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• Database structure for ecommerce site

  - by imanc

  Hey Guys, I have been tasked with designing an ecommerce solution. The aspect that is causing me the most problems is the database. Currently the site consists of 10+ country based shops each with their own database (all residing on the same mysql instance). For the new site I'd rather all these shop databases be merged into one database so that all tables (products, orders, customers etc.) have a shop_id field. From a programming perspective this seems to make the most sense as we won't have to manage data across multiple databases. Currently the entire site generates about 120k orders a year, but is experiencing fairly heavy growth and we need to design a solution that will scale. In 5 years there may be more than a million orders per year and a database that contains 5 years order history (archiving maybe a solution here). The question is - do we use a single database, or do we keep the database-per-shop structure? I am currently trying to find supporting evidence for either avenue. The company I am designing the solution for prefer the per-shop database structure because they believe it will allow the sites to scale. But my argument is that the shop's database probably won't get that busy over the next few years that they exceed the capacity of a mysql database and a "no expenses spared" hardware set-up. I am wondering if anyone has any advice either way? Does anyone have experience with websites / ecommerce sites that have tables containing millions of records? I know there is probably not a clear answer here, but at what stage do we have too many records or too large table files to have a fast loading site? Also, if anyone has any advice on sources of information - books, websites, etc. where I can do further research, it would be highly appreciated! Cheers, imanc

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• How do repos (SVN, GIT) work?

  - by masfenix

  I read SO nearly everyday and mostly there is a thread about source control. I have a few questions. I am going to use SVN as example. 1) There is a team (small, large dosnt matter). In the morning everyone checks out the code to start working. At noon Person A commits, while person B still works on it. What happens when person B commits? how will person B know that there is an updated file? 2) I am assuming the answer to the first question is "run an update command which tells you", ok so person B finds out that the file they have been working on all morning in changed. When they see the udpated file, it seems like person A has REWRITTEN the file for better performance. What does person B do? Seems like there whole day was a waste of time. Or if they commit their version then its a waste of person A's time? 3) What are branches? thanks, and if anyone knows a laymen terms pdf or something that explains it that would be awesome.

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• Group and sort blog posts by date in Rails

  - by Senthil

  I've searched all over web and have not found the answer. I'm trying to have a very standard archive option for my blog based on date. A request to url blog.com/archive/2009 shows all posts in 2009, blog.com/archive/2009/11 shows all posts in November 2009 etc. I found two different of code but not very helpful to me. def display_by_date year = params[:year] month = params[:month] day = params[:day] day = '0'+day if day && day.size == 1 @day = day if (year && month && day) render(:template => "blog/#{year}/#{month}/#{date}") elsif year render(:template => "blog/#{year}/list") end end def archive year = params[:year] month = params[:month] day = params[:day] day = '0'+day if day && day.size == 1 if (year && month && day) @posts_by_month = Blog.find(:all, :conditions => ["year is?", year]) else @posts_by_month = Blog.find(:all).group_by { |post| post.created_at.strftime("%B") } end end Any help is appreciated.

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• python os.mkfifo() for Windows

