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• Is It Incorrect to Make Domain Objects Aware of The Data Access Layer?

  - by Noah Goodrich

  I am currently working on rewriting an application to use Data Mappers that completely abstract the database from the Domain layer. However, I am now wondering which is the better approach to handling relationships between Domain objects: Call the necessary find() method from the related data mapper directly within the domain object Write the relationship logic into the native data mapper (which is what the examples tend to do in PoEAA) and then call the native data mapper function within the domain object. Either it seems to me that in order to preserve the 'Fat Model, Skinny Controller' mantra, the domain objects have to be aware of the data mappers (whether it be their own or that they have access to the other mappers in the system). Additionally it seems that Option 2 unnecessarily complicates the data access layer as it creates table access logic across multiple data mappers instead of confining it to a single data mapper. So, is it incorrect to make the domain objects aware of the related data mappers and to call data mapper functions directly from the domain objects? Update: These are the only two solutions that I can envision to handle the issue of relations between domain objects. Any example showing a better method would be welcome.

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• Help passing reference to class subroutine in Perl.

  - by stephenmm

  I am trying to pass a routine to another subroutine within a Perl module. But when I pass the sub reference the passed in ref no longer has the object data. Maybe its not possible to do it this way. The line I have a question about is the "unless" lines below: sub get_flag_end { my $self = shift; return ( -e "$self->{file}" ); } sub wait_for_end { my $self = shift; my $timeout = shift; my $poll_interval = shift; # Is it even possible to pass the oject subroutine and retain the objects data? #unless ( $self->timeout( $timeout, $poll_interval, $self->get_flag_end ) ) { # does not work unless ( $self->timeout( $timeout, $poll_interval, \&get_flag_end ) ) { # call happens but members are empty die "!!!ERROR!!! Timed out while waiting for wait_for_end: timeout=$timeout, poll_interval=$poll_interval \n"; } } sub timeout { my $self = shift; my $timeout = shift; my $poll_interval = shift; my $test_condition = shift; until ($test_condition->() || $timeout <= 0) { $timeout -= $poll_interval; sleep $poll_interval; } return $timeout > 0; # condition was met before timeout } I know that I could change the "get_flag_end" routine to take the value as an argument to the subroutine but what if there was a bunch of stuff done in "get_flag_end" and I needed more members from the object. I simplified the code a bit to make it a little easier to follow.

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• compareTo and nested Enums

  - by echox

  Hi, in "A Programmers Guide to Java SCJP Certification" I found an example which I can't follow. This the given enum: enum Scale3 { GOOD(Grade.C), BETTER(Grade.B), BEST(Grade.A); enum Grade {A, B, C} private Grade grade; Scale3(Grade grade) { this.grade = grade; } public Grade getGrade() { return grade; } } This is the given expression: Scale3.GOOD.getGrade().compareTo(Scale3.Grade.A) > 0; I don't understand why this expression will be true? The return value will be 2. compareTo() will return a value 0 if the given object is "less" than the object. Scale3.Grade.A is the "biggest" element of Grades, its ordinal number is 0. Scale3.GOOD is the "biggest" element of Scale3, its ordinal number is also 0. The constructor of Scale3 is called with Scale3.Grade.C, which ordinal number is 2. So the given expression is equal to the following code: Scale3.Grade.C.compareTo(Scale3.Grade.A) > 0; A is "bigger" than C, so shouldn't be the result < 0?

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• Powershell invoke-command with PSCredential in line

  - by jaffa

  I need to be able to run a command on another server. This script acts as a bootstrap to another script which is run on the actual server. This works great on servers on the same domain, but if I need to run this script on a remote server, I need to specify credentials. The command is kicked off from a Msbuild targets file like so: <Target Name="PreDeployment" Condition="true" BeforeTargets="MSDeployPublish"> <Exec Command="powershell.exe -ExecutionPolicy Bypass invoke-command bootstrapScript.ps1 -computername $(MyServer) -argumentlist param1, param2" /> </Target> However, I need to be able to supply the credentials by creating a new PSCredentials object with a secure password for my deployment script to run on a remote server: <Target Name="PreDeployment" Condition="true" BeforeTargets="MSDeployPublish"> <Exec Command="powershell.exe -ExecutionPolicy Bypass invoke-command bootstrapScript.ps1 -computername $(MyServer) -credential New-Object System.Management.Automation.PSCredential ('admin', (convertto-securestring $(Password) -asplaintext -force)) -argumentlist param1, param2" /> </Target> When I run the build, a dialog pops up with the username set to System.Management.Automation.PSCredential. I need to be able to create the credentials in-line on the executable target. How do I accomplish this?

