? Is indexing tables effective for range query or point query search? What is ThreadLocal and what is it used for? Method overloading vs Method overriding. What is the difference between the 2? What is dynamic binding? Now, imagine my poor head trying to understand these jargons (considering I use it almost everyday) PS The question was not a programming question, where you have a problem and write code to solve it. Rather, a thinking type question and you write answers (against the clock). Update I clearly didn't come out clearly as I should have. There are those that are technically "book smart" but with very little hands-on experience and vice versa. So, the question (in connection to what I've asked) is that are these technical test seeking "book smart" people or people with lots of hands-on experience (some who are not that well clued up with too much book-smart jargons). How effective is it then, for companies to look for developers if most of the questions are too terminology-centric? (if that's the correct term, :))

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• get_or_create generic relations in Django & python debugging in general

  - by rabidpebble

  I ran the code to create the generically related objects from this demo: http://www.djangoproject.com/documentation/models/generic_relations/ Everything is good intially: >>> bacon.tags.create(tag="fatty") <TaggedItem: fatty> >>> tag, newtag = bacon.tags.get_or_create(tag="fatty") >>> tag <TaggedItem: fatty> >>> newtag False But then the use case that I'm interested in for my app: >>> tag, newtag = bacon.tags.get_or_create(tag="wholesome") Traceback (most recent call last): File "<console>", line 1, in <module> File "/usr/local/lib/python2.6/dist-packages/django/db/models/manager.py", line 123, in get_or_create return self.get_query_set().get_or_create(**kwargs) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 343, in get_or_create raise e IntegrityError: app_taggeditem.content_type_id may not be NULL I tried a bunch of random things after looking at other code: >>> tag, newtag = bacon.tags.get_or_create(tag="wholesome", content_type=TaggedItem) ValueError: Cannot assign "<class 'generics.app.models.TaggedItem'>": "TaggedItem.content_type" must be a "ContentType" instance. or: >>> tag, newtag = bacon.tags.get_or_create(tag="wholesome", content_type=TaggedItem.content_type) InterfaceError: Error binding parameter 3 - probably unsupported type. etc. I'm sure somebody can give me the correct syntax, but the real problem here is that I have no idea what is going on. I have developed in strongly typed languages for over ten years (x86 assembly, C++ and C#) but am new to Python. I find it really difficult to follow what is going on in Python when things like this break. In the languages I mentioned previously it's fairly straightforward to figure things like this out -- check the method signature and check your parameters. Looking at the Django documentation for half an hour left me just as lost. Looking at the source for get_or_create(self, **kwargs) didn't help either since there is no method signature and the code appears very generic. A next step would be to debug the method and try to figure out what is happening, but this seems a bit extreme... I seem to be missing some fundamental operating principle here... what is it? How do I resolve issues like this on my own in the future?

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• jQyery bind on ajax load() event

  - by Andrei C

  Hi guys. I have a page which display multiple blocks with results details. Inside each block I have some tags with thichbox jQuery plugin attached( class="thichbox"). http://jquery.com/demo/thickbox/ here is an example of one kind of ampersant tag: <a class="thickbox" title="Please Sign In" href="userloginredir.php?height=220&width=350&deal=3"> Problem comes when I added a jQuery pagination to the page because of to many results displaying on the page. The div component with the results inside is updated through ajax load() event. Below is the pagination script. $(document).ready(function(){ //References var pages = $("#menu_deals li"); var loading = $("#loading_deals"); var content = $("#content_deals"); //show loading bar function showLoading(){ loading .css({visibility:"visible"}) .css({opacity:"1"}) .css({display:"block"}) ; } //hide loading bar function hideLoading(){ loading.fadeTo(1000, 0); }; //Manage click events pages.live('click',function(){ //show the loading bar showLoading(); //Highlight current page number pages.css({'background-color' : ''}); $(this).css({'background-color' : 'yellow'}); //Load content var pageNum = this.id; var targetUrl = "ajax_search_results.php?page=" + pageNum + "&" + $("#dealsForm").serialize() + " #content_d"; content.load(targetUrl, hideLoading); }); //default - 1st page $("#1").css({'background-color' : 'yellow'}); var targetUrl = "ajax_search_results.php?page=1&" + $("#dealsForm").serialize() + " #content_d"; showLoading(); content.load(targetUrl, hideLoading); }); When I added pagination(code above), the thickbox events are not recognized anymore and instead of poping out a window with the login form inside it opens the results in new page (is acting like clicking on a normal link) From my jQuery knowledge this means that the components are not defined in the DOM because the content is updated after document ready triggered. I'm trying to bind the load event with something like this: content.bind('load',???); But I don't know how to pass the load params, targetUrl and the callback function hideLoading, when binding the load event. Please help me out in this matter, already took me more time than possible allowed. Thank you!

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• Problems using FluentNHibernate + SQLite with .NET4?

  - by stiank81

  I have a WPF application running with VS2010 .Net3.5 using Nhibernate with FluentNHibernate + SQLite, and all works fine. Now I want to change to use .Net4, but this has turned into a more painful experience then I expected.. When setting up the connection a FluentConfigurationException is thrown from FluentConfiguration.BuildConfiguration saying: An invalid or incomplete configuration was used while creating a SessionFactory. Check PotentialReasons collection, and InnerException for more details. The inner exception gives us more information: Could not create the driver from NHibernate.Driver.SQLite20Driver, NHibernate, Version=2.1.2.4000, Culture=neutral, PublicKeyToken=aa95f207798dfdb4. It has an InnerException again: Exception has been thrown by the target of an invocation. Which again has an InnerException: The IDbCommand and IDbConnection implementation in the assembly System.Data.SQLite could not be found. Ensure that the assembly System.Data.SQLite is located in the application directory or in the Global Assembly Cache. If the assembly is in the GAC, use element in the application configuration file to specify the full name of the assembly. Now - to me it sounds like it doesn't find System.Data.SQLite.dll, but I can't understand this. Everywhere this is referenced I have "Copy Local", and I have verified that it is in every build folder for projects using SQLite. I have also copied it manually to every Debug folder of the solution - without luck. Notes: This is exactly the same code that worked just fine before I upgraded to .Net4. I did see some x64 x86 mismatch problems earlier, but I have switched to use x86 as the target platform and for all referenced dlls. I have verified that all files in the Debug-folder are x86. I have tried the precompiled Fluent dlls, I have tried compiling myself, and I have compiled my own version of Fluent using .Net4. I see that there are also others that have seen this problem, but I haven't really seen any solution yet. After @devio's answer I tried adding a reference to the SQLite dll. This didn't change anything, but I hope I made it right though.. This is what I added to the root node of the app.config file: <runtime> <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1"> <qualifyAssembly partialName="System.Data.SQLite" fullName="System.Data.SQLite, Version=1.0.60.0, Culture=neutral, PublicKeyToken=db937bc2d44ff139" /> </assemblyBinding> </runtime> Anyone out there using Fluent with .Net4 and SQLite successfully? Help! I'm lost...