  - by user302099

  Hello. Short version (if you can answer the short version it does the job for me, the rest is mainly for the benefit of other people with a similar task): In python in Windows, I want to create 2 file objects, attached to the same file (it doesn't have to be an actual file on the hard-drive), one for reading and one for writing, such that if the reading end tries to read it will never get EOF (it will just block until something is written). I think in linux os.mkfifo() would do the job, but in Windows it doesn't exist. What can be done? (I must use file-objects). Some extra details: I have a python module (not written by me) that plays a certain game through stdin and stdout (using raw_input() and print). I also have a Windows executable playing the same game, through stdin and stdout as well. I want to make them play one against the other, and log all their communication. Here's the code I can write (the get_fifo() function is not implemented, because that's what I don't know to do it Windows): class Pusher(Thread): def __init__(self, source, dest, p1, name): Thread.__init__(self) self.source = source self.dest = dest self.name = name self.p1 = p1 def run(self): while (self.p1.poll()==None) and\ (not self.source.closed) and (not self.source.closed): line = self.source.readline() logging.info('%s: %s' % (self.name, line[:-1])) self.dest.write(line) self.dest.flush() exe_to_pythonmodule_reader, exe_to_pythonmodule_writer =\ get_fifo() pythonmodule_to_exe_reader, pythonmodule_to_exe_writer =\ get_fifo() p1 = subprocess.Popen(exe, shell=False, stdin=subprocess.PIPE, stdout=subprocess.PIPE) old_stdin = sys.stdin old_stdout = sys.stdout sys.stdin = exe_to_pythonmodule_reader sys.stdout = pythonmodule_to_exe_writer push1 = Pusher(p1.stdout, exe_to_pythonmodule_writer, p1, '1') push2 = Pusher(pythonmodule_to_exe_reader, p1.stdin, p1, '2') push1.start() push2.start() ret = pythonmodule.play() sys.stdin = old_stdin sys.stdout = old_stdout

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• Best practices for (over)using Azure queues

  - by John

  Hi, I'm in the early phases of designing an Azure-based application. One of the things that attracts me to Azure is the scalability, given the variability of the demand I'm likely to expect. As such I'm trying to keep things loosely coupled so I can add instances when I need to. The recommendations I've seen for architecting an application for Azure include keeping web role logic to a minimum, and having processing done in worker roles, using queues to communicate and some sort of back-end store like SQL Azure or Azure Tables. This seems like a good idea to me as I can scale up either or both parts of the application without any issue. However I'm curious if there are any best practices (or if anyone has any experiences) for when it's best to just have the web role talk directly to the data store vs. sending data by the queue? I'm thinking of the case where I have a simple insert to do from the web role - while I could set this up as a message, send it on the queue, and have a worker role pick it up and do the insert, it seems like a lot of double-handling. However I also appreciate that it may be the case that this is better in the long run, in case the web role gets overwhelmed or more complex logic ends up being required for the insert. I realise this might be a case where the answer is "it depends entirely on the situation, check your perf metrics" - but if anyone has any thoughts I'd be very appreciative! Thanks John

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• How to copy files without slowing down my app?

  - by Kevin Gebhardt

  I have a bunch of little files in my assets which need to be copied to the SD-card on the first start of my App. The copy code i got from here placed in an IntentService works like a charm. However, when I start to copy many litte files, the whole app gets increddible slow (I'm not really sure why by the way), which is a really bad experience for the user on first start. As I realised other apps running normal in that time, I tried to start a child process for the service, which didn't work, as I can't acess my assets from another process as far as I understood. Has anybody out there an idea how a) to copy the files without blocking my app b) to get through to my assets from a private process (process=":myOtherProcess" in Manifest) or c) solve the problem in a complete different way Edit: To make this clearer: The copying allready takes place in a seperate thread (started automaticaly by IntentService). The problem is not to separate the task of copying but that the copying in a dedicated thread somehow affects the rest of the app (e.g. blocking to many app-specific resources?) but not other apps (so it's not blocking the whole CPU or someting) Edit2: Problem solved, it turns out, there wasn't really a problem. See my answer below.

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• Linking Apache to Tomcat with multiple domains.

  - by Royce Thigpen

  Okay, so I've been working for a while on this, and have been searching, but so far I have not found any answers that actually answer what I want to know. I'm a little bit at the end of my rope with this one, but I'm hoping I can figure this out sometime soon. So I have Apache 2 installed and serving up standard webpages, but I also have that linked to a Tomcat instance for one of my domains currently supported. However, I want to add another domain to the server via Apache that points to a separate code base from the one I already have. I have been coming at this from several different angles, and I have determined that I just don't know enough about setting up these servers to really do what I want to do. Little information on my server: Currently running a single Tomcat5.5 instance with Apache 2, using mod_jk to connect them together. I have a worker in workers.properties that points it's "host" field to "localhost" with the correct port my Tomcat instance, so that all works. In my Tomcat server.xml file, I have a host defined as "localhost" that points at my webapp that I am currently serving up, with that host set as the defaultHost as well. One thought I had was that I could add a new worker with a different host than "localhost" (i.e. host2) and then define a new host in my server.xml file called "host2" to match it, but after reading around some on the internet, It seems the "host" of the worker must point to a server, and not a hostname in the Tomcat instance, is this correct? Again, a simple rundown of what I want: Setup in apache/tomcat combo such that www.domain1.com points at "webapp1" and www.domain2.com points at "webapp2".

