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• Error when creating an image from a UIView

  - by Raphael Pinto

  Hi, I'm creating an image from a view whith the folowing code : UIGraphicsBeginImageContext(myView.bounds.size); [myView.layer renderInContext:UIGraphicsGetCurrentContext()]; UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); UIImageWriteToSavedPhotosAlbum(viewImage, nil, nil, nil); The image is created in the user album but in the consol I get this : 2010-05-11 10:17:17.974 myApp[3875:1807] sqlite error 8 [attempt to write a readonly database] 2010-05-11 10:17:18.014 myApp[3875:1807] Backtrace for sqlite error: (0x34e3a909 0x34e3d87f 0x34e3b029 0x34e3b22b 0x34e2f48b 0x34e2dccb 0x34e2d2f7 0x34e2d3bb 0x34e4dcd3 0x34e50515 0x34e51351 0x34e51681 0x34e513f5 0x34e511e3 0x303af57c 0x34e51163 0x303b06e8 0x303ac8e0 0x303ac6d8 0x303ac8c8 0x303aca80 0x30350d55 0x3034a12c) 2010-05-11 10:17:18.077 myApp[3875:1807] sqlite error 8 [attempt to write a readonly database] 2010-05-11 10:17:18.087 myApp[3875:1807] Backtrace for sqlite error: (0x34e3a909 0x34e3b053 0x34e3b22b 0x34e2f48b 0x34e2dccb 0x34e2d2f7 0x34e2d3bb 0x34e4dcd3 0x34e50515 0x34e51351 0x34e51681 0x34e513f5 0x34e511e3 0x303af57c 0x34e51163 0x303b06e8 0x303ac8e0 0x303ac6d8 0x303ac8c8 0x303aca80 0x30350d55 0x3034a12c) 2010-05-11 10:17:18.091 myApp[3875:1807] sqlite error 8 [attempt to write a readonly database] 2010-05-11 10:17:18.095 myApp[3875:1807] Backtrace for sqlite error: (0x34e3a909 0x34e3b085 0x34e3b22b 0x34e2f48b 0x34e2dccb 0x34e2d2f7 0x34e2d3bb 0x34e4dcd3 0x34e50515 0x34e51351 0x34e51681 0x34e513f5 0x34e511e3 0x303af57c 0x34e51163 0x303b06e8 0x303ac8e0 0x303ac6d8 0x303ac8c8 0x303aca80 0x30350d55 0x3034a12c) 2010-05-11 10:17:18.111 myApp[3875:1807] sqlite error 1 [SQL logic error or missing database] 2010-05-11 10:17:18.115 myApp[3875:1807] Backtrace for sqlite error: (0x34e3a909 0x34e3d87f 0x34e3b029 0x34e3b4dd 0x34e2f48b 0x34e2dccb 0x34e2d2f7 0x34e2d3bb 0x34e4dcd3 0x34e50515 0x34e51351 0x34e51681 0x34e513f5 0x34e511e3 0x303af57c 0x34e51163 0x303b06e8 0x303ac8e0 0x303ac6d8 0x303ac8c8 0x303aca80 0x30350d55 0x3034a12c) 2010-05-11 10:17:18.120 myApp[3875:1807] sqlite error 1 [SQL logic error or missing database] 2010-05-11 10:17:18.124 myApp[3875:1807] Backtrace for sqlite error: (0x34e3a909 0x34e3b053 0x34e3b4dd 0x34e2f48b 0x34e2dccb 0x34e2d2f7 0x34e2d3bb 0x34e4dcd3 0x34e50515 0x34e51351 0x34e51681 0x34e513f5 0x34e511e3 0x303af57c 0x34e51163 0x303b06e8 0x303ac8e0 0x303ac6d8 0x303ac8c8 0x303aca80 0x30350d55 0x3034a12c) 2010-05-11 10:17:18.129 myApp[3875:1807] sqlite error 1 [cannot commit - no transaction is active] 2010-05-11 10:17:18.133 myApp[3875:1807] Backtrace for sqlite error: (0x34e3a909 0x34e3b085 0x34e3b4dd 0x34e2f48b 0x34e2dccb 0x34e2d2f7 0x34e2d3bb 0x34e4dcd3 0x34e50515 0x34e51351 0x34e51681 0x34e513f5 0x34e511e3 0x303af57c 0x34e51163 0x303b06e8 0x303ac8e0 0x303ac6d8 0x303ac8c8 0x303aca80 0x30350d55 I don't know where the problem come from. Can you help me?

