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• Associating an object with another object for GC clearup

  - by thecoop

  Is there any way of associating an object instance (object A) with a second object (object B) in a generalised way, so that when B gets collected A becomes eligable for collection? The same behaviour that would happen if B had an instance variable pointing to A, but without explicitly changing the class definition of B, and being able to do this in a dynamic way? The same sort of effect could be done by using the Component.Disposed event in a funky way, but I don't want to make B disposable EDIT I'm basically creating a cache of objects that are associated with a single 'root' object, and I don't want the cache to be static, as there can be lots of root objects using different caches, so lots of memory will be used up when a root object is no longer used but the cached objects are still around. So, I want a collection of cached objects to be associated with each 'root' object, without changing the root object definition. Sort of like metadata of an extra object reference attached to each root object instance. That way, each collection will get collected when the root object is collected, and not hang around like they would if a static cache was used.

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• NSTask executed only once

  - by Eimantas

  I'm having trouble executing different NSTask's. Same launchPath, different arguments. I have a class who's instances administer own NSTask objects and depending on arguments those instances were initialized with - dependent NSTask object is being created. I have two initializers: // Method for finished task - (void)taskFinished:(NSNotification *)aNotification { [myTask release]; myTask = nil; [self createTask]; } // Designated initializer - (id) init { self = [super init]; if (self != nil) { [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(taskFinished:) name:NSTaskDidTerminateNotification object:nil]; [self createTask]; } return self; } // Convenience initializer - (id)initWithCommand:(NSString *)subCommand { self = [self init]; if (self) { [self setCommand:subCommand]; } return self; } And here 's the createTask method: - (void)createTask { // myTask is a property defined as NSTask* myTask = [[NSTask alloc] init]; [myTask setLaunchPath:@"/usr/bin/executable"]; } Say I have 3 buttons. Each one creates different class instance with different NSTask objects. But problem is that only first one gets executed. The second ones does not even triger "click" event (via target-action). I think it could be cause of launchPath I'm trying to use, 'cause simple /bin/ls works fine. The same command in terminal has 0 return value (i.e. all is fine). Any guides or gotchas are much appreciated.

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• Serial: write() throttling?

  - by damian

  Hi everyone, I'm working on a project sending serial data to control animation of LED lights, which need to stay in sync with a sound engine. There seems to be a large serial write buffer (OSX (POSIX) + FTDI chipset usb serial device), so without manually restricting the transmission rate, the animation system can get several seconds ahead of the serial transmission. Currently I'm manually restricting the serial write speed to the baudrate (8N1 = 10 bytes serial frame per 8 bytes data, 19200 bps serial - 1920 bytes per second max), but I am having a problem with the sound drifting out of sync over time - it starts fine, but after 10 minutes there's a noticeable (100ms+) lag between the sound and the lights. This is the code that's restricting the serial write speed (called once per animation frame, 'elapsed' is the duration of the current frame, 'baudrate' is the bps (19200)): void BufferedSerial::update( float elapsed ) { baud_timer += elapsed; if ( bytes_written > 1024 ) { // maintain baudrate float time_should_have_taken = (float(bytes_written)*10)/float(baudrate); float time_actually_took = baud_timer; // sleep if we have > 20ms lag between serial transmit and our write calls if ( time_should_have_taken-time_actually_took > 0.02f ) { float sleep_time = time_should_have_taken - time_actually_took; int sleep_time_us = sleep_time*1000.0f*1000.0f; //printf("BufferedSerial::update sleeping %i ms\n", sleep_time_us/1000 ); delayUs( sleep_time_us ); // subtract 128 bytes bytes_written -= 128; // subtract the time it should have taken to write 128 bytes baud_timer -= (float(128)*10)/float(baudrate); } } } Clearly there's something wrong, somewhere. A much better approach would be to be able to determine the number of bytes currently in the transmit queue, and try and keep that below a fixed threshold. Any advice appreciated.

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• How do I grab and use a variables coming back through ValueList from an AJAX call?