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• Determining if an unordered vector<T> has all unique elements

  - by Hooked

  Profiling my cpu-bound code has suggested I that spend a long time checking to see if a container contains completely unique elements. Assuming that I have some large container of unsorted elements (with < and = defined), I have two ideas on how this might be done: The first using a set: template <class T> bool is_unique(vector<T> X) { set<T> Y(X.begin(), X.end()); return X.size() == Y.size(); } The second looping over the elements: template <class T> bool is_unique2(vector<T> X) { typename vector<T>::iterator i,j; for(i=X.begin();i!=X.end();++i) { for(j=i+1;j!=X.end();++j) { if(*i == *j) return 0; } } return 1; } I've tested them the best I can, and from what I can gather from reading the documentation about STL, the answer is (as usual), it depends. I think that in the first case, if all the elements are unique it is very quick, but if there is a large degeneracy the operation seems to take O(N^2) time. For the nested iterator approach the opposite seems to be true, it is lighting fast if X[0]==X[1] but takes (understandably) O(N^2) time if all the elements are unique. Is there a better way to do this, perhaps a STL algorithm built for this very purpose? If not, are there any suggestions eek out a bit more efficiency?

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• Routing redirection decision

  - by programming late night

  I have really no idea why I'm asking this as this a really completely irrelevant question for which I should have figured out an answer within milliseconds, yet I'm doing it. So in my project I have a Router class which splits up the request and selects the right page to be loaded. Fine so far. Now I have a page displayed when the user requests a page that doesn't exist, you know, 404. So theoretically, if the user entered mydomain.com/404 (I use mod_rewrite with a requests collector via index.php?req=*) the 404 error would be shown to him, but in fact there was no error - the 404 page would be displayed as a perfectly normal page. So if someone would try out requesting the 404 page via /404, he would be shown the page but he can't tell if the 404 page he requested doesn't exist and he is actually getting a, you guessed it, 404 error or if he actually found some flaw in the system that makes him able to see an error page when there is no error. I don't know how dumb this whole thing here is but I'm sure some of you have in fact ran into this problem already. Short version: If the user enters mydomain.com/404 the 404 page is shown even though there is no 404 error. I know this is a completely irrelevant question, please don't tell me, but I just spontaneously wanted to hear your thoughts on it. Strange eh? Should I redirect direct access to my 404-page to the home page? Should I do nothing? Should I just go to bed and stop asking irrelevant stuff?

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• Saving a remote image with cURL?

  - by thebluefox

  Morning all, Theres a few questions around this but none that really answer my question, as far as I ca understand. Basically I have a GD script that deals with resizing and caching images on our server, but I need to do the same with images stored on a remote server. So, I'm wanting to save the image locally, then resize and display it as normal. I've got this far... $file_name_array = explode('/', $filename); $file_name_array_r = array_reverse($file_name_array); $save_to = 'system/cache/remote/'.$file_name_array_r[1].'-'.$file_name_array_r[0]; $ch = curl_init($filename); $fp = fopen($save_to, "wb"); // set URL and other appropriate options $options = array(CURLOPT_FILE => $fp, CURLOPT_HEADER => 0, CURLOPT_FOLLOWLOCATION => 1, CURLOPT_TIMEOUT => 60); // 1 minute timeout (should be enough) curl_setopt_array($ch, $options); curl_exec($ch); curl_close($ch); fclose($fp); This creates the image file, but does not copy it accross? Am I missing the point? Cheers guys.

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• How to convert between different currencies?

