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• Conditionally overriding a system method via categories in Objective-C?

  - by adib

  Hi Is there a way to provide a method implementation (that bears the exact same name of a method defined by the framework) only when the method isn't already defined in the system? For example method [NSSomeClass someMethod:] exists only in Mac OS X 10.6 and if my app runs in 10.5, I will provide that method's definition in a category. But when the app runs in 10.6, I want the OS-provided method to run. Background: I'm creating an app targeted for both 10.5 and 10.6. The problem is that I recently realized that method +[NSSortDescriptor sortDescriptorWithKey:ascending:] only exists in 10.6 and my code is already littered by that method call. I could provide a default implementation for it (since this time it's not too difficult to implement it myself), but I want the "native" one to be called whenever my app runs on 10.6. Furthermore if I encounter similar problems in the future (with more difficult-to-implement-myself methods), I might not be able to get away with providing a one-liner replacement. This question vaguely similar to Override a method via ObjC Category and call the default implementation? but the difference is that I want to provide implementations only when the system doesn't already has one. Thanks.

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• Linked List pop() function

  - by JKid314159

  Consider the following list: [LinkNode * head -- LinkNode * node1 -- LinkNode * node2] I'm creating a stack of FIFO. I Call pop() which I want to pop node1. LinkNode::LinkNode(int numIn) { this->numIn = numIn; next = null; } . . . int LinkNode::pop() { Link * temp = head->next; head = temp->next; int popped = head->nodeNum; delete temp; Return numOut; Question: 1) head should be a pointer or a LinkNode *? 2) Link * temp is created on the call stack and when pop finishes doesn't temp delete automatically? 3) My major confusion is on what is the value of temp-next? Does this point to node1.next which equals node2? Appreciate your help? My reference is C++ for Java Programmers by Weiss.

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• Problem running python/matplotlib in background after ending ssh session.

  - by Jamie

  Hi there, I have to VPN and then ssh from home to my work server and want to run a python script in the background, then log out of the ssh session. My script makes several histogram plots using matplotlib, and as long as I keep the connection open everything is fine, but if I log out I keep getting an error message in the log file I created for the script. File "/Home/eud/jmcohen/.local/lib/python2.5/site-packages/matplotlib/pyplot.py", line 2058, in loglog ax = gca() File "/Home/eud/jmcohen/.local/lib/python2.5/site-packages/matplotlib/pyplot.py", line 582, in gca ax = gcf().gca(**kwargs) File "/Home/eud/jmcohen/.local/lib/python2.5/site-packages/matplotlib/pyplot.py", line 276, in gcf return figure() File "/Home/eud/jmcohen/.local/lib/python2.5/site-packages/matplotlib/pyplot.py", line 254, in figure **kwargs) File "/Home/eud/jmcohen/.local/lib/python2.5/site-packages/matplotlib/backends/backend_tkagg.py", line 90, in new_figure_manager window = Tk.Tk() File "/Home/eud/jmcohen/.local/lib/python2.5/lib-tk/Tkinter.py", line 1647, in __init__ self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use) _tkinter.TclError: couldn't connect to display "localhost:10.0" I'm assuming that it doesn't know where to create the figures I want since I close my X11 ssh session. If I'm logged in while the script is running I don't see any figures popping up (although that's because I don't have the show() command in my script), and I thought that python uses tkinter to display figures. The way that I'm creating the figures is, loglog() hist(list,x) ylabel('y') xlabel('x') savefig('%s_hist.ps' %source.name) close() The script requires some initial input, so the way I'm running it in the background is python scriptToRun.py << start>& logfile.log& Is there a way around this, or do I just have to stay ssh'd into my machine? Thanks.