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• Writing language converter in ANTLR

  - by Stefan

  I'm writing a converter between some dialects of the same programming language. I've found a grammar on the net - it's complex and handles all the cases. Now I'm trying to write the appropriate actions. Most of the input is just going to be rewritten to output. What I need to do is parse function calls, do my magic (rename function, reorder arguments, etc) and write it. I'm using AST as output. When I come across a function call, I build a custom object structure (from classes defined in my target language), call the appropriate function and I have a string that represents the transformed function that I want to get. The problem is, what I'm supposed to do with that string? I'd like to replace the .text attribute of the enclosing rule, but setText() is only available on lexer rules and the rule's .text attribute is read-only. How to solve this problem? program : statement_list { output = $statement_list.text; } ; //... statement : expression_statement // ... ; expression_statement : function_call // ... ; function_call : ID '(' { /* build the object, assign name */ Function function = new Function(); //... } ( arg1 = expression { /* add first parameter */ } ( ',' arg2 = expression { /* add the rest of parameters */ } )* )? ')' { /* convert the function call */ string converted = Tools.Convert(function); // $setText(converted); // doesn't work // $functionCall.text = converted; // doesn't work } ;

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• ContextMenu not popping up on Long click

  - by primal

  Hi, The context menu is not popping up on the long click on the list items in the list view. I've extended the base adapter and used a view holder to implement the custom list with textviews and an imagebutton. adapter = new MyClickableListAdapter(this, R.layout.timeline, mObjectList); list.setAdapter(adapter); registerForContextMenu(list); Implementation of onCreateContextMenu @Override public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) { // TODO Auto-generated method stub super.onCreateContextMenu(menu, v, menuInfo); Log.d(TAG, "Entering Context Menu"); menu.setHeaderTitle("Context Menu"); menu.add(Menu.NONE, DELETE_ID, Menu.NONE, "Delete") .setIcon(R.drawable.icon); } The XML for listview is here <ListView android:id="@+id/list" android:layout_width="fill_parent" android:layout_height="wrap_content" /> I've been trying this for many days. I think its impossible to register Context-menu for a custom list view like this. Correct me if I am wrong (possibly with sample code). Now I am thinking of a adding a button to the list item and it displays a menu on clicking it. Is it possible with some other way than using Dialogs? Any help would be much appreciated..

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• APS.NET MVC Ajax: Passing a IList from the View to the Controller

  - by Bpimenta

  I need to pass the grid rows from the view to the controller using POST. The idea is to pass an IList of objects (people) that have the following structure: String Name String Address String ID I want to read the data from the JQGrid and pass it to the controller to fill the IList. I'm trying to build the data object to pass through the Ajax data parameter. Here is the Javascript code: $("#saveButton").click( function() { var returnData = '{'; var existingIDs = $('#listPeople').getDataIDs(); if (idsPeople.length > 0) { for (i=0;i<idsPeople.length;i++) { //Trying to build the obejct data ret = ret + '"people['+ i +'].Name":' $('#listPeople').getRowData(idsPeople[i]).Name + ','; ret = ret + '"people['+ i +'].Address":' $('#listPeople').getRowData(idsPeople[i]).Address+ ','; ret = ret + '"people['+ i +'].Id":' $('#listPeople').getRowData(idsPeople[i]).Id+ ','; //If it has more than one element if (idsPeople.length>1 && (i+1)<idsPeople.length) { ret = ret + ','; } } } ret = ret + '}'; My Ajax function for sending: var url_all = '<%=Url.Action("SaveData") %>; $.ajax({ type: "POST", url: url_all, data: ret, dataType: "json", success: function(){ alert("OK"); }, error: function(){ alert("Error: check SaveData"); } }); My controller: public ActionResult SaveData(IList<PeopleHeader> people){ // using debug to know if "people" variable has any values return Json(true); } The problem I'm getting is an error: "System.NotSupportedException: Fixed size collection", and no data is being delivered. I think my problem relies on creating the object... is there any simpler way of doing this procedure? Thanks in advance,

