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  • Diamond problem in C++

    - by Jack
    I know the diamond problem. I am using gcc compiler. I have some scenarios I need explanation about. 1) class A{ public: virtual void eat(){cout<<"A eat\n";} }; class B:public A{ public: void eat(){ cout<<"B eat\n";}}; class C:public A{ public: void eat(){ cout<<"C eat\n";}}; class D:public B,C{ public: void eat(){ cout<<"D eat\n";}}; int main() { A * a = new D(); a->eat(); getch(); return 0; } Why doesn't this work? 2) class A{ public: void eat(){cout<<"A eat\n";} }; class B:virtual public A{ public: void eat(){ cout<<"B eat\n";}}; class C:virtual public A{ public: void eat(){ cout<<"C eat\n";}}; class D: public B,C{ public: void eat(){ cout<<"D eat\n";}}; int main() { A * a = new D(); a->eat(); getch(); return 0; } When I do this what happens in the background. How does the ambiguity get removed. Is the concept of vtables involved here?

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  • binary files writing/reading problems...

    - by ScReYm0
    Ok i have problem with my code for reading binary file... First i will show you my writing code: void book_saving(char *file_name, struct BOOK *current) { FILE *out; BOOK buf; out = fopen(file_name, "wb"); if(out != NULL) { printf_s("Writting to file..."); do { if(current != NULL) { strcpy(buf.catalog_number, current-catalog_number); strcpy(buf.author, current-author); buf.price = current-price; strcpy(buf.publisher, current-publisher); strcpy(buf.title, current-title); buf.price = current-year_published; fwrite(&buf, sizeof(BOOK), 1, out); } current = current-next; }while(current != NULL); printf_s("Done!\n"); fclose(out); } } and here is my "version" for reading: int book_open(struct BOOK *current, char *file_name) { FILE *in; BOOK buf; BOOK *vnext; int count; int i; in = fopen("west", "rb"); printf_s("Reading database from %s...", file_name); if(!in) { printf_s("\nERROR!"); return 1; } i = fread(&buf,sizeof(BOOK), 1, in); while(!feof(in)) { if(current != NULL) { current = malloc(sizeof(BOOK)); current-next = NULL; } strcpy(current-catalog_number, buf.catalog_number); strcpy(current-title, buf.title); strcpy(current-publisher, buf.publisher); current-price = buf.price; current-year_published = buf.year_published; fread(&buf, 1, sizeof(BOOK), in); while(current-next != NULL) current = current-next; fclose(in); } printf_s("Done!"); return 0; } I just need to save my linked list in binary file and to be able to read it back ... please help me. The program just don't read it or its crash every time different situation ...

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  • c++ dynamic_cast error handling

    - by Nazgob
    Is there any good practice related to dynamic_cast error handling (except not using it when you don't have to)? I'm wondering how should I go about NULL and bad_cast it can throw. Should I check for both? And if I catch bad_cast or detect NULL I probably can't recover anyway... For now, I'm using assert to check if dynamic_cast returned not NULL value. Would you accept this solution on a code review?

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  • how to call any method of Project from classlibrary?

    - by Pankaj Mishra
    Hello I have Class Library Where a class of multithreading Of Producer and consumer based. private void WorkDeQueue() { while (true) { string Url = null; lock (locker) { if (queueList.Count > 0) { Url = queueList.Dequeue(); /* return if a null is found in the queue */ if (Url == null) return; } } if (Url != null) { /* if a job was found then process it */ GetData(Url); //This Is a Method } else { /* if a job was not found (meaning list is empty) then * wait till something is added to it*/ wh.WaitOne(); } } } this GetData method has no body on that class. How can i call any method of my project in palace of getdata. I tried with factory Pattern and also with reflection. but both didn't worked for me. So plz tell me how can i call any method of my project from here.