  - by Mel

  I'm trying the following code to execute a search and it's not working. On the search.cfm page, the only value coming back is the value I input into the search field (even if I click an autosuggest value, it's not coming back; only the letters I actually type myself come back). <cfform class="titleSearchForm" id="searchForm" action="search.cfm?GameID=#cfautosuggestvalue.GameID#" method="post"> <fieldset> <cfinput type="text" class="titleSearchField" name="TitleName" onChange="form.submit()" autosuggest="cfc:gz.cfcomp.search.AutoSuggestSearch({cfautosuggestvalue})"> <input type="button" class="titleSearchButton" value=" " /> </fieldset> </cfform> Query in CFC: <cfquery name="SearchResult" datasource="myDSN"> SELECT CONCAT(titles.TitleName, ' on ', platforms.PlatformAbbreviation) AS sResult, games.GameID FROM games Inner Join platforms ON games.PlatformID = platforms.PlatformID Inner Join titles ON titles.TitleID = games.TitleID WHERE UCase(titleName) LIKE Ucase('#ARGUMENTS.SearchString#%') ORDER BY titleName ASC; </cfquery> Two things: First of all, I would like to get the GameID back to the page making the AJAX request; I know why it is not coming back: Because I'm only returning sResult var, which does not include the GameID. Is there a way to return the GameID value without displaying it? The second thing: How to I grab a value from the auto-suggest once it is returned? Say I want to grab the GameID, or if I can't do that, the "TitleName" to use that in my query? I tried passing it to the form this way: action="search.cfm?GameID=#cfautosuggestvalue.GameID#" - but that does not work. How do I reference the autosuggestionvalue varaibles for use? Thanks

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• How to implement a Client-side Ajax Login on Asp.Net MVC (A link to the solution for Asp.Net Webform

  - by Matt

  Hi, I'm trying to implement a client-side ajax login on Asp.Net MVC. I used to have this set up just fine on WebForms, but now that I've moved to MVC it's giving me some troubles. If you'd like a tutorial on Client-side Ajax Login for Asp.Net Webforms, it can be found here -- Easy, A++ Now... for some reason it's not working for Asp.Net MVC. I used the exact same tutorial as for the Webforms, except when it executes the ssa.login() (equivalently: Sys.Services.AuthenticationService.login()) it's not doing anything. I have alerts in both the onLoginComplete() function and the onError() function. As well I have an alert before the ssa.login gets called and right after... function loginHandler() { var username = $("#login_UserName").val(); var password = $("#login_Password").val(); var isPersistent = $("#login_RememberMe").attr("checked"); var customInfo = null; var redirectUrl = null; // Log them in. alert("try login"); ssa.login(username, password, isPersistent, customInfo, redirectUrl, onLoginComplete, onError); alert("made it here"); } The first alert fires but the second one doesn't which means the function is failing. Here's the function I pulled from Asp.Net Ajax to show you: function(c, b, a, h, f, d, e, g) { this._invoke(this._get_path(), "Login", false, { userName: c, password: b, createPersistentCookie: a }, Function.createDelegate(this, this._onLoginComplete), Function.createDelegate(this, this._onLoginFailed), [c, b, a, h, f, d, e, g]); } Anyone have any idea of why it's failing?

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• Detecting Inheritence during compile time

  - by Jagannath

  I am unable to figure out why this code is returning false. I had the first version of partial specialization. It did not work, I tried with the second version. It did not work either. UPDATE: I wanted to check if "Derived" is publicly derived from "Base". template<class TBase, class TDerived> struct IsDerived { public: enum { isDerived = false }; }; template<class TBase> struct IsDerived<TBase, TBase> { public: enum { isDerived = true }; }; template<class TBase> struct IsDerived<TBase&, TBase&> { public: enum { isDerived = true }; }; int main() { cout << ((IsDerived<Base&, Derived&>::isDerived) ? "true" : "false") << endl; cout << ((IsDerived<const Derived*, const Base*>::isDerived) ? "true" : "false") << endl; }

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• Opening a pdf in .NET

  - by link664

  In the application we are working on we are trying to implement Help. We have a help pdf document and for the moment it has been deemed acceptable that when users click the help button it just opens the pdf. The application is a desktop app and the pdf file needs to be included in the install somehow and installed on the local machine. I essentially need two things: How would I add this pdf to the application so that it is available on the client machine after install? I can either put it in the resources of the project, or else I could put it in the Application Folder of the client setup installer. How would I open this pdf? I can either open this pdf by just launching the default pdf viewer for the file, or I can use the System.WinForms.WebBrowser tool to display it. However if I choose the second option, I am unsure of how to access the file stored in the resources or find it in the install folder. If you could please provide me with the code to do this (either in VB.Net or C#.Net) that would be great.

