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• Machine leaning algorithm for data classification.

  - by twk

  Hi all, I'm looking for some guidance about which techniques/algorithms I should research to solve the following problem. I've currently got an algorithm that clusters similar-sounding mp3s using acoustic fingerprinting. In each cluster, I have all the different metadata (song/artist/album) for each file. For that cluster, I'd like to pick the "best" song/artist/album metadata that matches an existing row in my database, or if there is no best match, decide to insert a new row. For a cluster, there is generally some correct metadata, but individual files have many types of problems: Artist/songs are completely misnamed, or just slightly mispelled the artist/song/album is missing, but the rest of the information is there the song is actually a live recording, but only some of the files in the cluster are labeled as such. there may be very little metadata, in some cases just the file name, which might be artist - song.mp3, or artist - album - song.mp3, or another variation A simple voting algorithm works fairly well, but I'd like to have something I can train on a large set of data that might pick up more nuances than what I've got right now. Any links to papers or similar projects would be greatly appreciated. Thanks!

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• MS Word opens documents hosted on WebDav share read-only on Windows Vista and 7 but only if no other

  - by rjmunro

  We have a WebDav server with some Word documents on it. (We are using PHP's HTTP_WebDAV_Server but get the same issue on tests with Apache mod_dav - both use digest authentication, basic auth doesn't work on Vista or later) We have a web page that opens the word documents using javascript like: Doc = new ActiveXObject("Sharepoint.OpenDocuments.3"); Doc.EditDocument(url, 'Word.Document'); which causes word to connect to the webdav server and open the document, bypassing IE and most of windows built in WebDav client. On Windows XP, this works perfectly, and (after prompting you to log in) allows you to edit the word document and save it back to the server. On Windows 7 and Windows Vista, this usually opens the document read only, but not in all cases. After quite a bit of trial and error, we found that it worked (i.e. opened read/write) if Explorer happened to be already connected to a WebDav server. Note that this works with any Webdav server, not neccesarily the one with the document that you are trying to edit. So other than telling our users to change settings on their machine, is there anything we can do in the javascript sharepoint call, or on the WebDav server that will fix this issue. Ps. We have the same problem when launching Word from an HTA file version of our system, with javascript like: wordApp = new ActiveXObject("Word.application"); wordApp = new ActiveXObject("Word.application"); wordApp.Visible = true; doc = wordApp.Documents.Open(url); Pps. Sorry if you think this question should be on Serverfault (or even SuperUser). I couldn't decide, but because we are programming the WebDav server ourself (in PHP) and I have more rep on this site than the others, I decided to post it here :-)

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• How to find Tomcat's PID and kill it in python?

  - by 4herpsand7derpsago

  Normally, one shuts down Apache Tomcat by running its shutdown.sh script (or batch file). In some cases, such as when Tomcat's web container is hosting a web app that does some crazy things with multi-threading, running shutdown.sh gracefully shuts down some parts of Tomcat (as I can see more available memory returning to the system), but the Tomcat process keeps running. I'm trying to write a simple Python script that: Calls shutdown.sh Runs ps -aef | grep tomcat to find any process with Tomcat referenced If applicable, kills the process with kill -9 <PID> Here's what I've got so far (as a prototype - I'm brand new to Python BTW): #!/usr/bin/python # Imports import sys import subprocess # Load from imported module. if __init__ == "__main__": main() # Main entry point. def main(): # Shutdown Tomcat shutdownCmd = "sh ${TOMCAT_HOME}/bin/shutdown.sh" subprocess.call([shutdownCmd], shell=true) # Check for PID grepCmd = "ps -aef | grep tomcat" grepResults = subprocess.call([grepCmd], shell=true) if(grepResult.length > 1): # Get PID and kill it. pid = ??? killPidCmd = "kill -9 $pid" subprocess.call([killPidCmd], shell=true) # Exit. sys.exit() I'm struggling with the middle part - with obtaining the grep results, checking to see if their size is greater than 1 (since grep always returns a reference to itself, at least 1 result will always be returned, methinks), and then parsing that returned PID and passing it into the killPidCmd. Thanks in advance!

