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• systematizing error codes for a web app in php?

  - by user151841

  I'm working on a class-based php web app. I have some places where objects are interacting, and I have certain situations where I'm using error codes to communicate to the end user -- typically when form values are missing or invalid. These are situations where exceptions are unwarranted ( and I'm not sure I could avoid the situations with exceptions anyways). In one object, I have some 20 code numbers, each of which correspond to a user-facing message, and a admin/developer-facing message, so both parties know what's going on. Now that I've worked over the code several times, I find that it's difficult to quickly figure out what code numbers in the series I've already used, so I accidentally create conflicting code numbers. For instance, I just did that today with 12, 13, 14 and 15. How can I better organize this so I don't create conflicting error codes? Should I create one singleton class, errorCodes, that has a master list of all error codes for all classes, systematizing them across the whole web app? Or should each object have its own set of error codes, when appropriate, and I just keep a list in the commentary of the object, to use and update that as I go along?

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• Redundant code in exception handling

  - by Nicola Leoni

  Hi, I've a recurrent problem, I don't find an elegant solution to avoid the resource cleaning code duplication: resource allocation: try { f() } catch (...) { resource cleaning code; throw; } resource cleaning code; return rc; So, I know I can do a temporary class with cleaning up destructor, but I don't really like it because it breaks the code flow and I need to give the class the reference to the all stack vars to cleanup, the same problem with a function, and I don't figure out how does not exists an elegant solution to this recurring problem.

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• Better way to ignore exception type: multiple catch block vs. type querying

  - by HuBeZa

  There are situations that we like to ignore a specific exception type (commonly ObjectDisposedException). It can be achieved with those two methods: try { // code that throws error here: } catch (SpecificException) { /*ignore this*/ } catch (Exception ex) { // Handle exception, write to log... } or try { // code that throws error here: } catch (Exception ex) { if (ex is SpecificException) { /*ignore this*/ } else { // Handle exception, write to log... } } What are the pros and cons of this two methods (regarding performance, readability, etc.)?

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• Capture KeyUp event on form when child control has focus

  - by Jon B

  I need to capture the KeyUp event in my form (to toggle a "full screen mode"). Here's what I'm doing: protected override void OnKeyUp(KeyEventArgs e) { base.OnKeyUp(e); if (e.KeyCode == Keys.F12) this.ToggleFullScreen(); } private void ToggleFullScreen() { // Snazzy code goes here } This works fine, unless a control on the form has focus. In that case, I don't get the event at all (also tried OnKeyDown - no luck there either). I could handle the KeyUp event from the child control, but the controls on the form are generated dynamically, and there may be many of them - each having many children of their own. Is there any way to do this without generating event handlers for every control on the screen (which I certainly could do with a recursive function)?

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• How best to associate code with events in jQuery?

  - by Ned Batchelder

  Suppose I have a <select> element on my HTML page, and I want to run some Javascript when the selection is changed. I'm using jQuery. I have two ways to associate the code with the element. Method 1: jQuery .change() <select id='the_select'> <option value='opt1'>One</option> <option value='opt2'>Two</option> </select> <script> $('#the_select').change(function() { alert('Changed!'); }); </script> Method 2: onChange attribute <select id='the_select' onchange='selectChanged();'> <option value='opt1'>One</option> <option value='opt2'>Two</option> </select> <script> function selectChanged() { alert('Changed!'); } </script> I understand the different modularity here: for example, method 1 keeps code references out of the HTML, but method 2 doesn't need to mention HTML ids in the code. What I don't understand is: are there operational differences between these two that would make me prefer one over the other? For example, are there edge-case browsers where one of these works and the other doesn't? Is the integration with jQuery better for either? Does the late-binding of the code to the event make a difference in the behavior of the page? Which do you pick and why?