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• img onload doesn't work well in IE7

  - by rmeador

  I have an img tag in my webapp that uses the onload handler to resize the image: <img onLoad="SizeImage(this);" src="foo" > This works fine in Firefox 3, but fails in IE7 because the image object being passed to the SizeImage() function has a width and height of 0 for some reason -- maybe IE calls the function before it finishes loading?. In researching this, I have discovered that other people have had this same problem with IE. I have also discovered that this isn't valid HTML 4. This is our doctype, so I don't know if it's valid or not: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> Is there a reasonable solution for resizing an image as it is loaded, preferably one that is standards-compliant? The image is being used for the user to upload a photo of themselves, which can be nearly any size, and we want to display it at a maximum of 150x150. If your solution is to resize the image server-side on upload, I know that is the correct solution, but I am forbidden from implementing it :( It must be done client side, and it must be done on display. Thanks. Edit: Due to the structure of our app, it is impractical (bordering on impossible) to run this script in the document's onload. I can only reasonably edit the image tag and the code near it (for instance I could add a <script> right below it). Also, we already have Prototype and EXT JS libraries... management would prefer to not have to add another (some answers have suggested jQuery). If this can be solved using those frameworks, that would be great. Edit 2: Unfortunately, we must support Firefox 3, IE 6 and IE 7. It is desirable to support all Webkit-based browsers as well, but as our site doesn't currently support them, we can tolerate solutions that only work in the Big 3.

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• NHibernate: how to handle entity-based validation using session-per-request pattern, without control

  - by Seth Petry-Johnson

  What is the best way to do entity-based validation (each entity class has an IsValid() method that validates its internal members) in ASP.NET MVC, with a "session-per-request" model, where the controller has zero (or limited) knowledge of the ISession? Here's the pattern I'm using: Get an entity by ID, using an IFooRepository that wraps the current NH session. This returns a connected entity instance. Load the entity with potentially invalid data, coming from the form post. Validate the entity by callings its IsValid() method. If valid, call IFooRepository.Save(entity). Otherwise, display error message. The session is currently opened when the request begins and flushed when the request ends. Since my entity is connected to a session, flushing the session attempts to save the changes even if the object is invalid. What's the best way to keep validation logic in the entity class, limit controller knowledge of NH, and avoid saving invalid changes at the end of a request? Option 1: Explicitly evict on validation failure, implicitly flush: if the validation fails, I could manually evict the invalid object in the action method. If successful, I do nothing and the session is automatically flushed. Con: error prone and counter-intuitive ("I didn't call .Save(), why are my invalid changes being saved anyways?") Option 2: Explicitly flush, do nothing by default: By default I can dispose of the session on request end, only flushing if the controller indicates success. I'd probably create a SaveChanges() method in my base controller that sets a flag indicating success, and then query this flag when closing the session at request end. Pro: More intuitive to troubleshoot if dev forgets this step [relative to option 1] Con: I have to call IRepository.Save(entity)' and SaveChanges(). Option 3: Always work with disconnected objects: I could modify my repositories to return disconnected/transient objects, and modify the Repo.Save() method to re-attach them. Pro: Most intuitive, given that controllers don't know about NH. Con: Does this defeat many of the benefits I'd get from NH?

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• WPF deployment strategy dilemma.clickonce(limited customization)+autoupdate vs installer(unlimited c

  - by black sensei

  Hello Experts!!! I've been facing a deployment problem.I've built a WPF application with visual studio 2008 and created an installer(msi) which works fine.But then it's pain to add automatic update to it. i've seen this article at windowsclient.net but it seems to be pretty old but could have been the perfect thing for me.Then i looked at the .Net Application updater block v2.0 which uses enterprise library june 2005 and for some reason it's not installing on my machine. I thought i will need to use a more recent Enterprise library so i installed and compiled Enterprise 4.1(october 2008) but nothing better happened.To i decided to give a try to CLickonce deployment.After struggling with it, it was almost perfect.I realized that when i was testing the updates provided by the clickonce on my machine which is XP i didn't notice the need of having sqlite dll in the GAC. surely it was already there.I noticed it when i moved to vista that there is a problem.After checking the net i know it's impossible to add a dll to the Global Assembly Cache. Now i'm stuck, i think i've hit a wall.Can any one share some of his experience? I'm willing to try the updater block if i can get help. Thanks for reading this!!

