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• How can I copy a queryset to a new model in django admin?

  - by user3806832

  I'm trying to write an action that allows the user to select the queryset and copy it to a new table. So: John, Mark, James, Tyler and Joe are in a table 1( called round 1) The user selects the action that say to "move to next round" and those same instances that were chosen are now also in the table for "round 2". I started trying with an action but don't really know where to go from here: def Round_2(modeladmin, request, queryset): For X in queryset: X.pk = None perform.short_description = "Move to Round 2" How can I copy them to the next table with all of their information (pk doesn't have to be the same)? Thanks

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• Object reference not set to an instance of an object - how to find the offending object name in the

  - by Jason

  This is the bane of my programming existence. After deploying an application, when this error crops up, no amount of debug dump tells you WHAT object was not instantiated. I have the call stack, that's great, it tells me roughly where the object is, but is there any way to get .NET to tell me the actual name of the object? If you catch them while debugging, of course the program breaks right on the offending creature, but if it happens after the program is in the wild, good luck. There has to be a way. I've explored the exceptions returned in these instances and there is just nothing helpful.

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• Using __str__ representation for printing objects in containers in Python

  - by BobDobbs

  I've noticed that when an instance with an overloaded str method is passed to the print() function as an argument, it prints as intended. However, when passing a container that contains one of those instances to print(), it uses the repr method instead. That is to say, print(x) displays the correct string representation of x, and print(x, y) works correctly, but print([x]) or print((x, y)) prints the repr representation instead. First off, why does this happen? Secondly, is there a way to correct that behavior of print() in this circumstance?

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• Designing constructors around type erasure in Java

  - by Internet Friend

  Yesterday, I was designing a Java class which I wanted to be initalized with Lists of various generic types: TheClass(List<String> list) { ... } TheClass(List<OtherType> list) { ... } This will not compile, as the constructors have the same erasure. I just went with factory methods differentiated by their names instead: public static TheClass createWithStrings(List<String> list) public static TheClass createWithOtherTypes(List<OtherType> list) This is less than optimal, as there isn't a single obvious location where all the different options for creating instances are available. I tried to search for better design ideas, but found surprisingly few results. What other patterns exist for designing around this problem?

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• What's the best way to write a maintainable web scraping app?

  - by Benj

  I wrote a perl script a while ago which logged into my online banking and emailed me my balance and a mini-statement every day. I found it very useful for keeping track of my finances. The only problem is that I wrote it just using perl and curl and it was quite complicated and hard to maintain. After a few instances of my bank changing their webpage I got fed up of debugging it to keep it up to date. So what's the best way of writing such a program in such a way that it's easy to maintain? I'd like to write a nice well engineered version in either Perl or Java which will be easy to update when the bank inevitably fiddle with their web site.

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• pywinauto: taking more than one app windows

  - by Denis Barmenkov

  I have a GUI application which can create many similar windows on desktop. All windows have same title. I have to enumerate all dialogs with same title and make some tests against each of such dialogs. If I call: dialog = app['Window Name'] pywinauto returns a WindowSpecification object which is useful along with accessing controls by name. When I call: dialogs = app.windows_(title='Window Name') pywinauto returns me a list of HwndWrapper instances which are not so useful. How to obtain a list of windows with specified title but as WindowSpecification objects?

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• I need to debug my BrowserHelperObject (BHO) (in C++ with Visual Studio 2008) after a internet explo

  - by BHOdevelopper

  Hi, here is the situation, i'm developping a Browser Helper Object (BHO) in C++ with Visual Studio 2008, and i learned that the memory wasn't managed the same way in Debug mode than in Release mode. So when i run my BHO in debug mode, internet explorer 8 works just fine and i got no erros at all, the browser stays alive forever, but as soon as i compile it in release mode, i got no errors, no message, nothing, but after 5 minutes i can see through the task manager that internet explorer instances are just eating memory and then the browser just stop responding every time. Please, I really need some hint on how to get a feedback on what could be the error. I heard that, often it was happening because of memory mismanagement. I need a software that just grab a memory dump or something when iexplorer crashes to help me find the problem. Any help is appreciated, I'll be looking for responses every single days, thank you.