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• System.Web.HttpException in asp.net mvc 2 on images and javascript files

  - by Rippo

  Hi I am getting the following errors reported by ELMAH on my asp.net mvc 2 site for javascript files, images etc. System.Web.HttpException: The remote host closed the connection I have done some research and it appears that the user/bot is clicking a link on the site before the page has fully loaded. Now this error never occurs on a controller action but always on a file that is on disk. e.g. /Content/CmsImages/logo.png /Content/CmsImages/MemberImages/Photo-001605.jpg /Content/jquery.tickertype.js So this means that all static files are being routed through the mvc pipeline. What options do I have?

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• Uncatchable errors in node.js

  - by Peter Burns

  So I'm trying to write a simple TCP socket server that broadcasts information to all connected clients. So when a user connects, they get added to the list of clients, and when the stream emits the close event, they get removed from the client list. This works well, except that sometimes I'm sending a message just as a user disconnects. I've tried wrapping stream.write() in a try/catch block, but no luck. It seems like the error is uncatchable.

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• How do I add information to an exception message without changing its class in ruby?

  - by Andrew Grimm

  How do I add information to an exception message without changing its class in ruby? The approach I'm currently using is strings.each_with_index do |string, i| begin do_risky_operation(string) rescue raise $!.class, "Problem with string number #{i}: #{$!}" end end Is there a better way?

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• I have an Errno 13 Permission denied with subprocess in python

  - by wDroter

  The line with the issue is ret=subprocess.call(shlex.split(cmd)) cmd = /usr/share/java -cp pig-hadoop-conf-Simpsons:lib/pig-0.8.1-cdh3u1-core.jar:lib/hadoop-core-0.20.2-cdh3u1.jar org.apache.pig.Main -param func=cat -param from =foo.txt -x mapreduce fsFunc.pig The error is. File "./run_pig.py", line 157, in process ret=subprocess.call(shlex.split(cmd)) File "/usr/lib/python2.7/subprocess.py", line 493, in call return Popen(*popenargs, **kwargs).wait() File "/usr/lib/python2.7/subprocess.py", line 679, in __init__ errread, errwrite) File "/usr/lib/python2.7/subprocess.py", line 1249, in _execute_child raise child_exception OSError: [Errno 13] Permission denied Let me know if any more info is needed. Any help is appreciated. Thanks.

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• How to get mouseposition when context menu appears?

  - by ikky

  Hi. I have a panel which holds many pictureboxes. Each picturebox has registered "contextRightMenu" as their context menu. What i want when the context menu pops up is to get the current mouseposition. I have tried getting the mouseposition by using mouseDown and click, but these events happens after one of the items of the context menu is clicked, and that is too late. the popup event of the context menu does not deliver mouse event args, so i don't know how to get the mouseposition. If i can get mouse event args it is easy. Then i just can: this.contextRightClick.Popup += new System.EventHandler(this.contextRightClick_Popup); // If EventArgs include mouseposition within the sender private void contextRightClick_Popup)(object sender, EventArgs e) { int iLocationX = sender.Location.X; int iLocationY = sender.Location.Y; Point pPosition = new Point(iLocationX + e.X, iLocationY + e.Y); // Location + position within the sender = current mouseposition } Can anyone help me either get some mouse event args, or suggest a event that will run before the contextmenu pop ups? Thanks in advance

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• How to roll back changes in gridview in case of incorrect input

  - by Mustafa A. Jabbar

  Hi, I have a DataGridView that is bound to a list of object. It has some columns that the user can edit. There are certain inputs that are not allowed for a row as a whole. How can I roll back if the user enters invalid inputs in some cell. I tried using the RowValidating event handler but it was not called after cell value has been changed. Even when I implemet CellValueChanged, I still cannot roll back the changes. Any idea how to accomplish this

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• How do I indicate that a class doesn't support certain operators?