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• Sharepoint NewForm adding attachments programatically

  - by CodeSpeaker

  I have a list with a custom form which contains a custom file upload control. As soon as the user selects a file and clicks upload, i want this file to go directly to the attachments list within that listitem. However, when adding the file to SPContext.Current.ListItem.Attachments on a new item, the attachment wont show up in the list after saving. If i instead use item.Update() on the new item after adding the attachment i get an error in Sharepoint, but when i then go back to the list, the item is there with its attachment. It seems like its trying to create 2 new entries at once when i save (item.Update) which results in the second of those crashing. What would be the correct way to add attachments this way? oSPWeb.AllowUnsafeUpdates = true; // Get the List item SPListItem listItem = SPContext.Current.ListItem; // Get the Attachment collection SPAttachmentCollection attachmentCollection = listItem.Attachments; Stream attachmentStream; Byte[] attachmentContent; // Get the file from the file upload control if (fileUpload.HasFile) { attachmentStream = fileUpload.PostedFile.InputStream; attachmentContent = new Byte[attachmentStream.Length]; attachmentStream.Read(attachmentContent, 0, (int)attachmentStream.Length); attachmentStream.Close(); attachmentStream.Dispose(); // Add the file to the attachment collection attachmentCollection.Add(fileUpload.FileName, attachmentContent); } // Update th list item listItem.Update();

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• UITouch Events and Table Views

  - by Andy

  I'm working on a navigation-based iPhone-only app that serves two main purposes: One, to present data in a hierarchical view, allowing users to drill down and eventually edit said data, and, two, to all users to perform a default action when the table view cell is tapped. I now need to offer a small set of options tied to the same data; however, both the didSelectRowAtIndexPath: and accessoryButtonTappedForRowAtIndexPath: methods are obviously taken. So, my options seem to be to implement a double-tap method, wherein the small list of additional options would be presented after (you guessed it) a double-tap on said table row; or, preferably, a tap-and-hold method. From what I can tell, tap-and-hold seems like the way to go in SDK 4.0 - which does me no good right this red-hot minute. I decided to go with the double-tap option, but I'm having a little trouble. First and foremost, the touchesBegan:withEvent: method does not seem to be getting called at all; a breakpoint placed within the method is never called while the application runs, and the table view responds exactly as it did before I inserted the method (which is to say, it performs the default action): - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *aTouch = [touches anyObject]; if (aTouch.tapCount == 2) { [NSObject cancelPreviousPerformRequestsWithTarget:self]; } } Second, I don't really need to handle a single-tap - the didSelectRowAtIndexPath: method can handle the single-tap just fine. The double-tap is the funky one I want to handle. I suspect the answer is going to contain the phrase, "You can't have the table view handle the single-tap and the touchesBegan: method handle the double-tap. The touch handling methods have to handle all of them." I would really appreciate some guidance from some of you who've dealt with this issue. Thanks in advance.

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• Is it bad use "display: table;" to organise a layout into 2 columns?

  - by Colen

  Hello, I am trying to make a 2 column layout, apparently the bane of CSS. I know you shouldn't use tables for layout, but I've settled on this CSS. Note the use of display: table etc. div.container { width: 600px; height: 300px; margin: auto; display: table; table-layout: fixed; } ul { white-space: nowrap; overflow: hidden; display: table-cell; width: 40%; } div.inner { display: table-cell; width: auto; } With this layout: <div class="container"> <ul> <li>First</li> <li>Second</li> <li>Third</li> </ul> <div class="inner"> <p>Hello world</p> </div> </div> This seems to work admirably. However, I can't help wondering - am I obeying the letter of the "don't use tables" rule, but not the spirit? I think it's ok, since there's no positioning markup in the HTML code, but I'm just not sure about the "right" way to do it. I can't use css float, because I want the columns to expand and contract with the available space. Please, stack overflow, help me resolve my existential sense of dread at these pseudo-tables.