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• .NET Regular Expression to find actual words in text

  - by Mehdi Anis

  I am using VB .NET to write a program that will get the words from a suplied text file and count how many times each word appears. I am using this regular expression:- parser As New Regex("\w+") It gives me almost 100% correct words. Except when I have words like "Ms Word App file name is word.exe." or "is this a c# statment If(ab?1,0) ?" In such cases I get [word & exe] AND [If, a, b, 1 and 0] as seperate words. it would be nice (for my purpose) that I received word.exe and (If(ab?1,0) as words. I guess \w+ looks for white space, sentence terminating punctuation mark and other punctuation marks to determine a word. I want a similar regular Expression that will not break a word by a punctuation mark, if the punctuation mark is not the end of the word. I think end-of-word can be defined by a trailing WhiteSpace, Sentence terminating Punctuation (you may think of others). if you can suggest some regular expression 9for VB .NET) that will be great help. Thanks.

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• How to efficiently convert String, integer, double, datetime to binary and vica versa?

  - by Ben

  Hi, I'm quite new to C# (I'm using .NET 4.0) so please bear with me. I need to save some object properties (their properties are int, double, String, boolean, datetime) to a file. But I want to encrypt the files using my own encryption, so I can't use FileStream to convert to binary. Also I don't want to use object serialization, because of performance issues. The idea is simple, first I need to somehow convert objects (their properties) to binary (array), then encrypt (some sort of xor) the array and append it to the end of the file. When reading first decrypt the array and then somehow convert the binary array back to object properties (from which I'll generate objects). I know (roughly =) ) how to convert these things by hand and I could code it, but it would be useless (too slow). I think the best way would be just to get properties' representation in memory and save that. But I don't know how to do it using C# (maybe using pointers?). Also I though about using MemoryStream but again I think it would be inefficient. I am thinking about class Converter, but it does not support toByte(datetime) (documentation says it always throws exception). For converting back I think the only options is class Converter. Note: I know the structure of objects and they will not change, also the maximum String length is also known. Thank you for all your ideas and time. EDIT: I will be storing only parts of objects, in some cases also parts of different objects (a couple of properties from one object type and a couple from another), thus I think that serialization is not an option for me.

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• Linq to SQL code generator features

  - by Anders Abel

  I'm very fond of Linq to SQL and the programming model it encourages. I think that in many cases when you are in control of both the database schema and the code it is not worth the effort to have different relational and object models for the data. Working with Linq to SQL makes it simple to have type safe data access from .NET, using the partial extension methods to implement business rules. Unfortunately I do not like the dbml designer due to the lack of a schema refresh function. So far I have used SqlMetal, but that lacks the customization options of the dbml designer. Because of that I've started working on a tool which regenerates the whole code file like SqlMetal, but has the ability to do the customizations that are available in the dbml designer (and maybe more in the future). The customizations will be described in an xml file which only contains those parts that shouldn't have default values. This should keep the xml file size down as well as the maintenance burden of it. To help me focus on the right features, I would like to know: What would be your favourite feature in a linq to sql code generator?

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• How can I make nested string splits?

  - by Statement

  I have what seemed at first to be a trivial problem but turned out to become something I can't figure out how to easily solve. I need to be able to store lists of items in a string. Then those items in turn can be a list, or some other value that may contain my separator character. I have two different methods that unpack the two different cases but I realized I need to encode the contained value from any separator characters used with string.Split. To illustrate the problem: string[] nested = { "mary;john;carl", "dog;cat;fish", "plainValue" } string list = string.Join(";", nested); string[] unnested = list.Split(';'); // EEK! returns 7 items, expected 3! This would produce a list "mary;john;carl;dog;cat;fish;plainValue", a value I can't split to get the three original nested strings from. Indeed, instead of the three original strings, I'd get 7 strings on split and this approach thus doesn't work at all. What I want is to allow the values in my string to be encoded so I can unpack/split the contents just the way before I packed/join them. I assume I might need to go away from string.Split and string.Join and that is perfectly fine. I might just have overlooked some useful class or method. How can I allow any string values to be packed / unpacked into lists? I prefer neat, simple solutions over bulky if possible. For the curious mind, I am making extensions for PlayerPrefs in Unity3D, and I can only work with ints, floats and strings. Thus I chose strings to be my data carrier. This is why I am making this nested list of strings.

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• Why doesn't C# do "simple" type inference on generics?

