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  • Write a signal handler to catch SIGSEGV

    - by Adi
    Hi all, I want to write a signal handler to catch SIGSEGV. First , I would protect a block of memory for read or writes using char *buffer; char *p; char a; int pagesize = 4096; " mprotect(buffer,pagesize,PROT_NONE) " What this will do is , it will protect the memory starting from buffer till pagesize for any reads or writes. Second , I will try to read the memory by doing something like p = buffer; a = *p This will generate a SIGSEGV and i have initialized a handler for this. The handler will be called . So far so good. Now the problem I am facing is , once the handler is called, I want to change the access write of the memory by doing mprotect(buffer, pagesize,PROT_READ); and continue my normal functioning of the code. I do not want to exit the function. On future writes to the same memory, I want again catch the signal and modify the write rights and then take account of that event. Here is the code I am trying : #include <signal.h> #include <stdio.h> #include <malloc.h> #include <stdlib.h> #include <errno.h> #include <sys/mman.h> #define handle_error(msg) \ do { perror(msg); exit(EXIT_FAILURE); } while (0) char *buffer; int flag=0; static void handler(int sig, siginfo_t *si, void *unused) { printf("Got SIGSEGV at address: 0x%lx\n",(long) si->si_addr); printf("Implements the handler only\n"); flag=1; //exit(EXIT_FAILURE); } int main(int argc, char *argv[]) { char *p; char a; int pagesize; struct sigaction sa; sa.sa_flags = SA_SIGINFO; sigemptyset(&sa.sa_mask); sa.sa_sigaction = handler; if (sigaction(SIGSEGV, &sa, NULL) == -1) handle_error("sigaction"); pagesize=4096; /* Allocate a buffer aligned on a page boundary; initial protection is PROT_READ | PROT_WRITE */ buffer = memalign(pagesize, 4 * pagesize); if (buffer == NULL) handle_error("memalign"); printf("Start of region: 0x%lx\n", (long) buffer); printf("Start of region: 0x%lx\n", (long) buffer+pagesize); printf("Start of region: 0x%lx\n", (long) buffer+2*pagesize); printf("Start of region: 0x%lx\n", (long) buffer+3*pagesize); //if (mprotect(buffer + pagesize * 0, pagesize,PROT_NONE) == -1) if (mprotect(buffer + pagesize * 0, pagesize,PROT_NONE) == -1) handle_error("mprotect"); //for (p = buffer ; ; ) if(flag==0) { p = buffer+pagesize/2; printf("It comes here before reading memory\n"); a = *p; //trying to read the memory printf("It comes here after reading memory\n"); } else { if (mprotect(buffer + pagesize * 0, pagesize,PROT_READ) == -1) handle_error("mprotect"); a = *p; printf("Now i can read the memory\n"); } /* for (p = buffer;p<=buffer+4*pagesize ;p++ ) { //a = *(p); *(p) = 'a'; printf("Writing at address %p\n",p); }*/ printf("Loop completed\n"); /* Should never happen */ exit(EXIT_SUCCESS); } The problem I am facing with this is ,only the signal handler is running and I am not able to return to the main function after catching the signal.. Any help in this will be greatly appreciated. Thanks in advance Aditya

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  • Exim 4 Virtual Domains and Catchall on Debian (Squeeze)

    - by parazuce
    Hello, I've been at it for about 4 hours now. Searching as well as trying different tutorials. Here's my setup: I have 2 domains, both under my own DNS server (MX records setup as well). I have exim4 successfully running, and it is able to send messages from both of those domains. I have tested this using sendmail, and manually setting the "From" attribute. Exim successfully delivers mail to users no matter which domain was specified. I'm fine with that, but I'm having an issue editing virtual domains, and adding custom delivery options (such as a catch all). I've been searching for about 4 hours, and I can't find any up-to-date documentation on how to do this. The old methods would be to add a line such as: domainlist local_domains = @:localhost:dsearch;/etc/exim4/virtual Once that line was added, I made a directory at /etc/exim4/virtual, then created files inside such as example.com which would then contain rules for delivery under that domain. This did not work, however. Searching further, I've found that exim no longer supports dsearch (I guess because they claim it never has?) This is where I'm stuck. I'm on a "split" configuration as well.