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• PHP & cUrl - POST problems in while loop.

  - by Max Hoff

  I have a while loop, with cUrl inside. (I can't use curl_multi for various reasons.) The problem is that cUrl seems to save the data it POSTS after each loop traversal. For instance, if parameter X is One the first loop through, and if it's Two the second loop through, cUrl posts: "One,Two". It should just POST "Two".(This is despite closing and unsetting the curl handle.) Here's a simplified version of the code (with unecessary info stripped out): while(true){ // code to form the $url. this code is local to the loop. so the variables should be "erased" and made new for each loop through. $ch = curl_init(); $userAgent = 'Googlebot/2.1 (http://www.googlebot.com/bot.html)'; curl_setopt($ch,CURLOPT_USERAGENT, $userAgent); curl_setopt($ch,CURLOPT_URL,$url); curl_setopt($ch,CURLOPT_POST,count($fields)); curl_setopt($ch,CURLOPT_POSTFIELDS,$fields_string); curl_setopt($ch, CURLOPT_FAILONERROR, true); curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true); curl_setopt($ch, CURLOPT_AUTOREFERER, true); curl_setopt($ch, CURLOPT_RETURNTRANSFER,true); curl_setopt($ch, CURLOPT_TIMEOUT, 10); $html = curl_exec($ch); curl_close($ch); unset($ch); $dom = new DOMDocument(); @$dom->loadHTML($html); $xpath = new DOMXPath($dom); $resultTable = $xpath->evaluate("/html/body//table"); // $resultTable is 20 the first time through the loop, and 0 everytime thereafter becauset he POSTing doesn't work right with the "saved" parameters. What am I doing wrong here?

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• Jasmine testing coffeescript expect(setTimeout).toHaveBeenCalledWith

  - by Lee Quarella

  In the process of learning Jasmine, I've come to this issue. I want a basic function to run, then set a timeout to call itself again... simple stuff. class @LoopObj constructor: -> loop: (interval) -> #do some stuff setTimeout((=>@loop(interval)), interval) But I want to test to make sure the setTimeout was called with the proper args describe "loop", -> xit "does nifty things", -> it "loops at a given interval", -> my_nifty_loop = new LoopObj interval = 10 spyOn(window, "setTimeout") my_nifty_loop.loop(interval) expect(setTimeout).toHaveBeenCalledWith((-> my_nifty_loop.loop(interval)), interval) I get this error: Expected spy setTimeout to have been called with [ Function, 10 ] but was called with [ [ Function, 10 ] ] Is this because the (-> my_nifty_loop.loop(interval)) function does not equal the (=>@loop(interval)) function? Or does it have something to do with the extra square brackets around the second [ [ Function, 10 ] ]? Something else altogther? Where have I gone wrong?

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• PHP: Next Available Value in an Array, starting with a non-indexed value

  - by Erik Smith

  I've been stumped on this PHP issue for about a day now. Basically, we have an array of hours formatted in 24-hour format, and an arbitrary value ($hour) (also a 24-hour). The problem is, we need to take $hour, and get the next available value in the array, starting with the value that immediately proceeds $hour. The array might look something like: $goodHours = array('8,9,10,11,12,19,20,21). Then the hour value might be: $hour = 14; So, we need some way to know that 19 is the next best time. Additionally, we might also need to get the second, third, or fourth (etc) available value. The issue seems to be that because 14 isn't a value in the array, there is not index to reference that would let us increment to the next value. To make things simpler, I've taken $goodHours and repeated the values several times just so I don't have to deal with going back to the start (maybe not the best way to do it, but a quick fix). I have a feeling this is something simple I'm missing, but I would be so appreciative if anyone could shed some light. Erik

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• PostgreSQL, Foreign Keys, Insert speed & Django