  - by Ken Birman

  Just curious: sure, we all know that the general case of type inference for generics is undecidable. And so C# won't do any kind of subtyping at all: if Foo<T> is a generic, Foo<int> isn't a subtype of Foo<T>, or Foo<Object> or of anything else you might cook up. And sure, we all hack around this with ugly interface or abstract class definitions. But... if you can't beat the general problem, why not just limit the solution to cases that are easy. For example, in my list above, it is OBVIOUS that Foo<int> is a subtype of Foo<T> and it would be trivial to check. Same for checking against Foo<Object>. So is there some other deep horror that would creep forth from the abyss if they were to just say, aw shucks, we'll do what we can? Or is this just some sort of religious purity on the part of the language guys at Microsoft?

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• Strange build issue using Flex Mojo. Looking for troubleshooting suggestions.

  - by WeeJavaDude

  I have ran into a strange issue and I was hoping for some suggeestion on how to attack the problem. Here is the environment. 1) We develop locally using Flex Builder. 2) We use QuickBuild with FlexMojo 3.4.2 for test builds and production 3) In both cases we don't believe optimization is enabled. What we are seeing is some strange behavior relating to the Ctrl-Enter key when doing testing on IE only in our test environment but not locally. By copying some files over locally I have narrowed the issue down to swf files differences. We do see a difference in the size of swf files in our test environment vs our local environments. Couple things that would help me in troubleshooting would be. 1) Is there a way to know what exactly is in the SWF file? What SWCs are included. 2) How does one compare compile settings between a maven mojo configuration and Flex IDE envioronment? Any thoughts or opinions would be very helpful.

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• Storing float numbers as strings in android database

  - by sandis

  So I have an app where I put arbitrary strings in a database and later extract them like this: Cursor DBresult = myDatabase.query(false, Constant.DATABASE_NOTES_TABLE_NAME, new String[] {"myStuff"}, where, null, null, null, null, null); DBresult.getString(0); This works fine in all cases except for when the string looks like a float number, for example "221.123123123". After saving it to the database I can extract the database to my computer and look inside it with a DB-viewer, and the saved number is correct. However, when using cursor.getString() the string "221.123" is returned. I cant for the life of me understand how I can prevent this. I guess I could do a cursor.getDouble() on every single string to see if this gives a better result, but that feels sooo ugly and inefficient. Any suggestions? Cheers, edit: I just made a small test program. This program prints "result: 123.123", when I would like it to print "result: 123.123123123" SQLiteDatabase database = openOrCreateDatabase("databas", Context.MODE_PRIVATE, null); database.execSQL("create table if not exists tabell (nyckel string primary key);"); ContentValues value = new ContentValues(); value.put("nyckel", "123.123123123"); database.insert("tabell", null, value); Cursor result = database.query("tabell", new String[]{"nyckel"}, null, null, null, null, null); result.moveToFirst(); Log.d("TAG","result: " + result.getString(0));

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• Are function-local typedefs visible inside C++0x lambdas?

  - by GMan - Save the Unicorns

  I've run into a strange problem. The following simplified code reproduces the problem in MSVC 2010 Beta 2: template <typename T> struct dummy { static T foo(void) { return T(); } }; int main(void) { typedef dummy<bool> dummy_type; auto x = [](void){ bool b = dummy_type::foo(); }; // auto x = [](void){ bool b = dummy<bool>::foo(); }; // works } The typedef I created locally in the function doesn't seem to be visible in the lambda. If I replace the typedef with the actual type, it works as expected. Here are some other test cases: // crashes the compiler, credit to Tarydon int main(void) { struct dummy {}; auto x = [](void){ dummy d; }; } // works as expected int main(void) { typedef int integer; auto x = [](void){ integer i = 0; }; } I don't have g++ 4.5 available to test it, right now. Is this some strange rule in C++0x, or just a bug in the compiler? From the results above, I'm leaning towards bug. Though the crash is definitely a bug. For now, I have filed two bug reports. All code snippets above should compile. The error has to do with using the scope resolution on locally defined scopes. (Spotted by dvide.) And the crash bug has to do with... who knows. :) Update According to the bug reports, they have both been fixed for the next release of Visual Studio 2010.