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  • Rails Catch All Route URL Helpers?

    - by viatropos
    If I have a catch-all-route like this: match '*request_path' => "pages#show", :as => :page ...and the pages can be arbitrarily nested, how do I make it so I can use the url helper methods? If I have a page structure like this: /about /about/people /about/story /about/story/in-depth Then I want to be able to write page_path(@page) and get /about/story/in-depth for the hypothetical "In Depth Story" page. But instead I'm just getting /in-depth. If I override Page#to_param, and do something like this: def to_param result = "" if parent result << parent.to_param result << "/" end result << super end ... it returns an encoded string like this: /about%2Fstory%2Fin-depth Is there a way to make this work?

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  • Catch enter key press in input text field in AS3

    - by Jonathan Barbero
    Hello, I want to catch the enter key press when the user is filling an input text field in AS3. I think I have to do something like this: inputText.addEventListener(Event. ? , func); function func(e:Event):void{ if(e. ? == "Enter"){ doSomething(); } } But I can't find the best way to do this. By the way, the input text has a restriction: inputText.restrict = "0-9"; Should I add the enter key to the restrictions? inputText.restrict = "0-9\n"; Thanks in advance.

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  • How and where do we write try catch block to handle Exception

    - by Arpita
    We are using C# language to develope a Windows application. Our windows application consists of three layers (UI,Business and DataAccess layer). In Business Layer there are some public (business) methods through which UI communicates wilh Business layer classes. These public methods also have some private methods to implement the required functionality. There are some methods in DataAcess layer which are called from Business layer class. In this situatuion where should i wrte try-catch? a) In Business Layer Public methods b) In Busyness Layer Private methods c) In DataAccess Layer methods d) In UI methods from where Business methods are called.

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  • Perl: catch error without die

    - by Pmarcoen
    I'm playing around with error handling and got a little problem. I connect with a database using the DBI module. I do my own error handling by using a subroutine that I call upon an error. I can catch my own dies and handle them just fine but when my database connection fails, the DBI module apparently prints out it's own die : DBI connect(...) failed: ORA-12154: TNS:could not resolve the connect identifier specified (DBD ERROR: OCIServerAttach) at ... How would I go about catching this ? I tried using $SIG{DIE} like so : local $SIG{__DIE__} = sub { my $e = shift; print "Error: " .$e; }; This is on the bottom of my main file, in this file I also call the connect subroutine that is available in a module of my own. I also tried putting this piece of code on the bottom of my module but it still prints the error without the "Error:" in front of it.

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  • How come you cannot catch Code Contract exceptions?

    - by Finglas
    System.Diagnostics.Contracts.ContractException is not accessiable in my test project. Note this code is purely myself messing around with my shiney new copy of Visual Studio, but I'd like to know what I'm doing wrong. I'm using the professional edition of VS, therefore I do not have static checking. In order to still use code contracts (which I like) I figured the only way my method can work is to catch the exception that is thrown at runtime, but I'm not finding this possible. TestMethod [TestMethod, ExpectedException(typeof(System.Diagnostics.Contracts.ContractException))] public void returning_a_value_less_than_one_throws_exception() { var person = new Person(); person.Number(); } Method public int Number() { Contract.Ensures(Contract.Result<int>() >= 0); return -1; } Error Error 1 'System.Diagnostics.Contracts.ContractException' is inaccessible due to its protection level.

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  • How to catch Keyboard and mouse events?

    - by Alexey Malistov
    I want to create an application. This application has to do something when a user presses special keys on keyboard or/and uses scroll wheel. This application is a service. It has no windows. I want to catch any keyboard or mouse events which were designed with other applications. For example, you are watching TV by 3rd party application. If you press Ctrl + Shift and use scroll wheel my application changes the volume. I use Windows 7 x64 and Visual Studio 2008.