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  • Rails Active Record Mysql find query HAVING clause

    - by meetraghu28
    Is there a way to use the HAVING clause in some other way without using group by. I am using rails and following is a sample sccenario of the problem that i am facing. In rails you can use the Model.find(:all,:select,conditions,:group) function to get data. In this query i can specify a having clause in the :group param. But what if i dont have a group by clause but want to have a having clause in the result set. Ex: Lets take a query select sum(x) as a,b,c from y where "some_conditions" group by b,c; This query has a sum() aggregation on one of the fields. No if there is nothing to aggregate then my result should be an empty set. But mysql return a NULL row. So this problem can be solved by using select sum(x) as a,b from y where "some_conditions" group by b having a NOT NULL; but what happens in case i dont have a group by clause?? a query like below select sum(x) as a,b from y where "some_conditions"; so how to specify that sum(x) should not be NULL? Any solution that would return an empty set in this case instead of a NULL row will help and also that solution should be doable in rails. We can use subqueries to get this condition working with sumthin like this select * from ((select sum(x) as b FROM y where "some_condition") as subq) where subq.b is not null; but is there a better way to do this thru sql/rails ??

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  • Detecting if Excel file has been closed

    - by Charlie
    Hi StackOverflow, I've spent the past 3 hours trawling the web for answers to no avail, so I hope you can help me. I'm writing an application which automates Excel. The application has an option to "show/hide the excel sheet" so you can look at it, make any final changes and so forth. Closing the application will naturally close the instance of Excel, however, there is a small chance that someone may exit out of Excel directly, without thinking. This breaks my application and I can't seem to find anyway of "checking if the same workbook is still open, and if not, re-opening it", before saving it I've tried all sorts of things: checking if the Excel Application is null (when it's !=null it will save correctly, but when it "is" null (or at least, something other than !=null it won't even hit the breakpoint so I'm completely lost :( Help please?

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  • Force 'Replace Into' to use a certain index

    - by Bobby
    I have a MySQL (5.0) table with 3 rows which are considered a combined Unique Index: CREATE TABLE `test`.`table_a` ( `Id` int(11) NOT NULL AUTO_INCREMENT, `field1` varchar(5) COLLATE latin1_swedish_ci NOT NULL DEFAULT '', `field2` varchar(5) COLLATE latin1_swedish_ci NOT NULL DEFAULT '', `field3` varchar(5) COLLATE latin1_swedish_ci NOT NULL DEFAULT '', PRIMARY KEY (`Id`), INDEX `IdxUnqiue` (`field1`(5),`field2`(5),`field3`(5)) ) ENGINE=MyISAM; This table should be filled with a REPLACE INTO query: REPLACE INTO table_a ( Field1, Field2, Field3 ) VALUES ( "Test1", "Test2", "Test3" ) The behavior I'd like to see is that this query always overrides the previous inserted row, because IdxUnique is...ahm, triggered. But unfortunately, there's still the primary index which seems to kick in and always inserts a new row. What I get: Query was executed 3 times: +---Id---+---Field1---+---Field2---+---Field3---+ | 1 | Test1 | Test2 | Test2 | | 2 | Test1 | Test2 | Test2 | | 3 | Test1 | Test2 | Test2 | +--------+------------+------------+------------+ What I want: Query was executed 3 times: +---Id---+---Field1---+---Field2---+---Field3---+ | 3 | Test1 | Test2 | Test2 | +--------+------------+------------+------------+ So, can I tell REPLACE INTO to use just a certain Index or to consider one 'more inportant' then another?

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  • Accessing Linq data in telerik grid ItemCreated method

    - by Jack
    Not sure if the title of this question makes sense, but here's my problem: I have a telerik grid bound to a Linq data object, however, I limit the fields returned: <IQueryable>filter = data.Select(x => new {x.ID, x.Name, x.Age}); I would like to access these fields in the ItemCreated method of the grid: protected void rgPeople_ItemCreated(object sender, GridItemEventArgs e) { Telerik.Web.UI.GridDataItem item = (GridDataItem)e.Item; ?????? Person = (???????)e.Item.DataItem; } What do I declare ?????? as so that I can use: String ID = Person.ID; String Name = Person.Name; etc

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  • Why i cant save a long text on my MySQL database?