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• asp.net mvc stand alone ascx control how do i link (css and js) most efficiently

  - by Julian

  Hi, I need some advice. I have developed some asp.net mvc web pages. Each page has a master and some ascx controls (between 2 - 6) embedded into it a js and css file. Up to now every thing was fine. In order to improve modularity, flexibility and testability the ascx's are now expected to be able to work as stand alone controls. (Each ascx has also got its own css and js files in some cases it has another control inside it) In order to meet this requirement we call the controller with the relevant parameters and it returns the ascx (partial) directly to the browser without all of the other parts of the original page . In order to get it to display correctly (css) and act correctly (js/jquery) all of the relevant files need to be added (as links or scripts eg. href="<%= ResolveUrl(styleSheet)%>") to the user control. This is "contradicting" the concept of positioning the files at the most logical place (could be the master page for example). How can I overcome this problem? Keep in mind that this is relevant for each "control" ascx file. Any thoughts will be appreciated.

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• In Ruby, why is a method invocation not be able to be treated as a unit when "do" and "end" is used?

  - by Jian Lin

  The following question is related to the question "Ruby Print Inject Do Syntax". My question is, can we insist on using do and end and make it work with puts or p? This works: a = [1,2,3,4] b = a.inject do |sum, x| sum + x end puts b # prints out 10 so, is it correct to say, inject is a class method of the Array class, which takes a block of code, and then returns a number. If so, then it should be no different from calling a function and getting back a return value: b = foo(3) puts b or b = circle.getRadius() puts b In the above two cases, we can directly say puts foo(3) puts circle.getRadius() so, there is no way to make it work directly by using the following 2 ways: a = [1,2,3,4] puts a.inject do |sum, x| sum + x end but it gives ch01q2.rb:7:in `inject': no block given (LocalJumpError) from ch01q2.rb:4:in `each' from ch01q2.rb:4:in `inject' from ch01q2.rb:4 grouping the method call using ( ) doesn't work either: a = [1,2,3,4] puts (a.inject do |sum, x| sum + x end) and this gives: ch01q3.rb:4: syntax error, unexpected kDO_BLOCK, expecting ')' puts (a.inject do |sum, x| ^ ch01q3.rb:4: syntax error, unexpected '|', expecting '=' puts (a.inject do |sum, x| ^ ch01q3.rb:6: syntax error, unexpected kEND, expecting $end end) ^ finally, the following version works: a = [1,2,3,4] puts a.inject { |sum, x| sum + x } but why doesn't the grouping of the method invocation using ( ) work in the earlier example? What if a programmer insist that he uses do and end, can it be made to work?

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• C standard addressing simplification inconsistency

  - by Chris Lutz

  Section §6.5.3.2 "Address and indirection operators" ¶3 says (relevant section only): The unary & operator returns the address of its operand. ... If the operand is the result of a unary * operator, neither that operator nor the & operator is evaluated and the result is as if both were omitted, except that the constraints on the operators still apply and the result is not an lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor the unary * that is implied by the [] is evaluated and the result is as if the & operator were removed and the [] operator were changed to a + operator. ... This means that this: int *i = NULL; printf("%p", (void *) (&*i) ); printf("%p", (void *) (&i[10]) ); Should be perfectly legal, printing the null pointer (probably 0) and the null pointer plus 10 (probably 10). The standard seems very clear that both of those cases are required to be optimized. However, it doesn't seem to require the following to be optimized: struct { int a; short b; } *s = 0; printf("%p", (void *) (&s->b) ); This seems awfully inconsistent. I can see no reason that the above code shouldn't print the null pointer plus sizeof(int) (possibly 4). Simplifying a &-> expression is going to be the same conceptually (IMHO) as &[], a simple address-plus-offset. It's even an offset that's going to be determinable at compile time, rather than potentially runtime with the [] operator. Is there anything in the rationale about why this is so seemingly inconsistent?

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• Regular expression for dividing country calling codes

  - by RickiG

  Hi I have a list of calling codes for all countries(the phone number prefixes), I would like to split them up in the country name and the actual code so I can put then into an xml. I have tried back and forth but can not get a regexp going that takes all cases into account. I think it is fairly simple for someone with a bit of experience. The codes have these formats: Afghanistan 93 Anguilla 1 264 Antarctica 6721 Antigua and Barbuda 1 268 Bosnia and Herzegovina 387 Canada 1 Congo, Republic of the 242 Cote d'Ivoire 225 Ireland (Eire) 353 United States of America 1 There are around 235 of them in total, but these are the regulars and the exceptions. ^[a-zA-Z]\s,'()] for between 1 and X words and then it is [0-9\s]{1,5}$ for the numbers: X XX XXX XXXX X XXX So if I should express it as a sentence it would be: "from beginning of a line, take all characters (1) including space,'() until you encounter digits, then take all of these including space(2) until you encounter a line break." I am using TextMate, and the docs says: TextMate uses the Oniguruma regular expression library by K. Kosako. I would appreciate any help given:) Thank you.