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• Flex Spark DropDownList selectedItem didn't update after dataProvider changed

  - by Candy Chiu

  I have two dataProvider's for one DropDownList. The following code can be compiled and run. <?xml version="1.0" encoding="utf-8"?> <s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark" xmlns:mx="library://ns.adobe.com/flex/mx" creationComplete="flipLast()" minWidth="955" minHeight="600"> <fx:Script> <![CDATA[ import mx.collections.ArrayCollection; public function flipLast():void { if( last ) { list.dataProvider = dp1; list.selectedItem = "Flex"; } else { list.dataProvider = dp2; list.selectedItem = "Catalyst"; } last = !last; } public var last:Boolean = true; public var dp1:ArrayCollection = new ArrayCollection( [ "Flex", "Air" ] ); public var dp2:ArrayCollection = new ArrayCollection( [ "Catalyst", "FlashBuilder" ] ); ]]> </fx:Script> <s:VGroup> <s:DropDownList id="list" requireSelection="true" /> <s:Label id="listSelectedItem" text="{list.selectedItem}" /> <s:Label id="listSelectedIndex" text="{list.selectedIndex}" /> <s:Button label="Flip" click="flipLast()" /> </s:VGroup> </s:Application> Scenario 1: dataProvider updated, but selectedIndex is the same. At startup: [ listSelectedItem=Flex, listSelectedIndex=1 ]. Click Flip: dataProvider is updated, but still [ listSelectedItem=Flex, listSelectedIndex=1 ]. Scenario 2: dataProvider updated, selectedIndex is also updated. At startup: [ listSelectedItem=Flex, listSelectedIndex=1 ]. Select Air from list: [ listSelectedItem=Air, listSelectedIndex=2 ]. Click Flip: dataProvider is updated, but still [ listSelectedItem=Catalyst, listSelectedIndex=1 ]. Seems to me that selectedItem is driven by selectedIndex. selectedItem updates only when selectedIndex updates. Shouldn't selectedItem be updated when dataProvider is updated? Is binding to selectedItem flawed?

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• Why don't my scrollbars work properly when programmatically hiding rows in silverlight Datagrid?

  - by Luke Vilnis

  I have a Silverlight datagrid with custom code that allows for +/- buttons on the lefthand side and can display a table with a tree structure. The +/- buttons are bound to a IsExpanded property on my ViewModelRows, as I call them. The visibility of rows is bound to an IsVisible property on the ViewModelRows which is determined based on whether or not all of the parent rows are expanded. Straightforward enough. This code works fine in that if I scroll up and down the grid with PageUp/PageDown or the arrow keys, all the right rows are hidden and everything has the right structure and I can play with the +/- buttons to my hearts content. However, the vertical scroll bar on the right hand side, although it starts off the correct size and it scrolls through the rows smoothly, when I collapse rows and then re-expand them, doesn't go back to its correct size. The scrollbar can still usually be moved around to scroll through the whole collection, but because it is too big, once the bar moves to the bottom, there are still more rows to go through and it sort of jerkily shoots all the way down to the bottom or sometimes fails to scroll at all. This is pretty hard to describe so I included a screenshot with the black lines drawn on to show the difference in scrollbar length even though the two grids have the same number of rows expanded. I think this might be a bug related to the way the Datagrid does virtualization of rows. It seems to me like it isn't properly keeping track of how tall each row is supposed to be when expansion states change. Is there a way to programmatically "poke" (read hack) it to recalculate its scrollbar size on LoadingRow or something ugly like that? I'd include a code sample but there's 2 c# files and 1 xaml file so I wanted to see if anyone else has heard of this sort of issue before I try to make it reproducible in a self-contained way. Once again, scrolling with the arrow keys works fine so I'm pretty sure the underlying logic and binding is working, there's just some issue with the row height not being calculated properly. Since I'm a new user, it won't let me use image tags so here's the link to a picture of the problem: http://img210.imageshack.us/img210/8760/messedupscrollbars.png

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• ProgressDialog does not display until after AsyncTask completes

  - by tedwards

  I am trying to display an indefinite ProgressDialog, while an AsyncTask binds to a RemoteService. The RemoteService builds a list of the users contacts when the service is first created. For a long list of contacts this may take 5~10 seconds. The problem I am having, is that the ProgressDialog does not display until after the RemoteService has built it's list of contacts. I even tried putting a Thread.sleep in to give the ProgressDialog time to show up. With the sleep statement the ProgressDialog loads and starts spinning, but then locks up as soon as the RemoteService starts doing it's work. If I just turn the AsyncTask into dummy code, and just let it sleep for a while, everything works fine. But when the task has to do actual work, it is like the UI just sits and waits. Any ideas on what Im doing wrong ? @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Log.d(IM,"Start Me UP!!"); setContentView(R.layout.main); Log.d(IM, "Building List View for Contacts"); restoreMe(); if (myContacts==null){ myContacts = new ArrayList<Contact>(); this.contactAdapter = new ContactAdapter(this, R.layout.contactlist, myContacts); setListAdapter(this.contactAdapter); new BindAsync().execute(); } else{ this.contactAdapter = new ContactAdapter(this, R.layout.contactlist, myContacts); setListAdapter(this.contactAdapter); } } private class BindAsync extends AsyncTask<Void, Void, RemoteServiceConnection>{ @Override protected void onPreExecute(){ super.onPreExecute(); Log.d(IM,"Showing Dialog"); showDialog(DIALOG_CONTACTS); } @Override protected RemoteServiceConnection doInBackground(Void... v) { Log.d(IM,"Binding to service in BindAsync"); try{ Thread.sleep(2000); } catch (InterruptedException e){ } RemoteServiceConnection myCon; myCon = new RemoteServiceConnection(); Intent i = new Intent(imandroid.this,MyRemoteService.class); bindService(i, myCon, Context.BIND_AUTO_CREATE); startService(i); Log.d(IM,"Bound to remote service"); return myCon; } @Override protected void onPostExecute(RemoteServiceConnection newConn){ super.onPostExecute(newConn); Log.d(IM,"Storing remote connection"); conn=newConn; } };

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• Mindblowing jQuery Weirdness