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• Generating Random Records Date Wise

  - by Julian

  I work for a non-profit organization where we send volunteers to aided schools everyday. I am creating a site to display this info and am using SQL server express. I want some help regarding a query so here's my first post We have 15 volunteers currently who will go to 4 different schools to teach. Here are some conditions: We have to create a 'new' group comprising of 1 Leader and 4 TeamSupporters 'every day' except Sunday who will go to teach everyday If a person becomes a Leader in a week, he cannot become a leader again for the same week. A leader can become a TeamSupporter in the same week. Moving ahead, we can have more number of school to target, so 4 is not a constant Here's how the output should look like School1 School2 School3 School4 Jun14 Leader V6 V6 V6 V6 Support1 V3 V3 V3 V3 Support2 V9 V9 V9 V9 Support3 V12 V12 V12 V12 Support4 V1 V1 V1 V1 Jun15 Leader V2 V2 V2 V2 Support1 V7 V7 V7 V7 Support2 V9 V9 V9 V9 Support3 V8 V8 V8 V8 Support4 V11 V11 V11 V11 Jun16 Leader V9 V9 V9 V9 Support1 V6 V6 V6 V6 Support2 V4 V4 V4 V4 Support3 V3 V3 V3 V3 Support4 V14 V14 V14 V14 and so on..

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• How to reuse results with a schema for end of day stock-data

  - by Vishalrix

  I am creating a database schema to be used for technical analysis like top-volume gainers, top-price gainers etc.I have checked answers to questions here, like the design question. Having taken the hint from boe100 's answer there I have a schema modeled pretty much on it, thusly: Symbol - char 6 //primary Date - date //primary Open - decimal 18, 4 High - decimal 18, 4 Low - decimal 18, 4 Close - decimal 18, 4 Volume - int Right now this table containing End Of Day( EOD) data will be about 3 million rows for 3 years. Later when I get/need more data it could be 20 million rows. The front end will be asking requests like "give me the top price gainers on date X over Y days". That request is one of the simpler ones, and as such is not too costly, time wise, I assume. But a request like " give me top volume gainers for the last 10 days, with the previous 100 days acting as baseline", could prove 10-100 times costlier. The result of such a request would be a float which signifies how many times the volume as grown etc. One option I have is adding a column for each such result. And if the user asks for volume gain in 10 days over 20 days, that would require another table. The total such tables could easily cross 100, specially if I start using other results as tables, like MACD-10, MACD-100. each of which will require its own column. Is this a feasible solution? Another option being that I keep the result in cached html files and present them to the user. I dont have much experience in web-development, so to me it looks messy; but I could be wrong ( ofc!) . Is that a option too? Let me add that I am/will be using mod_perl to present the response to the user. With much of the work on mysql database being done using perl. I would like to have a response time of 1-2 seconds.

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• iPhone application update (using Core Data on Sqlite)

  - by owen

  I have an app which is using Core Data on Sqlite, Now I have a update which has some DB structure changes say adding a new table I know when an app get updated, it updates the app binary only, nothing on document directory will be changed. When the app gets updated and launchs at the first time and run [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; It will find the difference between the data model and DB structure in Sqlite and will throw an exception and quit. Error: "The model used to open the store is incompatible with the one used to create the store" So, can anyone here give me some idea how to update an app when there is a DB structure change? I think we can run a DB script to create that new table when it launchs the update at the first time. But if there are other changes like changing the type of some fields or deleting some fields, and we need to migrate the old data, this is really a headache. In this case, Is the only way to do is creating a new app? Is there anyone tried something similar like this?

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• Resume Activity with back button

  - by Hallik

  I have an application I am creating with a DashboardActivity & a SettingsActivity. On the dashboard, I have one object displayed, but when I go into settings, I want to be able to select/deselect X options. Once the user clicks the back button, I save that data locally and to the server. Once the phone receives a success message from the server that it was stored properly, I want to reload the dashboard. I thought I would do this with the onPause and onResume, but they are called when the DashboardActivity is first created. What would be the best way to reload the dashboard by calling my web service after the settings were saved to the server? Here is what I am doing when the back button is hit @Override public boolean onKeyDown(int keyCode, KeyEvent event) { //Save data to the server once the user hits the back button if ((keyCode == KeyEvent.KEYCODE_BACK)) { SchoolSearchActivity.this.divisionProxy = new DivisionProxy(SchoolSearchActivity.this.saveUserDivisionHandler); SchoolSearchActivity.this.divisionProxy.submitUserDivisions(SchoolSearchActivity.this.userDivisions, SchoolSearchActivity.this.user_id); //SchoolSearchActivity.this.finish(); //Toast.makeText(SchoolSearchActivity.this, "Divisions Saved",Toast.LENGTH_LONG).show(); } return true; } The above opens an HTTP connection, and when the response is received, the handler processes the response. I am going to: 1) throw up a progress dialog box letting the user know it's being submitted to the server, and once a response is received, 2) go back to the previous activity and call the "refresh" webservice again. What's the best way to accomplish 1 & 2?

