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  • rails search nested set (categories and sub categories)

    - by bob
    Hello, I am using the http://github.com/collectiveidea/awesome_nested_set awesome nested set plugin and currently, if I choose a sub category as my category_id for an item, I can not search by its parent. Category.parent Category.Child I choose Category.child as the category that my item is in. So now my item has category_id of 4 stored in it. If I go to a page in my rails application, lets say teh Category page and I am on the Category.parent's page, I want to show products that have category_id's of all the descendants as well. So ideally i want to have a find method that can take into account the descendants. You can get the descendants of a root by calling root.descendants (a built in plugin method). How would I go about making it so I can query a find that gets the descendants of a root instead of what its doing now which is binging up nothing unless the product had a specific category_id of the Category.parent. I hope I am being clear here. I either need to figure out a way to create a find method or named_scope that can query and return an array of objects that have id's corresponding tot he descendants of a root OR if I have any other options, what are they? I thought about creating a field in my products table like parent_id which can keep track of the parent so i can then create two named scopes one finding the parent stuff and one finding the child stuff and chaining them. I know I can create a named scope for each child and chain them together for multiple children but this seems a very tedious process and also, if you add more children, you would need to specify more named scopes.

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  • How Do I Prevent Rails From Treating Updated Nested Attributes Differently From New Nested Attribute

    - by James
    I am using rails3 beta3 and couchdb via couchrest. I am not using active record. I want to add multiple "Sections" to a "Guide" and add and remove sections dynamically via a little javascript. I have looked at all the screencasts by Ryan Bates and they have helped immensely. The only difference is that I want to save all the sections as an array of sections instead of individual sections. Basically like this: "sections" => [{"title" => "Foo1", "content" => "Bar1"}, {"title" => "Foo2", "content" => "Bar2"}] So, basically I need the params hash to look like that when the form is submitted. When I create my form I am doing the following: <%= form_for @guide, :url => { :action => "create" } do |f| %> <%= render :partial => 'section', :collection => @guide.sections %> <%= f.submit "Save" %> <% end %> And my section partial looks like this: <%= fields_for "sections[]", section do |guide_section_form| %> <%= guide_section_form.text_field :section_title %> <%= guide_section_form.text_area :content, :rows => 3 %> <% end %> Ok, so when I create the guide with sections, it is working perfectly as I would like. The params hash is giving me a sections array just like I would want. The problem comes when I want edit guide/sections and save them again because rails is inserting the id of the guide in the id and name of each form field, which is screwing up the params hash on form submission. Just to be clear, here is the raw form output for a new resource: <input type="text" size="30" name="sections[][section_title]" id="sections__section_title"> <textarea rows="3" name="sections[][content]" id="sections__content" cols="40"></textarea> And here is what it looks like when editing an existing resource: <input type="text" value="Foo1" size="30" name="sections[cd2f2759895b5ae6cb7946def0b321f1][section_title]" id="sections_cd2f2759895b5ae6cb7946def0b321f1_section_title"> <textarea rows="3" name="sections[cd2f2759895b5ae6cb7946def0b321f1][content]" id="sections_cd2f2759895b5ae6cb7946def0b321f1_content" cols="40">Bar1</textarea> How do I force rails to always use the new resource behavior and not automatically add the id to the name and value. Do I have to create a custom form builder? Is there some other trick I can do to prevent rails from putting the id of the guide in there? I have tried a bunch of stuff and nothing is working. Thanks in advance!

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  • What's the reason exceptions are heavily used in managed (C# and Java) languages but not in C++? [on hold]

    - by ZijingWu
    AFAIK, a lot of C++ projects don't allow exceptions and deny them in coding guidelines. I have a lot of reasons, for example, exception is hard to handle correctly if your binary needs to be compiled by separate and different compilers. But it doesn't fully convince me, there is a lot of projects which are just using one compiler. Compared to C++, exceptions are heavily used in C# and Java and the reason can only be that exception are not bringing enough benefit. One point is debugbility in practice. Exception can not get the call stack in C++ code, but in C# and Java you can get the call stack from exception, it is significant and makes debugging easier. No-callstack is not the fault of the exception, it is the language difference, but it impacts the exception usage. So what's the reason that exceptions are frowned upon in c++ programs?