  - by sil3nt

  Hey there, this is part of a question i got in class, im at the final stretch but this has become a major problem. In it im given a certain value which is called the "gold value" and it is 40.5, this value changes in input. and i have these constants const int RUBIES_PER_DIAMOND = 5; // relative values. * const int EMERALDS_PER_RUBY = 2; const int GOLDS_PER_EMERALDS = 5; const int SILVERS_PER_GOLD = 4; const int COPPERS_PER_SILVER = 5; const int DIAMOND_VALUE = 50; // gold values. * const int RUBY_VALUE = 10; const int EMERALD_VALUE = 5; const float SILVER_VALUE = 0.25; const float COPPER_VALUE = 0.05; which means that basically for every diamond there are 5 rubies, and for every ruby there are 2 emeralds. So on and so forth. and the "gold value" for every diamond for example is 50 (diamond value = 50) this is how much one diamond is worth in golds. my problem is converting 40.5 into these diamonds and ruby values. I know the answer is 4rubies and 2silvers but how do i write the algorithm for this so that it gives the best estimate for every goldvalue that comes along?? please help!, im at my wits end

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• Avoiding mass propagation of properties and events for exposure to ViewModels.

  - by firoso

  I have an MVVM application I am developing that is to the point where I'm ready to start putting together a user interface (my client code is largely functional) I'm now running into the issue that I'm trying to get my application data to where I need it so that it can be consumed by the view model and then bound to the view. Unfortunately, it seems that I've either got a few structural oversights, or I'm just going to have to face the reality that I need to be propogating events and raising excessive amounts of errors to notify view models that thier properties have changed. Let me go into some examples of my issue: I have a class "Unit" contained in a class "Test", contained in a class "Session" contained in a class "TestManager" which is contained in "TestDataModel" which is utilized by "TestViewModel" which is databound to by my "TestView" .... WHOA. Now, consider that Unit (the bottom of the heiarchy) has a property called "Results" that is updated periodically, I want to expose that to my viewmodel and then databind it to my view, trouble is, the only way I can really think to do this is to perpetuate events WAY up a chain that say "I've been updated!" and then request the new value... This seems like an aweful way to do this. Alternatively, I could register a static event and raise it, and have the appropriate "Unit view model" grab the event and request the update. This SEEMS better... but... static events? Is that a taboo idea? Also, having an expression like: TestDataModel.TestManager.Session.Test.Unit.Results[i] Seems REALLY gross to have on a View Model. I know this all reeks of a bad design issue, but I can't figure out what I did wrong? Should I be using more singleton/container controlled lifetimes type objects? Register object instances with static helper containers? Obviously these are hard questions to answer without being intimate with the existing structure, but if you've run into situations like this, what did you do to refactor? Should I just live with this, add mass events, and propogate them?

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• wxPython: How to handle event binding and Show() properly.

  - by Gopal

  Hi all, I'm just starting out with wxPython and this is what I would like to do: a) Show a Frame (with Panel inside it) and a button on that panel. b) When I press the button, a dialog box pops up (where I can select from a choice). c) When I press ok on dialog box, the dialog box should disappear (destroyed), but the original Frame+Panel+button are still there. d) If I press that button again, the dialog box will reappear. My code is given below. Unfortunately, I get the reverse effect. That is, a) The Selection-Dialog box shows up first (i.e., without clicking on any button since the TopLevelframe+button is never shown). b) When I click ok on dialog box, then the frame with button appears. c) Clicking on button again has no effect (i.e., dialog box does not show up again). What am I doing wrong ? It seems that as soon as the frame is initialized (even before the .Show() is called), the dialog box is initialized and shown automatically. I am doing this using Eclipse+Pydev on WindowsXP with Python 2.6 ============File:MainFile.py=============== import wx import MyDialog #This is implemented in another file: MyDialog.py class TopLevelFrame(wx.Frame): def __init__(self,parent,id): wx.Frame.__init__(self,parent,id,"Test",size=(300,200)) panel=wx.Panel(self) button=wx.Button(panel, label='Show Dialog', pos=(130,20), size=(60,20)) # Bind EVENTS --> HANDLERS. button.Bind(wx.EVT_BUTTON, MyDialog.start(self)) # Run the main loop to start program. if __name__=='__main__': app=wx.PySimpleApp() TopLevelFrame(parent=None, id=-1).Show() app.MainLoop() ============File:MyDialog.py=============== import wx def start(parent): inputbox = wx.SingleChoiceDialog(None,'Choose Fruit', 'Selection Title', ['apple','banana','orange','papaya']) if inputbox.ShowModal()==wx.ID_OK: answer = inputbox.GetStringSelection() inputbox.Destroy()