  - by Jason

  ...at least to me. This code used to work fine. I'm pretty sure nothing has changed, but now all of the sudden it behaves oddly. Basically I'm trying to create inline editing functionality. When the user clicks on the link, it dynamically generates a textbox and a confirm and cancel link. I'm having problems with the cancel link not removing everything in the cell. HTML: ... <td class="bid"> <a href="javascript:" class="102093" title="Click to modify bid">$0.45</a> </td> ... Binding jQuery (in $(function())): $('.bid a').live('click', renderBidChange); .... $('.report_table .cancel').live('click', cancelUpdate); renderBidChange (this function creates the dynamic elements): function renderBidChange(){ var cpc = $(this); var value = cpc.text().replace('$', ''); var cell = cpc.parent('.bid'); cpc.hide(); var input = document.createElement('input'); $(input).attr({type:'text',class:'dynamic cpc-input'}).val(value); cell.append(input); var accept = document.createElement('a'); $(accept).addClass('accept').attr({'href':'javascript:', 'title':'Accept Changes'}).text('Accept Changes'); cell.append(accept); var cancel = document.createElement('a'); $(cancel).addClass('cancel').attr({'href':'javascript:', 'title':'Cancel Changes'}).text('Cancel Changes'); cell.append(cancel); $(input).focus(); input.select(); } cancelUpdate this function just removes everything visible (all the dynamic junk in this case) in the cell and shows what used to be there. function cancelUpdate(){ var cell = $(this).parent(); cell.find(':visible').remove(); cell.find(':hidden').show(); } However, for some reason, the cancel link remains after it is clicked! Everything else is removed except that. W T F Thanks for any insight you're able to provide! I'm sure it's just some stupid little detail I'm over[caffeinatedly]looking... UPDATE Immediately after posting this I epiphanied that it may be a CSS issue, but after double checking my code, it is not.

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• How can I make Swig correctly wrap a char* buffer that is modified in C as a Java Something-or-other

  - by Ukko

  I am trying to wrap some legacy code for use in Java and I was quite happy to see that Swig was able to handle the header file and it generate a great wrapper that almost works. Now I am looking for the deep magic that will make it really work. In C I have a function that looks like this DLL_IMPORT int DustyVoodoo(char *buff, int len, char *curse); This integer returned by this function is an error code in case it fails. The arguments are buff is a character buffer len is the length of the data in the buffer curse the another character buffer that contains the result of calling DustyVoodoo So, you can see where this is going, the result is actually coming back via the third argument. Also len is confusing since it may be the length of both buffers, they are always allocated as being the same size in calling code but given what DustyVoodoo does I don't think that they need be the same. To be safe both buffers should be the same size in practice, say 512 chars. The C code generated for the binding is as follows: SWIGEXPORT jint JNICALL Java_pemapiJNI_DustyVoodoo(JNIEnv *jenv, jclass jcls, jstring jarg1, jint jarg2, jstring jarg3) { jint jresult = 0 ; char *arg1 = (char *) 0 ; int arg2 ; char *arg3 = (char *) 0 ; int result; (void)jenv; (void)jcls; arg1 = 0; if (jarg1) { arg1 = (char *)(*jenv)->GetStringUTFChars(jenv, jarg1, 0); if (!arg1) return 0; } arg2 = (int)jarg2; arg3 = 0; if (jarg3) { arg3 = (char *)(*jenv)->GetStringUTFChars(jenv, jarg3, 0); if (!arg3) return 0; } result = (int)PemnEncrypt(arg1,arg2,arg3); jresult = (jint)result; if (arg1) (*jenv)->ReleaseStringUTFChars(jenv, jarg1, (const char *)arg1); if (arg3) (*jenv)->ReleaseStringUTFChars(jenv, jarg3, (const char *)arg3); return jresult; } It is correct for what it does; however, it misses the fact that cursed is not just an input, it is altered by the function and should be returned as an output. It also does not know that the java Strings are really buffers and should be backed by a suitably sized array. I think that Swig can do the right thing here, I just can't figure out from the documentation how to tell Swig what it needs to know. Any typemap masers in the house?

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• Asynchronous Silverlight 4 call to the World of Warcraft armoury streaming XML in C#

  - by user348446

  Hello - I have been stuck on this all weekend and failed miserably! Please help me to claw back my sanity!! Your challenge For my first Silverlight application I thought it would be fun to use the World of Warcraft armoury to list the characters in my guild. This involves making an asyncronous from Silverlight (duh!) to the WoW armoury which is XML based. SIMPLE EH? Take a look at this link and open the source. You'll see what I mean: http://eu.wowarmory.com/guild-info.xml?r=Eonar&n=Gifted and Talented Below is code for getting the XML (the call to ShowGuildies will cope with the returned XML - I have tested this locally and I know it works). I have not managed to get the expected returned XML at all. Notes: If the browser is capable of transforming the XML it will do so, otherwise HTML will be provided. I think it examines the UserAgent I am a seasoned asp.net web developer C# so go easy if you start talking about native to Windows Forms / WPF I can't seem to set the UserAgent setting in .net 4.0 - doesn't seem to be a property off the HttpWebRequest object for some reason - i think it used to be available. Silverlight 4.0 (created as 3.0 originally before I updated my installation of Silverlight to 4.0) Created using C# 4.0 Please explain as if you talking to a web developer and not a proper programming lol! Below is the code - it should return the XML from the wow armoury. private void button7_Click(object sender, RoutedEventArgs e) { // URL for armoury lookup string url = @"http://eu.wowarmory.com/guild-info.xml?r=Eonar&n=Gifted and Talented"; // Create the web request HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(url); // Set the user agent so we are returned XML and not HTML //httpWebRequest.Headers["User-Agent"] = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0)"; // Not sure about this dispatcher thing - it's late so i have started to guess. Dispatcher.BeginInvoke(delegate() { // Call asyncronously IAsyncResult asyncResult = httpWebRequest.BeginGetResponse(ReqCallback, httpWebRequest); // End the response and use the result using (HttpWebResponse httpWebResponse = (HttpWebResponse)httpWebRequest.EndGetResponse(asyncResult)) { // Load an XML document from a stream XDocument x = XDocument.Load(httpWebResponse.GetResponseStream()); // Basic function that will use LINQ to XML to get the list of characters. ShowGuildies(x); } }); } private void ReqCallback(IAsyncResult asynchronousResult) { // Not sure what to do here - maybe update the interface? } Really hope someone out there can help me! Thanks mucho! Dan. PS Yes, I have noticed the irony in the name of the guild :)

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• Error in facebook.dll facebooksdk

  - by Surendar Radhakrishnan

  I got the web application working with facebooksdk and when i deployed it...it is running fine for sometime and it is throwing the error like this... Server Error in '/' Application. Could not load file or assembly 'Facebook, Version=4.1.1.0, Culture=neutral, PublicKeyToken=58cb4f2111d1e6de' or one of its dependencies. Access is denied. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.IO.FileLoadException: Could not load file or assembly 'Facebook, Version=4.1.1.0, Culture=neutral, PublicKeyToken=58cb4f2111d1e6de' or one of its dependencies. Access is denied. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Assembly Load Trace: The following information can be helpful to determine why the assembly 'Facebook, Version=4.1.1.0, Culture=neutral, PublicKeyToken=58cb4f2111d1e6de' could not be loaded. WRN: Assembly binding logging is turned OFF. To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1. Note: There is some performance penalty associated with assembly bind failure logging. To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog]. Stack Trace: [FileLoadException: Could not load file or assembly 'Facebook, Version=4.1.1.0, Culture=neutral, PublicKeyToken=58cb4f2111d1e6de' or one of its dependencies. Access is denied.] Secured_Login.FacebookVerification() +0 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +25 System.Web.UI.Control.LoadRecursive() +71 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3048 Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.1 i got this method in pageload protected void Page_Load(object sender, EventArgs e) { FacebookVerification(); } protected void FacebookVerification() { try { FacebookApp fbApp = new FacebookApp(); if (fbApp.Session != null) { dynamic myinfo = fbApp.Get("me"); String firstname = myinfo.first_name; String lastname = myinfo.last_name; lblFBStatus.Text = "you signed in as " + firstname + " " + lastname ; } else { lblFBStatus.Text = "Please sign in with facebook"; } } catch (Exception) { throw; } }