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  • Producing Mini Dumps for _caught_ SEH exceptions in mixed code DLL

    - by Assaf Lavie
    I'm trying to use code similar to clrdump to create mini dumps in my managed process. This managed process invokes C++/CLI code which invokes some native C++ static lib code, wherein SEH exceptions may be thrown (e.g. the occasional access violation). C# WinForms -> C++/CLI DLL -> Static C++ Lib -> ACCESS VIOLATION Our policy is to produce mini dumps for all SEH exceptions (caught & uncaught) and then translate them to C++ exceptions to be handled by application code. This works for purely native processes just fine; but when the application is a C# application - not so much. The only way I see to produce dumps from SEH exceptions in a C# process is to not catch them - and then, as unhandled exceptions, use the Application.ThreadException handler to create a mini dump. The alternative is to let the CLR translate the SEH exception into a .Net exception and catch it (e.g. System.AccessViolationException) - but that would mean no dump is created, and information is lost (stack trace information in Exception isn't as rich as the mini dump). So how can I handle SEH exceptions by both creating a minidump and translating the exception into a .Net exception so that my application may try to recover?

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  • How to get rid of exceptions thrown by the .NET Framework

    - by Hans Løken
    In a recent project I'm using a lot of databinding and xml-serialization. I'm using C#/VS2008 and have downloaded symbol information for the .NET framework to help me when debugging. The app I'm working on has a global "catch all" exception handler to present a more presentable messages to users if there happens to be any uncaught exceptions being thrown. My problem is when I turn on Exceptions-Thrown to be able to debug exceptions before they are caught by the "catch all". It seems to me that the framework throws a lot of exceptions that are not immediately caught (for example in ReflectPropertyDescriptor) so that the exception I'm actually trying to debug gets lost in the noise. Is there any way to get rid of exceptions caused by the framework but keep the ones from my own code? Update: after more research and actually trying to get rid of the exceptions that get thrown by the framework (many which turn out to be known issues in the framework, example: http://stackoverflow.com/questions/1127431/xmlserializer-giving-filenotfoundexception-at-constructor) I finally found a solution that works for me, which is turning on "Just my code" in Tools Options Debugging General Enable Just My Code in VS2008.

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  • Accepts Nested Attributes For - edit form displays incorrect number of items ( + !map:ActiveSupport:

    - by Brightbyte8
    Hi, I have a teacher profile model which has many subjects (separate model). I want to add subjects to the profile on the same form for creating/editing a profile. I'm using accepts_nested_attributes for and this works fine for creation. However on the edit page I am getting a very strange error - instead of seeing 3 subjects (I added three at create and a look into the console confirms this), I see 12 subjects(!). #Profile model class Profile < ActiveRecord::Base has_many :subjects accepts_nested_attributes_for :subjects end #Subject Model class Subject < ActiveRecord::Base belongs_to :profile end #Profile Controller (only showing deviations from normal RESTFUL setup) def new @profile = Profile.new 3.times do @profile.subjects.build end end #Here's 1 of three parts of the subject output of = debug @profile errors: !ruby/object:ActiveRecord::Errors base: *id004 errors: !map:ActiveSupport::OrderedHash {} subjects: - &id001 !ruby/object:Subject attributes: exam: Either name: "7" created_at: 2010-04-15 10:38:13 updated_at: 2010-04-15 10:38:13 level: Either id: "31" profile_id: "3" attributes_cache: {} # Note that 3 of these attributes are displayed despite me seeing 12 subjects on screen Other info in case it's relevant. Rails: 2.3.5 Ruby 1.8.7 p149 HAML I've never had so much difficulty with a bug before - I've already lost about 8 hours to it. Would really appreciate any help! Thanks to any courageous takers Jack

