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  • Error handling in C++, constructors vs. regular methods

    - by Dennis Ritchie
    I have a cheesesales.txt CSV file with all of my recent cheese sales. I want to create a class CheeseSales that can do things like these: CheeseSales sales("cheesesales.txt"); //has no default constructor cout << sales.totalSales() << endl; sales.outputPieChart("piechart.pdf"); The above code assumes that no failures will happen. In reality, failures will take place. In this case, two kinds of failures could occur: Failure in the constructor: The file may not exist, may not have read-permissions, contain invalid/unparsable data, etc. Failure in the regular method: The file may already exist, there may not be write access, too little sales data available to create a pie chart, etc. My question is simply: How would you design this code to handle failures? One idea: Return a bool from the regular method indicating failure. Not sure how to deal with the constructor. How would seasoned C++ coders do these kinds of things?

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  • better way of handling nested list

    - by laspal
    Hi, I have list my_list = [ [1,2,3,4,5,6], [1,3,4],[34,56,56,56]] for item in my_list: var1,var2,var3,var4,var5,var6 = None if len(item) ==1: var1 = item[0] if len(item) == 2: var1 = item[0] var2 = item[1] if len(item) == 3: var1 = item[0] var2 = item[1] var3 = item[2] if len(item) == 4: var1 = item[0] var2 = item[1] var3 = item[2] var4 = item[3] fun(var1,var2,var3,var4,var5,var6) I have a function def fun(var1, var2 = None, var3 = None, var4 = None, var5=None, var6= None) Depending upon the values in my inner list. I am passing it to function. I hope I made it clear. Thanks

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  • SQL Server error handling: exceptions and the database-client contract

    - by gbn
    We’re a team of SQL Servers database developers. Our clients are a mixed bag of C#/ASP.NET, C# and Java web services, Java/Unix services and some Excel. Our client developers only use stored procedures that we provide and we expect that (where sensible, of course) they treat them like web service methods. Some our client developers don’t like SQL exceptions. They understand them in their languages but they don’t appreciate that the SQL is limited in how we can communicate issues. I don’t just mean SQL errors, such as trying to insert “bob” into a int column. I also mean exceptions such as telling them that a reference value is wrong, or that data has already changed, or they can’t do this because his aggregate is not zero. They’d don’t really have any concrete alternatives: they’ve mentioned that we should output parameters, but we assume an exception means “processing stopped/rolled back. How do folks here handle the database-client contract? Either generally or where there is separation between the DB and client code monkeys. Edits: we use SQL Server 2005 TRY/CATCH exclusively we log all errors after the rollback to an exception table already we're concerned that some of our clients won't check output paramaters and assume everything is OK. We need errors flagged up for support to look at. everything is an exception... the clients are expected to do some message parsing to separate information vs errors. To separate our exceptions from DB engine and calling errors, they should use the error number (ours are all 50,000 of course)

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  • PHP: Handling Multiple Submit Buttons

    - by sebb
    Would like to get a consensus as to what the best practice is in this scenario: Muliple submit buttons, is it better to handle this by having separate FORMS for each one of the submits, OR is it okay to have one form and check which button was pressed? thank you for your input :D

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  • powershell capture call stack after an error is thrown

    - by davidhayes
    Hi, I want to do something like this... try { # Something in this function throws an exception Backup-Server ... }catch { # Capture stack trace of where the error was thrown from Log-Error $error } Ideally I'd like to capture arguments to the function and line numbers etc. (like you see in get-pscallstack) Any ideas how to achieve this? Dave

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  • Handling close-to-impossible collisions on should-be-unique values

    - by balpha
    There are many systems that depend on the uniqueness of some particular value. Anything that uses GUIDs comes to mind (eg. the Windows registry or other databases), but also things that create a hash from an object to identify it and thus need this hash to be unique. A hash table usually doesn't mind if two objects have the same hash because the hashing is just used to break down the objects into categories, so that on lookup, not all objects in the table, but only those objects in the same category (bucket) have to be compared for identity to the searched object. Other implementations however (seem to) depend on the uniqueness. My example (that's what lead me to asking this) is Mercurial's revision IDs. An entry on the Mercurial mailing list correctly states The odds of the changeset hash colliding by accident in your first billion commits is basically zero. But we will notice if it happens. And you'll get to be famous as the guy who broke SHA1 by accident. But even the tiniest probability doesn't mean impossible. Now, I don't want an explanation of why it's totally okay to rely on the uniqueness (this has been discussed here for example). This is very clear to me. Rather, I'd like to know (maybe by means of examples from your own work): Are there any best practices as to covering these improbable cases anyway? Should they be ignored, because it's more likely that particularly strong solar winds lead to faulty hard disk reads? Should they at least be tested for, if only to fail with a "I give up, you have done the impossible" message to the user? Or should even these cases get handled gracefully? For me, especially the following are interesting, although they are somewhat touchy-feely: If you don't handle these cases, what do you do against gut feelings that don't listen to probabilities? If you do handle them, how do you justify this work (to yourself and others), considering there are more probable cases you don't handle, like a supernonva?