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• C# property in a form class only accessable after formload event

  - by Spooky2010

  using vs2008, c# Howdy, Im instantiating and calling Form B from Form A. FormB has some custom properties, to allow me to pass it things like sqlAdaptors and dataset instances. When i instantiate and show Form B from Form A as a dialog form with a Using statement, it all works fine, but i find the properties i pass are not available in Form B until after the form_load event has fired. I was under the impression the properties when passed to a instantiated class should be available from a constructor, but this is not the case. If it try to access the properties before the form load event i get a null reference exception. Is this correct behavior ? It is very annoying. thanks for any help

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• Is it a bad idea to use the new Dynamic Keyword as a replacement switch statement?

  - by WeNeedAnswers

  I like the new Dynamic keyword and read that it can be used as a replacement visitor pattern. It makes the code more declarative which I prefer. Is it a good idea though to replace all instances of switch on 'Type' with a class that implements dynamic dispatch. class VistorTest { public string DynamicVisit(object obj) { return Visit((dynamic)obj); } private string Visit(string str) { return "a string was called with value " + str; } private string Visit(int value) { return "an int was called with value " + value; } }

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• When to use Vanilla Javascript vs. jQuery?

  - by jondavidjohn

  I have noticed while monitoring/attempting to answer common jQuery questions, that there are certain practices using javascript, instead of jQuery, that actually enable you to write less and do ... well the same amount. And may also yield performance benefits. A specific example $(this) vs this Inside a click event referencing the clicked objects id jQuery $(this).attr("id"); Javascript this.id; Are there any other common practices like this? Where certain Javascript operations could be accomplished easier, without bringing jQuery into the mix. Or is this a rare case? (of a jQuery "shortcut" actually requiring more code) EDIT : While I appreciate the answers regarding jQuery vs. plain javascript performance, I am actually looking for much more quantitative answers. While using jQuery, instances where one would actually be better off (readability/compactness) to use plain javascript instead of using $(). In addition to the example I gave in my original question.

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• Azure flexibility in geolocation and specs

  - by bitbitbit

  Hi, I'm reading about Azure and there are a couple of things I don't understand: If I choose put a server on Europe, why can't I move it to another datacenter afterwards? If I choose a size for a worker/web role, could I upgrade it to a bigger one afterwards? I think I've read that I cannot put different instances of a worker/web role with different sizes working together? Am I right? And in affirmative case, why? What is cheaper? a big VM with a nicely multithreaded worker role or multiple single-threaded worker roles in several small VMs? Thanks in advance.

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• Are there any tools to optimize the number of consumer and producer threads on a JMS queue?

  - by lindelof

  I'm working on an application that is distributed over two JBoss instances and that produces/consumes JMS messages on several JMS queues. When we configured the application we had to determine which threading model we would use, in particular the number of producing and consuming threads per queue. We have done this in a rather ad-hoc fashion but after reading the most recent columns by Herb Sutter in Dr Dobbs (in particular this one) I would like to size our threads in a more rigorous manner. Are there any methods/tools to measure the throughput of JMS queues (in particular JBoss Messaging queues) as a function of the number of producing/consuming threads?

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• HOWTO: implement a jQuery version of ASP.Net MVC "Strongly Typed Partial Views"

  - by Sam Carleton

  I am working on a multi-page assessment form where the questions/responses are database driven. Currently I the basic system working with Html.BeginForm via standard ASP.Net MVC. At this point in time, the key to the whole system is the 'Strongly Typed Partial Views'. When the question/response is read from the database, the response type determines which derived model is created and added to the collection. The main view it iterates through the collection and uses the 'Strongly Typed Partial Views' system of ASP.Net MVC to determine which view to render the correct type of response (radio button, drop down, or text box). I would like to change this process from a Html.BeginForm to Ajax.BeginForm. The problem is I don't have a clue as to how to implement the dynamic creation of the question/response in the JavaScript/jQuery world. Any thoughts and/or suggestions? Here is the current code to generate the dynamic form: @using (Html.BeginForm(new { mdsId = @Model.MdsId, sectionId = @Model.SectionId })) { <div class="SectionTitle"> <span>Section @Model.SectionName - @Model.SectionDescription</span> <span style="float: right">@Html.CheckBoxFor(x => x.ShowUnansweredQuestions) Show only unaswered questions</span> </div> @Html.HiddenFor(x => x.PrevSectionId) @Html.HiddenFor(x => x.NextSectionId) for (var i = 0; i < Model.answers.Count(); i++) { @Html.EditorFor(m => m.answers[i]); } }

