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  • Handling very large lists of objects without paging?

    - by user246114
    Hi, I have a class which can contain many small elements in a list. Looks like: public class Farm { private ArrayList<Horse> mHorses; } just wondering what will happen if the mHorses array grew to something crazy like 15,000 elements. I'm assuming that trying to write and read this from the datastore would be crazy, because I'd get killed on the serialization process. It's important that I can get the entire array in one shot without paging, and each Horse element may only have two string properties in it, so they are pretty lightweight: public class Horse { private String mId; private String mName; } I don't need these horses indexed at all. Does it sound reasonable to just store the mHorse array as a raw Text field, and force my clients to do the deserialization? Something like: public class Farm { private Text mHorsesSerialized; } then whenever the client receives a Farm instance, it has to take the raw string of horses, and split it in order to reinstantiate the list, something like: // GWT client perhaps Farm farm = rpcCall.getMyFarm(); String horsesSerialized = farm.getHorses(); String[] horseBlocks = horsesSerialized.split(","); for (int i = 0; i < horseBlocks.length; i++) { // .. continue deserializing the individual objects ... } yeah... so hopefully it would be quick to read a Farm instance from the datastore, and the serialization penalty is paid by the client, Thanks

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  • Handling RSS Tags with NSXMLParser for iPhone

    - by MartinW
    I've found the following code for parsing through RSS but it does not seem to allow for nested elements: - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName{ NSLog(@"ended element: %@", elementName); if ([elementName isEqualToString:@"item"]) { // save values to an item, then store that item into the array... [item setObject:currentTitle forKey:@"title"]; [item setObject:currentLink forKey:@"link"]; [item setObject:currentSummary forKey:@"summary"]; [item setObject:currentDate forKey:@"date"]; [item setObject:currentImage forKey:@"media:thumbnail"]; The RSS to used is: <item><title>Knife robberies and burglaries up</title> <description>The number of robberies carried out at knife-point has increased sharply and burglaries are also up, latest crime figures indicate</description> <link>http://news.bbc.co.uk/go/rss/-/1/hi/uk/7844455.stm</link> <guid isPermaLink="false">http://news.bbc.co.uk/1/hi/uk/7844455.stm</guid> <pubDate>Thu, 22 Jan 2009 13:02:03 GMT</pubDate><category>UK</category> <media:thumbnail width="66" height="49" url="http://newsimg.bbc.co.uk/media/images/45400000/jpg/_45400861_policegeneric_pa.jpg"/> </item> I need to extract the "url" element from the "media" tag. Thanks Martin

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  • Confirmation before closing

    - by saeed
    Hi I am using c# .net windows form application. I have a combo box and a text box and a close window button. Now If I make any change in the combo box or textbox and click on the close window button, it should prompt the user to save the modifications.. If no modification are made ( The user will just run the application, doesnt make any modification) then it should not prompt the user. It should close directly.. How can I do this?

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  • Help me find article on Multi-threading and Event Handling in Java

    - by JDR
    I once read an article on how to properly write event handlers for multi-threading in Java, but I can't for the life of me find it anymore. It described the pitfalls and potentials for deadlocks that can occur when firing events (not Swing events mind you, but general events like model update notifications). To clarify, the situation would be as such: // let's say this is code from an MVC model somewhere public void setSomeProperty(String myProperty){ if(!this.myProperty.equals(myProperty)){ this.myProperty = myProperty; fireMyPropertyChangedEvent(...); } } The article described how passing control to arbitrary external listener code was a potential cause for deadlock. I now find myself in a situation where I need to fire such events in a multithreaded environment and I would very much like to read the article again to see what it has to say before I continue. Does anyone know the article I'm referring to? I believe it came as a (fairly short) PDF. It started off with an initial naive implementation and incrementally pointed out flaws and improved upon it. It ended with a sort of final proper-way-to-fire-multithreaded-events. I've searched endlessly in my browse history and on google, but all I could find were endless amounts topics on Swing event dispatch threads. Thank you.