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  • In FLEX, How can you stop ENTER Key from my Alert being caught by the control that initiated the Al

    - by WeeJavaDude
    I am having an issue where I show an AlertBox message when the user hits ENTER and the focus is in a text area. The pop up works fine, but when the user hits enter the Alert closes as expected, but the TextArea listener receives the ENTER event from the Alert and pops the dialog up again. I have tried a number of ways to catch and eat the event but so far I have not been lucky. Is there way to accomplish this? public function init():void { myTextInput.addEventListener(KeyboardEvent.KEY_UP, handleKeyStrokes); } public function handleKeyStrokes(evt:KeyboardEvent):void { if(evt.keyCode == Keyboard.ENTER) { myAlert = Alert.show("This is a test and only a test", "Title", 4, null, alertCallBack); } } <mx:TextInput id="myTextInput" left="600" top="10"> </mx:TextInput>

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  • problem in handling menu - submenu based on spring security

    - by Nirmal
    Hi All... I have configured spring security core plugin using requestmap table inside the database.. Now inside requestmap table I have all the possible urls and it's equivalent roles who can access that url... Now I want to generate menus and submenus based on the urls stored in requestmap table... So my requirement is to check the urls of menu & submenus against the logged in users privileges... And if logged in user has any one privilege then I need to display that main menu and the available submenus.... For e.g. I have a menu in my project called user which has a following submenus : **Users (main menu)** Manage Users (sub menu) Import Users (sub menu) Now inside my header.gsp I have successfully achieved the above requirement using if else condition, like : if ( privs.contains("/users/manageUsers") || privs.contains("/users/importUsers")) here privs are the list of urls from requestmap table for logged in user. But I want to achieve these using spring security tag lib, so for comparing urls I have find following tag from spring security core documentation : <sec:access url="/users/manageUsers"> But i am bit confuse that how I can replace or condition using tag library.. Is there any tag available which checks from multiple urls and evaluate it to true or false ? Of course I can do using sec:access tag with some flag logic, but is there any tags available which can fulfill my requirement directly ? Thanks in advance...

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  • Is there a browser-agnostic way to detect client-side script errors with Watin?

    - by Michael
    We're using WatiN to test our web portals. During the course of an E2E test, we'll occasionally see client-side script errors on the IE status bar. I'd like to chain a handler onto the script error event and record the error for later analysis and bug filing. Problem is, I don't know that there's a global script error event or how to chain into it. And if there's not a browser-agnostic way to accomplish this, I can create MyIE and MyFF subclasses but then this becomes two browser-specific questions. In essence, I'm thinking of something like this entirely made-up call: browser.ScriptEngine.SetCustomErrorHandler(LogScriptingError); ... where LogScriptErrors is my code that does the obvious. Many of our client-side scripting errors don't necessarily prevent the test from continuing (a pretty UI element didn't animate, for example, but the underlying form is still submittable), so I'd like to log the error and forge ahead in most cases.

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  • Rescuing a failed WCF call

    - by illdev
    Hello, I am happily using Castle's WcfFacility. From Monorail I know the handy concept of Rescues - consumer friendly results that often, but not necessarily, contain Data about what went wrong. I am creating a Silverlight application right now, doing quite a few WCF service calls. All these request return an implementation of public class ServiceResponse { private string _messageToUser = string.Empty; private ActionResult _result = ActionResult.Success; public ActionResult Result // Success, Failure, Timeout { get { return _result; } set { _result = value; } } public string MessageToUser { get { return _messageToUser; } set { _messageToUser = value; } } } public abstract class ServiceResponse<TResponseData> : ServiceResponse { public TResponseData Data { get; set; } } If the service has trouble responding the right way, I would want the thrown Exception to be intercepted and converted to the expected implementation. base on the thrown exception, I would want to pass on a nice message. here is how one of the service methods looks like: [Transaction(TransactionMode.Requires)] public virtual SaveResponse InsertOrUpdate(WarehouseDto dto) { var w = dto.Id > 0 ? _dao.GetById(dto.Id) : new Warehouse(); w.Name = dto.Name; _dao.SaveOrUpdate(w); return new SaveResponse { Data = new InsertData { Id = w.Id } }; } I need the thrown Exception for the Transaction to be rolled back, so i cannot actually catch it and return something else. Any ideas, where I could hook in?