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  • Updating nested attributes causes duplicate entries

    - by params_noob
    I have a has_many and belongs_to relationship between Job and Address. When I try to update Job and Address in the same form, it updates job but creates a duplicate entry for Address. Am I missing something here? The Edit and Update Actions from Jobs: def edit @job = Job.find(params[:id]) end def update @job = Job.find(params[:id]) if @job.update_attributes(job_params) flash[:success] = "Job Updated" redirect_to current_user else render 'edit' end end The edit form: <h1>Edit Job Information</h1> <div class="row"> <div class="span6 offset3"> <%= form_for(@job) do |f| %> <%= render 'shared/error_messages' %> <%= f.label :recipient %> <%= f.text_field :recipient %> <%= f.label :age %> <%= f.text_field :age %> <%= f.label :gender %> <%= f.text_field :gender %> <%= f.label :ethnicity %> <%= f.text_field :ethnicity %> <%= f.label :height %> <%= f.text_field :height %> <%= f.label :weight %> <%= f.text_field :weight %> <%= f.label :hair %> <%= f.text_field :hair %> <%= f.label :eyes %> <%= f.text_field :eyes %> <%= f.label :other_info %> <%= f.text_field :other_info %> <h3> Address Information </h3> <%= f.fields_for :addresses do |address| %> <%= address.label :label, "Label" %> <%= address.text_field :label %> <%= address.label :addy, "Address" %> <%= address.text_field :addy %> <%= address.label :apt, "Apt/Suite/etc" %> <%= address.text_field :apt %> <%= address.label :city, "City" %> <%= address.text_field :city %> <%= address.label :state, "State" %> <%= address.text_field :state %> <%= address.label :zip, "Zip code" %> <%= address.text_field :zip %> <% end %> <%= f.label :instructions, "Service Instructions" %> <%= f.text_field :instructions %> <%= check_box_tag(:rush) %> <%= label_tag(:rush, "Rush?") %> <%= f.submit "Update Job", class: "btn btn-large btn-primary" %> <% end %> </div> </div>

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  • Visual Studio Exceptions dialogs

    - by Daniel Moth
    Previously I covered step 1 of live debugging with start and attach. Once the debugger is attached, you want to go to step 2 of live debugging, which is to break. One way to break under the debugger is to do nothing, and just wait for an exception to occur in your code. This is true for all types of code that you debug in Visual Studio, and let's consider the following piece of C# code:3: static void Main() 4: { 5: try 6: { 7: int i = 0; 8: int r = 5 / i; 9: } 10: catch (System.DivideByZeroException) {/*gulp. sue me.*/} 11: System.Console.ReadLine(); 12: } If you run this under the debugger do you expect an exception on line 8? It is a trick question: you have to know whether I have configured the debugger to break when exceptions are thrown (first-chance exceptions) or only when they are unhandled. The place you do that is in the Exceptions dialog which is accessible from the Debug->Exceptions menu and on my installation looks like this: Note that I have checked all CLR exceptions. I could have expanded (like shown for the C++ case in my screenshot) and selected specific exceptions. To read more about this dialog, please read the corresponding Exception Handling debugging msdn topic and all its subtopics. So, for the code above, the debugger will break execution due to the thrown exception (exactly as if the try..catch was not there), so I see the following Exception Thrown dialog: Note the following: I can hit continue (or hit break and then later continue) and the program will continue fine since I have a catch handler. If this was an unhandled exception, then that is what the dialog would say (instead of first chance exception) and continuing would crash the app. That hyperlinked text ("Open Exception Settings") opens the Exceptions dialog I described further up. The coolest thing to note is the checkbox - this is new in this latest release of Visual Studio: it is a shortcut to the checkbox in the Exceptions dialog, so you don't have to open it to change this setting for this specific exception - you can toggle that option right from this dialog. Finally, if you try the code above on your system, you may observe a couple of differences from my screenshots. The first is that you may have an additional column of checkboxes in the Exceptions dialog. The second is that the last dialog I shared may look different to you. It all depends on the Debug->Options settings, and the two relevant settings are in this screenshot: The Exception assistant is what configures the look of the UI when the debugger wants to indicate exception to you, and the Just My Code setting controls the extra column in the Exception dialog. You can read more about those options on MSDN: How to break on User-Unhandled exceptions (plus Gregg’s post) and Exception Assistant. Before I leave you to go play with this stuff a bit more, please note that this level of debugging is now available for JavaScript too, and if you are looking at the Exceptions dialog and wondering what the "GPU Memory Access Exceptions" node is about, stay tuned on the C++ AMP blog ;-) Comments about this post by Daniel Moth welcome at the original blog.