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• How should I handle expected errors? eg. "username already exists"

  - by Pheter

  I am struggling to understand how I should design the error handling parts of my code. I recently asked a similar question about how I should go about returning server error codes to the user, eg. 404 errors. I learnt that I should handle the error from within the current part of the application; seem's simple enough. However, what should I do when I can't handle the error from the current link in the chain? For example, I may have a class that is used to manage authentication. One of it's methods could be createUser($username, $password). Within that function, I need to determine if the username already exists. If this is true, how should I alert the calling code about this? Returning null instead of a user object is one way. But how do I then know what caused the error? How should I handle errors in such a way that calling code can easily find out what caused the error? Is there a design pattern commonly used for this kind of situation?

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• How to specify multiple values in where with AR query interface in rails3

  - by wkhatch

  Per section 2.2 of rails guide on Active Record query interface here: which seems to indicate that I can pass a string specifying the condition(s), then an array of values that should be substituted at some point while the arel is being built. So I've got a statement that generates my conditions string, which can be a varying number of attributes chained together with either AND or OR between them, and I pass in an array as the second arg to the where method, and I get: ActiveRecord::PreparedStatementInvalid: wrong number of bind variables (1 for 5) which leads me to believe I'm doing this incorrectly. However, I'm not finding anything on how to do it correctly. To restate the problem another way, I need to pass in a string to the where method such as "table.attribute = ? AND table.attribute1 = ? OR table.attribute1 = ?" with an unknown number of these conditions anded or ored together, and then pass something, what I thought would be an array as the second argument that would be used to substitute the values in the first argument conditions string. Is this the correct approach, or, I'm just missing some other huge concept somewhere and I'm coming at this all wrong? I'd think that somehow, this has to be possible, short of just generating a raw sql string.

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• Standard term for a thread I/O reorder buffer?

  - by Crashworks

  I have a case where many threads all concurrently generate data that is ultimately written to one long, serial file. I need to somehow serialize these writes so that the file gets written in the right order. ie, I have an input queue of 2048 jobs j0..jn, each of which produces a chunk of data oi. The jobs run in parallel on, say, eight threads, but the output blocks have to appear in the file in the same order as the corresponding input blocks — the output file has to be in the order o0o1o2... The solution to this is pretty self evident: I need some kind of buffer that accumulates and writes the output blocks in the correct order, similar to a CPU reorder buffer in Tomasulo's algorithm, or to the way that TCP reassembles out-of-order packets before passing them to the application layer. Before I go code it, I'd like to do a quick literature search to see if there are any papers that have solved this problem in a particularly clever or efficient way, since I have severe realtime and memory constraints. I can't seem to find any papers describing this though; a Scholar search on every permutation of [threads, concurrent, reorder buffer, reassembly, io, serialize] hasn't yielded anything useful. I feel like I must just not be searching the right terms. Is there a common academic name or keyword for this kind of pattern that I can search on?

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• Where do you put your dependencies?

  - by The All Foo

  If I use the dependency injection pattern to remove dependencies they end up some where else. For example, Snippet 1, or what I call Object Maker. I mean you have to instantiate your objects somewhere...so when you move dependency out of one object, you end up putting it another one. I see that this consolidates all my dependencies into one object. Is that the point, to reduce your dependencies so that they all reside in a single ( as close to as possible ) location? Snippet 1 - Object Maker <?php class ObjectMaker { public function makeSignUp() { $DatabaseObject = new Database(); $TextObject = new Text(); $MessageObject = new Message(); $SignUpObject = new ControlSignUp(); $SignUpObject->setObjects($DatabaseObject, $TextObject, $MessageObject); return $SignUpObject; } public function makeSignIn() { $DatabaseObject = new Database(); $TextObject = new Text(); $MessageObject = new Message(); $SignInObject = new ControlSignIn(); $SignInObject->setObjects($DatabaseObject, $TextObject, $MessageObject); return $SignInObject; } public function makeTweet( $DatabaseObject = NULL, $TextObject = NULL, $MessageObject = NULL ) { if( $DatabaseObject == 'small' ) { $DatabaseObject = new Database(); } else if( $DatabaseObject == NULL ) { $DatabaseObject = new Database(); $TextObject = new Text(); $MessageObject = new Message(); } $TweetObject = new ControlTweet(); $TweetObject->setObjects($DatabaseObject, $TextObject, $MessageObject); return $TweetObject; } public function makeBookmark( $DatabaseObject = NULL, $TextObject = NULL, $MessageObject = NULL ) { if( $DatabaseObject == 'small' ) { $DatabaseObject = new Database(); } else if( $DatabaseObject == NULL ) { $DatabaseObject = new Database(); $TextObject = new Text(); $MessageObject = new Message(); } $BookmarkObject = new ControlBookmark(); $BookmarkObject->setObjects($DatabaseObject,$TextObject,$MessageObject); return $BookmarkObject; } }