  - by romeovs

  I'm writing a class that represents an ordinal scale, but has no logical zero-point (eg time). This scale should permit addition and substraction (operator+, operator+=, ...) but not multiplication. Yet, I always felt it to be a good practice that when one overloads one operator of a certain group (in this case the math operators), one should also overload all the others that belong to that group. In this case that would mean I should need to overload the multiplication and division operators also, because if a user can use A+B he would probable expect to be able the other operators. Is there a method that I can use to throw an error for this at compiler time? The easiest method would be just no to overload the operators operator*, ... yet it would seem appropriate to add a bit more explaination than operator* is not know for class "time". Or is this something that I really should not care about (RTFM user)?

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• Preventing EF4 ConstraintException when invoking TryUpdateModel

  - by twk

  Given following ASP.NET MVC controller code: [HttpPost] public ActionResult Create(FormCollection collection) { string[] whitelist = new []{ "CompanyName", "Address1", "Address2", ... }; Partner newPartner = new Partner(); if (TryUpdateModel(newPartner, whitelist, collection)) { var db = new mainEntities(); db.Partners.AddObject(newPartner); db.SaveChanges(); return RedirectToAction("Details/" + newPartner.ID); } else { return View(); } } The problem is with the Entity Framework 4: the example Partner entity is mapped to a database table with it's fields NOT ALLOWED to be NULL (which is ok by design - they're required). Unfortunately, invoking TryUpdateModel when some of the properties are nulls produces ConstraintException which is not expected! I do expect that TryUpdateModel return false in this case. It is ok that EF wouldn't allow set a property value to null if it should not be, but the TryUpdateMethod should handle that, and add the error to ModelState errors collection. I am wrong, or somebody screwed the implementation of TryUpdateModel method?

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• I need data structure for effective handling with dates

  - by ante.sabo

  What I need is something like Hashtable which I will fill with prices that were actual at desired days. For example: I will put two prices: January 1st: 100USD, March 5th: 89USD. If I search my hashtable for price: hashtable.get(February 14th) I need it to give me back actual price which was entered at Jan. 1st because this is the last actual price. Normal hashtable implementation won't give me back anything, since there is nothing put on that dat. I need to see if there is such implementation which can find quickly object based on range of dates.

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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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• Tell SQL Server the error is "handled" in try...catch

  - by Restless Archer

  Hi. I'd like to indicate to SQL Server 2005, in my BEGIN CATCH...END CATCH block that the error is "handled"... That is, clear the error. Is that possible?? Thanks. A.

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• handling the logout functionality on the iPhone

  - by Nanz

  This is the first iPhone application i am working on. To use the application, the user has to login to our server. I am done with that part. Now the problem i am facing is how to logout the user from the server, deallocate all the memory and start afresh without quitting the app. After the user logs out, i want the exact same things to happen as in applicationdidfinishlaunching method. But i dont know how to go about it. The app has a tab bar which is set up in mainWindow.xib.

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• How to make Net::Msmnr run?