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  • Windows vista firewall exceptions unchangeable

    - by user61099
    Hey, I want to allow a program (iTunes) through my windows firewall, so i check it in the program or port list under the exceptions tab (in my windows firewall settings), then i click OK. When i reopen the window the box is unchecked again. Which means i can never get the program through my windows firewall. I think this is a problem due to administrators rights. Because I also can not delete the program from the list. I can however delete other programs from the list. Anybody have any ideas, tips, remarks?

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  • If the model is validating the data, shouldn't it throw exceptions on bad input?

    - by Carlos Campderrós
    Reading this SO question it seems that throwing exceptions for validating user input is frowned upon. But who should validate this data? In my applications, all validations are done in the business layer, because only the class itself really knows which values are valid for each one of its properties. If I were to copy the rules for validating a property to the controller, it is possible that the validation rules change and now there are two places where the modification should be made. Is my premise that validation should be done on the business layer wrong? What I do So my code usually ends up like this: <?php class Person { private $name; private $age; public function setName($n) { $n = trim($n); if (mb_strlen($n) == 0) { throw new ValidationException("Name cannot be empty"); } $this->name = $n; } public function setAge($a) { if (!is_int($a)) { if (!ctype_digit(trim($a))) { throw new ValidationException("Age $a is not valid"); } $a = (int)$a; } if ($a < 0 || $a > 150) { throw new ValidationException("Age $a is out of bounds"); } $this->age = $a; } // other getters, setters and methods } In the controller, I just pass the input data to the model, and catch thrown exceptions to show the error(s) to the user: <?php $person = new Person(); $errors = array(); // global try for all exceptions other than ValidationException try { // validation and process (if everything ok) try { $person->setAge($_POST['age']); } catch (ValidationException $e) { $errors['age'] = $e->getMessage(); } try { $person->setName($_POST['name']); } catch (ValidationException $e) { $errors['name'] = $e->getMessage(); } ... } catch (Exception $e) { // log the error, send 500 internal server error to the client // and finish the request } if (count($errors) == 0) { // process } else { showErrorsToUser($errors); } Is this a bad methodology? Alternate method Should maybe I create methods for isValidAge($a) that return true/false and then call them from the controller? <?php class Person { private $name; private $age; public function setName($n) { $n = trim($n); if ($this->isValidName($n)) { $this->name = $n; } else { throw new Exception("Invalid name"); } } public function setAge($a) { if ($this->isValidAge($a)) { $this->age = $a; } else { throw new Exception("Invalid age"); } } public function isValidName($n) { $n = trim($n); if (mb_strlen($n) == 0) { return false; } return true; } public function isValidAge($a) { if (!is_int($a)) { if (!ctype_digit(trim($a))) { return false; } $a = (int)$a; } if ($a < 0 || $a > 150) { return false; } return true; } // other getters, setters and methods } And the controller will be basically the same, just instead of try/catch there are now if/else: <?php $person = new Person(); $errors = array(); if ($person->isValidAge($age)) { $person->setAge($age); } catch (Exception $e) { $errors['age'] = "Invalid age"; } if ($person->isValidName($name)) { $person->setName($name); } catch (Exception $e) { $errors['name'] = "Invalid name"; } ... if (count($errors) == 0) { // process } else { showErrorsToUser($errors); } So, what should I do? I'm pretty happy with my original method, and my colleagues to whom I have showed it in general have liked it. Despite this, should I change to the alternate method? Or am I doing this terribly wrong and I should look for another way?