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• Can't add to NSMutableArray from SecondaryView

  - by Antonio

  Hi guys, I've searched and read and still haven't found a concrete answer. Brief: I have an application where I declare an NSMutableArray in my AppDelegate to synthesize when the application loads. (code below). I have a SecondaryViewController call this function, and I have it output a string to let me know what the array size is. Every time I run it, it executes but it does not add any objects to the array. How do I fix this? AppDelegate.h file #import <UIKit/UIKit.h> @class arrayTestViewController; @interface arrayTestAppDelegate : NSObject <UIApplicationDelegate> { UIWindow *window; arrayTestViewController *viewController; NSMutableArray *myArray3; } @property (nonatomic, retain) NSMutableArray *myArray3; @property (nonatomic, retain) IBOutlet UIWindow *window; @property (nonatomic, retain) IBOutlet arrayTestViewController *viewController; -(void)addToArray3; @end AppDelegate.m file #import "arrayTestAppDelegate.h" #import "arrayTestViewController.h" @implementation arrayTestAppDelegate @synthesize window; @synthesize viewController; @synthesize myArray3; #pragma mark - #pragma mark Application lifecycle - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { myArray3 = [[NSMutableArray alloc] init]; // Override point for customization after application launch. // Add the view controller's view to the window and display. [window addSubview:viewController.view]; [window makeKeyAndVisible]; return YES; } -(void)addToArray3{ NSLog(@"Array Count: %d", [myArray3 count]); [myArray3 addObject:@"Test"]; NSLog(@"Array triggered from SecondViewController"); NSLog(@"Array Count: %d", [myArray3 count]); } SecondViewController.m file #import "SecondViewController.h" #import "arrayTestAppDelegate.h" @implementation SecondViewController -(IBAction)addToArray{ arrayTestAppDelegate *object = [[arrayTestAppDelegate alloc] init]; [object addToArray3]; }

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• Most efficient way to LIMIT results in a JOIN?

  - by johnnietheblack

  I have a fairly simple one-to-many type join in a MySQL query. In this case, I'd like to LIMIT my results by the left table. For example, let's say I have an accounts table and a comments table, and I'd like to pull 100 rows from accounts and all the associated comments rows for each. Thy only way I can think to do this is with a sub-select in in the FROM clause instead of simply selecting FROM accounts. Here is my current idea: SELECT a.*, c.* FROM (SELECT * FROM accounts LIMIT 100) a LEFT JOIN `comments` c on c.account_id = a.id ORDER BY a.id However, whenever I need to do a sub-select of some sort, my intermediate level SQL knowledge feels like it's doing something wrong. Is there a more efficient, or faster, way to do this, or is this pretty good? By the way... This might be the absolute simplest way to do this, which I'm okay with as an answer. I'm simply trying to figure out if there IS another way to do this that could potentially compete with the above statement in terms of speed.

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• Element not found blocks execution in Selenium