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• Silverlight with MVVM Inheritance: ModelView and View matching the Model

  - by moonground.de

  Hello Stackoverflowers! :) Today I have a special question on Silverlight (4 RC) MVVM and inheritance concepts and looking for a best practice solution... I think that i understand the basic idea and concepts behind MVVM. My Model doesn't know anything about the ViewModel as the ViewModel itself doesn't know about the View. The ViewModel knows the Model and the Views know the ViewModels. Imagine the following basic (example) scenario (I'm trying to keep anything short and simple): My Model contains a ProductBase class with a few basic properties, a SimpleProduct : ProductBase adding a few more Properties and ExtendedProduct : ProductBase adding another properties. According to this Model I have several ViewModels, most essential SimpleProductViewModel : ViewModelBase and ExtendedProductViewModel : ViewModelBase. Last but not least, according Views SimpleProductView and ExtendedProductView. In future, I might add many product types (and matching Views + VMs). 1. How do i know which ViewModel to create when receiving a Model collection? After calling my data provider method, it will finally end up having a List<ProductBase>. It containts, for example, one SimpleProduct and two ExtendedProducts. How can I transform the results to an ObservableCollection<ViewModelBase> having the proper ViewModel types (one SimpleProductViewModel and two ExtendedProductViewModels) in it? I might check for Model type and construct the ViewModel accordingly, i.e. foreach(ProductBase currentProductBase in resultList) if (currentProductBase is SimpleProduct) viewModels.Add( new SimpleProductViewModel((SimpleProduct)currentProductBase)); else if (currentProductBase is ExtendedProduct) viewModels.Add( new ExtendedProductViewModels((ExtendedProduct)currentProductBase)); ... } ...but I consider this very bad practice as this code doesn't follow the object oriented design. The other way round, providing abstract Factory methods would reduce the code to: foreach(ProductBase currentProductBase in resultList) viewModels.Add(currentProductBase.CreateViewModel()) and would be perfectly extensible but since the Model doesn't know the ViewModels, that's not possible. I might bring interfaces into game here, but I haven't seen such approach proven yet. 2. How do i know which View to display when selecting a ViewModel? This is pretty the same problem, but on a higher level. Ended up finally having the desired ObservableCollection<ViewModelBase> collection would require the main view to choose a matching View for the ViewModel. In WPF, there is a DataTemplate concept which can supply a View upon a defined DataType. Unfortunately, this doesn't work in Silverlight and the only replacement I've found was the ResourceSelector of the SLExtensions toolkit which is buggy and not satisfying. Beside that, all problems from Question 1 apply as well. Do you have some hints or even a solution for the problems I describe, which you hopefully can understand from my explanation? Thank you in advance! Thomas

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• Web-Frameworks for Education Management Systems?

  - by Indebi

  So, I'm working on an idea and I'll go into a brief overview of that but my question is, What are some good web frameworks for this situation? I have some experience in the following languages: C# Python I have considerably more experience in C# than Python, however I am expecting to learn new things. My idea is this, a completely web-based community-oriented Education Management System that focuses on making students and teachers day-to-day lives easier. For students it will provide a centralized place for them to do homework, study for tests, and reinforce concepts learned previously in class. For teachers it will give them a centralized place to handle assignments, attendance, homework, tests, and all other major parts of classroom management. All of that, but in a community-oriented fashion. Everything a teacher does is shared and open to constructive criticism, allowing other teachers to use their assignments/tests and for students or other teachers to comment, rate and criticize their assignments. This encourages an environment of openness that will allow teacher's to focus on teaching and student's to focus on learning. And that community wouldn't be limited to one school or school-district, this system would be completely school-independent. Please note that I have no problem with hearing constructive criticism on this idea, however I would prefer if this post was more focused on my question. I have somewhat explored about the following options: Django ASP.NET Ruby on Rails Silverlight (1) I have Django installed and I played with it for a little bit, I really like how easy setting up databases are and how it handles the database completely for you. I don't really know how to use it very well and I don't quite understand the Model-View-Controller paradigm(?) for it yet but I haven't thought about it much. I also like the fact that it uses Python. (2) I don't really like Visual Studio for developing in ASP.NET, I hate the way the web-designer works and it just feels clunky and old. I like the server-side development part though. I don't like how expensive ASP.NET and overall Visual Studio is, even if I do get it for free for now using DreamSpark (3) I haven't been able to explore much with this, I could not get Rails (or maybe Ruby) properly installed. I first installed it within RadRails and that didn't work so I uninstalled RadRails and then installed the latest version of Ruby off the official Windows Installer and then installed Ruby on Rails through gem and even after all that it still didn't work, so I installed Netbeans and attempted to use it there but it still did not work (4) I like Silverlight in some extents, I've played with this one the most, it's very similar to WPF (which I've used the most) in a lot of ways but I don't like how database connectivity works, at least in comparison to Django. I also dislike how expensive everything with Microsoft is, even if I get it for free for now with DreamSpark. I would like to hear some suggestions from experienced web-developers as to what I should use and why, or at least what some good options are for my scenario Your help would be very appreciated

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• How to properly set a datatable to an gridview in code with an ObjectDataSource?