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• How to get around LazyInitializationException in scheduled jobs?

  - by Shreerang

  I am working on a J2EE server application which is deployed on Tomcat. I use Spring source as MVC framework and Hibernate as ORM provider. My object model has lot of Lazy relationships (dependent objects are fetched on request). The high level design is like Service level methods call a few DAO methods to perform database operation. The service method is called either from the Flex UI or as a scheduled job. When it is called from Flex UI, the service method works fine i.e. it fetches some objects using DAO methods and even Lazy loading works. This is possible by the use of OpenSessionInViewFilter configured with the UI servlet. But when the same service method is called as scheduled Job, it gives LazyInitializationException. I can not configure OpenSessionInViewFilter because there is no servlet or UI request associated with that. I tried configuring Transaction around the scheduled job method so that service method starts a transaction and all the DAO methods participate in that same transaction, hoping that the transaction will remain active and hibernate session will be available. But it does not work. Please suggest if anyone has ever been able to get such a configuration working. If needed, I can post the Hibernate configuration and log messages. Thanks a lot for help! Shreerang

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• Should frontend and backend be handled by different controllers?

  - by DR

  In my previous learning projects I always used a single controller, but now I wonder if that is good practice or even always possible. In all RESTful Rails tutorials the controllers have a show, an edit and an index view. If an authorized user is logged on, the edit view becomes available and the index view shows additional data manipulation controls, like a delete button or a link to the edit view. Now I have a Rails application which falls exactly into this pattern, but the index view is not reusable: The normal user sees a flashy index page with lots of pictures, complex layout, no Javascript requirement, ... The Admin user index has a completly different minimalistic design, jQuery table and lots of additional data, ... Now I'm not sure how to handle this case. I can think of the following: Single controller, single view: The view is split into two large blocks/partials using an if statement. Single controller, two views: index and index_admin. Two different controllers: BookController and BookAdminController None of these solutions seems perfect, but for now I'm inclined to use the 3rd option. What's the preferred way to do this?

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• How much is too much memory allocation in NDK?

  - by Maximus

  The NDK download page notes that, "Typical good candidates for the NDK are self-contained, CPU-intensive operations that don't allocate much memory, such as signal processing, physics simulation, and so on." I came from a C background and was excited to try to use the NDK to operate most of my OpenGL ES functions and any native functions related to physics, animation of vertices, etc... I'm finding that I'm relying quite a bit on Native code and wondering if I may be making some mistakes. I've had no trouble with testing at this point, but I'm curious if I may run into problems in the future. For example, I have game struct defined (somewhat like is seen in the San-Angeles example). I'm loading vertex information for objects dynamically (just what is needed for an active game area) so there's quite a bit of memory allocation happening for vertices, normals, texture coordinates, indices and texture graphic data... just to name the essentials. I'm quite careful about freeing what is allocated between game areas. Would I be safer setting some caps on array sizes or should I charge bravely forward as I'm going now?

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• accordion tab open at different times

  - by user3279193

  I am using an asp classic and on the page I have a J-Query accordion. I want one tab to be open if the value that the asp prints out is greater than zero, if not , I want them all to be closed, this is an example of what I've got: J-Query: $(function() { $( "#accordion" ).accordion({ heightStyle: "content", collapsible: true, active: false }); }); HTML/ASP: <div id="accordion"> <h3>Tab1</h3> <div> <p>Hello World</p> </div> <h3>Tab2</h3> <div> <p>Hello World</p> </div> <h3>Tab3</h3> <div> <p>Hello World</p> </div> <h3>Results (<%=number%>)</h3> <!--if number > 0 then open tab else close all tabs--> <div> <p>Hello World</p> </div> </div>

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• Git rebase and semi-tracked per-developer config files.