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• How to serialize data from processing.js to rails application ?

  - by railscoder

  Hi I am creating a simple canvas using processing.js , how to pass values from rails application to Processing.js void drawBox(int bx, int by, int bs, int bs){ strokeWeight(3); stroke(50,50,50); // Test if the cursor is over the box if (mouseX > bx-bs && mouseX < bx+bs && mouseY > by-bs && mouseY < by+bs) { bover = true; if(!locked) { fill(181,213,255); } } else { fill(255); bover = false; } fill(192); stroke(64); roundRect(bx, by,80,30,10,10); // put in text if (!isRight) { text("Box Value", x-size+5, y-5); //Here i need to pass value from my controller } else { text("Box Value", x+5, y-5); //Here i need to pass value from my controller } } Instead of static string "Box Value" , I need to pass the value from the ex @post.name through ajax

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• Accessing the stringValue from NSTextFields on different NIBs

  - by Kyle Zaragoza

  I'm having an extremely difficult time trying to access information from an object (e.g. an NSTextField) that is located on a NIB other than my "MainMenu.nib". My current setup: I have a MainMenu.xib that contains only a toolbar at the top and an NSView. I have four other .xib files containing custom NSViews and each of their File Owner's are assigned to a NSViewController subclass which I have created for each. My MainMenu.xib contains an object that is set to my WindowController subclass that takes care of swapping the fours views into the NSView on my MainMenu.xib. All of this works fantastic. Where I have a problem: I have another class that acts as the brains to my application which sends and receives data from an online server, all of the methods I have created rely on inputs from the user that are located on the individual .xibs that swap into my MainMenu.xib's NSview. Unfortunately I have no idea on how to grab the information from the NSTextFields, textViews, etc. that are located on my individual .xib files. What I've tried: I have tried setting the File Owner's of the four individual .xibs to my "brains" class and connecting outlets defined in my "brains".h, but when I call [textField stringValue] I receive a NULL response. I'm thinking this is because I'm creating multiple instances of my "brains" class but not totally sure. Any help on accessing information from textFields from other nibs would be a great benefit, thanks in advance.

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• asp.net mvc: What is the correct way to return html from controller to refresh select list?

  - by Mark Redman

  Hi, I am new to ASP.NET MVC, particularly ajax operations. I have a form with a jquery dialog for adding items to a drop-down list. This posts to the controller action. If nothing (ie void method) is returned from the Controller Action the page returns having updated the database, but obviously there no chnage to the form. What would be the best practice in updating the drop down list with the added id/value and selecting the item. I think my options are: 1) Construct and return the html manually that makes up the new <select> tag [this would be easy enough and work, but seems like I am missing something] 2) Use some kind of "helper" to construct the new html [This seems to make sense] 3) Only return the id/value and add this to the list and select the item [This seems like an overkill considering the item needs to be placed in the correct order etc] 4) Use some kind of Partial View [Does this mean creating additional forms within ascx controls? not sure how this would effect submitting the main form its on? Also unless this is reusable by passing in parameters(not sure how thats done) maybe 2 is the option?] UPDATE: Having looked around a bit, it seems that generating html withing the controller is not a good idea. I have seen other posts that render partialviews to strings which I guess is what I need and separates concerns (since the html bits are in the ascx). Any comments on whether that is good practice.

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• Simulating mouse clicks on Mac OS X does not work for some applications.