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• Avoiding null point exception in el in JSF

  - by Buddhika Ariyaratne

  I am developing a JSF application with JPA(EclipseLink 2.0) and Primefaces. I want to know is there any way to avoid null point exception when el calls a property of a null object. I have described the situation. I have Bill class. There may be no or more BillItem objects with a Bill objects. Each BillItem object have Objects like Make, Country, Manufacturer, etc objects. I am displaying several properties of a bill within a single JSF file like this. "#{billControlled.bill.billItem.modal.name}" But if a bill is not selected, or when there are no bill items for a selected bill, the properties accessing in the el are null. I can avoid this by creating new objects for every bill, for example, new make for a new bill item, etc or by creating new properties in the controller itself for all the properties. But that is a very long way and feel like rudimentory. Is there any good practice to avoid this null point exception in el in JSF?

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• Trying to insert a row using stored procedured with a parameter binded to an expression.

  - by Arvind Singh

  Environment: asp.net 3.5 (C# and VB) , Ms-sql server 2005 express Tables Table:tableUser ID (primary key) username Table:userSchedule ID (primary key) thecreator (foreign key = tableUser.ID) other fields I have created a procedure that accepts a parameter username and gets the userid and inserts a row in Table:userSchedule Problem: Using stored procedure with datalist control to only fetch data from the database by passing the current username using statement below works fine protected void SqlDataSourceGetUserID_Selecting(object sender, SqlDataSourceSelectingEventArgs e) { e.Command.Parameters["@CurrentUserName"].Value = Context.User.Identity.Name; } But while inserting using DetailsView it shows error Procedure or function OASNewSchedule has too many arguments specified. I did use protected void SqlDataSourceCreateNewSchedule_Selecting(object sender, SqlDataSourceSelectingEventArgs e) { e.Command.Parameters["@CreatedBy"].Value = Context.User.Identity.Name; } DetailsView properties: autogen fields: off, default mode: insert, it shows all the fields that may not be expected by the procedure like ID (primary key) not required in procedure and CreatedBy (user id ) field . So I tried removing the 2 fields from detailsview and shows error Cannot insert the value NULL into column 'CreatedBy', table 'D:\OAS\OAS\APP_DATA\ASPNETDB.MDF.dbo.OASTest'; column does not allow nulls. INSERT fails. The statement has been terminated. For some reason parameters value is not being set. Can anybody bother to understand this and help?

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• Jquery Ajax json Serializable

  - by willsonchan

  I am learing using jquery ajax to hander the JSON..i writre a demo code. HTMLCODE $(function () { $("#add").click(function () { var json = '{ "str":[{"Role_ID":"2","Customer_ID":"155","Brands":"Chloe;","Country_ID":"96;"}]}'; $.ajax({ url: "func.aspx/GetJson", type: "POST", contentType: "application/json", dataType: 'json', data: json, success: function (result) { alert(result); }, error: function () { alert("error"); } }); }); }); <div> <input type="button" value="add" id="add" /> </div> i got a input and bind a script function to it, now the proble is comeing.. my C# functiong like that. [WebMethod] public static string GetJson(object str) { return str.ToString();//good for work } [Serializable] public class TestClass { public TestClass() { } public TestClass(string role_id, string customer_id, string brands, string countryid) { this.Role_ID = role_id; this.Customer_ID = customer_id; this.Brands = brands; this.Country_ID = countryid; } public string Role_ID { get; set; } public string Customer_ID { get; set; } public string Brands { get; set; } public string Country_ID { get; set; } } when i user public static string GetJson(object str) everything is so good.~~ no error at all but . when i try to use my own class TestClass. firebug tell me that "Type 'TestClass' is not supported for deserialization of an array." .any body can give me help:XD

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• Can I use manifests to consume a COM server without specifying its version?

  - by sharptooth

  Two of our programs use the same COM server (also made by us) with the same class ids. Each program when installing copies the COM server files into its folder and regsvr32s the COM server. The problem is how to install the COM server so that the user can install either one or both of our programs into different folders in any order and likely of different versions. Clearly it's impossible without changing the class ids and that's lots of hassle with configurations. Ideally we would like to use manifests for that and go without regsvr32. The problem is every time I read about reg-free COM (for example, here) there's the version attribute in the assemblyIdentity. The version number should change every nightly build and I totally don't like the idea of (automatically) adjusting it. I understand why specifying dependency on a specific version is good, but it's completely useless in our scenarion. Is there a way to write manifests for both the COM server and the consumer so that they don't specify versions and just work with whatever version of the file happens to be in the folder? Also is there a way to restrict the search to the same folder as the consumer?