    - by DomingoSL
    im trying to save to my data base a long text (about 2500 chars) input by my users using a web form and passed to the server using php. When i look in phpmyadmin, the text gets crop. How can i config my table in order to get the complete text? This is my table config: CREATE TABLE `extra_879` ( `id` bigint(20) NOT NULL auto_increment, `id_user` bigint(20) NOT NULL, `title` varchar(300) NOT NULL, `content` varchar(3000) NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY `id_user` (`id_user`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ; Take a look of the field content that have a limit of 3000 chars, but the texts always gets crop at 690 chars. Thanks for any help! EDIT: I found the problem but i dont know how to solve it. The query is getting crop always in the same char, an special char: ù EDIT 2: This is the cropped query: INSERT INTO extra_879 (id,id_user,title,content) VALUES (NULL,'1','Informazione Extra',' Riconoscimenti Laurea di ingegneria presa a le 22 anni e in il terso posto della promozione Diploma analista di sistemi ottenuto il rating massimo 20/20, primo posto della promozione. Borsa di Studio (offerta dal Ministero Esteri Italiano) vinta nel 2010 (Valutazione del territorio attraverso le nueve tecnologie) Pubblicazione di paper; Stima del RCS della nave CCGS radar sulla base dei risultati di H. Leong e H. Wilson. http://www.ing.uc.edu.vek-azozayalarchivospdf/PAPER-Sarmiento.pdf Tesi di laurea: PROGETTAZIONE E REALIZZAZIONE DI UN SIS-TEMA DI TELEMETRIA GSM PER IL CONTROLLO DELLO STATO DI TRANSITO VEICOLARE E CLIMA (ottenuto il punteggio pi') It gets crop just when the (ottenuto il punteggio più alto) phrase, just when ù appear... EDIT 3: I using jquery + ajax to send the query $.ajax({type: "POST", url: "handler.php", data: "e_text="+ $('#e_text').val() + "&e_title="+ $('#extra_title').val(),

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  • How to implement dynamic queries for MNesia?

    - by Kerem
    I'm trying to implement a function that generates dynamic queries for MNesia. For example, when function is called with these arguments; dyn_query(list, person, [name, age], ["jack", 21]) I want to query MNesia to list items whose name is "jack" and age is 21 in person table. I've tried to implement this by using qlc:q(ListComprehension) and qlc:string_to_handle("ListComprehension"). First failed because of compile errors, compiler didn't let me to use functions instead of ListComprehentions and variables instead of record names like "Item#Table.Member". Second failed, because erl_eval couldn't handle records and throwed exceptions like {undefined_record, person}. Which method should I use? How could i solve these problems? Or should I use a different method? Thanks.

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  • Please help optimizing a long running query (left outer join, with 2 subqueries)

    - by 46and2
    Hi all. The query I need help with is: SELECT d.bn, d.4700, d.4500, ... , p.`Activity Description` FROM ( SELECT temp.bn, temp.4700, temp.4500, .... FROM `tdata` temp GROUP BY temp.bn HAVING (COUNT(temp.bn) = 1) ) d LEFT OUTER JOIN ( SELECT temp2.bn, max(temp2.FPE) AS max_fpe, temp2.`Activity Description` FROM `pdata` temp2 GROUP BY temp2.bn ) p ON p.bn = d.bn; The ... represents other fields that aren't really important to solving this problem. The issue is on the the second subquery - it is not using the index I have created and I am not sure why, it seems to be because of the way TEXT fields are handled. The first subquery uses the index I have created and runs quite snappy, however an explain on the second shows a 'Using temporary; Using filesort'. Please see the indexes I have created in the below table create statements. Can anyone help me optimize this? By way of quick explanation the first subquery is meant to only select records that have unique bn's, the second, while it looks a bit wacky (with the max function there which is not being used in the result set) is making sure that only one record from the right part of the join is included in the result set. My table create statements are CREATE TABLE `tdata` ( `BN` varchar(15) DEFAULT NULL, `4000` varchar(3) DEFAULT NULL, `5800` varchar(3) DEFAULT NULL, .... KEY `BN` (`BN`), KEY `idx_t3010`(`BN`,`4700`,`4500`,`4510`,`4520`,`4530`,`4570`,`4950`,`5000`,`5010`,`5020`,`5050`,`5060`,`5070`,`5100`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 CREATE TABLE `pdata` ( `BN` varchar(15) DEFAULT NULL, `FPE` datetime DEFAULT NULL, `Activity Description` text, .... KEY `BN` (`BN`), KEY `idx_programs_2009` (`BN`,`FPE`,`Activity Description`(100)) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 Thanks!