  - by Xaisoft

  Hello, I have an ObjectDataSource with an ID of ObjectDataSource1 on a webpage. I also have a gridview in which I am binding the ObjectDataSource.ID to the GridView.DataSourceID. The problem I get is when text is changed in a textbox, the code calls BrokerageTransactions.GetAllWithDt which returns a DataTable. I want to set this datatable as the DataSource for the GridView, but it is telling me that I can't set the DataSouce and DataSourceId together. How can I fix this? Code is below. Also. Why can't you set a DataSourceID and a DataSource when using an ObjectDataSource? Thanks, X protected void BrokerageChange(Object sender, EventArgs e) { BrokerageTransactions brokerageaccountdetails = new BrokerageTransactions(); DataSet ds = BrokerageAccount.GetBrkID2(new Guid(Membership.GetUser().ProviderUserKey.ToString()), ddlBrokerageDetails.SelectedItem.Text.ToString()); foreach (DataRow dr in ds.Tables[0].Rows) { brokerageaccountdetails.BrokerageId = new Guid(dr["BrkrgId"].ToString()); } ddlBrokerageDetails.SelectedItem.Value = brokerageaccountdetails.BrokerageId.ToString(); if (txtTransactionsTo.Text != "" && txtTransactionsFrom.Text != "") ObjectDataSource1.FilterExpression = "convert(CreateDt,System.DateTime)>Convert('" + Convert.ToDateTime(txtTransactionsFrom.Text) + "',System.DateTime) and Convert(CreateDt,System.DateTime)<convert('" + Convert.ToDateTime(txtTransactionsTo.Text.ToString()) + "',System.DateTime)"; else if (txtTransactionsFrom.Text != "") ObjectDataSource1.FilterExpression = "convert(CreateDt,System.DateTime)>convert('" + Convert.ToDateTime(txtTransactionsFrom.Text) + "',System.DateTime)"; else if (txtTransactionsTo.Text != "") ObjectDataSource1.FilterExpression = "convert(CreateDt,System.DateTime) <convert('" + Convert.ToDateTime(txtTransactionsTo.Text.ToString()) + "',System.DateTime)"; else ObjectDataSource1.FilterExpression = " "; grvBrokerage.DataSourceID = ObjectDataSource1.ID; grvBrokerage.DataBind(); DateTime dtTransFrom = Convert.ToDateTime("1/1/1900"); DateTime dtTransTo = System.DateTime.Today; //TransactionsTo Box is Empty if ((txtTransactionsFrom.Text.Length > 2) && (txtTransactionsTo.Text.Length < 2)) { dtTransFrom = Convert.ToDateTime(txtTransactionsFrom.Text); dtTransTo = System.DateTime.Today; } //TransactionsFrom Box is Empty if ((txtTransactionsFrom.Text.Length < 2) && (txtTransactionsTo.Text.Length > 2)) { dtTransFrom = Convert.ToDateTime("1/1/1900"); dtTransTo = Convert.ToDateTime(txtTransactionsTo.Text); } //TransactionsFrom Box and TransactionsTo Box is Not Empty if ((txtTransactionsFrom.Text.Length > 2) && (txtTransactionsTo.Text.Length > 2)) { dtTransFrom = Convert.ToDateTime(txtTransactionsFrom.Text); dtTransTo = Convert.ToDateTime(txtTransactionsTo.Text); } // Fails Here grvBrokerage.DataSource = BrokerageTransactions.GetAllWithDt(brokerageaccountdetails.BrokerageId, dtTransFrom, dtTransTo); grvBrokerage.DataBind(); }

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• Using Complex datatype with python SUDS client

  - by sachin

  hi, I am trying to call webservice from python client using SUDS. When I call a function with a complex data type as input parameter, it is not passed correctly, but complex data type is getting returned correctly froma webservice call. Webservice Type: Soap Binding 1.1 Document/Literal Webserver: Weblogic 10.3 Python Version: 2.6.5, SUDS version: 0.3.9 here is the code I am using: Python Client: from suds.client import Client url = 'http://192.168.1.3:7001/WebServiceSecurityOWSM-simple_ws-context-root/SimpleServicePort?WSDL' client = Client(url) print client #simple function with no operation on input... result = client.service.sopHello() print result result = client.service.add10(10) print result params = client.factory.create('paramBean') print params params.intval = 10 params.longval = 20 params.strval = 'string value' #print "params" print params try: result = client.service.printParamBean(params) print result except WebFault, e: print e try: result = client.service.modifyParamBean(params) print result except WebFault, e: print e print params webservice java class: package simple_ws; import javax.jws.Oneway; import javax.jws.WebMethod; import javax.jws.WebService; import javax.jws.soap.SOAPBinding; public class SimpleService { public SimpleService() { } public void sopHello(int i) { System.out.println("sopHello: hello"); } public int add10(int i) { System.out.println("add10:"); return 10+i; } public void printParamBean(ParamBean pb) { System.out.println(pb); } public ParamBean modifyParamBean(ParamBean pb) { System.out.println(pb); pb.setIntval(pb.getIntval()+10); pb.setStrval(pb.getStrval()+"blah blah"); pb.setLongval(pb.getLongval()+200); return pb; } } and the bean Class: package simple_ws; public class ParamBean { int intval; String strval; long longval; public void setIntval(int intval) { this.intval = intval; } public int getIntval() { return intval; } public void setStrval(String strval) { this.strval = strval; } public String getStrval() { return strval; } public void setLongval(long longval) { this.longval = longval; } public long getLongval() { return longval; } public String toString() { String stri = "\nInt val:" +intval; String strstr = "\nstrval val:" +strval; String strl = "\nlong val:" +longval; return stri+strstr+strl; } } so, as issue is like this: on call: client.service.printParamBean(params) in python client, output on server side is: Int val:0 strval val:null long val:0 but on call: client.service.modifyParamBean(params) Client output is: (reply){ intval = 10 longval = 200 strval = "nullblah blah" } What am i doing wrong here??

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• How to communicate between Client and Server in a Client-Server Application?

  - by Sanoj

  I would like to implement an Client-Server Application, where the business-logic, security validations and a database are at the server and the user interface are at the client. I would like to implement clients in different languages i.e. one in WPF/.NET, one Swing/Java , one in Android/Java and maybe one HTML/JavaScript client. The server will be on Internet, so I would like to be able to have encrypted communication. The client will send some lists of items to be added to the database, or update items, and do some transactions. The server will check if the items are already updated by another client, or update the item, add new items or delete items. How do I solve the communication between clients and the server in such a system? I have been thinking about: http/https webserver, and sending messages in JSON or XML and use Web Sockets for bi-directional communication. Use http in a RESTful way, except when WebSockets are needed. But I guess there are better solutions for native desktop applications than http? CORBA - I have just heard about it, and it's old and complex. Not much talk about it these days. XMPP/Jabber - I have just heard about it and I don't know if it fits me at all. EJabberd seams to be a popular implementation. AMQP - I have just heard about it and I don't know if it fits me at all. RabbitMQ seams to be a popular implementation. Windows Communication Foundation, Java RMI, Java Message Service - but are they language independent? I guess some of these alternatives are on different levels, maybe I can have i.e xmpp or amqp in web sockets over https? What technologys are used for this problem in companies today? and what is recommended to use? I have no experience of them other than webservers and http. Please give me some guidance in this jungle. What are the pros and cons of these technologies in my situation?