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  • Validating event usurps button click on Windows Form

    - by triskelion
    I have a ComboBox and a Save button on my Windows Form. When I change the selected value in the ComboBox then click the Save button, the ComboBox validating event fires but the button click is lost. When the selected value is valid this results in the user thinking they have saved the change when in fact they have not. Why is the button click lost if the ComboBox is valid? Is there a work around?

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  • How to handle touch events on UI Controls

    - by Sreelatha
    Hi, I have a query related to Touch events on the UI controls. I have 4 controls on the screen ( UITextField, UISlider, UISwitch, UIButton ). If the user touches any of the control on the screen, I want to fire touchesBegan and touchesEnded events on those controls in which I would implement some code. Please let me know how to fire these events. Thanks in advance, Sreelatha.

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  • Socket select() Handling Abrupt Disconnections

    - by Genesis
    I am currently trying to fix a bug in a proxy server I have written relating to the socket select() call. I am using the Poco C++ libraries (using SocketReactor) and the issue is actually in the Poco code which may be a bug but I have yet to receive any confirmation of this from them. What is happening is whenever a connection abruptly terminates the socket select() call is returning immediately which is what I believe it is meant to do? Anyway, it returns all of the disconnected sockets within the readable set of file descriptors but the problem is that an exception "Socket is not connected" is thrown when Poco tries to fire the onReadable event handler which is where I would be putting the code to deal with this. Given that the exception is silently caught and the onReadable event is never fired, the select() call keeps returning immediately resulting in an infinite loop in the SocketReactor. I was considering modifying the Poco code so that rather than catching the exception silently it fires a new event called onDisconnected or something like that so that a cleanup can be performed. My question is, are there any elegant ways of determining whether a socket has closed abnormally using select() calls? I was thinking of using the exception message to determine when this has occured but this seems dirty to me.

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  • Programmatic binding of accelerators in wxPython

    - by Inductiveload
    I am trying to programmatically create and bind a table of accelerators in wxPython in a loop so that I don't need to worry about getting and assigning new IDs to each accelerators (and with a view to inhaling the handler list from some external resource, rather than hard-coding them). I also pass in some arguments to the handler via a lambda since a lot of my handlers will be the same but with different parameters (move, zoom, etc). The class is subclassed from wx.Frame and setup_accelerators() is called during initialisation. def setup_accelerators(self): bindings = [ (wx.ACCEL_CTRL, wx.WXK_UP, self.on_move, 'up'), (wx.ACCEL_CTRL, wx.WXK_DOWN, self.on_move, 'down'), (wx.ACCEL_CTRL, wx.WXK_LEFT, self.on_move, 'left'), (wx.ACCEL_CTRL, wx.WXK_RIGHT, self.on_move, 'right'), ] accelEntries = [] for binding in bindings: eventId = wx.NewId() accelEntries.append( (binding[0], binding[1], eventId) ) self.Bind(wx.EVT_MENU, lambda event: binding[2](event, binding[3]), id=eventId) accelTable = wx.AcceleratorTable(accelEntries) self.SetAcceleratorTable(accelTable) def on_move(self, e, direction): print direction However, this appears to bind all the accelerators to the last entry, so that Ctrl+Up prints "right", as do all the other three. How to correctly bind multiple handlers in this way?

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  • Java - Handling Non-Blocking Calls

    - by sarav
    In my application I am using a third-party API. It is a non-blocking method which returns immediately. I have a collection of elements over which I have to invoke this method. Now, my problem is that I have to find a way till all the method execution gets completed and do my next operation. How can I handle this? I cannot modify the third-party API. In short it looks like this for(Object object: objects){ methodA(object); //this is a non-blocking call and returns immediately } // here I want to do my next task only after all the methodA calls completed execution

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  • Php string handling triks