  - by dougkiwi

  This is my first SO question and I'm new-ish to Git as well. Background: I am supposed to be the version control guru for Git in my group of about 8 developers. As I don't have a lot of Git experience, this is exciting. I decided we need a shared repository that would be the authoritative master for the production code and the main meeting-point for the development code. As we work for a corporation, we really do need to show an authoritive source for the production code at least. I have instructed the developers to pull-rebase when pulling from the shared repository, then push the commits that they want to share. We have been running into problems with a particular type of file. One of these files, which I currently assume is typical of the problem, is called web.config. We want a version-controlled master web.config for devs to clone, but each dev may make minor edits to this file that they wish to locally save but not share. The problem is this: how do I tell git not to consider local changes or commits to this file to be relevent for rebasing and pushing? Gitignore does not seem to solve the problem, but maybe that's because I put web.config into .gitignore too late? In some simple situations we have stacked local changes, rebased, pushed, and popped the stack, but that doesn't seem to work all of the time. I haven't picked up the pattern quite yet. The published documentation on pull --rebase tends to deal with simplier situations. Or do I have the wrong idea entirely? Are we misusing Git? Dougkiwi

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• How to detect whether an EventWaitHandle is waiting?

  - by AngryHacker

  I have a fairly well multi-threaded winforms app that employs the EventWaitHandle in a number of places to synchronize access. So I have code similar to this: List<int> _revTypes; EventWaitHandle _ewh = new EventWaitHandle(false, EventResetMode.ManualReset); void StartBackgroundTask() { _ewh.Reset(); Thread t = new Thread(new ThreadStart(LoadStuff)); t.Start(); } void LoadStuff() { _revTypes = WebServiceCall.GetRevTypes() // ...bunch of other calls fetching data from all over the place // using the same pattern _ewh.Set(); } List<int> RevTypes { get { _ewh.WaitOne(); return _revTypes; } } Then I just call .RevTypes somewehre from the UI and it will return data to me when LoadStuff has finished executing. All this works perfectly correctly, however RevTypes is just one property - there are actually several dozens of these. And one or several of these properties are holding up the UI from loading in a fast manner. Short of placing benchmark code into each property, is there a way to see which property is holding the UI from loading? Is there a way to see whether the EventWaitHandle is forced to actually wait?

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• sum of square of each elements in the vector using for_each

  - by pierr

  Hi, As the function accepted by for_each take only one parameter (the element of the vector), I have to define a static int sum = 0 somewhere so that It can be accessed after calling the for_each . I think this is awkward. Any better way to do this (still use for_each) ? #include <algorithm> #include <vector> #include <iostream> using namespace std; static int sum = 0; void add_f(int i ) { sum += i * i; } void test_using_for_each() { int arr[] = {1,2,3,4}; vector<int> a (arr ,arr + sizeof(arr)/sizeof(arr[0])); for_each( a.begin(),a.end(), add_f); cout << "sum of the square of the element is " << sum << endl; } In Ruby, We can do it this way: sum = 0 [1,2,3,4].each { |i| sum += i*i} #local variable can be used in the callback function puts sum #=> 30 Would you please show more examples how for_each is typically used in practical programming (not just print out each element)? Is it possible use for_each simulate 'programming pattern' like map and inject in Ruby (or map /fold in Haskell). #map in ruby >> [1,2,3,4].map {|i| i*i} => [1, 4, 9, 16] #inject in ruby [1, 4, 9, 16].inject(0) {|aac ,i| aac +=i} #=> 30 EDIT: Thank you all. I have learned so much from your replies. We have so many ways to do the same single thing in C++ , which makes it a little bit difficult to learn. But it's interesting :)

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• When is a try catch not a try catch?