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  • Throwing exceptions as well as catching exceptions?

    - by Eric S
    I was wondering how Java takes the following scenario public static void main(String[] args) throws IndexOutOfBoundsException, CoordinateException, MissionException, SQLException, ParserConfigurationException { try { doSomething(); } catch (Exception e) { e.printStackTrace(); } } In the above code, I am declaring the main function to throw many different exceptions, but inside the function, I am catching the generic Exception. I am wondering how java takes this internally? I.e., say doSomething() throws an IndexOutOfBounds exception, will the e.printStackTrace() get called in the last catch (Exception e) {...} block? I know if an exception not declared in the throws area of the function gets thrown, the try/catch will handle it, but what about exceptions mentioned in the declaration?

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  • C++ non-member functions for nested template classes

    - by beldaz
    I have been writing several class templates that contain nested iterator classes, for which an equality comparison is required. As I believe is fairly typical, the comparison is performed with a non-member (and non-friend) operator== function. In doing so, my compiler (I'm using Mingw32 GCC 4.4 with flags -O3 -g -Wall) fails to find the function and I have run out of possible reasons. In the rather large block of code below there are three classes: a Base class, a Composed class that holds a Base object, and a Nested class identical to the Composed class except that it is nested within an Outer class. Non-member operator== functions are supplied for each. These classes are in templated and untemplated forms (in their own respective namespaces), with the latter equivalent to the former specialised for unsigned integers. In main, two identical objects for each class are compared. For the untemplated case there is no problem, but for the templated case the compiler fails to find operator==. What's going on? #include <iostream> namespace templated { template<typename T> class Base { T t_; public: explicit Base(const T& t) : t_(t) {} bool equal(const Base& x) const { return x.t_==t_; } }; template<typename T> bool operator==(const Base<T> &x, const Base<T> &y) { return x.equal(y); } template<typename T> class Composed { typedef Base<T> Base_; Base_ base_; public: explicit Composed(const T& t) : base_(t) {} bool equal(const Composed& x) const {return x.base_==base_;} }; template<typename T> bool operator==(const Composed<T> &x, const Composed<T> &y) { return x.equal(y); } template<typename T> class Outer { public: class Nested { typedef Base<T> Base_; Base_ base_; public: explicit Nested(const T& t) : base_(t) {} bool equal(const Nested& x) const {return x.base_==base_;} }; }; template<typename T> bool operator==(const typename Outer<T>::Nested &x, const typename Outer<T>::Nested &y) { return x.equal(y); } } // namespace templated namespace untemplated { class Base { unsigned int t_; public: explicit Base(const unsigned int& t) : t_(t) {} bool equal(const Base& x) const { return x.t_==t_; } }; bool operator==(const Base &x, const Base &y) { return x.equal(y); } class Composed { typedef Base Base_; Base_ base_; public: explicit Composed(const unsigned int& t) : base_(t) {} bool equal(const Composed& x) const {return x.base_==base_;} }; bool operator==(const Composed &x, const Composed &y) { return x.equal(y); } class Outer { public: class Nested { typedef Base Base_; Base_ base_; public: explicit Nested(const unsigned int& t) : base_(t) {} bool equal(const Nested& x) const {return x.base_==base_;} }; }; bool operator==(const Outer::Nested &x, const Outer::Nested &y) { return x.equal(y); } } // namespace untemplated int main() { using std::cout; unsigned int testVal=3; { // No templates first typedef untemplated::Base Base_t; Base_t a(testVal); Base_t b(testVal); cout << "a=b=" << testVal << "\n"; cout << "a==b ? " << (a==b ? "TRUE" : "FALSE") << "\n"; typedef untemplated::Composed Composed_t; Composed_t c(testVal); Composed_t d(testVal); cout << "c=d=" << testVal << "\n"; cout << "c==d ? " << (c==d ? "TRUE" : "FALSE") << "\n"; typedef untemplated::Outer::Nested Nested_t; Nested_t e(testVal); Nested_t f(testVal); cout << "e=f=" << testVal << "\n"; cout << "e==f ? " << (e==f ? "TRUE" : "FALSE") << "\n"; } { // Now with templates typedef templated::Base<unsigned int> Base_t; Base_t a(testVal); Base_t b(testVal); cout << "a=b=" << testVal << "\n"; cout << "a==b ? " << (a==b ? "TRUE" : "FALSE") << "\n"; typedef templated::Composed<unsigned int> Composed_t; Composed_t c(testVal); Composed_t d(testVal); cout << "c=d=" << testVal << "\n"; cout << "d==c ? " << (c==d ? "TRUE" : "FALSE") << "\n"; typedef templated::Outer<unsigned int>::Nested Nested_t; Nested_t e(testVal); Nested_t f(testVal); cout << "e=f=" << testVal << "\n"; cout << "e==f ? " << (e==f ? "TRUE" : "FALSE") << "\n"; // Above line causes compiler error: // error: no match for 'operator==' in 'e == f' } cout << std::endl; return 0; }