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  • How to catch printf from a dll?

    - by Xarx
    I've got a C++ console application that uses a third-party dll (jvm.dll, indirectly) that uses printf to print various error messages (Java stacktrace). I need to catch these stacktraces to a string in order to process them further, or at least to see them printed on the console. The thing is that I see the stacktrace only when debugging my application in VisualStudio (VS 2010). When I run my application in the "normal way", i.e. from the command line, nothing is printed on the console. So VS is able to somehow interfere the java output and display it. I need to be able to do the same thing. I've already tried freopen(), but without success. Also, I've found this question on the same problem, but without a clear answer.

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  • Validating an integer or String without try-catch

    - by Phil
    Ok, I'm lost. I am required to figure out how to validate an integer and String, but for some stupid reason, I can't use the Try-Catch method. I know this is the easiest way and so all the solutions on the internet are using it. I'm writing in Java. The deal is this, I need someone to put in an numerical ID and String name. If either one of the two inputs are invalid I must tell them they made a mistake. Can someone help me?

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  • How can I catch runtime error in C++

    - by Yan Cheng CHEOK
    By referring to http://stackoverflow.com/questions/315948/c-catching-all-exceptions try { int i = 0; int j = 0/i; /* Division by 0 */ int *k = 0; std::cout << *k << std::endl; /* De-reference invalid memory location. */ } catch (...) { std::cout << "Opps!" << std::endl; } The above run-time error are unable to be detected. Or, am I having wrong expectation on C++ exception handling feature?

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  • How can a client try to reconnect to a server after a first failed try with WCF?

    - by djerry
    Hey guys, I'm using a client - server app. When a client starts, he gets a login-screen. When the server is not up yet, the call to the server will throw an exception which i catch (EndpointNotFoundException). I show a messagebox telling the user the server is offline. When he tries to reconnect again, it will throw another exception (CommunicationObjectFaultedException), even though the server is online. When a new client starts then, he can connect to the server. But the client who attempted before, still gets the error. My question now is how can the first client login after a failed first try without having to start his program again. So i want to clear the communicationchannel of its faulted state or something like that. Thanks in advance.

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  • Check if Database raises a particular exception

    - by mcabral
    using Nhibernate; I'm trying to insert several values a on table which has an unique index on some columns. I'd like to know if a particular insert raises an exception for having violated the unique constraint. So, which particular exception type should i catch? I only want to catch this particular one and let all others go up. Thanks a lot!

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  • VLC player event catch

    - by user350632
    In my C# application i need to trigger some events when a VLC player (preferably) starts playback (a play button is pressed in VLC for example).Tried Windows Media Player classic with Microsoft Spy++ and observed messages that are sent when playback starts\repeats but i don't know how i could "catch" those messages in my C# code.So my question: is there any way to hook up to event in VLC (or WMP) and get notified about playback status (play, stop, start of repeat). My goal is to create a C# function that waits for start of playback event in player and then triggers some actions in my application (this should also happen when playback ends and starts repeating). What approach should i take here? Just to clearify: I don't want to embedded a new instance of VLC in my app, but instead control/read the "real" full version of VLC, started seperatly by the user

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  • Python continue from the point where exception was thrown

    - by James Lin
    Hi is there a way to continue from the point where exception was thrown? eg I have the following psudo code unique code 1 unique code 2 unique code 3 if I want to ignore the exceptions of any of the unique code statements I will have to do it like this: try: #unique code 1 except: pass try: #unique code 2 except: pass try: #unique code 3 except: pass but this isn't elegant to me, and for the life of me I can't remember how I resolved this kind of problem last time... what I want to have is something like try: unique code 1 unique code 2 unique code 3 except: continue from last exception raised

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  • Catch unhandled exception of invisible thread

    - by user346804
    In my C++ application i use an activeX component that runs its own thread (or several I don't know). Sometimes this components throws exceptions. I would like to catch these exceptions and do recovery instead of my entire application crashing. But since I don't have access to its source code or thread I am unsure how it would be done. The only solution I can think of is to run it in its own process. Using something like CreateProcess and then CreateRemoteThread, unsure how it could be implemented. Any suggestion on how to go about solving this?