  - by Dearmash

  I have a fun issue where during application shutdown, try / catch blocks are being seemingly ignored in the stack. I don't have a working test project (yet due to deadline, otherwise I'd totally try to repro this), but consider the following code snippet. public static string RunAndPossiblyThrow(int index, bool doThrow) { try { return Run(index); } catch(ApplicationException e) { if(doThrow) throw; } return ""; } public static string Run(int index) { if(_store.Contains(index)) return _store[index]; throw new ApplicationException("index not found"); } public static string RunAndIgnoreThrow(int index) { try { return Run(index); } catch(ApplicationException e) { } return ""; } During runtime this pattern works famously. We get legacy support for code that relies on exceptions for program control (bad) and we get to move forward and slowly remove exceptions used for program control. However, when shutting down our UI, we see an exception thrown from "Run" even though "doThrow" is false for ALL current uses of "RunAndPossiblyThrow". I've even gone so far as to verify this by modifying code to look like "RunAndIgnoreThrow" and I'll still get a crash post UI shutdown. Mr. Eric Lippert, I read your blog daily, I'd sure love to hear it's some known bug and I'm not going crazy. EDIT This is multi-threaded, and I've verified all objects are not modified while being accessed

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• Recoverable error while running XSL

  - by Kate

  XSL: <?xml version="1.0" encoding="utf-8"?> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:ve="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math" xmlns:v="urn:schemas-microsoft-com:vml" xmlns:wp="http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawing" xmlns:w10="urn:schemas-microsoft-com:office:word" xmlns:w="http://schemas.openxmlformats.org/wordprocessingml/2006/main" xmlns:wne="http://schemas.microsoft.com/office/word/2006/wordml" exclude-result-prefixes="wp wne w10 w ve o r m v" version="2.0"> <xsl:output method="text"/> <xsl:param name="styleName"/> <xsl:template match="w:p"> <xsl:apply-templates/><xsl:text>&#10;</xsl:text> </xsl:template> <xsl:template match="w:r[not ((parent::w:hyperlink[@w:anchor[matches(.,concat('^(',$styleName,')')),'i']]))]"> <xsl:value-of select="replace(., '.', '&#xFF00;')"/> </xsl:template> </xsl:stylesheet> While processing the above XSL, I am getting the below error, Recoverable Error: Recoverable error on line 11 FORG0006: An error occurred matching pattern {w:r[not ((parent::w:hyperlink[@w:anchor[matches(.,concat('^(',$styleName,')')),'i']]))]}: Effective boolean value is not defined for a sequence of two or more items starting with a boolean Please Help. I am not able to figure out this.

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• How to start matching and saving matched from exact point in a text

  - by yuliya

  I have a text and I write a parser for it using regular expressions and perl. I can match what I need with two empty lines (I use regexp), because there is a pattern that allows recognize blocks of text after two empty lines. But the problem is that the whole text has Introduction part and some text in the end I do not need. Here is a code which matches text when it finds two empty lines #!/usr/bin/perl use strict; use warnings; my $file = 'first'; open(my $fh, '<', $file); my $empty = 0; my $block_num = 1; open(OUT, '>', $block_num . '.txt'); while (my $line = <$fh>) { chomp ($line); if ($line =~ /^\s*$/) { $empty++; } elsif ($empty == 2) { close(OUT); open(OUT, '>', ++$block_num . '.txt'); $empty = 0; } else { $empty = 0;} print OUT "$line\n"; } close(OUT); This is example of the text I need (it's really small :)) this is file example I think that I need to iterate over the text till the moment it will find the word LOREM IPSUM with regexps this kind "/^LOREM IPSUM/", because it is the point from which needed text starts(and save the text in one file when i reach the word). And I need to finish iterating over the text when INDEX word is fount or save the text in separate file. How could I implement it. Should I use next function to proceed with lines or what? BR, Yuliya

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• JavaScript Keycode 46 is DEL Function key or (.) period sign?

  - by Omar

  Im writing some logic in JavaScript using jquery, where i must check the input content against a REGEX pattern ex: "^[a-zA-Z0-9_]*$" //Alpha-numeric and _ The logic is almost done, i just have a little problem filtering the function key DEL, my logic goes like this: var FunctionsKey = new Array(8, 9, 13, 16, 35, 36, 37, 39, 46); function keypressValidation(key) { if (config.regexExp != null) { if ($.inArray(key, FunctionsKey) != -1) { return true; } else { var keyChar = String.fromCharCode(key); return RegexCheck(keyChar); } } return true; } If the KeyCode is one of those in the array, i let it pass, if not i get the char and compare it against the REGEX. The problem is: in some Browsers the DEL and '.' (period sign) have the same key Code 46. So is there a better logic to filter the function keys or must i write a condition for that case, maybe removing the 46 from the array and try to convert it to char and if is (.) let it go to the Regex function if not let it pass? The other question will be are there more shared Key Codes in some browsers? EDIT: My suggested solution wont work because it doesn't matter which key the user pressed (DEL or period) i always get (.) as CHAR at least on OPERA and FF =(.