    - by Dam
    Hi my question Need to get the 10 word before and 10 words after for the given text . i mean need to start the 10 words before the keyword and end with 10 word after the key word. Given text : "Twenty-three" The main trick : content having some html tags etc .. tags need to keep that tag with this content only . need to display the words from 10before - 10after content is bellow : <div id="hpFeatureBoxInt"><h3><a href="/go/homepage/i/int/news/world/1/-/news/1/hi/world/europe/8592190.stm">Suicide bombings hit Moscow Metro</a></h3><p>Past suicide bombings in Moscow have been blamed on Islamist rebels At least 35 people have been killed after two female suicide bombers blew themselves up on Moscow Metro trains in the morning rush hour,<h2><span class="dy">Top News Story</span></h2> officials say.<img height="150" width="201" alt="Emergency services carry a body from a Metro station in Moscow (29 March 2010)" src="http://wwwimg.bbc.co.uk/feedengine/homepage/images/_47550689_moscowap203_201x150.jpg">Twenty-three died in the first blast at 0756 (0356 GMT) as a<a href="#"> train stood </a>at the central Lubyanka station, beneath the offices of the FSB intelligence agency.About 40 minutes later, a second explosion ripped through a train at Park Kultury, leaving another 12 dead.No-one has said they carried out the worst attack in the capital since 2004. </p><p id="fbilisten"><a href="/go/homepage/i/int/news/heading/-/news/">More from BBC News</a></p></div> Thank you

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  • why cannot use uncaught_exception in dtor?

    - by camino
    Hi , Herb Sutter in his article http://www.gotw.ca/gotw/047.htm pointed out that we cannot use uncaught_exception in desturctor function, // Why the wrong solution is wrong // U::~U() { try { T t; // do work } catch( ... ) { // clean up } } If a U object is destroyed due to stack unwinding during to exception propagation, T::~T will fail to use the "code that could throw" path even though it safely could. but I write a test program, and T::~T in fact didn't use the "code that could throw" #include <exception> #include <iostream> using namespace std; class T { public: ~T() { if( !std::uncaught_exception() ) { cout<<"can throw"<<endl; throw 1; } else { cout<<"cannot throw"<<endl; } } }; struct U { ~U() { try { T t; } catch( ... ) { } } }; void f() { U u; throw 2; } int main() { try { f(); } catch(...) {} } output is : cannot throw did I miss something? Thanks

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  • Strange exception phenomenon in Windows 7

    - by Level 2
    I spot some interesting articles about exception handle in CodeProject http://www.codeproject.com/KB/cpp/seexception.aspx After reading, I decided to do some experiment. The first time I try to execute the following code char *p; p[0] = 0; The program died without question. But After several times when I executed the same problem binary code, it magically did fine. Even the following code is doing well. Any clue or explanation? char *p p[1000] = 'd'; cout<<p[1000]<<endl; My O/S is Windows 7 64bit and compiler is VS2008 rc1.

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  • How to know the file type of the file which you are forcing the user to download?

    - by Starx
    I am trying to force the user to download a file. For that my script is: $file = "file\this.zip"; header("Cache-Control: public"); header("Content-Description: File Transfer"); header("Content-Disposition: attachment; filename=$file"); header("Content-Type: application/zip"); //This is what I need header("Content-Transfer-Encoding: binary"); readfile($file); The files I am going to upload my not be .zip all the time so I want to know the content type of the image I am going to receive in $file. How to accomplish this

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  • How can a client gracefully detect when a server disconnects?

    - by Ummar
    I am working on a client-server application. The client continuously reads data from server, so when a server is closed or disconnects then the client crashes. I tried a try/catch block, but it didn't work. My client application is written in C++. I want the client to display some proper message like "Server disconnected," then exit.

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  • Swing and handling threads

    - by James P.
    There's a couple questions here on StackOverflow on the subject of threading with the Swing api but things still aren't clear. What is the issue with the EDT, what is the proper way to initiate a Thread with Swing and in what cases should it be used? P.S: Any sources in terms of good practises would be appreciated.