  - by Miles

  A few days ago, I ran into an unexpected performance problem with a pretty standard Django setup. For an upcoming feature, we have to regenerate a table hourly, containing about 100k rows of data, 9M on the disk, 10M indexes according to pgAdmin. The problem is that inserting them by whatever method literally takes ages, up to 3 minutes of 100% disk busy time. That's not something you want on a production site. It doesn't matter if the inserts were in a transaction, issued via plain insert, multi-row insert, COPY FROM or even INSERT INTO t1 SELECT * FROM t2. After noticing this isn't Django's fault, I followed a trial and error route, and hey, the problem disappeared after dropping all foreign keys! Instead of 3 minutes, the INSERT INTO SELECT FROM took less than a second to execute, which isn't too surprising for a table <= 20M on the disk. What is weird is that PostgreSQL manages to slow down inserts by 180x just by using 3 foreign keys. Oh, disk activity was pure writing, as everything is cached in RAM; only writes go to the disks. It looks like PostgreSQL is working very hard to touch every row in the referred tables, as 3MB/sec * 180s is way more data than the 20MB this new table takes on disk. No WAL for the 180s case, I was testing in psql directly, in Django, add ~50% overhead for WAL logging. Tried @commit_on_success, same slowness, I had even implemented multi row insert and COPY FROM with psycopg2. That's another weird thing, how can 10M worth of inserts generate 10x 16M log segments? Table layout: id serial primary, a bunch of int32, 3 foreign keys to small table, 198 rows, 16k on disk large table, 1.2M rows, 59 data + 89 index MB on disk large table, 2.2M rows, 198 + 210MB So, am I doomed to either drop the foreign keys manually or use the table in a very un-Django way by defining saving bla_id x3 and skip using models.ForeignKey? I'd love to hear about some magical antidote / pg setting to fix this.

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• How to query MySQL for exact length and exact UTF-8 characters

  - by oskarae

  I have table with words dictionary in my language (latvian). CREATE TABLE words ( value varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL ) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci; And let's say it has 3 words inside: INSERT INTO words (value) VALUES ('teja'); INSERT INTO words (value) VALUES ('vejš'); INSERT INTO words (value) VALUES ('feja'); What I want to do is I want to find all words that is exactly 4 characters long and where second character is 'e' and third character is 'j' For me it feels that correct query would be: SELECT * FROM words WHERE value LIKE '_ej_'; But problem with this query is that it returs not 2 entries ('teja','vejš') but all three. As I understand it is because internally MySQL converts strings to some ASCII representation? Then there is BINARY addition possible for LIKE SELECT * FROM words WHERE value LIKE BINARY '_ej_'; But this also does not return 2 entries ('teja','vejš') but only one ('teja'). I believe this has something to do with UTF-8 2 bytes for non ASCII chars? So question: What MySQL query would return my exact two words ('teja','vejš')? Thank you in advance

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• Designing a general database interface in PHP

  - by lamas

  I'm creating a small framework for my web projects in PHP so I don't have to do the basic work over and over again for every new website. It is not my goal to create a second CakePHP or Codeigniter and I'm also not planning to build my websites with any of the available frameworks as I prefer to use things I've created myself in general. I have no problems in designing that framework when it comes to parts like the core structure, request handling, and so on but I'm getting stuck with designing the database interface for my modules. I've already thought about using the MVC pattern but thought that it would be a bit of a overkill. So the exact problem I'm facing is how my frameworks modules (viewCustomers could be a module, for example) should interact with the database. Is it a good idea to write SQL directly in PHP (mysql_query( 'SELECT firstname, lastname(.....))? How could I abstract a query like SELECT firstname, lastname FROM customers WHERE id=X Would MySQL helper functions like $this->db->get( array('firstname', 'lastname'), array('id'=>X) ) be a good idea? I suppose not because they actually make everything more complicated by requiring arrays to be created and passed. Is the Model pattern from MVC my only real option?