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  • Where to handle fatal exceptions

    - by Stephen Swensen
    I am considering a design where all fatal exceptions will be handled using a custom UncaughtExceptionHandler in a Swing application. This will include unanticipated RuntimeExceptions but also custom exceptions which are thrown when critical resources are unavailable or otherwise fail (e.g. a settings file not found, or a server communication error). The UncaughtExceptionHandler will do different things depending on the specific custom exception (and one thing for all the unanticipated), but in all cases the application will show the user an error message and exit. The alternative would be to keep the UncaughtExceptionHandler for all unanticipated exceptions, but handle all other fatal scenarios close to their origin. Is the design I'm considering sound, or should I use the alternative?

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  • CLR 4.0: Corrupted State Exceptions

    - by Scott Dorman
    Corrupted state exceptions are designed to help you have fewer bugs in your code by making it harder to make common mistakes around exception handling. A very common pattern is code like this: public void FileSave(String name) { try { FileStream fs = new FileStream(name, FileMode.Create); } catch (Exception e) { MessageBox.Show("File Open Error"); throw new Exception(IOException); } The standard recommendation is not to catch System.Exception but rather catch the more specific exceptions (in this case, IOException). While this is a somewhat contrived example, what would happen if Exception were really an AccessViolationException or some other exception indicating that the process state has been corrupted? What you really want to do is get out fast before persistent data is corrupted or more work is lost. To help solve this problem and minimize the chance that you will catch exceptions like this, CLR 4.0 introduces Corrupted State Exceptions, which cannot be caught by normal catch statements. There are still places where you do want to catch these types of exceptions, particularly in your application’s “main” function or when you are loading add-ins.  There are also rare circumstances when you know code that throws an exception isn’t dangerous, such as when calling native code. In order to support these scenarios, a new HandleProcessCorruptedStateExceptions attribute has been added. This attribute is added to the function that catches these exceptions. There is also a process wide compatibility switch named legacyCorruptedStateExceptionsPolicy which when set to true will cause the code to operate under the older exception handling behavior. Technorati Tags: CLR 4.0, .NET 4.0, Exception Handling, Corrupted State Exceptions

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  • I've been told that Exceptions should only be used in exceptional cases. How do I know if my case is exceptional?