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• Rails: Obfuscating Image URLs on Amazon S3? (security concern)

  - by neezer

  To make a long explanation short, suffice it to say that my Rails app allows users to upload images to the app that they will want to keep in the app (meaning, no hotlinking). So I'm trying to come up with a way to obfuscate the image URLs so that the address of the image depends on whether or not that user is logged in to the site, so if anyone tried hotlinking to the image, they would get a 401 access denied error. I was thinking that if I could route the request through a controller, I could re-use a lot of the authorization I've already built into my app, but I'm stuck there. What I'd like is for my images to be accessible through a URL to one of my controllers, like: http://railsapp.com/images/obfuscated?member_id=1234&pic_id=7890 If the user where to right-click on the image displayed on the website and select "Copy Address", then past it in, it would be the SAME url (as in, wouldn't betray where the image is actually hosted). The actual image would be living on a URL like this: http://s3.amazonaws.com/s3username/assets/member_id/pic_id.extension Is this possible to accomplish? Perhaps using Rails' render method? Or something else? I know it's possible for PHP to return the correct headers to make the browser think it's an image, but I don't know how to do this in Rails... UPDATE: I want all users of the app to be able to view the images if and ONLY if they are currently logged on to the site. If the user does not have a currently active session on the site, accessing the images directly should yield a generic image, or an error message.

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• How to detect a Socket disconnection?

  - by AngryHacker

  I've implemented a task using the async Sockets pattern in Silverlight 3. I started with Michael Schwarz's implementation and built on top of that. So basically, my Silverlight app establishes a persistent socket connection to a device and then data flows both ways as necessary between the device and the Silverlight app. One thing I am struggling with is how to detect disconnection. I could think of 2 approaches: Keep-Alive. I know this can be done at the Sockets level, but I am not sure how to do this in an async model. How would the Socket class let me know there has been a disconnection. Manual keep alive. Basically, I am having the Silverlight app send a dummy packet every 20 seconds or so. If it fails, I'd assume disconnection. However, incredibly, SocketAsyncEventArgs.SocketError always reports success, even if I simply unplug the device that the Silverlight app is connected to. I am not sure whether this is a bug or what or perhaps I need to upgrade to SL4. Any ideas, direction or implementation would be appreciated.

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• Writing a synchronized thread-safety wrapper for NavigableMap

  - by polygenelubricants

  java.util.Collections currently provide the following utility methods for creating synchronized wrapper for various collection interfaces: synchronizedCollection(Collection<T> c) synchronizedList(List<T> list) synchronizedMap(Map<K,V> m) synchronizedSet(Set<T> s) synchronizedSortedMap(SortedMap<K,V> m) synchronizedSortedSet(SortedSet<T> s) Analogously, it also has 6 unmodifiedXXX overloads. The glaring omission here are the utility methods for NavigableMap<K,V>. It's true that it extends SortedMap, but so does SortedSet extends Set, and Set extends Collection, and Collections have dedicated utility methods for SortedSet and Set. Presumably NavigableMap is a useful abstraction, or else it wouldn't have been there in the first place, and yet there are no utility methods for it. So the questions are: Is there a specific reason why Collections doesn't provide utility methods for NavigableMap? How would you write your own synchronized wrapper for NavigableMap? Glancing at the source code for OpenJDK version of Collections.java seems to suggest that this is just a "mechanical" process Is it true that in general you can add synchronized thread-safetiness feature like this? If it's such a mechanical process, can it be automated? (Eclipse plug-in, etc) Is this code repetition necessary, or could it have been avoided by a different OOP design pattern?