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• Managing logs/warnings in Python extensions

  - by Dimitri Tcaciuc

  TL;DR version: What do you use for configurable (and preferably captured) logging inside your C++ bits in a Python project? Details follow. Say you have a a few compiled .so modules that may need to do some error checking and warn user of (partially) incorrect data. Currently I'm having a pretty simplistic setup where I'm using logging framework from Python code and log4cxx library from C/C++. log4cxx log level is defined in a file (log4cxx.properties) and is currently fixed and I'm thinking how to make it more flexible. Couple of choices that I see: One way to control it would be to have a module-wide configuration call. # foo/__init__.py import sys from _foo import import bar, baz, configure_log configure_log(sys.stdout, WARNING) # tests/test_foo.py def test_foo(): # Maybe a custom context to change the logfile for # the module and restore it at the end. with CaptureLog(foo) as log: assert foo.bar() == 5 assert log.read() == "124.24 - foo - INFO - Bar returning 5" Have every compiled function that does logging accept optional log parameters. # foo.c int bar(PyObject* x, PyObject* logfile, PyObject* loglevel) { LoggerPtr logger = default_logger("foo"); if (logfile != Py_None) logger = file_logger(logfile, loglevel); ... } # tests/test_foo.py def test_foo(): with TemporaryFile() as logfile: assert foo.bar(logfile=logfile, loglevel=DEBUG) == 5 assert logfile.read() == "124.24 - foo - INFO - Bar returning 5" Some other way? Second one seems to be somewhat cleaner, but it requires function signature alteration (or using kwargs and parsing them). First one is.. probably somewhat awkward but sets up entire module in one go and removes logic from each individual function. What are your thoughts on this? I'm all ears to alternative solutions as well. Thanks,

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• After travelling back in Firefox history, javascript won't run.

  - by Patonza

  When I use the back button on Firefox to reach a previously visited page, scripts on that page won't run again. Is there any fix/workaround to have the scripts execute again when viewing the page the second time? Please note that I have tested the same pages on Google Chrome and Internet Explorer and they work as intended. Here are the files and the steps I used to test the problem: (navigate to 0.html, click to get to 1.html, back button) 0.html <html><body> <script type="text/javascript"> window.onload = function() { alert('window.onload alert'); }; alert('inline alert'); </script> <a href="1.html">Click Me!</a> </body></html> 1.html <html><body> <p>Go BACK!</p> </body></html>

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• Using the contents of an array to set individual pixels in a Quartz bitmap context

  - by Magic Bullet Dave

  I have an array that contains the RGB colour values for each pixel in a 320 x 180 display. I would like to be able to set individual pixel values in the a bitmap context of the same size offscreen then display the bitmap context in a view. It appears that I have to create 1x1 rects and either put a stroke on them or a line of length 1 at the point in question. Is that correct? I'm looking for a very efficient way of getting the array data onto the graphics context as you can imagine this is going to be an image buffer that cycles at 25 frames per second and drawing in this way seems inefficient. I guess the other question is should I use OPENGL ES instead? Thoughts/best practice would be much appreciated. Regards Dave OK, have come a short way, but can't make the final hurdle and I am not sure why this isn't working: - (void) displayContentsOfArray1UsingBitmap: (CGContextRef)context { long bitmapData[WIDTH * HEIGHT]; // Build bitmap int i, j, h; for (i = 0; i < WIDTH; i++) { for (j = 0; j < HEIGHT; j++) { h = frameBuffer01[i][j]; bitmapData[i * j] = h; } } // Blit the bitmap to the context CGDataProviderRef providerRef = CGDataProviderCreateWithData(NULL, bitmapData,4 * WIDTH * HEIGHT, NULL); CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB(); CGImageRef imageRef = CGImageCreate(WIDTH, HEIGHT, 8, 32, WIDTH * 4, colorSpaceRef, kCGImageAlphaFirst, providerRef, NULL, YES, kCGRenderingIntentDefault); CGContextDrawImage(context, CGRectMake(0.0, HEIGHT, WIDTH, HEIGHT), imageRef); CGImageRelease(imageRef); CGColorSpaceRelease(colorSpaceRef); CGDataProviderRelease(providerRef); }

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• Extension methods for encapsulation and reusability