  - by Mariano

  In my test, I try to verify if certain text exists (after an action) using find_element_by_xpath. If I use the right expression and my test pass, the routine ends correctly in no time. However if I try a wrong text (meaning that the test will fail) it hangs forever and I have to kill the script otherwise it does not end. Here is my test (the expression Thx user, client or password you entered is incorrect does not exist in the system, no matter what the user does): # -*- coding: utf-8 -*- import gettext import unittest from selenium import webdriver class TestWrongLogin(unittest.TestCase): def setUp(self): self.driver = webdriver.Firefox() self.driver.get("http://10.23.1.104:8888/") # let's check the language try: self.lang = self.driver.execute_script("return navigator.language;") self.lang = self.lang("-")[0] except: self.lang = "en" language = gettext.translation('app', '/app/locale', [self.lang], fallback=True) language.install() self._ = gettext.gettext def tearDown(self): self.driver.quit() def test_wrong_client(self): # test wrong client inputElement = self.driver.find_element_by_name("login") inputElement.send_keys("root") inputElement = self.driver.find_element_by_name("client") inputElement.send_keys("Unleash") inputElement = self.driver.find_element_by_name("password") inputElement.send_keys("qwerty") self.driver.find_element_by_name("form.submitted").click() # wait for the db answer self.driver.implicitly_wait(10) ret = self.driver.find_element_by_xpath( "//*[contains(.,'{0}')]".\ format(self._(u"Thx user, client or password you entered is incorrect"))) self.assertTrue(isinstance(ret, webdriver.remote.webelement.WebElement)) if __name__ == '__main__': unittest.main() Why does it do that and how can I prevent it?

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• Groovy htmlunit getFirstByXPath returning null

  - by StartingGroovy

  I have had a few issues with HtmlUnit returning nulls lately and am looking for guidance. each of my results for grabbing the first row of a website have returned null. I am wondering if someone can A) explain why they might be returning null B) explain better ways (if there are some) to go about getting the information Here is my current code (URL is in the source): client = new WebClient(BrowserVersion.FIREFOX_3) client.javaScriptEnabled = false def url = "http://www.hidemyass.com/proxy-list/" page = client.getPage(url) IpAddress = page.getFirstByXPath("//html/body/div/div/form/table/tbody/tr/td[2]").getValue() println "IP Address is: $data" //returns null //Port_Number is an Image Country = page.getFirstByXPath("//html/body/div/div/form/table/tbody/tr/td[4][@class='country']/@rel").getValue() println "Country abbreviation is: $Country" //differentiate speed and connection by name of gif? Type = page.getFirstByXPath("//html/body/div/div/form/table/tbody/tr/td[7]").getValue() println "Proxy type is: $Type" Anonymity = page.getFirstByXPath("//html/body/div/div/form/table/tbody/tr/td[8]").getValue() println "Anonymity Level is: $Anonymity" client.closeAllWindows() Right now all of my XPaths return null and .getValue() obviously doesn't work on null. I also have questions as to what I should do about the PORT since it is an image? Is there a better alternative than downloading it and attempting to solve it by OCR? Side Note There is no significance in this site, I was just looking for a site that I could practice scraping on (the last one I ran into issues of fragment identities and couldn't get an answer to: HtmlUnit getByXpath returns null and HtmlUnit and Fragment Identities )

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• Two Problems I'm having with UIButton and UIView.

  - by Andy

  Hi all, I haven't been programming on the iPhone for very long, but I'm picking it up slowly by googling problems I get. Unfortunately I haven't been able to find an answer for these. I have started a new View-based application in Xcode 3.2.2 and immediately added the following files: myUIView.m and myUIView.h, which are subclasses of UIView. In Interface Builder, I set the subclass of the default UIView to be myUIView. I made a button in the drawRect method. Problem one: The title of the button only appears AFTER I click the screen, why? Problem two: I want the button to produce the modalview - is this possible? The code is as follow: #import "myUIView.h" @implementation myUIView - (void)drawRect:(CGRect)rect { // Drawing code button = [UIButton buttonWithType:UIButtonTypeRoundedRect]; button.frame = CGRectMake(0,0,100,100); [button setTitle:@"butty" forState:UIControlStateNormal]; [button addTarget:self action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside]; [self addSubview:button]; } -(void)buttonPressed:(id)sender{ NSLog(@"Button pressed"); //present modal view somehow..? } I can't see how to post attachments, but if anyone thinks it will help I can upload the source. Many thanks, Andy

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• When I Add <DIV> Bottom Scroll Bar Appears, Even Though It Is Not Greater Than The Page Width