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• JSR-299 (CDI) configuration at runtime

  - by nsn

  I need to configure different @Alternatives, @Decorators and @Injectors for different runtime environments (think testing, staging and production servers). Right now I use maven to create three wars, and the only difference between those wars are in the beans.xml files. Is there a better way to do this? I do have @Alternative @Stereotypes for the different environments, but even then I need to alter beans.xml, and they don't work for @Decorators (or do they?) Is it somehow possible to instruct CDI to ignore the values in beans.xml and use a custom configuration source? Because then I could for example read a system property or other environment variable. The application exclusively runs in containers that use Weld, so a weld-specific solution would be ok. I already tried to google this but can't seem to find good search terms, and I asked the Weld-Users-Forums, but to no avail. Someone over there suggested to write my own custom extension, but I can't find any API to actually change the container configuration at runtime. I think it would be possible to have some sort of @ApplicationScoped configuration bean and inject that into all @Decorators which could then decide themselves whether they should be active or not and then in order to configure @Alternatives write @Produces methods for every interface with multiple implementations and inject the config bean there too. But this seems to me like a lot of unnecessary work to essentially duplicate functionality already present in CDI?

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• Efficient database access when dealing with multiple abstracted repositories

  - by Nathan Ridley

  I want to know how most people are dealing with the repository pattern when it involves hitting the same database multiple times (sometimes transactionally) and trying to do so efficiently while maintaining database agnosticism and using multiple repositories together. Let's say we have repositories for three different entities; Widget, Thing and Whatsit. Each repository is abstracted via a base interface as per normal decoupling design processes. The base interfaces would then be IWidgetRepository, IThingRepository and IWhatsitRepository. Now we have our business layer or equivalent (whatever you want to call it). In this layer we have classes that access the various repositories. Often the methods in these classes need to do batch/combined operations where multiple repositories are involved. Sometimes one method may make use of another method internally, while that method can still be called independently. What about, in this scenario, when the operation needs to be transactional? Example: class Bob { private IWidgetRepository _widgetRepo; private IThingRepository _thingRepo; private IWhatsitRepository _whatsitRepo; public Bob(IWidgetRepository widgetRepo, IThingRepository thingRepo, IWhatsitRepository whatsitRepo) { _widgetRepo = widgetRepo; _thingRepo= thingRepo; _whatsitRepo= whatsitRepo; } public void DoStuff() { _widgetRepo.StoreSomeStuff(); _thingRepo.ReadSomeStuff(); _whatsitRepo.SaveSomething(); } public void DoOtherThing() { _widgetRepo.UpdateSomething(); DoStuff(); } } How do I keep my access to that database efficient and not have a constant stream of open-close-open-close on connections and inadvertent invocation of MSDTS and whatnot? If my database is something like SQLite, standard mechanisms like creating nested transactions are going to inherently fail, yet the business layer should not have to be concerning itself with such things. How do you handle such issues? Does ADO.Net provide simple mechanisms to handle this or do most people end up wrapping their own custom bits of code around ADO.Net to solve these types of problems?

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• How to set buffer size in client-server app using sockets?

  - by nelly

  First of all i am new to networking so i may say dumb thing in here. Considering a client-server application using sockets(.net with c# if that matters). The client sends some data, the server process it and sends back a string. The client sends some other data, the serve process it, queries the db and sends back several hundreds of items from the database The client sends some other type of data and the server notifies some other clients . My question is how to set the buffer size correctly for reading/writing operation. Should i do something like this: byte[] buff = new byte[client.ReceiveBufferSize] ? I am thinking of something like this: Client sends data to the server(and the server will follow the same pattern) byte[] bytesToSend=new byte[2048] //2048 to be standard for any command send by the client bytes 0..1 ->command type bytes 1..2047 ->command parameters byte[] bytesToReceive=new byte[8]/byte[64]/byte[8192] //switch(command type) But..what is happening when a client is notified by the server without sending data? What is the correct way to accomplish what i am trying to do? Thanks for reading.

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• How to make ActiveRecord work with legacy partitioned/sharded databases/tables?