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  • Magento: Why do controller action predispatch events not fire if the controller is rewritten?

    - by mattalexx
    Why do controller action predispatch events not fire if the controller is rewritten? Here is a snippet of store/app/code/core/Mage/Core/Controller/Varien/Action.php: abstract class Mage_Core_Controller_Varien_Action { // [...] public function preDispatch() { // [...] if ($this->_rewrite()) { return; // [What is the purpose if this?] } // [...] // [This is where my event needs to be firing, but this code never gets // executed because the controller is rewritten] Mage::dispatchEvent( 'controller_action_predispatch_'.$this->getFullActionName(), array('controller_action'=>$this) ); } // [...] } I don't know where to start fixing this problem. Anyone out there ever dealt with this before?

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  • ASP.NET MVC - How to Preserve ModelState Errors Across RedirectToAction?

    - by RPM1984
    Hi Guys, I have the following two action methods (simplified for question): [HttpGet] public ActionResult Create(string uniqueUri) { // get some stuff based on uniqueuri, set in ViewData. return View(); } [HttpPost] public ActionResult Create(Review review) { // validate review if (validatedOk) { return RedirectToAction("Details", new { postId = review.PostId}); } else { ModelState.AddModelError("ReviewErrors", "some error occured"); return RedirectToAction("Create", new { uniqueUri = Request.RequestContext.RouteData.Values["uniqueUri"]}); } } So, if the validation passes, i redirect to another page (confirmation). If an error occurs, i need to display the same page with the error. If i do return View(), the error is displayed, but if i do return RedirectToAction (as above), it loses the Model errors. I'm not surprised by the issue, just wondering how you guys handle this? I could of course just return the same View instead of the redirect, but i have logic in the "Create" method which populates the view data, which i'd have to duplicate. Any suggestions?

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  • In a client-server relationship, should the server always rethrow the exception to the client?

    - by dotnetdev
    I have a set of web services (the server), and an app which consumes this (client). In this sort of relationship, should the server always throw exceptions (ie in the throw block, rethrow the caught exception), and the client catch this. Exceptions which the server can handle, it will deal with and not rethrow, but everything else will be thrown to the calling layer for further action (the consuming app can raise a msg box or whatever). Is this a good example of an exception that can be dealt with: A file cannot be written because the directory requires special privileges, so if this raises an exception, the file is written somewhere which does not require admin rights. Thanks

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  • Method with throws Exception: Where is it actually handled?

    - by Esq
    Here is an example code, I am throwing an exception here, it works perfectly fine without the try/catch block of code for some reason. Do I have to handle this inside this method "EntryDelete" or Do I have to handle this where the method is called from? If so can I see an example, what do I have to import in there? What is the acceptable syntax or method to do this? public boolean EntryDelete(int entryId) throws SQLException{ this.open(); kDatabase.delete(kENTRY_TABLE, kENTRY_ENTRY_ID + "=" + entryId, null); this.close(); return true; } Thanks

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  • C++ Storing variables and inheritance

    - by Kaa
    Hello Everyone, Here is my situation: I have an event driven system, where all my handlers are derived from IHandler class, and implement an onEvent(const Event &event) method. Now, Event is a base class for all events and contains only the enumerated event type. All actual events are derived from it, including the EventKey event, which has 2 fields: (uchar) keyCode and (bool)isDown. Here's the interesting part: I generate an EventKey event using the following syntax: Event evt = EventKey(15, true); and I ship it to the handlers: EventDispatch::sendEvent(evt); // void EventDispatch::sendEvent(const Event &event); (EventDispatch contains a linked list of IHandlers and calls their onEvent(const Event &event) method with the parameter containing the sent event. Now the actual question: Say I want my handlers to poll the events in a queue of type Event, how do I do that? x Dynamic pointers with reference counting sound like too big of a solution. x Making copies is more difficult than it sounds, since I'm only receiving a reference to a base type, therefore each time I would need to check the type of event, upcast to EventKey and then make a copy to store in a queue. Sounds like the only solution - but is unpleasant since I would need to know every single type of event and would have to check that for every event received - sounds like a bad plan. x I could allocate the events dynamically and then send around pointers to those events, enqueue them in the array if wanted - but other than having reference counting - how would I be able to keep track of that memory? Do you know any way to implement a very light reference counter that wouldn't interfere with the user? What do you think would be a good solution to this design? I thank everyone in advance for your time. Sincerely, Kaa