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• rpy2: Converting a data.frame to a numpy array

  - by Mike Dewar

  I have a data.frame in R. It contains a lot of data : gene expression levels from many (125) arrays. I'd like the data in Python, due mostly to my incompetence in R and the fact that this was supposed to be a 30 minute job. I would like the following code to work. To understand this code, know that the variable path contains the full path to my data set which, when loaded, gives me a variable called immgen. Know that immgen is an object (a Bioconductor ExpressionSet object) and that exprs(immgen) returns a data frame with 125 columns (experiments) and tens of thousands of rows (named genes). robjects.r("load('%s')"%path) # loads immgen e = robjects.r['data.frame']("exprs(immgen)") expression_data = np.array(e) This code runs, but expression_data is simply array([[1]]). I'm pretty sure that e doesn't represent the data frame generated by exprs() due to things like: In [40]: e._get_ncol() Out[40]: 1 In [41]: e._get_nrow() Out[41]: 1 But then again who knows? Even if e did represent my data.frame, that it doesn't convert straight to an array would be fair enough - a data frame has more in it than an array (rownames and colnames) and so maybe life shouldn't be this easy. However I still can't work out how to perform the conversion. The documentation is a bit too terse for me, though my limited understanding of the headings in the docs implies that this should be possible. Anyone any thoughts?

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• Passing youtube video id from video feed to flash

  - by Grant Anderson

  I'm working on a flash web application (Actionscript 2.0) for my honours project but am having trouble embedding youtube videos. Basically the user selects symbols which queries the youtube api with certain tags depending on the symbols chosenand a random video is then picked from the first 30 videos. I have this working using the following code: on (release) { url="http://gdata.youtube.com/feeds/api/videos?q=danger+passion&orderby=published&start-index="+random(30)+"&max-results=1&v=2" getURL(url); } but this just displays a webpage with a link to the youtube video. This is the code I'll be using as the foundations for the player: // create a MovieClip to load the player into var ytplayer:MovieClip = _root.createEmptyMovieClip("ytplayer", 1); // create a listener object for the MovieClipLoader to use var ytPlayerLoaderListener:Object = { onLoadInit: function() { // When the player clip first loads, we start an interval to // check for when the player is ready loadInterval = setInterval(checkPlayerLoaded, 250); } }; var loadInterval:Number; function checkPlayerLoaded():Void { // once the player is ready, we can subscribe to events, or in the case of // the chromeless player, we could load videos if (ytplayer.isPlayerLoaded()) { ytplayer.addEventListener("onStateChange", onPlayerStateChange); ytplayer.addEventListener("onError", onPlayerError); clearInterval(loadInterval); } } function onPlayerStateChange(newState:Number) { trace("New player state: "+ newState); } function onPlayerError(errorCode:Number) { trace("An error occurred: "+ errorCode); } // create a MovieClipLoader to handle the loading of the player var ytPlayerLoader:MovieClipLoader = new MovieClipLoader(); ytPlayerLoader.addListener(ytPlayerLoaderListener); // load the player ytPlayerLoader.loadClip("http://www.youtube.com/v/pv5zWaTEVkI", ytplayer); can anyone help me on how to get the id of the video (for example: pv5zWaTEVkI) from the feed? Or how to send a query from flash which will return the video url/id as opposed to the url of a feed. Any help would be much appreciated as my hand in rather soon. Thanks

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• Hazelcast Distributed Executor Service KeyOwner