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• Drawing an honeycomb with as3

  - by vitto

  Hi, I'm trying to create an honeycomb with as3 but I have some problem on cells positioning. I've already created the cells (not with code) and for cycled them to a funcion and send to it the parameters which what I thought was need (the honeycomb cell is allready on a sprite container in the center of the stage). to see the structure of the cycle and which parameters passes, please see the example below, the only thing i calculate in placeCell is the angle which I should obtain directly inside tha called function Note: the angle is reversed but it isn't important, and the color are useful in example only for visually divide cases. My for cycle calls placeCell and passes cell, current_case, counter (index) and the honeycomb cell_lv (cell level). I thought it was what i needed but I'm not skilled in geometry and trigonometry, so I don't know how to position cells correctly: function placeCell (cell:Sprite, current_case:int, counter:int, cell_lv:int):void { var margin:int = 2; var angle:Number = (360 / (cell_lv * 6)) * (current_case + counter); var radius:Number = (cell.width + margin) * cell_lv; cell.x = radius * Math.cos (angle); cell.y = radius * Math.sin (angle); trace ("LV " + cell_lv + " current_case " + current_case + " counter " + counter + " angle " + angle + " radius " + radius) } how can I do to solve it?

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• Firefox extension: How to inject javascript into page and run it?

  - by el griz

  I'm writing a Firefox extension to allow users to annotate any page with text and/or drawings and then save an image of the page including the annotations. Use cases would be clients reviewing web pages, adding feedback to the page, saving the image of this and emailing it back to the web developer or testers taking annotated screenshots of GUI bugs etc. I wrote the annotation/drawing functionality in javascript before developing the extension. This script adds a <canvas> element to the page to draw upon as well as a toolbar (in a <div>) that contains buttons (each <canvas> elements) for the different draw tools e.g. line, box, ellipse, text, etc. This works fine when manually included in a page. I now need a way for the extension to: Inject this script into any page including pages I don't control. This needs to occur when the user invokes the extension, which can be after the page has loaded. Once injected the init() function in this script that adds the canvas and toolbar elements etc. needs to be run somehow, but I can't determine how to call this from the extension. Note that once injected I don't need this script to interact with the extension (as the extension just takes a screenshot of the entire document (and removes the added page elements) when the user presses the save button in the extension chrome).

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• How to generate a number in arbitrary range using random()={0..1} preserving uniformness and density?

  - by psihodelia

  Generate a random number in range [x..y] where x and y are any arbitrary floating point numbers. Use function random(), which returns a random floating point number in range [0..1] from P uniformly distributed numbers (call it "density"). Uniform distribution must be preserved and P must be scaled as well. I think, there is no easy solution for such problem. To simplify it a bit, I ask you how to generate a number in interval [-0.5 .. 0.5], then in [0 .. 2], then in [-2 .. 0], preserving uniformness and density? Thus, for [0 .. 2] it must generate a random number from P*2 uniformly distributed numbers. The obvious simple solution random() * (x - y) + y will generate not all possible numbers because of the lower density for all abs(x-y)>1.0 cases. Many possible values will be missed. Remember, that random() returns only a number from P possible numbers. Then, if you multiply such number by Q, it will give you only one of P possible values, scaled by Q, but you have to scale density P by Q as well.

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• Determine the folder of a SAS source file

  - by exhuma

  When I open a SAS file in enterprise guide and run it, it is executed on the server. The source file itself is located either on the production site or the development site. In both cases, it is executed the same server however. I want to be able to tell my script to store results in a relative folder. But if I write something like libname lib_out xport "..\tmp\foobar.xpt"; I get an error, because the working folder of the SAS Enterprise Guide process is not the location of my source file, but a folder on the server. And the folder ..\tmp does not exist there. Even if it would, the server process does not have write permission in that folder. I would like to determine from which folder the .sas file was loaded and set the working folder accordingly. In one case it's S:\Development\myproject\sas\foobar.sas and in the other case it's S:\Production\myproject\sas\foobar.sas It this possible at all? Or how would you do this?