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• How to combine designable components with dependency injection

  - by Wim Coenen

  When creating a designable .NET component, you are required to provide a default constructor. From the IComponent documentation: To be a component, a class must implement the IComponent interface and provide a basic constructor that requires no parameters or a single parameter of type IContainer. This makes it impossible to do dependency injection via constructor arguments. (Extra constructors could be provided, but the designer would ignore them.) Some alternatives we're considering: Service Locator Don't use dependency injection, instead use the service locator pattern to acquire dependencies. This seems to be what IComponent.Site.GetService is for. I guess we could create a reusable ISite implementation (ConfigurableServiceLocator?) which can be configured with the necessary dependencies. But how does this work in a designer context? Dependency Injection via properties Inject dependencies via properties. Provide default instances if they are necessary to show the component in a designer. Document which properties need to be injected. Inject dependencies with an Initialize method This is much like injection via properties but it keeps the list of dependencies that need to be injected in one place. This way the list of required dependencies is documented implicitly, and the compiler will assists you with errors when the list changes. Any idea what the best practice is here? How do you do it? edit: I have removed "(e.g. a WinForms UserControl)" since I intended the question to be about components in general. Components are all about inversion of control (see section 8.3.1 of the UMLv2 specification) so I don't think that "you shouldn't inject any services" is a good answer. edit 2: It took some playing with WPF and the MVVM pattern to finally "get" Mark's answer. I see now that visual controls are indeed a special case. As for using non-visual components on designer surfaces, I think the .NET component model is fundamentally incompatible with dependency injection. It appears to be designed around the service locator pattern instead. Maybe this will start to change with the infrastructure that was added in .NET 4.0 in the System.ComponentModel.Composition namespace.

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• Why does my ko computed observable not update bound UI elements when its value changes?

  - by Allen

  I'm trying to wrap a cookie in a computed observable (which I'll later turn into a protectedObservable) and I'm having some problems with the computed observable. I was under the opinion that changes to the computed observable would be broadcast to any UI elements that have been bound to it. I've created the following fiddle JavaScript: var viewModel = {}; // simulating a cookie store, this part isnt as important var cookie = function () { // simulating a value stored in cookies var privateZipcode = "12345"; return { 'write' : function (val) { privateZipcode = val; }, 'read': function () { return privateZipcode; } } }(); viewModel.zipcode = ko.computed({ read: function () { return cookie.read(); }, write: function (value) { cookie.write(value); }, owner: viewModel }); ko.applyBindings(viewModel);? HTML: zipcode: <input type='text' data-bind="value: zipcode"> <br /> zipcode: <span data-bind="text: zipcode"></span>? I'm not using an observable to store privateZipcode since that's really just going to be in a cookie. I'm hoping that the ko.computed will provide the notifications and binding functionality that I need, though most of the examples I've seen with ko.computed end up using a ko.observable underneath the covers. Shouldn't the act of writing the value to my computed observable signal the UI elements that are bound to its value? Shouldn't these just update? Workaround I've got a simple workaround where I just use a ko.observable along side of my cookie store and using that will trigger the required updates to my DOM elements but this seems completely unnecessary, unless ko.computed lacks the signaling / dependency type functionality that ko.observable has. My workaround fiddle, you'll notice that the only thing that changes is that I added a seperateObservable that isn't used as a store, its only purpose is to signal to the UI that the underlying data has changed. // simulating a cookie store, this part isnt as important var cookie = function () { // simulating a value stored in cookies var privateZipcode = "12345"; // extra observable that isnt really used as a store, just to trigger updates to the UI var seperateObservable = ko.observable(privateZipcode); return { 'write' : function (val) { privateZipcode = val; seperateObservable(val); }, 'read': function () { seperateObservable(); return privateZipcode; } } }(); This makes sense and works as I'd expect because viewModel.zipcode depends on seperateObservable and updates to that should (and does) signal the UI to update. What I don't understand, is why doesn't a call to the write function on my ko.computed signal the UI to update, since that element is bound to that ko.computed? I suspected that I might have to use something in knockout to manually signal that my ko.computed has been updated, and I'm fine with that, that makes sense. I just haven't been able to find a way to accomplish that.

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• Forcing a checkbox bound to a DataSource to update when it has not been viewed yet.

  - by Scott Chamberlain

  Here is a test framework to show what I am doing: create a new project add a tabbed control on tab 1 put a button on tab 2 put a check box paste this code for its code (use default names for controls) public partial class Form1 : Form { private List<bool> boolList = new List<bool>(); BindingSource bs = new BindingSource(); public Form1() { InitializeComponent(); boolList.Add(false); bs.DataSource = boolList; checkBox1.DataBindings.Add("Checked", bs, ""); this.button1.Click += new System.EventHandler(this.button1_Click); this.checkBox1.CheckedChanged += new System.EventHandler(this.checkBox1_CheckedChanged); } bool updating = false; private void button1_Click(object sender, EventArgs e) { updating = true; boolList[0] = true; bs.ResetBindings(false); Application.DoEvents(); updating = false; } private void checkBox1_CheckedChanged(object sender, EventArgs e) { if (!updating) MessageBox.Show("CheckChanged fired outside of updating"); } } The issue is if you run the program and look at tab 2 then press the button on tab 1 the program works as expected, however if you press the button on tab 1 then look at tab 2 the event for the checkbox will not fire untill you look at tab 2. The reason for this is the controll on tab 2 is not in the "created" state, so its binding to change the checkbox from unchecked to checked does not happen until after the control has been "Created". checkbox1.CreateControl() does not do anything because according to MSDN CreateControl does not create a control handle if the control's Visible property is false. You can either call the CreateHandle method or access the Handle property to create the control's handle regardless of the control's visibility, but in this case, no window handles are created for the control's children. I tried getting the value of Handle(there is no public CreateHandle() for CheckBox) but still the same result. Any suggestions other than have the program quickly flash all of my tabs that have data-bound check boxes when it first loads? EDIT-- per Jaxidian's suggestion I created a new class public class newcheckbox : CheckBox { public new void CreateHandle() { base.CreateHandle(); } } I call CreateHandle() right after updating = true same results as before.

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• Validating against a Schema with JAXB

  - by fwgx

  I've been looking for solutions to this problem for far too long considering how easy it sounds so I've come for some help. I have an XML Schema which I have used with xjc to create my JAXB binding. This works fine when the XML is well formed. Unfortunately it also doesn't complain when the XML is not well formed. I cannot figure out how to do proper full validation against the schema when I try to unmarshall an XML file. I have managed to use a ValidationEventCollector to handle events, which works for XML parsing errors such as mismatched tags but doesn't raise any events when there is a tag that is required but is completely absent. From what I have seen validation can be done againsta schema, but you must know the path to the schema in order to pass it into the setSchema() method. The problem I have is that the path to the schema is stored in the XML header and I can't knwo at run time where the schema is going to be. Which is why it's stored in the XML file: <?xml version="1.0" encoding="utf-8"?> <DDSSettings xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="/a/big/long/path/to/a/schema/file/DDSSettings.xsd"> <Field1>1</Field1> <Field2>-1</Field2> ...etc Every example I see uses setValidating(true), which is now deprecated, so throws an exception. This is the Java code I have so far, which seems to only do XML validation, not schema validation: try { JAXBContext jc = new JAXBContext() { private final JAXBContext jaxbContext = JAXBContext.newInstance("blah"); @Override public Unmarshaller createUnmarshaller() throws JAXBException { Unmarshaller unmarshaller = jaxbContext.createUnmarshaller(); ValidationEventCollector vec = new ValidationEventCollector() { @Override public boolean handleEvent(ValidationEvent event) throws RuntimeException { ValidationEventLocator vel = event.getLocator(); if (event.getSeverity() == event.ERROR || event.getSeverity() == event.FATAL_ERROR) { String error = "XML Validation Exception: " + event.getMessage() + " at row: " + vel.getLineNumber() + " column: " + vel.getColumnNumber(); System.out.println(error); } m_unmarshallingOk = false; return false; } }; unmarshaller.setEventHandler(vec); return unmarshaller; } @Override public Marshaller createMarshaller() throws JAXBException { throw new UnsupportedOperationException("Not supported yet."); } @Override @SuppressWarnings("deprecation") public Validator createValidator() throws JAXBException { throw new UnsupportedOperationException("Not supported yet."); } }; Unmarshaller unmarshaller = jc.createUnmarshaller(); m_ddsSettings = (com.ultra.DDSSettings)unmarshaller.unmarshal(new File(xmlfileName)); } catch (UnmarshalException ex) { Logger.getLogger(UniversalDomainParticipant.class.getName()).log( Level.SEVERE, null, ex); } catch (JAXBException ex) { Logger.getLogger(UniversalDomainParticipant.class.getName()).log( Level.SEVERE, null, ex); } So what is the proper way to do this validation? I was expecting there to be a validate() method on the JAXB generated classes, but I guess that would be too simple for Java.