  - by Clay Dempsey

  I have searched for this with no answer. My page loads up perfectly when I load the header, navigation and then center image...all 3 different divs. However I have more I need to add and the div tags change the size of the page even though the css I'm using isn't larger than the page. I have no idea what is happening. Here's the code page where everything is fine: http://www.thehdmgroup.com/midwaymissionary/test.php When I add the below div tag with the below css I get a bottom scrollbar on the page and I don't know why. Can someone please explain it to me? #middleTextBox1 { position: absolute; top:507px; left:172px; width:180px; height:180px; background-color:#411b42; border: 1px solid #434343; padding:10px; color: #FFFFFF; font-size: 10px; font-family: Arial, Helvetica, sans-serif; } <div id="middleTextBox1"> <h3 align="center">Mission:</h3> Words </div> I really have no idea why this is happening, could someone please help me out? Thanks for your time.

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• ASP.NET SqlDataSource update and create FK reference

  - by William

  The short version: I have a grid view bound to a data source which has a SelectCommand with a left join in it because the FK can be null. On Update I want to create a record in the FK table if the FK is null and then update the parent table with the new records ID. Is this possible to do with just SqlDataSources? The detailed version: I have two tables: Company and Address. The column Company.AddressId can be null. On my ascx page I am using a SqlDataSource to select a left join of company and address and a GridView to display the results. By having my UpdateCommand and DeleteCommand of the SqlDataSource execute two statements separated by a semi-colon I am able to use the GridView's Edit and Delete functionality to update both table simultaneously. The problem I have is when the Company.AddressId is null. What I need to have happen is have the data source create a record in the Address table and then update the Company table with the new Address.ID then proceed with the update as usual. I would like to do this with just data sources if possible for consistency/simplicity sake. Is it possible to have my data source do this, or perhaps add a second data source to the page to handle some of this? Once I have that working I can probably figure out how to make it work with the InsertCommand as well but if you are on a roll and have an answer for how to make that fly as well feel free to provide it. Thanks.

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• Which OpenGL functions are not GPU-accelerated?

  - by Xavier Ho

  I was shocked when I read this (from the OpenGL wiki): glTranslate, glRotate, glScale Are these hardware accelerated? No, there are no known GPUs that execute this. The driver computes the matrix on the CPU and uploads it to the GPU. All the other matrix operations are done on the CPU as well : glPushMatrix, glPopMatrix, glLoadIdentity, glFrustum, glOrtho. This is the reason why these functions are considered deprecated in GL 3.0. You should have your own math library, build your own matrix, upload your matrix to the shader. For a very, very long time I thought most of the OpenGL functions use the GPU to do computation. I'm not sure if this is a common misconception, but after a while of thinking, this makes sense. Old OpenGL functions (2.x and older) are really not suitable for real-world applications, due to too many state switches. This makes me realise that, possibly, many OpenGL functions do not use the GPU at all. So, the question is: Which OpenGL function calls don't use the GPU? I believe knowing the answer to the above question would help me become a better programmer with OpenGL. Please do share some of your insights.

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• Using items in a list as arguments

  - by Travis Brown

  Suppose I have a function with the following type signature: g :: a -> a -> a -> b I also have a list of as—let's call it xs—that I know will contain at least three items. I'd like to apply g to the first three items of xs. I know I could define a combinator like the following: ($$$) :: (a -> a -> a -> b) -> [a] -> b f $$$ (x:y:z:_) = f x y z Then I could just use g $$$ xs. This makes $$$ a bit like uncurry, but for a function with three arguments of the same type and a list instead of a tuple. Is there a way to do this idiomatically using standard combinators? Or rather, what's the most idiomatic way to do this in Haskell? I thought trying pointfree on a non-infix version of $$$ might give me some idea of where to start, but the output was an abomination with 10 flips, a handful of heads and tails and aps, and 28 parentheses. (NB: I know this isn't a terribly Haskelly thing to do in the first place, but I've come across a couple of situations where it seems like a reasonable solution, especially when using Parsec. I'll certainly accept "don't ever do this in real code" if that's the best answer, but I'd prefer to see some clever trick involving the ((->) r) monad or whatever.)