    - by tieTYT
    My specific case here is that the user can pass in a string into the application, the application parses it and assigns it to structured objects. Sometimes the user may type in something invalid. For example, their input may describe a person but they may say their age is "apple". Correct behavior in that case is roll back the transaction and to tell the user an error occurred and they'll have to try again. There may be a requirement to report on every error we can find in the input, not just the first. In this case, I argued we should throw an exception. He disagreed, saying, "Exceptions should be exceptional: It's expected that the user may input invalid data, so this isn't an exceptional case" I didn't really know how to argue that point, because by definition of the word, he seems to be right. But, it's my understanding that this is why Exceptions were invented in the first place. It used to be you had to inspect the result to see if an error occurred. If you failed to check, bad things could happen without you noticing. Without exceptions every level of the stack needs to check the result of the methods they call and if a programmer forgets to check in one of these levels, the code could accidentally proceed and save invalid data (for example). Seems more error prone that way. Anyway, feel free to correct anything I've said here. My main question is if someone says Exceptions should be exceptional, how do I know if my case is exceptional?

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  • Can I enable/disable breaking on Exceptions programatically?

    - by Tony Lambert
    I want to be able to break on Exceptions when debugging... like in Visual Studio 2008's Menu Debug/Exception Dialog, except my program has many valid exceptions before I get to the bit I wish to debug. So instead of manually enabling and disabling it using the dialog every time is it possible to do it automatically with a #pragma or some other method so it only happens in a specific piece of code?

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  • C# Checked exceptions

    - by Ryan B.
    One feature I really liked in Java that isn't in C# is checked exceptions, Is there any way to simulate or turn on checked exceptions in Visual Studio? Yes I know a lot of people dislike them, but I find they can be helpful.

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  • Performances des exceptions C++, un article de Vlad Lazarenko traduit par LittleWhite

    Bonjour à tous, Je vous présente une nouvelle traduction de l'article de Vlad Lazarenko discutant des performances des exceptions en C++. Souvent, lorsque l'on écrit du code, on se demande l'impact des exceptions sur les performances de notre programme. Cet article apporte donc des éléments de réponse détaillés à cette question. Performances des exceptions C++ Avez-vous évité d'utiliser des exceptions pour préserver les performances ? Dans quel cas avez vo...

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  • C++ custom exceptions: run time performance and passing exceptions from C++ to C

    - by skyeagle
    I am writing a custom C++ exception class (so I can pass exceptions occuring in C++ to another language via a C API). My initial plan of attack was to proceed as follows: //C++ myClass { public: myClass(); ~myClass(); void foo() // throws myException int foo(const int i, const bool b) // throws myException } * myClassPtr; // C API #ifdef __cplusplus extern "C" { #endif myClassPtr MyClass_New(); void MyClass_Destroy(myClassPtr p); void MyClass_Foo(myClassPtr p); int MyClass_FooBar(myClassPtr p, int i, bool b); #ifdef __cplusplus }; #endif I need a way to be able to pass exceptions thrown in the C++ code to the C side. The information I want to pass to the C side is the following: (a). What (b). Where (c). Simple Stack Trace (just the sequence of error messages in order they occured, no debugging info etc) I want to modify my C API, so that the API functions take a pointer to a struct ExceptionInfo, which will contain any exception info (if an exception occured) before consuming the results of the invocation. This raises two questions: Question 1 1. Implementation of each of the C++ methods exposed in the C API needs to be enclosed in a try/catch statement. The performance implications for this seem quite serious (according to this article): "It is a mistake (with high runtime cost) to use C++ exception handling for events that occur frequently, or for events that are handled near the point of detection." At the same time, I remember reading somewhere in my C++ days, that all though exception handling is expensive, it only becmes expensive when an exception actually occurs. So, which is correct?. what to do?. Is there an alternative way that I can trap errors safely and pass the resulting error info to the C API?. Or is this a minor consideration (the article after all, is quite old, and hardware have improved a bit since then). Question 2 I wuld like to modify the exception class given in that article, so that it contains a simple stack trace, and I need some help doing that. Again, in order to make the exception class 'lightweight', I think its a good idea not to include any STL classes, like string or vector (good idea/bad idea?). Which potentially leaves me with a fixed length C string (char*) which will be stack allocated. So I can maybe just keep appending messages (delimted by a unique separator [up to maximum length of buffer])... Its been a while since I did any serious C++ coding, and I will be grateful for the help. BTW, this is what I have come up with so far (I am intentionally, not deriving from std::exception because of the performance reasons mentioned in the article, and I am instead, throwing an integral exception (based on an exception enumeration): class fast_exception { public: fast_exception(int what, char const* file=0, int line=0) : what_(what), line_(line), file_(file) {/*empty*/} int what() const { return what_; } int line() const { return line_; } char const* file() const { return file_; } private: int what_; int line_; char const[MAX_BUFFER_SIZE] file_; }

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  • What's the best way to manage error logging for exceptions?