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  • multipart file-upload post request from java

    - by Martin
    I'm trying to make a program that uploads a image to a webserver that accepts multipart file-uploads. More specificly i want to make a http POST request to http://iqs.me that sends a file in the variable "pic". I've made a lot of tries but i don't know if i've even been close. The hardest part seems to be to get a HttpURLConnection to make a request of the type POST. The response i get looks like it makes a GET. (And i want to do this without any third party libs) UPDATE: non-working code goes here (no errors but doesn't seem to do a POST): HttpURLConnection conn = null; BufferedReader br = null; DataOutputStream dos = null; DataInputStream inStream = null; InputStream is = null; OutputStream os = null; boolean ret = false; String StrMessage = ""; String exsistingFileName = "myScreenShot.png"; String lineEnd = "\r\n"; String twoHyphens = "--"; String boundary = "*****"; int bytesRead, bytesAvailable, bufferSize; byte[] buffer; int maxBufferSize = 1*1024*1024; String responseFromServer = ""; String urlString = "http://iqs.local.com/index.php"; try{ FileInputStream fileInputStream = new FileInputStream( new File(exsistingFileName) ); URL url = new URL(urlString); conn = (HttpURLConnection) url.openConnection(); conn.setDoInput(true); conn.setDoOutput(true); conn.setRequestMethod("POST"); conn.setUseCaches(false); conn.setRequestProperty("Connection", "Keep-Alive"); conn.setRequestProperty("Content-Type", "multipart/form-data;boundary="+boundary); dos = new DataOutputStream( conn.getOutputStream() ); dos.writeBytes(twoHyphens + boundary + lineEnd); dos.writeBytes("Content-Disposition: form-data; name=\"pic\";" + " filename=\"" + exsistingFileName +"\"" + lineEnd); dos.writeBytes(lineEnd); bytesAvailable = fileInputStream.available(); bufferSize = Math.min(bytesAvailable, maxBufferSize); buffer = new byte[bufferSize]; bytesRead = fileInputStream.read(buffer, 0, bufferSize); while (bytesRead > 0){ dos.write(buffer, 0, bufferSize); bytesAvailable = fileInputStream.available(); bufferSize = Math.min(bytesAvailable, maxBufferSize); bytesRead = fileInputStream.read(buffer, 0, bufferSize); } dos.writeBytes(lineEnd); dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd); fileInputStream.close(); dos.flush(); dos.close(); }catch (MalformedURLException ex){ System.out.println("Error:"+ex); }catch (IOException ioe){ System.out.println("Error:"+ioe); } try{ inStream = new DataInputStream ( conn.getInputStream() ); String str; while (( str = inStream.readLine()) != null){ System.out.println(str); } inStream.close(); }catch (IOException ioex){ System.out.println("Error: "+ioex); }

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  • PHP: Need help with simple XML

    - by Jack
    I am beginner in PHP. I am trying to parse this xml file. <relationship> <target> <following type="boolean">true</following> <followed_by type="boolean">true</followed_by> <screen_name>xxxx</screen_name> <id type="integer">xxxx</id> </target> <source> <notifications_enabled nil="true"/> <following type="boolean">true</following> <blocking nil="true"/> <followed_by type="boolean">true</followed_by> <screen_name>xxxx</screen_name> <id type="integer">xxxxx</id> </source> </relationship> I need to get the value of the field 'following type="boolean" ' for the target and here's my code - $xml = simplexml_load_string($response); foreach($xml->children() as $child) { if ($child->getName() == 'target') { foreach($child->children() as $child_1) if ( $child_1->getName() == 'following') { $is_my_friend = (bool)$child_1; break; } break; } } but I am not getting the correct output. I think the ' type="boolean" ' part of the field is creating problems. Please help.