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• Yes, another thread question...

  - by Michael

  I can't understand why I am loosing control of my GUI even though I am implementing a thread to play a .wav file. Can someone pin point what is incorrect? #!/usr/bin/env python import wx, pyaudio, wave, easygui, thread, time, os, sys, traceback, threading import wx.lib.delayedresult as inbg isPaused = False isStopped = False class Frame(wx.Frame): def __init__(self): print 'Frame' wx.Frame.__init__(self, parent=None, id=-1, title="Jasmine", size=(720, 300)) #initialize panel panel = wx.Panel(self, -1) #initialize grid bag sizer = wx.GridBagSizer(hgap=20, vgap=20) #initialize buttons exitButton = wx.Button(panel, wx.ID_ANY, "Exit") pauseButton = wx.Button(panel, wx.ID_ANY, 'Pause') prevButton = wx.Button(panel, wx.ID_ANY, 'Prev') nextButton = wx.Button(panel, wx.ID_ANY, 'Next') stopButton = wx.Button(panel, wx.ID_ANY, 'Stop') #add widgets to sizer sizer.Add(pauseButton, pos=(1,10)) sizer.Add(prevButton, pos=(1,11)) sizer.Add(nextButton, pos=(1,12)) sizer.Add(stopButton, pos=(1,13)) sizer.Add(exitButton, pos=(5,13)) #initialize song time gauge #timeGauge = wx.Gauge(panel, 20) #sizer.Add(timeGauge, pos=(3,10), span=(0, 0)) #initialize menuFile widget menuFile = wx.Menu() menuFile.Append(0, "L&oad") menuFile.Append(1, "E&xit") menuBar = wx.MenuBar() menuBar.Append(menuFile, "&File") menuAbout = wx.Menu() menuAbout.Append(2, "A&bout...") menuAbout.AppendSeparator() menuBar.Append(menuAbout, "Help") self.SetMenuBar(menuBar) self.CreateStatusBar() self.SetStatusText("Welcome to Jasime!") #place sizer on panel panel.SetSizer(sizer) #initialize icon self.cd_image = wx.Image('cd_icon.png', wx.BITMAP_TYPE_PNG) self.temp = self.cd_image.ConvertToBitmap() self.size = self.temp.GetWidth(), self.temp.GetHeight() wx.StaticBitmap(parent=panel, bitmap=self.temp) #set binding self.Bind(wx.EVT_BUTTON, self.OnQuit, id=exitButton.GetId()) self.Bind(wx.EVT_BUTTON, self.pause, id=pauseButton.GetId()) self.Bind(wx.EVT_BUTTON, self.stop, id=stopButton.GetId()) self.Bind(wx.EVT_MENU, self.loadFile, id=0) self.Bind(wx.EVT_MENU, self.OnQuit, id=1) self.Bind(wx.EVT_MENU, self.OnAbout, id=2) #Load file usiing FileDialog, and create a thread for user control while running the file def loadFile(self, event): foo = wx.FileDialog(self, message="Open a .wav file...", defaultDir=os.getcwd(), defaultFile="", style=wx.FD_MULTIPLE) foo.ShowModal() self.queue = foo.GetPaths() self.threadID = 1 while len(self.queue) != 0: self.song = myThread(self.threadID, self.queue[0]) self.song.start() while self.song.isAlive(): time.sleep(2) self.queue.pop(0) self.threadID += 1 def OnQuit(self, event): self.Close() def OnAbout(self, event): wx.MessageBox("This is a great cup of tea.", "About Jasmine", wx.OK | wx.ICON_INFORMATION, self) def pause(self, event): global isPaused isPaused = not isPaused def stop(self, event): global isStopped isStopped = not isStopped class myThread (threading.Thread): def __init__(self, threadID, wf): self.threadID = threadID self.wf = wf threading.Thread.__init__(self) def run(self): global isPaused global isStopped self.waveFile = wave.open(self.wf, 'rb') #initialize stream self.p = pyaudio.PyAudio() self.stream = self.p.open(format = self.p.get_format_from_width(self.waveFile.getsampwidth()), channels = self.waveFile.getnchannels(), rate = self.waveFile.getframerate(), output = True) self.data = self.waveFile.readframes(1024) isPaused = False isStopped = False #main play loop, with pause event checking while self.data != '': # while isPaused != True: # if isStopped == False: self.stream.write(self.data) self.data = self.waveFile.readframes(1024) # elif isStopped == True: # self.stream.close() # self.p.terminate() self.stream.close() self.p.terminate() class App(wx.App): def OnInit(self): self.frame = Frame() self.frame.Show() self.SetTopWindow(self.frame) return True def main(): app = App() app.MainLoop() if __name__=='__main__': main()

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• SQLAlchemy unsupported type error - and table design issues?