    - by Peter Boughton
    Introduction If an error occurs on a website or system, it is of course useful to log it, and show the user a polite message with a reference code for the error. And if you have lots of systems, you don't want this information dotted around - it is good to have a single centralised place for it. At the simplest level, all that's needed is an incrementing id and a serialized dump of the error details. (And possibly the "centralised place" being an email inbox.) At the other end of the spectrum is perhaps a fully normalised database that also allows you to press a button and see a graph of errors per day, or identifying what the most common type of error on system X is, whether server A has more database connection errors than server B, and so on. What I'm referring to here is logging code-level errors/exceptions by a remote system - not "human-based" issue tracking, such as done with Jira,Trac,etc. Questions I'm looking for thoughts from developers who have used this type of system, specifically with regards to: What are essential features you couldn't do without? What are good to have features that really save you time? What features might seem a good idea, but aren't actually that useful? For example, I'd say a "show duplicates" function that identifies multiple occurrence of an error (without worrying about 'unimportant' details that might differ) is pretty essential. A button to "create an issue in [Jira/etc] for this error" sounds like a good time-saver. Just to re-iterate, what I'm after is practical experiences from people that have used such systems, preferably backed-up with why a feature is awesome/terrible. (If you're going to theorise anyway, at the very least mark your answer as such.)

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  • What is the correct way to unit test areas around exceptions

    - by Codek
    Hi, Looking at our code coverage of our unit tests we're quite high. But the last few % is tricky because a lot of them are catching things like database exceptions - which in normal circumstances just dont happen. For example the code prevents fields being too long etc, so the only possible database exceptions are if the DB is broken/down, or if the schema is changed under our feet. So is the only way to Mock the objects such that the exception can be thrown? That seems a little bit pointless. Perhaps it's better to just accept not getting 100% code coverage? Thanks, Dan

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  • where to store web service exceptions?

    - by ICoder
    Hello all, I am working on building a web service (using c#) and this web service will use MS Sql server database. Now, I am trying to build an (exceptions log system) for this web service. Simply, I want to save every exception on the web service for future use (bug tracing), so, where is the best place to save these exceptions? Is it good idea to save it in the database? What if the exception is in the connection to the database itself? I really appreciate your help and your ideas. Thanks

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  • How To Deal With Exceptions In Large Code Bases

    - by peter
    Hi All, I have a large C# code base. It seems quite buggy at times, and I was wondering if there is a quick way to improve finding and diagnosing issues that are occuring on client PCs. The most pressing issue is that exceptions occur in the software, are caught, and even reported through to me. The problem is that by the time they are caught the original cause of the exception is lost. I.e. If an exception was caught in a specific method, but that method calls 20 other methods, and those methods each call 20 other methods. You get the picture, a null reference exception is impossible to figure out, especially if it occured on a client machine. I have currently found some places where I think errors are more likely to occur and wrapped these directly in their own try catch blocks. Is that the only solution? I could be here a long time. I don't care that the exception will bring down the current process (it is just a thread anyway - not the main application), but I care that the exceptions come back and don't help with troubleshooting. Any ideas? I am well aware that I am probably asking a question which sounds silly, and may not have a straightforward answer. All the same some discussion would be good.

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  • C++ exceptions binary compatibility

    - by aaa
    hi. my project uses 2 different C++ compilers, g++ and nvcc (cuda compiler). I have noticed exception thrown from nvcc object files are not caught in g++ object files. are C++ exceptions supposed to be binary compatible in the same machine? what can cause such behavior?

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