  - by tzaman

  In C++ programming, it's generally considered good practice to "prefer non-member non-friend functions" instead of instance methods. This has been recommended by Scott Meyers in this classic Dr. Dobbs article, and repeated by Herb Sutter and Andrei Alexandrescu in C++ Coding Standards (item 44); the general argument being that if a function can do its job solely by relying on the public interface exposed by the class, it actually increases encapsulation to have it be external. While this confuses the "packaging" of the class to some extent, the benefits are generally considered worth it. Now, ever since I've started programming in C#, I've had a feeling that here is the ultimate expression of the concept that they're trying to achieve with "non-member, non-friend functions that are part of a class interface". C# adds two crucial components to the mix - the first being interfaces, and the second extension methods: Interfaces allow a class to formally specify their public contract, the methods and properties that they're exposing to the world. Any other class can choose to implement the same interface and fulfill that same contract. Extension methods can be defined on an interface, providing any functionality that can be implemented via the interface to all implementers automatically. And best of all, because of the "instance syntax" sugar and IDE support, they can be called the same way as any other instance method, eliminating the cognitive overhead! So you get the encapsulation benefits of "non-member, non-friend" functions with the convenience of members. Seems like the best of both worlds to me; the .NET library itself providing a shining example in LINQ. However, everywhere I look I see people warning against extension method overuse; even the MSDN page itself states: In general, we recommend that you implement extension methods sparingly and only when you have to. So what's the verdict? Are extension methods the acme of encapsulation and code reuse, or am I just deluding myself?

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• Allow paste in worksheet without overwriting locked cells

  - by jjeaton

  I have a protected worksheet that users would like to copy and paste into. I have no control over the workbook they are copying from. The protected worksheet has some rows that are available for data entry, and other rows that are locked and greyed out to the user. The users would like to be able to paste over the top of the entire worksheet from another random workbook and have all the cells available for data entry filled in, while the locked cells are undisturbed. In the current state, the user gets an error when they try to paste, because it cannot paste over the locked cells. Example: Worksheet 1: Act1 100 100 100 Act2 100 100 100 Act3 100 100 100 Worksheet 2: (The second row is locked) Act1 300 300 300 Act2 200 200 200 Act3 100 100 100 After copying/pasting Worksheet 2 should look like this: Act1 100 100 100 Act2 200 200 200 Act3 100 100 100 The values from worksheet 1 are populated and the locked rows are undisturbed. I've been thinking along the lines of having a hook where on paste, the locked cells are unlocked so that the paste can happen, and then are reverted to their original values and relocked. Is there some way I can loop through the cells in the clipboard and only paste cells where the target isn't locked? It is preferable to not create a separate button for paste, so there is less impact on the users, but if that's the only way, I'm not opposed to it. Currently, I plan on grouping the locked rows together, so that the data entry cells are contiguous, but then the accounts will be out of order, which is not preferred.

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• Is there a practical benefit to casting a NULL pointer to an object and calling one of its member fu

  - by zdawg

  Ok, so I know that technically this is undefined behavior, but nonetheless, I've seen this more than once in production code. And please correct me if I'm wrong, but I've also heard that some people use this "feature" as a somewhat legitimate substitute of a lacking aspect of the current C++ standard, namely, the inability to obtain the address (well, offset really) of a member function. For example, this is out of a popular implementation of a PCRE (Perl-compatible Regular Expression) library: #ifndef offsetof #define offsetof(p_type,field) ((size_t)&(((p_type *)0)->field)) #endif One can debate whether the exploitation of such a language subtlety in a case like this is valid or not, or even necessary, but I've also seen it used like this: struct Result { void stat() { if(this) // do something... else // do something else... } }; // ...somewhere else in the code... ((Result*)0)->stat(); This works just fine! It avoids a null pointer dereference by testing for the existence of this, and it does not try to access class members in the else block. So long as these guards are in place, it's legitimate code, right? So the question remains: Is there a practical use case, where one would benefit from using such a construct? I'm especially concerned about the second case, since the first case is more of a workaround for a language limitation. Or is it? PS. Sorry about the C-style casts, unfortunately people still prefer to type less if they can.

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• Do complex JOINs cause high coupling and maintenance problems ?