  - by Utensil

  thanks for your time first...after all the searching on google, github and here, and got more confused about the big words(partition/shard/fedorate),I figure that I have to describe the specific problem I met and ask around. My company's databases deals with massive users and orders, so we split databases and tables in various ways, some are described below: way database and table name shard by (maybe it's should be called partitioned by?) YZ.X db_YZ.tb_X order serial number last three digits YYYYMMDD. db_YYYYMMDD.tb date YYYYMM.DD db_YYYYMM.tb_ DD date too The basic concept is that databases and tables are seperated acording to a field(not nessissarily the primary key), and there are too many databases and too many tables, so that writing or magically generate one database.yml config for each database and one model for each table isn't possible or at least not the best solution. I looked into drnic's magic solutions, and datafabric, and even the source code of active record, maybe I could use ERB to generate database.yml and do database connection in around filter, and maybe I could use named_scope to dynamically decide the table name for find, but update/create opertions are bounded to "self.class.quoted_table_name" so that I couldn't easily get my problem solved. And even I could generate one model for each table, because its amount is up to 30 most. But this is just not DRY! What I need is a clean solution like the following DSL: class Order < ActiveRecord::Base shard_by :order_serialno do |key| [get_db_config_by(key), #because some or all of the databaes might share the same machine in a regular way or can be configed by a hash of regex, and it can also be a const get_db_name_by(key), get_tb_name_by(key), ] end end Can anybody enlight me? Any help would be greatly appreciated~~~~

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• Mysql count and sum from two diferent tables

  - by Agent_x

  Hi all, i have a problem with some querys in php and mysql: I have 2 diferent tables with one field in common: table 1 id | hits | num_g | cats | usr_id |active 1 | 10 | 11 | 1 | 53 | 1 2 | 13 | 16 | 3 | 53 | 1 1 | 10 | 22 | 1 | 22 | 1 1 | 10 | 21 | 3 | 22 | 1 1 | 2 | 6 | 2 | 11 | 1 1 | 11 | 1 | 1 | 11 | 1 table 2 id | usr_id | points 1 | 53 | 300 Now i use this statement to sum just the total from the table 1 every id count + 1 too SELECT usr_id, COUNT( id ) + SUM( num_g + hits ) AS tot_h FROM table1 WHERE usr_id!='0' GROUP BY usr_id ASC LIMIT 0 , 15 and i get the total for each usr_id usr_id| tot_h | 53 | 50 22 | 63 11 | 20 until here all is ok, now i have a second table with extra points (table2) I try this: SELECT usr_id, COUNT( id ) + SUM( num_g + hits ) + (SELECT points FROM table2 WHERE usr_id != '0' ) AS tot_h FROM table1 WHERE usr_id != '0' GROUP BY usr_id ASC LIMIT 0 , 15 but it seems to sum the 300 extra points to all users: usr_id| tot_h | 53 | 350 22 | 363 11 | 320 Now how i can get the total like the first try but + the secon table in one statement? because now i have just one entry in the second table but i can be more there. thanks for all the help. =============================================================================== hi thomas thanks for your reply, i think is in the right direction, but im getting weirds results, like usr_id | tot_h 22 | NULL <== i think the null its because that usr_id as no value in the table2 53 | 1033 Its like the second user is getting all the the values. then i try this one: SELECT table1.usr_id, COUNT( table1.id ) + SUM( table1.num_g + table1.hits + table2.points ) AS tot_h FROM table1 LEFT JOIN table2 ON table2.usr_id = table1.usr_id WHERE table1.usr_id != '0' AND table2.usr_id = table1.usr_id GROUP BY table1.usr_id ASC Same result i just get the sum of all values and not by each user, i need something like this result: usr_id | tot_h 53 | 53 <==== plus 300 points on table1 22 | 56 <==== plus 100 points on table2 /////////the result i need //////////// usr_id | tot_h 53 | 353 <==== plus 300 points on table2 22 | 156 <==== plus 100 points on table2 I think the structure need to be something like this Pseudo statements ;) from table1 count all id to get the number of record where the usr_id are then sum hits + num_g and from table2 select the extra points where the usr_id are the same as table1 and get teh result: usr_id | tot_h 53 | 353 22 | 156

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• Code refactoring c# question around several if statements performing the same check

  - by James Radford

  I have a method that has a load of if statements that seems a bit silly although I'm not sure how to improve the code. Here's an example. This logic was inside the view which is now in the controller which is far better but is there something I'm missing, maybe a design pattern that stops me having to check against panelCount < NumberOfPanelsToShow and handling the panelCount every condition? Maybe not, just feels ugly! Many thanks if (model.Train && panelCount < NumberOfPanelsToShow) { panelTypeList.Add(TheType.Train); panelCount++; } if (model.Car && panelCount < NumberOfPanelsToShow) { panelTypeList.Add(TheType.Car); panelCount++; } if (model.Hotel && panelCount < NumberOfPanelsToShow) { panelTypeList.Add(TheType.Hotel); panelCount++; } ...

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