  - by codeholic

  There's Net::Msmgr module on CPAN. It's written clean and the code looks trustworthy at the first glance. However this module seems to be beta and there is little documentation and no tests :-/ Has anyone used this module in production? I haven't managed to make it run by now, because it requires all event loop processing to be done in the application and as I've already said there is little documentation and no working examples to study. That's where I've gone so far: #!/usr/bin/perl use strict; use warnings; use Event; use Net::Msmgr::Object; use Net::Msmgr::Session; use Net::Msmgr::User; use constant DEBUG => 511; use constant EVENT_TIMEOUT => 5; # seconds my ($username, $password) = qw/[email protected] my.password/; my $buddy = '[email protected]'; my $user = Net::Msmgr::User->new(user => $username, password => $password); my $session = Net::Msmgr::Session->new; $session->debug(DEBUG); $session->login_handler(\&login_handler); $session->user($user); my $conv; sub login_handler { my $self = shift; print "LOGIN\n"; $self->ui_state_nln; $conv = $session->ui_new_conversation; $conv->invite($buddy); } our %watcher; sub ConnectHandler { my ($connection) = @_; warn "CONNECT\n"; my $socket = $connection->socket; $watcher{$connection} = Event->io(fd => $socket, cb => [ $connection, '_recv_message' ], poll => 're', desc => 'recv_watcher', repeat => 1); } sub DisconnectHandler { my $connection = shift; print "DISCONNECT\n"; $watcher{$connection}->cancel; } $session->connect_handler(\&ConnectHandler); $session->disconnect_handler(\&DisconnectHandler); $session->Login; Event::loop(); That's what it outputs: Dispatch Server connecting to: messenger.hotmail.com:1863 Dispatch Server connected CONNECT Dispatch Server >>>VER 1 MSNP2 CVR0 --> VER 1 MSNP2 CVR0 Dispatch Server >>>USR 2 MD5 I [email protected] --> USR 2 MD5 I [email protected] Dispatch Server <<<VER 1 CVR0 <-- VER 1 CVR0 And that's all, here it hangs. The handler on login is not being triggered. What am I doing wrong?

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• Where is this exception caught and handled?

  - by Zaki

  In some code I've been reading, I've come across this : class Someclass { public static void main(String[] args) throws IOException { //all other code here...... } } If main() throws an exception, in this case its an IOException, where is it caught and handled?

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• Several client waiting for the same event

  - by ff8mania

  I'm developing a communication API to be used by a lot of generic clients to communicate with a proprietary system. This proprietary system exposes an API, and I use a particular classes to send and wait messages from this system: obviously the system alert me that a message is ready using an event. The event is named OnMessageArrived. My idea is to expose a simple SendSyncMessage(message) method that helps the user/client to simply send a message and the method returns the response. The client: using ( Communicator c = new Communicator() ) { response = c.SendSync(message); } The communicator class is done in this way: public class Communicator : IDisposable { // Proprietary system object ExternalSystem c; String currentRespone; Guid currentGUID; private readonly ManualResetEvent _manualResetEvent; private ManualResetEvent _manualResetEvent2; String systemName = "system"; String ServerName = "server"; public Communicator() { _manualResetEvent = new ManualResetEvent(false); //This methods are from the proprietary system API c = SystemInstance.CreateInstance(); c.Connect(systemName , ServerName); } private void ConnectionStarter( object data ) { c.OnMessageArrivedEvent += c_OnMessageArrivedEvent; _manualResetEvent.WaitOne(); c.OnMessageArrivedEvent-= c_OnMessageArrivedEvent; } public String SendSync( String Message ) { Thread _internalThread = new Thread(ConnectionStarter); _internalThread.Start(c); _manualResetEvent2 = new ManualResetEvent(false); String toRet; int messageID; currentGUID = Guid.NewGuid(); c.SendMessage(Message, "Request", currentGUID.ToString()); _manualResetEvent2.WaitOne(); toRet = currentRespone; return toRet; } void c_OnMessageArrivedEvent( int Id, string root, string guid, int TimeOut, out int ReturnCode ) { if ( !guid.Equals(currentGUID.ToString()) ) { _manualResetEvent2.Set(); ReturnCode = 0; return; } object newMessage; c.FetchMessage(Id, 7, out newMessage); currentRespone = newMessage.ToString(); ReturnCode = 0; _manualResetEvent2.Set(); } } I'm really noob in using waithandle, but my idea was to create an instance that sends the message and waits for an event. As soon as the event arrived, checks if the message is the one I expect (checking the unique guid), otherwise continues to wait for the next event. This because could be (and usually is in this way) a lot of clients working concurrently, and I want them to work parallel. As I implemented my stuff, at the moment if I run client 1, client 2 and client 3, client 2 starts sending message as soon as client 1 has finished, and client 3 as client 2 has finished: not what I'm trying to do. Can you help me to fix my code and get my target? Thanks!