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• JOIN (SELECT DISTINCT [..] substitute

  - by FRKT

  Hello, I'd like to find a substitute for using SELECT DISTINCT in a derived table. Let's say I have three tables: CREATE TABLE `trades` ( `tradeID` int(11) unsigned NOT NULL AUTO_INCREMENT, `employeeID` int(11) unsigned NOT NULL, `corporationID` int(11) unsigned NOT NULL, `profit` int(11) NOT NULL, KEY `tradeID` (`tradeID`), KEY `employeeID` (`employeeID`), KEY `corporationID` (`corporationID`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 CREATE TABLE `corporations` ( `corporationID` int(11) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(255) NOT NULL, PRIMARY KEY (`corporationID`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 CREATE TABLE `employees` ( `employeeID` int(11) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(255) NOT NULL, PRIMARY KEY (`employeeID`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 Let's say I'd like to find out how much profit a specific employee has generated. Simple: SELECT SUM(profit) FROM trades JOIN employees ON trades.employeeID = employees.employeeID AND employees.employeeID = 1; It gets trickier if I'd like to query how much revenue a specific corporation has, however. I cannot simply replicate the aforementioned query, because two or more employees from the same company might be involved in the same trade. This query should do the trick: SELECT SUM(profit) FROM trades JOIN (SELECT DISTINCT tradeID FROM trades WHERE trades.corporationID = 1) ... unfortunately, DISTINCT JOINs seem crazy ineffective. Is there any alternative I can use to determine how much revenue a corporation has, taking into account that a corporation might be listed several times with the same tradeID?

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• Type casting in C++ by detecting the current 'this' object type

  - by Elroy

  My question is related to RTTI in C++ where I'm trying to check if an object belongs to the type hierarchy of another object. The BelongsTo() method checks this. I tried using typeid, but it throws an error and I'm not sure about any other way how I can find the target type to convert to at runtime. #include <iostream> #include <typeinfo> class X { public: // Checks if the input type belongs to the type heirarchy of input object type bool BelongsTo(X* p_a) { // I'm trying to check if the current (this) type belongs to the same type // hierarchy as the input type return dynamic_cast<typeid(*p_a)*>(this) != NULL; // error C2059: syntax error 'typeid' } }; class A : public X { }; class B : public A { }; class C : public A { }; int main() { X* a = new A(); X* b = new B(); X* c = new C(); bool test1 = b->BelongsTo(a); // should return true bool test2 = b->BelongsTo(c); // should return false bool test3 = c->BelongsTo(a); // should return true } Making the method virtual and letting derived classes do it seems like a bad idea as I have a lot of classes in the same type hierarchy. Or does anybody know of any other/better way to the do the same thing? Please suggest.

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• Loop through multiple tables to execute same query

  - by pcvnes

  Hi, I have a database wherein per day a table is created to log process instances. The tables are labeled MESSAGE_LOG_YYYYMMDD Currently i want to sequentially execute the same QUERY against all those tables. I wrote the PL/SQL below, but got stuck at line 10. How can i execute the SQL statement against successfully against all tables here ? DECLARE CURSOR all_tables IS SELECT table_name FROM all_tables WHERE TABLE_NAME like 'MESSAGE_LOG_2%' ORDER BY TABLE_NAME ; BEGIN FOR msglog IN all_tables LOOP SELECT count(*) FROM TABLE msglog.TABLE_NAME ; END LOOP; END; / Cheers, Peter

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• Asynchrous calls cause StaleObjectStateException