  - by Thomi

  I'm writing an application for Mac OS X 10.6 and later in C++. One part of the application needs to simulate mouse movement and mouse clicks. I do this currently by posting CGEvent objects using CGEventPost(kCGHIDEventTap, event);. This works, for the most part - I can simulate mouse movement and clicks just fine, but it seems to fail in some areas. For example: In Mozilla Firefox and Safari, I can click on all the menus, but cannot click on a link within a website. When I try, the link is highlighted, but the browser never follows the link. However, I can right-click on a link, select "open link in new tab", and everything works as expected. Solved - creating the mouse event using CGEventCreateMouseEvent(...) makes the event work within web browser. I can click on the "Dashboard" icon to brink up the dashboard, but I cannot click on the "i" button on any of the dashboard widgets. Similarly, clicking on any of the search results from the spotlight search widget doesn't work either. This inconsistency is along application boundaries. What might be the cause?

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• Dumping an ADODB recordset to XML, then back to a recordset, then saving to the db

  - by Mark Biek

  I've created an XML file using the .Save() method of an ADODB recordset in the following manner. dim res dim objXML: Set objXML = Server.CreateObject("MSXML2.DOMDocument") 'This returns an ADODB recordset set res = ExecuteReader("SELECT * from some_table) With res Call .Save(objXML, 1) Call .Close() End With Set res = nothing Let's assume that the XML generated above then gets saved to a file. I'm able to read the XML back into a recordset like this: dim res : set res = Server.CreateObject("ADODB.recordset") res.open server.mappath("/admin/tbl_some_table.xml") And I can loop over the records without any problem. However what I really want to do is save all of the data in res to a table in a completely different database. We can assume that some_table already exists in this other database and has the exact same structure as the table I originally queried to make the XML. I started by creating a new recordset and using AddNew to add all of the rows from res to the new recordset dim outRes : set outRes = Server.CreateObject("ADODB.recordset") dim outConn : set outConn = Server.CreateObject("ADODB.Connection") dim testConnStr : testConnStr = "DRIVER={SQL Server};SERVER=dev-windows\sql2000;UID=myuser;PWD=mypass;DATABASE=Testing" outConn.open testConnStr outRes.activeconnection = outConn outRes.cursortype = adOpenDynamic outRes.locktype = adLockOptimistic outRes.source = "product_accessories" outRes.open while not res.eof outRes.addnew for i=0 to res.fields.count-1 outRes(res.fields(i).name) = res(res.fields(i).name) next outRes.movefirst res.movenext wend outRes.updatebatch But this bombs the first time I try to assign the value from res to outRes. Microsoft OLE DB Provider for ODBC Drivers error '80040e21' Multiple-step OLE DB operation generated errors. Check each OLE DB status value, if available. No work was done. Can someone tell me what I'm doing wrong or suggest a better way for me to copy the data loaded from XML to a different database?

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• Deserializing JSON in WCF throws xml errors in .Net 4.0

  - by Syg

  Hi there. I'm going slidely mad over here, maybe someone else can figure out what's going on here. I have a WCF service exposing a function using webinvoke, like so: [OperationContract] [WebInvoke(Method = "POST", BodyStyle = WebMessageBodyStyle.Wrapped, RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json, UriTemplate = "registertokenpost" )] void RegisterDeviceTokenForYoumiePost(test token); The datacontract for the test class looks like this: [DataContract(Namespace="Zooma.Test", Name="test", IsReference=true)] public class test { string waarde; [DataMember(Name="waarde", Order=0)] public string Waarde { get { return waarde; } set { waarde = value; } } } When sending the following json message to the service, { "test": { "waarde": "bla" } } the trace log gives me errors (below). I have tried this with just a string instead of the datatype (void RegisterDeviceTokenForYoumiePost(string token); ) but i get the same error. All help is appreciated, can't figure it out. It looks like it's creating invalid xml from the json message, but i'm not doing any custom serialization here. The formatter threw an exception while trying to deserialize the message: Error in deserializing body of request message for operation 'RegisterDeviceTokenForYoumiePost'. Unexpected end of file. **Following elements are not closed**: waarde, test, root.</Message><StackTrace> at System.ServiceModel.Dispatcher.OperationFormatter.DeserializeRequest(Message message, Object[] parameters)

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• Which to use, XMP or RDF?