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  • null checking edit textbox android

    - by sara brown
    i want to make empty textbox checking for android. i tried try catch but it was force to close. below is my codes try{ name = (EditText)findViewById(R.id.name); }catch(NullPointerException ex){ new AlertDialog.Builder(KawalanAppXTVT.this).setTitle("Error" ) .setMessage("That's not a number") .setPositiveButton("OK", null).show(); can someone help me?

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  • Which event to catch for application shut down?

    - by xueru
    I am using jQueryMobile and phoneGap for a cross-device mobile application. I use html 5 local storage to persist records that worked on by user. I don't know which phoneGap event to catch just before application shut-down so I can make sure data is saved before shutdown completes. Base on suggestion from naughtur, I tried both unload and beforeunload events, neither of them got fired during app shutdown. Following is my code snip: function persistTasks(){ alert ("is unloading the app"); offlineTasklist.set("tasks", tasklist); } function init() { document.addEventListener("unload", persistTasks, false); login(); } $(document).ready(init);

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  • Is there a 'catch' with FastFormat?

    - by Roddy
    I just read about the FastFormat C++ i/o formatting library, and it seems too good to be true: Faster even than printf, typesafe, and with what I consider a pleasing interface: // prints: "This formats the remaining arguments based on their order - in this case we put 1 before zero, followed by 1 again" fastformat::fmt(std::cout, "This formats the remaining arguments based on their order - in this case we put {1} before {0}, followed by {1} again", "zero", 1); // prints: "This writes each argument in the order, so first zero followed by 1" fastformat::write(std::cout, "This writes each argument in the order, so first ", "zero", " followed by ", 1); This looks almost too good to be true. Is there a catch? Have you had good, bad or indifferent experiences with it? CW on this question, as there's probably no right answer...

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  • Catch/Raise event on table data update C#

    - by Incognito
    Hi, I have 24/7 service which keeps setup (configuration data) for charging, routing and etc in the Sql Server. Once it is started it loads the data from table using Linq2SQL and use the data through all the application. And we need a solution to update the setup data in the table without restarting the application. So I am interested is it possible to catch/determine that the table was updated so I can refresh the setup data in the application. I mean is it possible to have events which will raise when there is any delete, update or insert on the table. Thank you.

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  • Twitter 2 for Android crash every time I try uploading multi photos [closed]