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• Given a main function and a cleanup function, how (canonically) do I return an exit status in Bash/Linux?

  - by Zac B

  Context: I have a bash script (a wrapper for other scripts, really), that does the following pseudocode: do a main function if the main function returns: $returncode = $? #most recent return code if the main function runs longer than a timeout: kill the main function $returncode = 140 #the semi-canonical "exceeded allowed wall clock time" status run a cleanup function if the cleanup function returns an error: #nonzero return code exit $? #exit the program with the status returned from the cleanup function else #cleanup was successful .... Question: What should happen after the last line? If the cleanup function was successful, but the main function was not, should my program return 0 (for the successful cleanup), or $returncode, which contains the (possibly nonzero and unsuccessful) return code of the main function? For a specific application, the answer would be easy: "it depends on what you need the script for." However, this is more of a general/canonical question (and if this is the wrong place for it, kill it with fire): in Bash (or Linux in general) programming, do you typically want to return the status that "means" something (i.e. $returncode) or do you ignore such subjectivities and simply return the code of the most recent function? This isn't Bash-specific: if I have a standalone executable of any kind, how, canonically should it behave in these cases? Obviously, this is somewhat debatable. Even if there is a system for these things, I'm sure that a lot of people ignore it. All the same, I'd like to know. Cheers!

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• C++ iterators, default initialization and what to use as an uninitialized sentinel.

  - by Hassan Syed

  The Context I have a custom template container class put together from a map and vector. The map resolves a string to an ordinal, and the vector resolves an ordinal (only an initial string to ordinal lookup is done, future references are to the vector) to the entry. The entries are modified intrusively to contain a a bool "assigned" and an iterator_type which is a const_iterator to the container class's map. My container class will use RCF's serialization code (which models boost::serialization) to serialize my container classes to nodes in a network. Serializing iterator's is not possible, or a can of worms, and I can easily regenerate them onces the vectors and maps are serialized on the remote site. The Question I need to default initialize, and be able to test that the iterator has not been assigned to (if it is assigned it is valid, if not it is invalid). Since map iterators are not invalidated upon operations performed on it (unless of course items are removed :D) am I to assume that map<x,y>::end() is a valid sentinel (regardless of the state of the map -- i.e., it could be empty) to initialize to ? I will always have access to the parent map, I'm just unsure wheather end() is the same as the map contents change. I don't want to use another level of indirection (--i.e., boost::optional) to achieve my goal, I'd rather forego compiler checks to correct logic, but it would be nice if I didn't need to. Misc This question exists, but most of its content seems non-sense. Assigning a NULL to an iterator is invalid according to g++ and clang++. This is another similar question, but it focuses on the common use-cases of iterators, which generally tends to be using the iterator to iterate, ofcourse in this use-case the state of the container isn't meant to change whilst iteration is going on.

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• How do I programatically verify, create, and update SQL table structure?

  - by JYelton

  Scenario: I have an application (C#) that expects a SQL database and login, which are set by a user. Once connected, it checks for the existence of several table and creates them if not found. I'd like to expand on this by having the program be capable of adding columns to those tables if I release a new version of the program which relies upon the new columns. Question: What is the best way to programatically check the structure of an existing SQL table and create or update it to match an expected structure? I am planning to iterate through the list of required columns and alter the existing table whenever it does not contain the new column. I can't help but wonder if there's an approach that is different or better. Criteria: Here are some of my expectations and self-imposed rules: Newer versions of the program might no longer use certain columns, but they would be retained for data logging purposes. In other words, no columns will be removed. Existing data in the table must be preserved, so the table cannot simply be dropped and recreated. In all cases, newly added columns would allow null data, so the population of old records is taken care of by having default null values. Example: Here is a sample table (because visual examples help!): id sensor_name sensor_status x1 x2 x3 x4 1 na019 OK 0.01 0.21 1.41 1.22 Then, in a new version, I may want to add the column x5. The "x-columns" are all data-storage columns that accept null.