  - by Mulone

  Hi all, I'm struggling with a Grails service. The service gets AJAX calls from the clients and behaves like a simple local cache for remote objects: void **someCallFromClient**() { // extract params def results = remoteService.queryService(params) results.each{ // try to fetch result object from local DB def obj = SomeClass.findBySomeField(result.someField) if (!obj){ obj = new Result(params) obj.save() } // do stuff on obj } } The service works fine when only one client is connected, but as soon as 2 or more clients start bombing the server with requests, I start getting: 2010-05-24 13:09:49,764 [30893094@qtp-26315919-2] ERROR errors.GrailsExceptionResolver - Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [ some object #892901] org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [ some object #892901] // very long stactrace It probably happens when 2 calls are trying to create the same object concurrently. I suppose this is a rather typical situation to end up in. Could you recommend any pattern/good practice to fix this issue? For example, is there a way to say to one of the service instances to hang on and wait for the other to finish its stuff and try again? Cheers!

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• Is it possible to navigate to the parent node of a matched node during XSLT processing?

  - by Darin

  I'm working with an OpenXML document, processing the main document part with some XSLT. I've selected a set of nodes via <xsl:template match="w:sdt"> </xsl:template> In most cases, I simply need to replace that matched node with something else, and that works fine. BUT, in some cases, I need to replace not the w:sdt node that matched, but the closest w:p ancestor node (ie the first paragraph node that contains the sdt node). The trick is that the condition used to decide one or the other is based on data derived from the attributes of the sdt node, so I can't use a typical xslt xpath filter. I'm trying to do something like this <xsl:template match="w:sdt"> <xsl:choose> <xsl:when test={first condition}> {apply whatever templating is necessary} </xsl:when> <xsl:when test={exception condition}> <!-- select the parent of the ancestor w:p nodes and apply the appropriate templates --> <xsl:apply-templates select="(ancestor::w:p)/.." mode="backout" /> </xsl:when> </xsl:choose> </xsl:template> <!-- by using "mode", only this template will be applied to those matching nodes from the apply-templates above --> <xsl:template match="node()" mode="backout"> {CUSTOM FORMAT the node appropriately} </xsl:template> This whole concept works, BUT no matter what I've tried, It always applies the formatting from the CUSTOM FORMAT template to the w:p node, NOT it's parent node. It's almost as if you can't reference a parent from a matching node. And maybe you can't, but I haven't found any docs that say you can't Any ideas?

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• inheritance problem OOP extend

  - by hsmit

  If a Father is a Parent and a Parent is a Person and a Person has a Father I create the following: class Person{ Father father; } class Parent extends Person{} class Father extends Parent{} Instances: Person p1 = new Person(); Person p2 = new Person(); p1.father = p2; //father is of the type Father This doesn't work... Now try casting:: Person p1 = new Person(); Person p2 = new Person(); p1.father = (Father)p2; This doesn't work either. What does work for this case?

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• Auto injecting logger with guice

  - by koss

  With reference to Guice's custom injections article, its TypeListener performs a check for InjectLogger.class annotation - which can be optional. Removing that check will inject to all Logger.class types. class Log4JTypeListener implements TypeListener { public <T> void hear(TypeLiteral<T> typeLiteral, TypeEncounter<T> typeEncounter) { for (Field field : typeLiteral.getRawType().getDeclaredFields()) { if (field.getType() == Logger.class && field.isAnnotationPresent(InjectLogger.class)) { typeEncounter.register(new Log4JMembersInjector<T>(field)); } } } } I'm tempted to remove "&& field.isAnnotationPresent(InjectLogger.class)" from the listener. If we're using Guice to inject all instances of our Logger, is there any reason not to do it automatically (without need to annotate)?