    - by Hazz
    Hello, I'm using the new Twitter 2 on Android 2.1. Whenever I hit the button which enables me to upload multiple photos in a single tweet, I always get the error "The application Camera (process com.sonyericsson.camera) has stopped unexpectidly. Please try again". However, uploading a single photo using the camera button in Twitter have no problem, it works. My phone is Sony Ericsson x10 mini pro. I tried signing out and back in, same result. Anything I can do to fix this? This is the log info I got using Log Collector: 02-23 15:05:57.328 I/ActivityManager( 1240): Starting activity: Intent { act=com.twitter.android.post.status cmp=com.twitter.android/.PostActivity } 02-23 15:05:57.338 D/PhoneWindow(15095): couldn't save which view has focus because the focused view com.android.internal.policy.impl.PhoneWindow$DecorView@45726938 has no id. 02-23 15:05:57.688 I/ActivityManager( 1240): Displayed activity com.twitter.android/.PostActivity: 340 ms (total 340 ms) 02-23 15:05:59.018 I/ActivityManager( 1240): Starting activity: Intent { act=android.intent.action.PICK typ=vnd.android.cursor.dir/image cmp=com.sonyericsson.camera/com.sonyericsson.album.grid.GridActivity } 02-23 15:05:59.038 I/ActivityManager( 1240): Start proc com.sonyericsson.camera for activity com.sonyericsson.camera/com.sonyericsson.album.grid.GridActivity: pid=15113 uid=10057 gids={1006, 1015, 3003} 02-23 15:05:59.128 I/dalvikvm(15113): Debugger thread not active, ignoring DDM send (t=0x41504e4d l=38) 02-23 15:05:59.158 I/dalvikvm(15113): Debugger thread not active, ignoring DDM send (t=0x41504e4d l=50) 02-23 15:05:59.448 I/ActivityManager( 1240): Displayed activity com.sonyericsson.camera/com.sonyericsson.album.grid.GridActivity: 423 ms (total 423 ms) 02-23 15:05:59.458 W/dalvikvm(15113): threadid=15: thread exiting with uncaught exception (group=0x4001e160) 02-23 15:05:59.458 E/AndroidRuntime(15113): Uncaught handler: thread AsyncTask #1 exiting due to uncaught exception 02-23 15:05:59.468 E/AndroidRuntime(15113): java.lang.RuntimeException: An error occured while executing doInBackground() 02-23 15:05:59.468 E/AndroidRuntime(15113): at android.os.AsyncTask$3.done(AsyncTask.java:200) 02-23 15:05:59.468 E/AndroidRuntime(15113): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273) 02-23 15:05:59.468 E/AndroidRuntime(15113): at java.util.concurrent.FutureTask.setException(FutureTask.java:124) 02-23 15:05:59.468 E/AndroidRuntime(15113): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307) 02-23 15:05:59.468 E/AndroidRuntime(15113): at java.util.concurrent.FutureTask.run(FutureTask.java:137) 02-23 15:05:59.468 E/AndroidRuntime(15113): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068) 02-23 15:05:59.468 E/AndroidRuntime(15113): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561) 02-23 15:05:59.468 E/AndroidRuntime(15113): at java.lang.Thread.run(Thread.java:1096) 02-23 15:05:59.468 E/AndroidRuntime(15113): Caused by: java.lang.IllegalArgumentException: Unsupported MIME type. 02-23 15:05:59.468 E/AndroidRuntime(15113): at com.sonyericsson.album.grid.GridActivity$AlbumTask.doInBackground(GridActivity.java:202) 02-23 15:05:59.468 E/AndroidRuntime(15113): at com.sonyericsson.album.grid.GridActivity$AlbumTask.doInBackground(GridActivity.java:124) 02-23 15:05:59.468 E/AndroidRuntime(15113): at android.os.AsyncTask$2.call(AsyncTask.java:185) 02-23 15:05:59.468 E/AndroidRuntime(15113): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305) 02-23 15:05:59.468 E/AndroidRuntime(15113): ... 4 more 02-23 15:05:59.628 E/SemcCheckin(15113): Get crash dump level : java.io.FileNotFoundException: /data/semc-checkin/crashdump 02-23 15:05:59.628 W/ActivityManager( 1240): Unable to start service Intent { act=com.sonyericsson.android.jcrashcatcher.action.BUGREPORT_AUTO cmp=com.sonyericsson.android.jcrashcatcher/.JCrashCatcherService (has extras) }: not found 02-23 15:05:59.648 I/Process ( 1240): Sending signal. PID: 15113 SIG: 3 02-23 15:05:59.648 I/dalvikvm(15113): threadid=7: reacting to signal 3 02-23 15:05:59.778 I/dalvikvm(15113): Wrote stack trace to '/data/anr/traces.txt' 02-23 15:06:00.388 E/SemcCheckin( 1673): Get Crash Level : java.io.FileNotFoundException: /data/semc-checkin/crashdump 02-23 15:06:01.708 I/DumpStateReceiver( 1240): Added state dump to 1 crashes 02-23 15:06:02.008 D/iddd-events( 1117): Registering event com.sonyericsson.idd.probe.android.devicemonitor::ApplicationCrash with 4314 bytes payload. 02-23 15:06:06.968 D/dalvikvm( 1673): GC freed 661 objects / 126704 bytes in 124ms 02-23 15:06:11.928 D/dalvikvm( 1379): GC freed 19753 objects / 858832 bytes in 84ms 02-23 15:06:13.038 I/Process (15113): Sending signal. PID: 15113 SIG: 9 02-23 15:06:13.048 I/WindowManager( 1240): WIN DEATH: Window{4596ecc0 com.sonyericsson.camera/com.sonyericsson.album.grid.GridActivity paused=false} 02-23 15:06:13.048 I/ActivityManager( 1240): Process com.sonyericsson.camera (pid 15113) has died. 02-23 15:06:13.048 I/WindowManager( 1240): WIN DEATH: Window{459db5e8 com.sonyericsson.camera/com.sonyericsson.album.grid.GridActivity paused=false} 02-23 15:06:13.078 I/UsageStats( 1240): Unexpected resume of com.twitter.android while already resumed in com.sonyericsson.camera 02-23 15:06:13.098 W/InputManagerService( 1240): Window already focused, ignoring focus gain of: com.android.internal.view.IInputMethodClient$Stub$Proxy@456e7168 02-23 15:06:21.278 D/dalvikvm( 1745): GC freed 2032 objects / 410848 bytes in 60ms