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• Executing logic before save or validation with EF Code-First Models

  - by Ryan Norbauer

  I'm still getting accustomed to EF Code First, having spent years working with the Ruby ORM, ActiveRecord. ActiveRecord used to have all sorts of callbacks like before_validation and before_save, where it was possible to modify the object before it would be sent off to the data layer. I am wondering if there is an equivalent technique in EF Code First object modeling. I know how to set object members at the time of instantiation, of course, (to set default values and so forth) but sometimes you need to intervene at different moments in the object lifecycle. To use a slightly contrived example, say I have a join table linking Authors and Plays, represented with a corresponding Authoring object: public class Authoring { public int ID { get; set; } [Required] public int Position { get; set; } [Required] public virtual Play Play { get; set; } [Required] public virtual Author Author { get; set; } } where Position represents a zero-indexed ordering of the Authors associated to a given Play. (You might have a single "South Pacific" Play with two authors: a "Rodgers" author with a Position 0 and a "Hammerstein" author with a Position 1.) Let's say I wanted to create a method that, before saving away an Authoring record, it checked to see if there were any existing authors for the Play to which it was associated. If no, it set the Position to 0. If yes, it would find set the Position of the highest value associated with that Play and increment by one. Where would I implement such logic within an EF code first model layer? And, in other cases, what if I wanted to massage data in code before it is checked for validation errors? Basically, I'm looking for an equivalent to the Rails lifecycle hooks mentioned above, or some way to fake it at least. :)

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• Multi threading in WCF RIA Services

  - by synergetic

  I use WCF RIA Services to update customer database. In domain service: public void UpdateCustomer(Customer customer) { this.ObjectContext.Customers.AttachAsModified(customer); syncCustomer(customer); } After update, a database trigger launches and depending on the columns updated it may insert a new record in CustomerChange table. syncCustomer(customer) method is executed to check for a new record in the CustomerChange table and if found it will create a text file which contains customer information and forwards that file to external system for import. Now this synchronization may take a time so I wanted to execute it in different thread. So: private void syncCustomer(Customer customer) { this.ObjectContext.SaveChanges(); new Thread(() => syncCustomerInfo(customer.CustomerID)) { IsBackground = true }.Start(); } private void syncCustomerInfo(int customerID) { //Thread.Sleep(2000); //does real job here ... ... } The problem is in most cases syncCustomerInfo method cannot find any new CustomerChange record even if it was definitely there. If I force thread sleep then it finds a new record. I also looked Entity Framework events but the only event provided by object context is SavingChanges which occur before changes are saved. Please suggest me what else to try.

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• Qt/PyQt dialog with togglable fullscreen mode - problem on Windows

  - by Guard

  I have a dialog created in PyQt. It's purpose and functionality don't matter. The init is: class MyDialog(QWidget, ui_module.Ui_Dialog): def __init__(self, parent=None): super(MyDialog, self).__init__(parent) self.setupUi(self) self.installEventFilter(self) self.setWindowFlags(Qt.Dialog | Qt.WindowTitleHint) self.showMaximized() Then I have event filtering method: def eventFilter(self, obj, event): if event.type() == QEvent.KeyPress: key = event.key() if key == Qt.Key_F11: if self.isFullScreen(): self.setWindowFlags(self._flags) if self._state == 'm': self.showMaximized() else: self.showNormal() self.setGeometry(self._geometry) else: self._state = 'm' if self.isMaximized() else 'n' self._flags = self.windowFlags() self._geometry = self.geometry() self.setWindowFlags(Qt.Tool | Qt.FramelessWindowHint) self.showFullScreen() return True elif key == Qt.Key_Escape: self.close() return QWidget.eventFilter(self, obj, event) As can be seen, Esc is used for dialog hiding, and F11 is used for toggling full-screen. In addition, if the user changed the dialog mode from the initial maximized to normal and possibly moved the dialog, it's state and position are restored after exiting the full-screen. Finally, the dialog is created on the MainWindow action triggered: d = MyDialog(self) d.show() It works fine on Linux (Ubuntu Lucid), but quite strange on Windows 7: if I go to the full-screen from the maximized mode, I can't exit full-screen (on F11 dialog disappears and appears in full-screen mode again). If I change the dialog's mode to Normal (by double-clicking its title), then go to full-screen and then return back, the dialog is shown in the normal mode, in the correct position, but without the title line. Most probably the reason for both cases is the same - the setWindowFlags doesn't work. But why? Is it also possible that it is the bug in the recent PyQt version? On Ubuntu I have 4.6.x from apt, and on Windows - the latest installer from the riverbank site.

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