  - by ashkan.kh.nazary

  Our project has ~40 tables with complex relations.A colleague believes in using long join queries which enforces me to learn about tables outside of my module but I think I should not concern about tables not directly related to my module and use data access functions (written by those responsible for other modules) when I need data from them. Let me clarify: I am responsible for the ContactVendor module which enables the customers to contact the vendor and start a conversation about some specific product. Products module has it's own complex tables and relations with functions that encapsulate details (for example i18n, activation, product availability etc ...). Now I need to show the product title of some product related to some conversation between the vendor and customers. I may either write a long query that retrieves the product info along with conversation stuff in one shot (which enforces me to learn about Product tables) OR I may pass the relevant product_id to the get_product_info(int) function. First approach is obviously demanding and introduces many bad practices and things I normally consider fault in programming. The problem with the second approach seems to be the countless mini queries these access functions cause and performance loss is a concern when a loop tries to fetch product titles for 100 products using functions that each perform a separate query. So I'm stuck between "don't code to the implementation, code to interface" and performance. What is the right way of doing things ? UPDATE: I'm specially concerned about possible future modifications to those tables outside of my module. What if the Products module decided to change the way they are doing things? or for some reason modify the schema? It means some other modules would break or malfunction until the change is integrated to them. The usual ripple effect problem.

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• Some web pages (especially Apple documentation) cause heavy CPU usage in Windows IE8

  - by Mark Lutton

  Maybe this belongs in Server Fault instead, but some of you may have noticed this issue (particularly those developing on Mac, using a Windows machine to read the reference material). I posted the same question on a Microsoft forum and got one answer from someone who reproduced the problem, so it's not just my machine. No solution yet. Ever since this month's security updates, I find that many web pages cause the CPU to run at maximum for as long as the web page is visible. This happens in both IE7 and IE8 on at least three different computers (two with Windows XP, one with Vista). Here is one of the pages, running on XP with IE 8: http://learning2code.blogspot.com/2007/11/update-using-subversion-with-xcode-3.html Here is one that does it in Vista with IE8: http://developer.apple.com/iphone/library/documentation/Cocoa/Reference/Foundation/Classes/NSString_Class/Reference/NSString.html You can leave the page open for hours and the CPU is still at high usage. This doesn't happen every time. It is not always reproduceable. Sometimes it is OK the second or third time it loads. In IE7 the high usage is in ieframe.dll, version 7.0.6000.16890. In IE8 the high usage is in iertutil.dll, version 8.0.6001.18806.

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• How to repeatedly show a Dialog with PyGTK / Gtkbuilder?

  - by Julian

  I have created a PyGTK application that shows a Dialog when the user presses a button. The dialog is loaded in my __init__ method with: builder = gtk.Builder() builder.add_from_file("filename") builder.connect_signals(self) self.myDialog = builder.get_object("dialog_name") In the event handler, the dialog is shown with the command self.myDialog.run(), but this only works once, because after run() the dialog is automatically destroyed. If I click the button a second time, the application crashes. I read that there is a way to use show() instead of run() where the dialog is not destroyed, but I feel like this is not the right way for me because I would like the dialog to behave modally and to return control to the code only after the user has closed it. Is there a simple way to repeatedly show a dialog using the run() method using gtkbuilder? I tried reloading the whole dialog using the gtkbuilder, but that did not really seem to work, the dialog was missing all child elements (and I would prefer to have to use the builder only once, at the beginning of the program). [SOLUTION] As pointed out by the answer below, using hide() does the trick. But one has to take care that the dialog is in fact destroyed if one does not catch its "delete-event". A simple example that works is: import pygtk import gtk class DialogTest: def rundialog(self, widget, data=None): self.dia.show_all() result = self.dia.run() def destroy(self, widget, data=None): gtk.main_quit() def closedialog(self, widget, data=None): self.dia.hide() return True def __init__(self): self.window = gtk.Window(gtk.WINDOW_TOPLEVEL) self.window.connect("destroy", self.destroy) self.dia = gtk.Dialog('TEST DIALOG', self.window, gtk.DIALOG_MODAL | gtk.DIALOG_DESTROY_WITH_PARENT) self.dia.vbox.pack_start(gtk.Label('This is just a Test')) self.dia.connect("delete-event", self.closedialog) self.button = gtk.Button("Run Dialog") self.button.connect("clicked", self.rundialog, None) self.window.add(self.button) self.button.show() self.window.show() if __name__ == "__main__": testApp = DialogTest() gtk.main()

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