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  • Proper error handling in a custom Zend_Autoloader?

    - by Pekka
    I'm building a custom autoloader based on Zend Framework's autoloading (related question here). The basic approach, taken from that question, is class My_Autoloader implements Zend_Loader_Autoloader_Interface { public function autoload($class) { // add your logic to find the required classes in here } } and then binding the new autoloader class to a class prefix. Now what I'm unsure about is how to handle errors inside the autoload method (for example, "class file not found") in a proper, ZF compliant way. I'm new to the framework, its conventions and style. Do I quietly return false and let the class creation process crash? Do I output an error or log message somehow (which would be nice to pinpoint the problem) and return false? If so, what is the Zend way of doing that? Do I trigger an error? Do I throw an exception? If so, what kind?

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  • handling javaScript alerts when running a selenium test?

    - by Mo
    Hi I am am running some selenium tests(ruby) on my web page and as i enter an invalid characters in to a text box i have the JavaScript throw a alert like so if(isNaN($(this).val()) || Number($(this).val().valueOf() <=0)){ alert("Please Enter A Number"); } how can i handle this alert when its made and close the pop up? i tried to use the wait_for_pop_up() and close() but i think that's only for browser pop up's and not JavaScript alerts. any ideas? thanks

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  • Writing exceptions in multihreaded windows service to event log

    - by Ziplin
    I have a multithreaded windows service that will unpredictably stop running once every 24 hours or so. I am writing to the event log and that's going through just fine, but whenever the service crashes there are no messages in the event log (even that the service stopped, despite having AutoLog=true). Is there a way to have uncaught exceptions written straight to the log, even if they aren't in the original thread?

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  • Ideal way to set global uncaught exception Handler in Android

    - by Samuh
    I want to set a global uncaught exception handler for all the threads in my Android application. So, in my Application subclass I set an implementation of Thread.UncaughtExceptionHandler as default handler for uncaught exceptions. Thread.setDefaultUncaughtExceptionHandler( new DefaultExceptionHandler(this)); In my implementation, I am trying to display an AlertDialog displaying appropriate exception message. However, this doesn't seem to work. Whenever, an exception is thrown for any thread which goes un-handled, I get the stock, OS-default dialog (Sorry!-Application-has-stopped-unexpectedly dialog). What is the correct and ideal way to set a default handler for uncaught exceptions? Thanks.

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  • WCF net.tcp server disconnects - how to handle properly on client side?

    - by RoastedBattleSquirrel
    I'm stuck with a bit of an annoying problem right now. I've got a Silverlight 4 application (which runs OOB by default). It uses WCF with net.tcp as means of communicating with the server. The client uses a central instance of the wcf client proxy. As long as everything keeps running on the server side, everything's fine. If i kill the server in the middle of everything, i drown in an avalanche of exceptions on the client side (connection lost, channel faulted etc etc). Now i'm looking for a way to handle this in a clean and centralized way (if centralized is possible). The SL app has one central client object sitting in App.cs (public static MyClient Client { get;set;}), which gets initialized on application start. Any idea how to properly handle any connectivity problems on the client object?

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  • Python - from file to data structure?

    - by Seafoid
    Hi, I have large file comprising ~100,000 lines. Each line corresponds to a cluster and each entry within each line is a reference i.d. for another file (protein structure in this case), e.g. 1hgn 1dju 3nmj 8kfn 9opu 7gfb 4bui I need to read in the file as a list of lists where each line is a sublist, thus preserving the integrity of the cluster, e.g. nested_list = [['1hgn', '1dju', '3nmj', '8kfn'], ['9opu', '7gfb'], ['4bui']] My current code creates a nested list but the entries within each list are a single string and not comma separated. Therefore, I cannot splice the list with indices so easily. Any help greatly appreciated. Thanks, S :-)

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