  - by zotty

  What's the difference between RDF and XMP? From what I can tell, XMP is derived from RDF... so what does it offer that RDF doesn't? My particular situation is this: I've got some images which need tagging with details of how an experiment was performed, and what sort of data analysis has been performed on the images. A colleague of mine is pushing for XMP, but he's thinking of the images as photos - they're not really, they're just bits of data. From what I've seen (mainly by opening images in notepad++) the XMP data looks very similar to RDF - even so far as using RDF in the tag names (e.g. <rdf:Seq>). I'd like this data to be usable by other people who use similar instruments for similar experiments, so creating a mini standard (schema?) seems like the way to go. Apologies for the lack of fundemental understanding - I'm a Doctor, not a programmer! If it makes any difference, the language of choice will be C#. Edit for more information: First off, thanks for the excellent replies - thinking of XMP as a vocabulary for RDF makes things a lot clearer. The sort of data I'll be storing wont be avaliable in any of the pre-defined sets. It'll detail experimental set ups, locations and results. I think using RDF is the way to go.

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• Apply a Quartz filter while saving PDF under Mac OS X 10.6.3

  - by olpa

  Using Mac OS X API, I'm trying to save a PDF file with a Quartz filter applied, just like it is possible from the "Save As" dialog in the Preview application. So far I've written the following code (using Python and pyObjC, but it isn't important for me): -- filter-pdf.py: begin from Foundation import * from Quartz import * import objc page_rect = CGRectMake (0, 0, 612, 792) fdict = NSDictionary.dictionaryWithContentsOfFile_("/System/Library/Filters/Blue \ Tone.qfilter") in_pdf = CGPDFDocumentCreateWithProvider(CGDataProviderCreateWithFilename ("test .pdf")) url = CFURLCreateWithFileSystemPath(None, "test_out.pdf", kCFURLPOSIXPathStyle, False) c = CGPDFContextCreateWithURL(url, page_rect, fdict) np = CGPDFDocumentGetNumberOfPages(in_pdf) for ip in range (1, np+1): page = CGPDFDocumentGetPage(in_pdf, ip) r = CGPDFPageGetBoxRect(page, kCGPDFMediaBox) CGContextBeginPage(c, r) CGContextDrawPDFPage(c, page) CGContextEndPage(c) -- filter-pdf.py: end Unfortunalte, the filter "Blue Tone" isn't applied, the output PDF looks exactly as the input PDF. Question: what I missed? How to apply a filter? Well, the documentation doesn't promise that such way of creating and using "fdict" should cause that the filter is applied. But I just rewritten (as far as I can) sample code /Developer/Examples/Quartz/Python/filter-pdf.py, which was distributed with older versions of Mac (meanwhile, this code doesn't work too): ----- filter-pdf-old.py: begin from CoreGraphics import * import sys, os, math, getopt, string def usage (): print ''' usage: python filter-pdf.py FILTER INPUT-PDF OUTPUT-PDF Apply a ColorSync Filter to a PDF document. ''' def main (): page_rect = CGRectMake (0, 0, 612, 792) try: opts,args = getopt.getopt (sys.argv[1:], '', []) except getopt.GetoptError: usage () sys.exit (1) if len (args) != 3: usage () sys.exit (1) filter = CGContextFilterCreateDictionary (args[0]) if not filter: print 'Unable to create context filter' sys.exit (1) pdf = CGPDFDocumentCreateWithProvider (CGDataProviderCreateWithFilename (args[1])) if not pdf: print 'Unable to open input file' sys.exit (1) c = CGPDFContextCreateWithFilename (args[2], page_rect, filter) if not c: print 'Unable to create output context' sys.exit (1) for p in range (1, pdf.getNumberOfPages () + 1): #r = pdf.getMediaBox (p) r = pdf.getPage(p).getBoxRect(p) c.beginPage (r) c.drawPDFDocument (r, pdf, p) c.endPage () c.finish () if __name__ == '__main__': main () ----- filter-pdf-old.py: end

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• What's wrong with this jQuery fading gallery code?