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  • Handling large datasets with PHP/Drupal

    - by jo
    Hi all, I have a report page that deals with ~700k records from a database table. I can display this on a webpage using paging to break up the results. However, my export to PDF/CSV functions rely on processing the entire data set at once and I'm hitting my 256MB memory limit at around 250k rows. I don't feel comfortable increasing the memory limit and I haven't got the ability to use MySQL's save into outfile to just serve a pre-generated CSV. However, I can't really see a way of serving up large data sets with Drupal using something like: $form = array(); $table_headers = array(); $table_rows = array(); $data = db_query("a query to get the whole dataset"); while ($row = db_fetch_object($data)) { $table_rows[] = $row->some attribute; } $form['report'] = array('#value' => theme('table', $table_headers, $table_rows); return $form; Is there a way of getting around what is essentially appending to a giant array of arrays? At the moment I don't see how I can offer any meaningful report pages with Drupal due to this. Thanks

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  • Handling large (object) datasets with PHP

    - by Aron Rotteveel
    I am currently working on a project that extensively relies on the EAV model. Both entities as their attributes are individually represented by a model, sometimes extending other models (or at least, base models). This has worked quite well so far since most areas of the application only rely on filtered sets of entities, and not the entire dataset. Now, however, I need to parse the entire dataset (IE: all entities and all their attributes) in order to provide a sorting/filtering algorithm based on the attributes. The application currently consists of aproximately 2200 entities, each with aproximately 100 attributes. Every entity is represented by a single model (for example Client_Model_Entity) and has a protected property called $_attributes, which is an array of Attribute objects. Each entity object is about 500KB, which results in an incredible load on the server. With 2000 entities, this means a single task would take 1GB of RAM (and a lot of CPU time) in order to work, which is unacceptable. Are there any patterns or common approaches to iterating over such large datasets? Paging is not really an option, since everything has to be taken into account in order to provide the sorting algorithm.

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  • Ruby Methods: return an usage string when insufficient arguments are given

    - by Shyam
    Hi, After creating a serious bunch of classes, with initialize methods, loading them in IRb requires to look back at the code. However, I think it should be easy enough to return a usage message, instead of: ArgumentError: wrong number of arguments (0 for 9) So I prefer to return a string with the human readable arguments, by example using "puts" or just a return of a string. Now I have seen the rescue keyword inside begin-end code, but I wonder how I could catch the ArgumentError when the initialize method is called. Thank you for your answers, feedback and comments!

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  • Creating interruptible process in python

    - by Glycerine
    I'm creating a python script of which parses a large (but simple) CSV. It'll take some time to process. I would like the ability to interrupt the parsing of the CSV so I can continue at a later stage. Currently I have this - of which lives in a larger class: (unfinished) Edit: I have some changed code. But the system will parse over 3 million rows. def parseData(self) reader = csv.reader(open(self.file)) for id, title, disc in reader: print "%-5s %-50s %s" % (id, title, disc) l = LegacyData() l.old_id = int(id) l.name = title l.disc_number = disc l.parsed = False l.save() This is the old code. def parseData(self): #first line start fields = self.data.next() for row in self.data: items = zip(fields, row) item = {} for (name, value) in items: item[name] = value.strip() self.save(item) Thanks guys.

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  • Flexible string handling in Visual Studio 2008 C++

    - by David
    I'm slowly starting to get the hang of the _T stuff in Visual Studio 2008 c++, but a few things still elude me. I can see the benefit of the flexibility, but if I can't get the basics soon, I think I'll go back to the standard way of doing this - much less confusing. The idea with the code below is that it scans the parameters for -d and then stores the text that follows that in the string variable fileDir. It also ignores any other parameters. Any help is appreciated. //Console application Parameters::Parameters(int argc, _TCHAR* argv[]) { _Tstring fileDir; // Is there some kind of _t variable to use here for a string? for (int i = 0; i < argc; i = i + 1) { if (_tccmp(argv[i], _T("-d")) == 0) // this appeared to accept anything starting with - { i = i + 1; fileDir = argv[i] } } _tprintf("Parameter value found: %s\n", fileDir); }

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