  - by János Veres

  I have problem understanding the concept of Hazelcast Distributed Execution. It is said to be able to perform the execution on the owner instance of a specific key. From Documentation: <T> Future<T> submitToKeyOwner(Callable<T> task, Object key) Submits task to owner of the specified key and returns a Future representing that task. Parameters: task - task key - key Returns: a Future representing pending completion of the task I believe that I'm not alone to have a cluster built with multiple maps which might actually use the same key for different purposes, holding different objects (e.g. something along the following setup): IMap<String, ObjectTypeA> firstMap = HazelcastInstance.getMap("firstMap"); IMap<String, ObjectTypeA_AppendixClass> secondMap = HazelcastInstance.getMap("secondMap"); To me it seems quite confusing what documentation says about the owner of a key. My real frustration is that I don't know WHICH - in which map - key does it refer to? The documentation also gives a "demo" of this approach: import com.hazelcast.core.Member; import com.hazelcast.core.Hazelcast; import com.hazelcast.core.IExecutorService; import java.util.concurrent.Callable; import java.util.concurrent.Future; import java.util.Set; import com.hazelcast.config.Config; public void echoOnTheMemberOwningTheKey(String input, Object key) throws Exception { Callable<String> task = new Echo(input); HazelcastInstance hz = Hazelcast.newHazelcastInstance(); IExecutorService executorService = hz.getExecutorService("default"); Future<String> future = executorService.submitToKeyOwner(task, key); String echoResult = future.get(); } Here's a link to the documentation site: Hazelcast MultiHTML Documentation 3.0 - Distributed Execution Did any of you guys figure out in the past what key does it want?

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• Problem using structured data with sproxy-generated proxy c++ class

  - by Odrade

  I am attempting to communicate structured data types between a Visual C++ client application and an ASP.NET web service. I'm am having issues whenever any parameter or return type is not a basic type (e.g. string, int, float, etc). To illustrate the issue, I created the following ASP.NET web service: namespace TestWebService { [WebService(Namespace = "http://localhost/TestWebService")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] [ToolboxItem(false)] public class Service1 : System.Web.Services.WebService { [WebMethod] public TestData StructuredOutput() { TestData td = new TestData(); td.data = 1729; return td; } } public class TestData { public int data; } } To consume the service, I created a dirt-simple Visual C++ client in VS2005. I added a web reference to the project, which caused sproxy to generate a proxy class for me. With the generated header properly included, I attempted to invoke the service like this: int _tmain(int argc, _TCHAR* argv[]) { CoInitialize(NULL); Service1::CService1 ws; Service1::TestData td; HRESULT hr = ws.StructuredOutput(&td); //data is returned as expected CoUninitialize(); return 0; } // crashes here with access violation The call to StructuredOutput returns the data as expected, but an access violation occurs on destruction of the CService1 object. The access violation is occurring here (from atlsoap.h): void UninitializeSOAP() { if (m_spReader.p != NULL) { m_spReader->putContentHandler(NULL); //access violation m_spReader.Release(); } } I see the same behavior when using a TestData object as an input parameter, or when using any other structured data types as input or output. When I use basic types for input/output from the web service I do not experience these errors. Any ideas about why this might be happening? Is sproxy screwing something up, or am I? NOTE: I'm aware of gSOAP and the wsdl2h tool, but those aren't freely available for commercial use (and nobody here is going to buy a license). I am open to alternatives for generating the c++ proxy, as long as they are free for commercial use.

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• How to pass parameters to manage_shared_memory.construct() in Boost.Interprocess

  - by recipriversexclusion

  I've stared at the Boost.Interprocess documentation for hours but still haven't been able to figure this out. In the doc, they have an example of creating a vector in shared memory like so: //Define an STL compatible allocator of ints that allocates from the managed_shared_memory. //This allocator will allow placing containers in the segment typedef allocator<int, managed_shared_memory::segment_manager> ShmemAllocator; //Alias a vector that uses the previous STL-like allocator so that allocates //its values from the segment typedef vector<int, ShmemAllocator> MyVector; int main(int argc, char *argv[]) { //Create a new segment with given name and size managed_shared_memory segment(create_only, "MySharedMemory", 65536); //Initialize shared memory STL-compatible allocator const ShmemAllocator alloc_inst (segment.get_segment_manager()); //Construct a vector named "MyVector" in shared memory with argument alloc_inst MyVector *myvector = segment.construct<MyVector>("MyVector")(alloc_inst); Now, I understand this. What I'm stuck is how to pass a second parameter to segment.construct() to specify the number of elements. The interprocess document gives the prototype for construct() as MyType *ptr = managed_memory_segment.construct<MyType>("Name") (par1, par2...); but when I try MyVector *myvector = segment.construct<MyVector>("MyVector")(100, alloc_inst); I get compilation errors. My questions are: Who actually gets passed the parameters par1, par2 from segment.construct, the constructor of the object, e.g. vector? My understanding is that the template allocator parameter is being passed. Is that correct? How can I add another parameter, in addition to alloc_inst that is required by the constructor of the object being created in shared memory? There's very little information other than the terse Boost docs on this.