  - by Meep3D

  So I am creating a fading gallery and am a bit of a noob to javascript (but not to programming). I have no idea what is wrong though. Here's the function in question: /* */ function show_next () { // Hide current $('.s_gallery_images li.s_current').fadeTo(200, .2); $('.s_gallery_images li.s_current').css("border","1px green solid"); // if ($('.s_gallery_images li').hasClass ('.s_current')) { console.log ('Incrementing existing'); // Class already exists $('.s_current:first').removeClass('s_current').next().addClass('s_current'); // Was that the last one? if ($('.s_gallery_images li').hasClass ('.s_current')) { console.log ('Current found'); } else { // Class doesn't exist - add to first $('.s_gallery_images li:first').addClass ('.s_current'); console.log ('Wrapping'); } } else { console.log ('Adding new class'); // Class doesn't exist - add to first $('.s_gallery_images li:first').addClass ('.s_current'); } // Show new marked item $('.s_gallery_images li.s_current').fadeTo(200, .8); } The HTML is a very simple: <ul class="s_gallery_images"> <li><img src="imagename" alt="alt" /></li> <li><img src="imagename" alt="alt" /></li> <li><img src="imagename" alt="alt" /></li> </ul> And it displays the list and the images fine. I am using firebugs console.log for debugging, plus have a class set for s_current (bright border) but nothing happens at all. The firebug console log says: Adding New Class Incrementing Existing Current Found Incrementing Existing Current Found Incrementing Existing Current Found Incrementing Existing Current Found ... to infinity The function is called on a setInterval timer, and as far as I can tell it should be working (and I have done something similar before), but it just isn't happening :(

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• Windows service threading call to WCF service

  - by Sam Brinsted

  Hi, I have a windows service that is reading data from a database and then submitting it to a WCF serivce. Once that has finished it is stamping a processed date on the original record. Trouble I am currently having is to do with threading. The call to the WCF serivce is relatively long and I want to have a number of concurrent calls to the service to help improve the throughput of the windows service. Currently I have a submitToService method on a new worker class. Upon reading a new row from the database I am creating a new thread which is calling this method. This obviously isn't too good as the number of threads quickly shoots up and overburdens the WCF service. I have put a thread.sleep in the submit method and am sure to call System.Threading.Thread.CurrentThread.Abort(); after the submission has finished. However, I don't seem to see the number of threads go down. How can I just have a fixed number of threads that can be used in the windows service? I did think about using a thread pool but read somewhere that wasn't a good choice for a windows service. Thanks very much.

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• item-not-found(404) when trying to get a node using Smackx pubsub

  - by DustMason

  I'm trying to use the latest Smackx trunk to get and then subscribe to a pubsub node. However, openfire just sends me a back an error: item not found (404). I am instantiating the java objects from ColdFusion, so my code snippets might look funny but maybe someone will be able to tell me what I've forgotten. Here's how I create the node: ftype = createObject("java", "org.jivesoftware.smackx.pubsub.FormType"); cform = createObject("java", "org.jivesoftware.smackx.pubsub.ConfigureForm").init(ftype.submit); cform.setPersistentItems(true); cform.setDeliverPayloads(true); caccess = createObject("java", "org.jivesoftware.smackx.pubsub.AccessModel"); cform.setAccessModel(caccess.open); cpublish = createObject("java", "org.jivesoftware.smackx.pubsub.PublishModel"); cform.setPublishModel(cpublish.open); cform.setMaxItems(99); manager = createObject("java", "org.jivesoftware.smackx.pubsub.PubSubManager").init(XMPPConnection); myNode = manager.createNode("subber", cform); And here's how I am trying to get to it (in a different section of code): manager = createObject("java", "org.jivesoftware.smackx.pubsub.PubSubManager").init(XMPPConnection); myNode = manager.getNode("subber"); Immediately upon creating the node I seem to be able to publish to it like so: payload = createObject("java", "org.jivesoftware.smackx.pubsub.SimplePayload").init("book","pubsub:test:book","<book xmlns='pubsub:test:book'><title>Lord of the Rings</title></book>"); item = createObject("java", "org.jivesoftware.smackx.pubsub.Item").init(payload); myNode.publish(item); However, it is the getNode() call that is causing my code to error. I have verified that the nodes are being created by checking the DB used by my openfire server. I can see them in there, properly attributed as leaf nodes, etc. Any advice? Anyone else out there doing anything with XMPP and ColdFusion? I have had great success sending and receiving messages with CF and Smack just haven't had the pubsub working yet :) Thanks!