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  • Really frustrated: Help writing a sample twitter app

    - by Jack
    I have installed WAMP. I have enable cURL in php.ini. I want to implement a twitter app that posts a new status message for a user. Here's my code <?php function updateTwitter($status) { $username = 'xxxxxx'; $password = 'xxxx'; $url = 'http://twitter.com/statuses/update.xml'; $postargs = 'status='.urlencode($status); $responseInfo=array(); $ch = curl_init($url); curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 2); curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); curl_setopt($ch, CURLOPT_PROXY,"localhost:80"); curl_setopt ($ch, CURLOPT_POST, true); // Give CURL the arguments in the POST curl_setopt ($ch, CURLOPT_POSTFIELDS, $postargs); // Set the username and password in the CURL call curl_setopt($ch, CURLOPT_USERPWD, $username.':'.$password); // Set some cur flags (not too important) $response = curl_exec($ch); if($response === false) { echo 'Curl error: ' . curl_error($ch); } else { echo 'Operation completed without any errors<br/>'; } // Get information about the response $responseInfo=curl_getinfo($ch); // Close the CURL connection curl_close($ch); // Make sure we received a response from Twitter if(intval($responseInfo['http_code'])==200){ // Display the response from Twitter echo $response; }else{ // Something went wrong echo "Error: " . $responseInfo['http_code']; } curl_close($ch); } updateTwitter("Just finished a sweet tutorial on http://brandontreb.com"); ?> I am getting the following output Operation completed without any errors Error: 404 Please help.

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  • iPhone OS syntax highlighting UITextField

    - by Jack
    Hi, I am working on an application and would like to apply some syntax highlighting to some user entered text. I have looked around and some people are suggesting that this can be done in OS 3.2+ but posts seem to be from before the NDA was lifted. Does anyone have any suggestions as to how to go about doing this? I would be interested in releasing the code on github if I could get it implemented well, as I have never done so before. Thanks

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  • jQuery JSON .each problem

    - by Aran
    I have a JSON object that looks like this. [ { "id" : "23", "event_id" : "0", "sport_title" : null, "event_title" : null, "title" : "Under 1 day!", "content" : "It\\'s all hotting up and battle commences in under one day!", "link" : "" }, { "id" : "20", "event_id" : "0", "sport_title" : null, "event_title" : null, "title" : "Getting Exciting", "content" : "Less than two days till it all kicks off, with cricket....", "link" : "" }] and I am trying to get the details out of this JSON Object and prepend them to a <ul> the code that I am currently trying looks like this and is having problems var writeup_list = writeuplist; $.getJSON('../json/getWriteups.json', function(data) { $.each(data.items, function(i, item) { writeup_list.html(function() { var output; output = '<li><a href="/writeups/index.php#writeup_' + item.id + '">'; if(item.sport_title != null) { output += item.sport_title + ' - '; } output += item.title + '</a></li>'; return output; }); }); }); writeuplist is just the ul object. I am also worried about overriding information that is already in the list or just adding again. Don't want to keep adding the same data. What is a good way to avoid this? I seem to be having a problem in getting the data out of the JSON file I believe it has something to do with the way am trying to access it in the .each function. Can anyone spot where am going wrong?

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  • Groovy / Scala / Java under the hood

    - by Jack
    I used Java for like 6-7 years, then some months ago I discovered Groovy and started to save a lot of typing.. then I wondered how certain things worked under the hood (because groovy performance is really poor) and understood that to give you dynamic typing every Groovy object is a MetaClass object that handles all the things that the JVM couldn't handle by itself. Of course this introduces a layer in the middle between what you write and what you execute that slows down everything. Then somedays ago I started getting some infos about Scala. How these two languages compare in their byte code translations? How much things they add to the normal structure that it would be obtained by plain Java code? I mean, Scala is static typed so wrapper of Java classes should be lighter, since many things are checked during compile time but I'm not sure about the real differences of what's going inside. (I'm not talking about the functional aspect of Scala compared to the other ones, that's a different thing) Can someone enlighten me? From WizardOfOdds it seems like that the only way to get less typing and same performance would be to write an intermediate translator that translates something in Java code (letting javac compile it) without alterating how things are executed, just adding synctatic sugar withour caring about other fallbacks of the language itself.