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• Calling same function until it connect to server

  - by user171523

  I am in the process of designing a system where i need to keep on trying to connect to MQ server unitl i get a connection. By default if the MQ is not availlble it will thorugh exception. How can call the same method again and again until i get the connection. I know i can use recursion, is there any better way to do it . Becuase i would like to avoid infinite loops. I also want to wait the the furthere processing until i get connection. I am using .net 2.0 with C#. It is window Service application.

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• Error debugging - Conversion from String to Double

  - by Jamie Taylor

  I'm doing some error debugging trying to get the errors on our website down to a minimum and there seems to be an error that is popping up quite a lot Conversion from string "" to type 'Double' is not valid. I'm unable to replicate this problem but I can see that it is happening. I've been looking through the code in one of the pages and strolled across this Dim varWeek As String If varWeek < 10 Then 'Do something' End If Could this be causing the problem as it is trying to see if a String is less than 10 which is an Integer? As I said before as I am unable to see this error in the first place so changing this to an Integer doesn't change anything on my system. Thanks.

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• Iterating through Event Log Entry Collection, IndexOutOutOfBoundsException

  - by fjdumont

  Hello, in a service application I am iterating through the Windows application event log to parse Events in order react depanding on the entry message. In the case that the event log is full (Windows usually makes sure there is enough space by deleting old entries - this is configurable in the eventvwr.exe settings), the service always runs into an IndexOutOfBoundsException while iterating through the EventLog.Entries collection. No matter how I iterate (for-loop, using the collections enumerator, copying the collection into an array, ...), I can't seem to get rid of this ´bug´. Currently, I ensure that the log is not full in order to keep the service running by regularly deleting the last few item by parsing the event log file and deleting the last few nodes (Don't beat me up, I couldn't find a better alternative...). How can I iterate through the collection without trying to access already deleted entries? Is there probably a more elegant method? I am only trying to acces the logs written during the last x seconds (even LINQ failed to select those when the log is full - same exception), could this help? Thanks for any advice and hints Frank Edit: I forgot to mention that my assumption is the loops are accessing entries which are being deleted during iteration by Windows. Basically that is why I tried to clone the collection. Is there perhaps a way to lock the collection for a small amount of time for just my application?

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• How to handle different roles with different previliges in PHP?

  - by user261002

  I would like to know how we can create different "user Roles" for different users in PHP. example: Administrator can create all types of users, add, view, manipulate data, delete managers, viewers, and workers, etc managers can only create, workers and viewers, can add and view data, workers can't create new users, but can only add data and view data, viewers can only view data that has been added to the DB by workers, managers and administrators. I though its better to use different sessions like : $_SESSION['admin'] $_SESSION['manager'] $_SESSION['worker'] $_SESSION['viewvers'] and for every page check which of them have a true or yes value, but I want to know how do they do it in real and big projects??? is there any other way???

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• Handling missing/incomplete data in R

  - by doug

  As you would expect from a DSL aimed at data analysts, R handles missing/incomplete data very well, for instance: Many R functions have an 'na.rm' flag that you can set to 'T' to remove the NAs, but if you want to deal with this before the function call, then: to replace each 'NA' w/ 0: ifelse(is.na(vx), 0, vx) to remove each 'NA': vx = vx[!is.na(a)] to remove entire each row that contains 'NA' from a data frame: dfx = dfx[complete.cases(dfx),] All of these functions remove 'NA' or rows with an 'NA' in them. Sometimes this isn't quite what you want though--making an 'NA'-excised copy of the data frame might be necessary for the next step in the workflow but in subsequent steps you often want those rows back (e.g., to calculate a column-wise statistic for a column that has missing rows caused by a prior call to 'complete cases' yet that column has no 'NA' values in it). to be as clear as possible about what i'm looking for: python/numpy has a class, 'masked array', with a 'mask' method, which lets you conceal--but not remove--NAs during a function call. Is there an analogous function in R?

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