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• How to make active services highly available?

  - by Jader Dias

  I know that with Network Load Balancing and Failover Clusteringwe can make passive services highly available. But what about active apps? Example: One of my apps retrieves some content from a external resource in a fixed interval. I have imagined the following scenarios: Run it in a single machine. Problem: if this instance falls, the content won't be retrieved Run it in each machine of the cluster. Problem: the content will be retrieved multiple times Have it in each machine of the cluster, but run it only in one of them. Each instance will have to check some sort of common resource to decide whether it its turn to do the task or not. When I was thinking about the solution #3 I have wondered what should be the common resource. I have thought of creating a table in the database, where we could use it to get a global lock. Is this the best solution? How does people usually do this? By the way it's a C# .NET WCF app running on Windows Server 2008

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• Redirect uploaded files to another server, using nginx

  - by Serg ikS

  I am creating a web service of scheduled posts to some soc. network.Need help dealing with file uploads under high traffic. Process overview: User uploads files to SomeServer (not mine). SomeServer then responds with a JSON string. My web app should store that JSON response. Opt. 1 — Save, cURL POST, delete tmp The stupid way I made it work: User uploads files to MyWebApp; MyWebApp cURL's the file further to SomeServer, getting the response. Opt.2 — JS magic The smart way it could be perfect: User uploads the file directly to SomeServer, from within an iFrame; MyWebApp gets the response through JavaScript. But this is(?) impossible due to the 'Same Origin Policy', isn't it? Opt. 3 — nginx proxying? The better way for a production server: User uploads files to MyWebApp; nginx intercepts the file uploads and sends them directly to the SomeServer; JSON response is also intercepted by nginx and processed by MyWebApp. Does this make any sense, and what would be the nginx config for, say, /fileupload Location to proxy it to SomeServer ?

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• Slow Python HTTP server on localhost

  - by Abiel

  I am experiencing some performance problems when creating a very simple Python HTTP server. The key issue is that performance is varying depending on which client I use to access it, where the server and all clients are being run on the local machine. For instance, a GET request issued from a Python script (urllib2.urlopen('http://localhost/').read()) takes just over a second to complete, which seems slow considering that the server is under no load. Running the GET request from Excel using MSXML2.ServerXMLHTTP also feels slow. However, requesting the data Google Chrome or from RCurl, the curl add-in for R, yields an essentially instantaneous response, which is what I would expect. Adding further to my confusion is that I do not experience any performance problems for any client when I am on my computer at work (the performance problems are on my home computer). Both systems run Python 2.6, although the work computer runs Windows XP instead of 7. Below is my very simple server example, which simply returns 'Hello world' for any get request. from BaseHTTPServer import BaseHTTPRequestHandler, HTTPServer class MyHandler(BaseHTTPRequestHandler): def do_GET(self): print("Just received a GET request") self.send_response(200) self.send_header("Content-type", "text/html") self.end_headers() self.wfile.write('Hello world') return def log_request(self, code=None, size=None): print('Request') def log_message(self, format, *args): print('Message') if __name__ == "__main__": try: server = HTTPServer(('localhost', 80), MyHandler) print('Started http server') server.serve_forever() except KeyboardInterrupt: print('^C received, shutting down server') server.socket.close() Note that in MyHandler I override the log_request() and log_message() functions. The reason is that I read that a fully-qualified domain name lookup performed by one of these functions might be a reason for a slow server. Unfortunately setting them to just print a static message did not solve my problem. Also, notice that I have put in a print() statement as the first line of the do_GET() routine in MyHandler. The slowness occurs prior to this message being printed, meaning that none of the stuff that comes after it is causing a delay.