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  • How to convert CFStringRef to NSString?

    - by papr
    NSString *aNSString; CFStringRef aCFString; aCFString = CFStringCreateWithCString(NULL, [aNSString UTF8String], NSUTF8StringEncoding); aCFString = CFXMLCreateStringByUnescapingEntities(NULL, aCFString, NULL); How can I get a new NSString from aCFString?

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  • Optional Argument: compile time constant issue

    - by Jack
    Why is this working: public int DoesEmailAddressExistsExcludingEmailAddressID( string emailAddress, string invitationCode, int emailAddressID = 0, int For = (int) Enums.FOR.AC) whereas this doesn't public int DoesEmailAddressExistsExcludingEmailAddressID( string emailAddress, string invitationCode, int emailAddressID = 0, int For = Enums.FOR.AC.GetHashCode()) where AC is enum. Can enums's hashcode change at runtime?

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  • Adding metadata attributes to MySQL table

    - by Jack
    I would like to add custom attributes to a MySQL table which I can read via php. These attributes are not to interfere with the table itself - they are primarily accessed by php code during code generation time and these attributes HAVE to reside in the DB itself. Something similar in concept to .NET reflection. Does MySQL support anything like this? Thanks.

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  • Problem when copying array of different types using Arrays.copyOf

    - by Shervin
    I am trying to create a method that pretty much takes anything as a parameter, and returns a concatenated string representation of the value with some delimiter. public static String getConcatenated(char delim, Object ...names) { String[] stringArray = Arrays.copyOf(names, names.length, String[].class); //Exception here return getConcatenated(delim, stringArray); } And the actual method public static String getConcatenated(char delim, String ... names) { if(names == null || names.length == 0) return ""; StringBuilder sb = new StringBuilder(); for(int i = 0; i < names.length; i++) { String n = names[i]; if(n != null) { sb.append(n.trim()); sb.append(delim); } } //Remove the last delim return sb.substring(0, sb.length()-1).toString(); } And I have the following JUnit test: final String two = RedpillLinproUtils.getConcatenated(' ', "Shervin", "Asgari"); Assert.assertEquals("Result", "Shervin Asgari", two); //OK final String three = RedpillLinproUtils.getConcatenated(';', "Shervin", "Asgari"); Assert.assertEquals("Result", "Shervin;Asgari", three); //OK final String four = RedpillLinproUtils.getConcatenated(';', "Shervin", null, "Asgari", null); Assert.assertEquals("Result", "Shervin;Asgari", four); //OK final String five = RedpillLinproUtils.getConcatenated('/', 1, 2, null, 3, 4); Assert.assertEquals("Result", "1/2/3/4", five); //FAIL However, the test fails on the last part with the exception: java.lang.ArrayStoreException at java.lang.System.arraycopy(Native Method) at java.util.Arrays.copyOf(Arrays.java:2763) Can someone spot the error?

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  • Why is django admin not accepting Nullable foreign keys?

    - by p.g.l.hall
    Here is a simplified version of one of my models: class ImportRule(models.Model): feed = models.ForeignKey(Feed) name = models.CharField(max_length=255) feed_provider_category = models.ForeignKey(FeedProviderCategory, null=True) target_subcategories = models.ManyToManyField(Subcategory) This class manages a rule for importing a list of items from a feed into the database. The admin system won't let me add an ImportRule without selecting a feed_provider_category despite it being declared in the model as nullable. The database (SQLite at the moment) even checks out ok: >>> .schema ... CREATE TABLE "someapp_importrule" ( "id" integer NOT NULL PRIMARY KEY, "feed_id" integer NOT NULL REFERENCES "someapp_feed" ("id"), "name" varchar(255) NOT NULL, "feed_provider_category_id" integer REFERENCES "someapp_feedprovidercategory" ("id"), ); ... I can create the object in the python shell easily enough: f = Feed.objects.get(pk=1) i = ImportRule(name='test', feed=f) i.save() ...but the admin system won't let me edit it, of course. How can I get the admin to let me edit/create objects without specifying that foreign key?

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