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• Debugging unexpected error message - possible memory management problem?

  - by Ben Packard

  I am trying to debug an application that is throwing up strange (to my untutored eyed) errors. When I try to simply log the count of an array... NSLog(@"Array has %i items", [[self startingPlayers] count]); ...I sometimes get an error: -[NSCFString count]: unrecognized selector sent to instance 0x1002af600 or other times -[NSConcreteNotification count]: unrecognized selector sent to instance 0x1002af600 I am not sending 'count' to any NSString or NSNotification, and this line of code works fine normally. A Theory... Although the error varies, the crash happens at predictable times, immediately after I have run through some other code where I'm thinking I might have a memory management issue. Is it possible that the object reference is still pointing to something that is meant to be destroyed? Sorry if my terms are off, but perhaps it's expecting the array at the address it calls 'count' on, but finds another previous object that shouldn't still be there (eg an NSString)? Would this cause the problem? If so, what is the most efficient way to debug and find out what is that address? Most of my debugging up until now involves inserting NSLogs, so this would be a good opportunity to learn how to use the debugger.

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• PHPUnit - multiple stubs of same class

  - by keithjgrant

  I'm building unit tests for class Foo, and I'm fairly new to unit testing. A key component of my class is an instance of BarCollection which contains a number of Bar objects. One method in Foo iterates through the collection and calls a couple methods on each Bar object in the collection. I want to use stub objects to generate a series of responses for my test class. How do I make the Bar stub class return different values as I iterate? I'm trying to do something along these lines: $stubs = array(); foreach ($array as $value) { $barStub->expects($this->any()) ->method('GetValue')) ->will($this->returnValue($value)); $stubs[] = $barStub; } // populate stubs into `Foo` // assert results from `Foo->someMethod()` So Foo->someMethod() will produce data based on the results it receives from the Bar objects. But this gives me the following error whenever the array is longer than one: There was 1 failure: 1) testMyTest(FooTest) with data set #2 (array(0.5, 0.5)) Expectation failed for method name is equal to <string:GetValue> when invoked zero or more times. Mocked method does not exist. /usr/share/php/PHPUnit/Framework/MockObject/Mock.php(193) : eval()'d code:25 One thought I had was to use ->will($this->returnCallback()) to invoke a callback method, but I don't know how to indicate to the callback which Bar object is making the call (and consequently what response to give). Another idea is to use the onConsecutiveCalls() method, or something like it, to tell my stub to return 1 the first time, 2 the second time, etc, but I'm not sure exactly how to do this. I'm also concerned that if my class ever does anything other than ordered iteration on the collection, I won't have a way to test it.

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• Optimizing processing and management of large Java data arrays

  - by mikera

  I'm writing some pretty CPU-intensive, concurrent numerical code that will process large amounts of data stored in Java arrays (e.g. lots of double[100000]s). Some of the algorithms might run millions of times over several days so getting maximum steady-state performance is a high priority. In essence, each algorithm is a Java object that has an method API something like: public double[] runMyAlgorithm(double[] inputData); or alternatively a reference could be passed to the array to store the output data: public runMyAlgorithm(double[] inputData, double[] outputData); Given this requirement, I'm trying to determine the optimal strategy for allocating / managing array space. Frequently the algorithms will need large amounts of temporary storage space. They will also take large arrays as input and create large arrays as output. Among the options I am considering are: Always allocate new arrays as local variables whenever they are needed (e.g. new double[100000]). Probably the simplest approach, but will produce a lot of garbage. Pre-allocate temporary arrays and store them as final fields in the algorithm object - big downside would be that this would mean that only one thread could run the algorithm at any one time. Keep pre-allocated temporary arrays in ThreadLocal storage, so that a thread can use a fixed amount of temporary array space whenever it needs it. ThreadLocal would be required since multiple threads will be running the same algorithm simultaneously. Pass around lots of arrays as parameters (including the temporary arrays for the algorithm to use). Not good since it will make the algorithm API extremely ugly if the caller has to be responsible for providing temporary array space.... Allocate extremely large arrays (e.g. double[10000000]) but also provide the algorithm with offsets into the array so that different threads will use a different area of the array independently. Will obviously require some code to manage the offsets and allocation of the array ranges. Any thoughts on which approach would be best (and why)?