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• In Java it seems Public constructors are always a bad coding practice

  - by Adam Gent

  This maybe a controversial question and may not be suited for this forum (so I will not be insulted if you choose to close this question). It seems given the current capabilities of Java there is no reason to make constructors public ... ever. Friendly, private, protected are OK but public no. It seems that its almost always a better idea to provide a public static method for creating objects. Every Java Bean serialization technology (JAXB, Jackson, Spring etc...) can call a protected or private no-arg constructor. My questions are: I have never seen this practice decreed or written down anywhere? Maybe Bloch mentions it but I don't own is book. Is there a use case other than perhaps not being super DRY that I missed? EDIT: I explain why static methods are better. .1. For one you get better type inference. For example See Guava's http://code.google.com/p/guava-libraries/wiki/CollectionUtilitiesExplained .2. As a designer of the class you can later change what is returned with a static method. .3. Dealing with constructor inheritance is painful especially if you have to pre-calculate something.

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• Canceling a WSK I/O operation when driver is unloading

  - by eaducac

  I've been learning how to write drivers with the Windows DDK recently. After creating a few test drivers experimenting with system threads and synchronization, I decided to step it up a notch and write a driver that actually does something, albeit something useless. Currently, my driver connects to my other computer using Winsock Kernel and just loops and echoes back whatever I send to it until it gets the command "exit", which causes it to break out of the loop. In my loop, after I call WskReceive() to get some data from the other computer, I use KeWaitForMultipleObjects() to wait for either of two SynchronizationEvents. BlockEvent gets set by my IRP's CompletionRoutine() to let my thread know that it's received some data from the socket. EndEvent gets set by my DriverUnload() routine to tell the thread that it's being unloaded and it needs to terminate. When I send the "exit" command, the thread terminates with no problems, and I can safely unload the driver afterward. If I try to stop the driver while it's still waiting on data from the other computer, however, it blue screens with the error DRIVER_UNLOADED_WITHOUT_CANCELLING_PENDING_OPERATIONS. After I get the EndEvent but before I exit the loop, I've tried canceling the IRP with IoCancelIrp() and completing it with IoCompleteRequest(), but both of those give me DRIVER_IRQL_NOT_LESS_OR_EQUAL errors. I then tried calling WskDisconnect(), hoping that would cause the receive operation to complete, but that took me back to the CANCELLING_PENDING_OPERATIONS error. How do I cancel my pending I/O operation from my WSK socket at the IRQL I'm running at when the driver is unloaded?

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• Value get changed even though I'm not using reference

  - by atch

  In code: struct Rep { const char* my_data_; Rep* my_left_; Rep* my_right_; Rep(const char*); }; typedef Rep& list; ostream& operator<<(ostream& out, const list& a_list) { int count = 0; list tmp = a_list;//----->HERE I'M CREATING A LOCAL COPY for (;tmp.my_right_;tmp = *tmp.my_right_) { out << "Object no: " << ++count << " has name: " << tmp.my_data_; //tmp = *tmp.my_right_; } return out;//------>HERE a_list is changed } I've thought that if I'll create local copy to a_list object I'll be operating on completely separate object. Why isn't so? Thanks.

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• Python: two loops at once

  - by Stephan Meijer

  I've got a problem: I am new to Python and I want to do multiple loops. I want to run a WebSocket client (Autobahn) and I want to run a loop which shows the filed which are edited in a specific folder (pyinotify or else Watchdog). Both are running forever, Great. Is there a way to run them at once and send a message via the WebSocket connection while I'm running the FileSystemWatcher, like with callbacks, multithreading, multiprocessing or just separate files? factory = WebSocketClientFactory("ws://localhost:8888/ws", debug=False) factory.protocol = self.webSocket connectWS(factory) reactor.run() If we run this, it will have success. But if we run this: factory = WebSocketClientFactory("ws://localhost:8888/ws", debug=False) factory.protocol = self.webSocket connectWS(factory) reactor.run() # Websocket client running now,running the filewatcher wm = pyinotify.WatchManager() mask = pyinotify.IN_DELETE | pyinotify.IN_CREATE # watched events class EventHandler(pyinotify.ProcessEvent): def process_IN_CREATE(self, event): print "Creating:", event.pathname def process_IN_DELETE(self, event): print "Removing:", event.pathname handler = EventHandler() notifier = pyinotify.Notifier(wm, handler) wdd = wm.add_watch('/tmp', mask, rec=True) notifier.loop() This will create 2 loops, but since we already have a loop, the code after 'reactor.run()' will not run at all.. For your information: this project is going to be a sync client. Thanks a lot!

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