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• Objective-C - Unloading loaded view when it is swapped

  - by teepusink

  Hi, What is the best way to do view management in a multiview application? Right now I have this ViewSwitcher method/function that comes from a custom delegate I created. The code is a whole bunch of if else like this MyViewController *c = [[MyViewController alloc] initWithNibName:@"MyViewController" bundle:nil]; c.delegate = self; self.myViewController = c; [self.viewHolder insertSubview:c.view atIndex:0]; [c release]; That works fine, but when I visited the function a second time, is there going to be 2 instances of MyViewController now or just 1? How do I unload MyViewController when I switch to another view? Or is there a better way to manage my views? Thanks, Tee

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• Ember Data Sycn - LocalStorage+REST+RealTime+Online/Offline

  - by Miguel Madero

  We have a combination of requirements in terms o data access. Pre-load some reference data. We need reference data to survive browser restarts instead of just living in memory to avoid loading it all the time. I'm currently using the LocalStorageAdapter for that. Once we have it, we would like to sync changes (polling or using Socket.IO in the background and updating the LocalStorage could do the trick) There're other models that are more transactional, where we would need to directly go to the Server and get/save them. It would be nice to use something like the RESTAdapter for that. Lastly, there're some operations that should work off-line and changes should be synced later. To make it more concrete: * We pre-load vendor and "favorite products" into Local Storage. We work offline with those. * We need to sync server changes to vendor and product information. * If they search the full catalog, that requires them to be online. * When offline, we need to allow users to add something to their cart or even submit and order. We would like to queue this action and submit it when they have an Internet Connection. So a few questions are derived from this: * Is there a way to user RESTAdapter in combination with LocalStorage? * Is there some Socket.IO support? (Happy to do this part manually) * Is there Queueing support? Ideally at the Ember-Data level. I know we will have to do a lot of this manually and pull together the different lego pieces, but I wanted to ask for some perspective from experience Ember devs.

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• Creating Instance of Python Extension Type in C

  - by Brad Zeis

  I am writing a simple Vector implementation as a Python extension module in C that looks mostly like this: typedef struct { PyObject_HEAD double x; double y; } Vector; static PyTypeObject Vector_Type = { ... }; It is very simple to create instances of Vector while calling from Python, but I need to create a Vector instance in the same extension module. I looked in the documentation but I couldn't find a clear answer. What's the best way to do this?

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• In Mercurial, can I apply changes from one file to another file in the same branch?

  - by Stephen

  In the good old days of Subversion, I would sometimes derive a new file from an existing one using svn copy. Then if something changed in sections they had in common, I could still use svn merge to update the derived version. To use the example from hginit.com, say the "guac" recipe already exists, and I want to create a "superguac" that includes instructions on how to serve guacamole to 1000 raving soccer fans. Using the process I just described, I could: svn cp guac superguac svn ci -m "Created superguac by copying guac" (edit superguac) svn ci -m "Added instructions for serving 1000 raving soccer fans to superguac" (edit guac) svn ci -m "Fixed a typo in guac" svn merge -r3:4 guac superguac and thus the typo fix would be applied to superguac. Mercurial provides an hg copy command that marks a file as a copy of the original, but I'm not sure the repository structure supports a similar workflow. Here's the same example, and I carefully only edit a single file in the commit I want to use in the merge: hg cp guac superguac hg ci -m "Created superguac by copying guac" (edit superguac) hg ci -m "Added instructions for serving 1000 raving soccer fans to superguac" (edit guac) hg ci -m "Fixed a typo in guac" I now want to apply the change in guac to superguac. Is that possible? If so, what's the right command? Is there a different workflow in Mercurial that achieves the same results (limited to a single branch)?

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• How to access Session values from layers beneath the web application layer.

  - by Matthew Vines

  We have many instances in our application where we would like to be able to access things like the currently logged in user id in our business domain and data access layer. On log we push this information to the session, so all of our front end code has access to it fairly easily of course. However, we are having huge issues getting at the data in lower layers of our application. We just can't seem to find a way to store a value in the business domain that has global scope just for the user (static classes and properties are of course shared by the application domain, which means all users in the session share just one copy of the object). We have considered passing in the session to our business classes, but then our domain is very tightly coupled to our web application. We want to keep the prospect of a winforms version of the application possible going forward. I find it hard to believe we are the first people to have this sort of issue. How are you handling this problem in your applications?

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