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• Core principles, rules, and habits for CS students

  - by Asad Butt

  No doubt there is a lot to read on blogs, in books, and on Stack Overflow, but can we identify some guidelines for CS students to use while studying? For me these are: Finish your course books early and read 4-5 times more material relative to your course work. Programming is the one of the fastest evolving professions. Follow the blogs on a daily basis for the latest updates, news, and technologies. Instead of relying on assignments and exams, do at least one extra, non-graded, small to medium-sized project for every programming course. Fight hard for internships or work placements even if they are unpaid, since 3 months of work 1 year at college. Practice everything, every possible and impossible way. Try doing every bit of your assignments project yourself; i.e. fight for every inch. Rely on documentation as the first source for help and samples, Google, and online forums as the last source. Participate often in online communities and forums to learn the best possible approach for every solution to your problem. (After doing your bit.) Make testing one of your habits as it is getting more important everyday in programming. Make writing one of your habits. Write something productive once or twice a week and publish it.

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• Dragging a copy of all selected elements from a select box--possible?

  - by Sean

  I have a picklist web interface: a pair of select elements with a pair of buttons (a left-pointing arrow and a right-pointing arrow) between them. Users can move items between the two columns by, eg, selecting one of options in the left column and clicking on the right-pointing arrow. Now I have an enhancement request: someone wants to be able to drag-and-drop items between the two columns instead of clicking a button. The problem with my initial two-select-box setup is that as soon as I click one of the highlighted options to initiate a drag, all of the other selected options are deselected. Using jQuery, I've attached mousedown event handlers to both the select boxes and each individual option that just call preventDefault() on the event object, but this isn't sufficient. On Firefox 3 the clicked-on option loses focus immediately, but all other options are still deseleted, and on IE6 (which I regrettably still have to support) it makes no difference at all. So I thought I could maybe create a reasonable facsimile of a select box using list elements or divs or something. I can create something reasonable-looking that works on Firefox, but on IE6, if I shift-click on an element of my pseudo-select object (in order to select a range of options), IE selects all of the text between where I click and the last place I clicked. Again, I've attached preventDefault-ing mousedown, mouseup, and click handlers to all of the elements involved, but it doesn't help. I've even tried overlaying transparent divs over both my original select boxes and my pseudo-select objects, thinking to intercept mouse clicks and manage the selections manually, but I can't make it work on IE. If I use a select box, I can't prevent clicks from changing the selection, and if I use text that just looks like a select element, I can't prevent it from selecting a range of text on a shift-click. Is there some general solution, or am I just out of luck?

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• Calling QAxWidget method outside of the GUI thread

  - by user304361

  I'm beginning to wonder if this is impossible, but I thought I'd ask in case there's a clever way to get around the problems I'm having. I have a Qt application that uses an ActiveX control. The control is held by a QAxWidget, and the QAxWidget itself is contained within another QWidget (I needed to add additional signals/slots to the widget, and I couldn't just subclass QAxWidget because the class doesn't permit that). When I need to interact with the ActiveX control, I call a method of the QWidget, which in turn calls the dynamicCall method of the QAxWidget in order to invoke the appropriate method of the ActiveX control. All of that is working fine. However, one method of the ActiveX control takes several seconds to return. When I call this method, my entire GUI locks up for a few seconds until the method returns. This is undesirable. I'd like the ActiveX control to go off and do its processing by itself and come back to me when it's done without locking up the Qt GUI. I've tried a few things without success: Creating a new QThread and calling QAxWidget::dynamicCall from the new thread Connecting a signal to the appropriate slot method of the QAxWidget and calling the method using signals/slots instead of using dynamicCall Calling QAxWidget::dynamicCall using QtConcurrent::run Nothing seems to affect the behavior. No matter how or where I use dynamicCall (or trigger the appropriate slot of the QAxWidget), the GUI locks until the ActiveX control completes its operation. Is there any way to detach this ActiveX processing from the Qt GUI thread so that the GUI doesn't lock up while the ActiveX control is running a method? Is there something clever I can do with QAxBase or QAxObject to get my desired results?

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