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  • How to: generate UnhandledException?

    - by serhio
    I use this code to catch the WinForm application UnhandledException. [STAThread] static void Main(string[] args) { // Add the event handler for handling UI thread exceptions to the event. Application.ThreadException += new System.Threading.ThreadExceptionEventHandler(Application_ThreadException); // Set the unhandled exception mode to force all Windows Forms errors // to go through our handler. Application.SetUnhandledExceptionMode(UnhandledExceptionMode.CatchException); // Add the event handler for handling non-UI thread exceptions to the event. AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(CurrentDomain_UnhandledException); try { Application.Run(new MainForm()); } catch.... There I will try to restart the application. Now my problem is to simulate a exception like this. I tried before try (in main): throw new NullReferenceException("test"); VS caught it. Tried also in MainForm code with button : private void button1_Click(object sender, EventArgs ev) { ThreadPool.QueueUserWorkItem(new WaitCallback(TestMe), null); } protected void TestMe(object state) { string s = state.ToString(); } did not help, VS caught it, even in Release mode. How should I, finally, force the application generate UnhandleldException? Will I be able to restart the application in CurrentDomain_UnhandledException?

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  • Better way to catch trouble points

    - by mac
    User submits a CSV file which is consumed by a program. Values which are used throughout the program come from the CSV, natually if values are missed it is a problem. Below is my solution. Ip on top private List<String> currentFieldName = new ArrayList<String>(); As part of the method: try { setCurrentFieldName("Trim Space"); p.setTrimSpace(currentLineArray[dc.getTRIM_POSITION()].equals("yes") ? true : false); setCurrentFieldName("Ignore Case"); p.setIgnoreCase(currentLineArray[dc.getIGNORE_CASE_POSITION()].equals("yes") ? true : false); } catch (NullPointerException e) { throw new InputSpreadsheetValueUnassignedException("\"Type\" field not set: " + currentFieldName); } And the method which keeps track of a current field being looked at: private void setCurrentFieldName(String fieldName) { currentFieldName.clear(); currentFieldName.add(fieldName); } The idea there is that if user fails to submit value and i will end up getting null, before throwing an exception, i will know what value was not assigned. So, this being said, specific questions: Is what i have shown below an acceptable solution? Can you suggest something more elegant?

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  • How to use NSPredicate to catch child objects?

    - by Konstantin
    I'm new to core data and try to get all children objects of various types with one query. Say there's an "Animal" type as parent and "Cat", "Dog" and "Bird" as children. I'd like to get both cats and dogs, but not Birds in single query returned as Animal objects. Is it possible?

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  • Continue executing with thrown exception?

    - by fsdfa
    There's something really weird, I have (in C++): func(); cout << "Heeey" << endl; And func, throws an exception: "throw string("ERROR");". But the cout is done, and the exception is successfully catched. Why it prints "Heeey" if there was an exception before?.

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