  - by Az

  Hi there, back again with some more SQLAlchemy shenanigans. Let me step through this. My table is now set up as so: engine = create_engine('sqlite:///:memory:', echo=False) metadata = MetaData() students_table = Table('studs', metadata, Column('sid', Integer, primary_key=True), Column('name', String), Column('preferences', Integer), Column('allocated_rank', Integer), Column('allocated_project', Integer) ) metadata.create_all(engine) mapper(Student, students_table) Fairly simple, and for the most part I've been enjoying the ability to query almost any bit of information I want provided I avoid the error cases below. The class it is mapped from is: class Student(object): def __init__(self, sid, name): self.sid = sid self.name = name self.preferences = collections.defaultdict(set) self.allocated_project = None self.allocated_rank = 0 def __repr__(self): return str(self) def __str__(self): return "%s %s" %(self.sid, self.name) Explanation: preferences is basically a set of all the projects the student would prefer to be assigned. When the allocation algorithm kicks in, a student's allocated_project emerges from this preference set. Now if I try to do this: for student in students.itervalues(): session.add(student) session.commit() It throws two errors, one for the allocated_project column (seen below) and a similar error for the preferences column: sqlalchemy.exc.InterfaceError: (InterfaceError) Error binding parameter 4 - probably unsupported type. u'INSERT INTO studs (sid, name, allocated_rank, allocated_project) VALUES (?, ?, ?, ?, ?, ?, ?)' [1101, 'Muffett,M.', 1, 888 Human-spider relationships (Supervisor id: 123)] If I go back into my code I find that, when I'm copying the preferences from the given text files, it actually refers to the Project class which is mapped to a dictionary, using the unique project id's (pid) as keys. Thus, as I iterate through each student via their rank and to the preferences set, it adds not a project id, but the reference to the project id from the projects dictionary. students[sid].preferences[int(rank)].add(projects[int(pid)]) Now this is very useful to me since I can find out all I want to about a student's preferred projects without having to run another check to pull up information about the project id. The form you see in the error has the object print information passed as: return "%s %s (Supervisor id: %s)" %(self.proj_id, self.proj_name, self.proj_sup) My questions are: I'm trying to store an object in a database field aren't I? Would the correct way then, be copying the project information (project id, name, etc) into its own table, referenced by the unique project id? That way I can just have the project id field for one of the student tables just be an integer id and when I need more information, just join the tables? So and so forth for other tables? If the above makes sense, then how does one maintain the relationship with a column of information in one table which is a key index on another table? Does this boil down into a database design problem? Are there any other elegant ways of accomplishing this? Apologies if this is a very long-winded question. It's rather crucial for me to solve this, so I've tried to explain as much as I can, whilst attempting to show that I'm trying (key word here sadly) to understand what could be going wrong.

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• Who calls the Destructor of the class when operator delete is used in multiple inheritance.

  - by dicaprio-leonard

  This question may sound too silly, however , I don't find concrete answer any where else. With little knowledge on how late binding works and virtual keyword used in inheritance. As in the code sample, when in case of inheritance where a base class pointer pointing to a derived class object created on heap and delete operator is used to deallocate the memory , the destructor of the of the derived and base will be called in order only when the base destructor is declared virtual function. Now my question is : 1) When the destructor of base is not virtual, why the problem of not calling derived dtor occur only when in case of using "delete" operator , why not in the case given below: derived drvd; base *bPtr; bPtr = &drvd; //DTOR called in proper order when goes out of scope. 2) When "delete" operator is used, who is reponsible to call the destructor of the class? The operator delete will have an implementation to call the DTOR ? or complier writes some extra stuff ? If the operator has the implementation then how does it looks like , [I need sample code how this would have been implemented]. 3) If virtual keyword is used in this example, how does operator delete now know which DTOR to call? Fundamentaly i want to know who calls the dtor of the class when delete is used. Sample Code class base { public: base() { cout<<"Base CTOR called"<<endl; } virtual ~base() { cout<<"Base DTOR called"<<endl; } }; class derived:public base { public: derived() { cout<<"Derived CTOR called"<<endl; } ~derived() { cout<<"Derived DTOR called"<<endl; } }; I'm not sure if this is a duplicate, I couldn't find in search. int main() { base *bPtr = new derived(); delete bPtr;// only when you explicitly try to delete an object return 0; }

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• Silverlight MVVM MEF ViewInjection

  - by silverfighter

  Hi all, since my title is buzzword compliant I hope I will get lots of answers to my question or any pointers to the right direction. OK what I usually do is have a ViewModel which contains a list of ViewModels itself. public class MasterViewModel { public ObservableCollection<DetailViewModel> DetailViewModels { get; set; } public DetailViewModel Detail { get; set; } } <ItemsControl ItemsSource="{Binding DetailViewModels}"> <ItemsControl> <ItemsPanelTemplate> <StackPanel /> </ItemsPanelTemplate> </ItemsControl> <ItemsControl.ItemTemplate> <DataTemplate> <views:DetailsView /> </DataTemplate> </ItemsControl.ItemTemplate> </ItemsControl> With this in mind I will now come to my questions. I read a lot of good things about MEF and also saw the dashboard sample of Glenn Block but this was not helping me enough. What I want to do is sidbar (like the windows sidebar). Sidebar = StackPanel ListItems = Gadget ButI want it MVVM style OK I have something like a contract IGadget I implemented an custom Export. [ExportGadget(GadgetType = GadgetTypes.News)] I have my NewsGadgetView.xaml (which implements IGadget) and imports the NewsGadgetViewModel and also makes itself available as ExportGadget. so far so good. With this I can create a set of gadgets. Then I have my SidbarView.xaml which imports a sidebarViewModel. and now I get lost... I thought of something like a GadgetFactory which uses PartCreator to create my Gadgets. but this would sit in my SidebarView.xaml But I want to have control over my Gadgets to add and remove them from my sidebar. So I thought about something like an ObserveableCollection... Which I bind to The GadgetHost is basicaly Grid which will dynamicaly load the Gadget.... So how would I create my sidebar containing different gadgets without knowing which Gadgets are available and have a ViewModel for the sidebar as well as for each gadget?... Thanks for any help....

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• dynamic Grid columns

  - by stck777

  Hi, I need help with dynamic columns in a DataGrid. I use GenericFrame front-end with PHP backend. If I use static columns like this: <? ... ?> <DataGrid id="DataGrid1" width="100%"> <columns> <DataGridColumn headerText="name" dataField="@username" width="150"/> <DataGridColumn headerText="Nahcname" dataField="@secondname" width="150"/> <DataGridColumn headerText="alter" dataField="@age" width="40"/> </columns> </DataGrid> <? ... ?> It is working fine. But I try to create the columns dynamic with PHP. <generic> <template target="gridbox"> <VBox id="dynamic" height="100%"> <!-- DataGrid --> <DataGrid id="DataGrid1" width="100%" > <columns> <?php $columns = array( //Spalte => (Breite, Datenfeld) "name" => array(150,"@username"), "Nahcname" => array(150,"@secondname"), "alter"=> array(40,"@age") ); foreach ($columns as $key => $value) { ?> <DataGridColumn headerText="<? echo $key; ?>" dataField="<? echo $value[0]; ?>" width="<? echo $value[0];?>"/> <?php } ?> </columns> </DataGrid> <Binding source="templatedata.data1.item" destination="DataGrid1.dataProvider" /> </VBox> </template> <templatedata> <data1> <!-- Daten --> <item username="User1" secondname="Nachname1" age="22"/> <item username="User2" secondname="Nachname2" age="25"/> <item username="User3" secondname="Nachname3" age="27"/> <item username="User4" secondname="Nachname4" age="32"/> </data1> </templatedata> The DataGrid is displayed correctly, but without data? any idea why?

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