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• Dynamic use of :default_url in Paperclip

  - by dgilperez

  I'm trying to configure Paperclip to provide different missing images based on the instance's category attribute. Every category of the object has its own missing image. This is my first take: EDIT to add full models: class Service < ActiveRecord::Base attr_accessible :logo, :logo_file_name, :logo_content_type, :logo_file_size, :logo_updated_at belongs_to :category, :counter_cache => true has_attached_file :logo, :path => "/:id-:style-:filename", :url => ":s3_eu_url", :default_url => "/logos/:style/#{self.category.name]}.png", :styles => { :large => "600x400>", :medium => "300x200>", :small => "100x75>", :thumb => "60x42>" } end class Category < ActiveRecord::Base attr_accessible nil has_many :services end In my view, image_tag service.logo.url(:thumb) outputs: undefined method `category' for #<Class:0x0000010a731620> Any ideas? EDIT2: A working default_url is :default_url => "/logos/:style/missing.png", SOLUTION: See my own answer below.

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• Memcache error: Failed reading line from stream (0) Array

  - by daviddripps

  I get some variation of the following error when our server gets put under any significant load. I've Googled for hours about it and tried everything (including upgrading to the latest versions and clean installs). I've read all the posts about it here on SA, but can't figure it out. A lot of people are having the same problem, but no one seems to have a definitive answer. Any help would be greatly appreciated. Thanks in advance. Fatal error: Uncaught exception 'Zend_Session_Exception' with message 'Zend_Session::start() - /var/www/trunk/library/Zend/Cache/Backend/Memcached.php(Line:180): Error #8 Memcache::get() [memcache.get]: Server localhost (tcp 11211) failed with: Failed reading line from stream (0) Array We have a copy of our production environment for testing and everything works great until we start load-testing. I think the biggest object stored is about 170KB, but it will probably be about 500KB when all is said and done (well below the 1MB limit). Just FYI: Memcache gets hit about 10-20 times per page load. Here's the memcached settings: PORT="11211" USER="memcached" MAXCONN="1024" CACHESIZE="64" OPTIONS="" I'm running Memcache 1.4.5 with version 2.2.6 of the PHP-memcache module. PHP is version 5.2.6. memcache details from php -i: memcache memcache support = enabled Active persistent connections = 0 Version = 2.2.6 Revision = $Revision: 303962 $ Directive = Local Value = Master Value memcache.allow_failover = 1 = 1 memcache.chunk_size = 8192 = 8192 memcache.default_port = 11211 = 11211 memcache.default_timeout_ms = 1000 = 1000 memcache.hash_function = crc32 = crc32 memcache.hash_strategy = standard = standard memcache.max_failover_attempts = 20 = 20 Thanks everyone

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• Adapting pseudocode to java implementation for finding the longest word in a trie

  - by user1766888

  Referring to this question I asked: How to find the longest word in a trie? I'm having trouble implementing the pseudocode given in the answer. findLongest(trie): //first do a BFS and find the "last node" queue <- [] queue.add(trie.root) last <- nil map <- empty map while (not queue.empty()): curr <- queue.pop() for each son of curr: queue.add(son) map.put(son,curr) //marking curr as the parent of son last <- curr //in here, last indicate the leaf of the longest word //Now, go up the trie and find the actual path/string curr <- last str = "" while (curr != nil): str = curr + str //we go from end to start curr = map.get(curr) return str This is what I have for my method public static String longestWord (DTN d) { Queue<DTN> holding = new ArrayQueue<DTN>(); holding.add(d); DTN last = null; Map<DTN,DTN> test = new ArrayMap<DTN,DTN>(); DTN curr; while (!holding.isEmpty()) { curr = holding.remove(); for (Map.Entry<String, DTN> e : curr.children.entries()) { holding.add(curr.children.get(e)); test.put(curr.children.get(e), curr); } last = curr; } curr = last; String str = ""; while (curr != null) { str = curr + str; curr = test.get(curr); } return str; } I'm getting a NullPointerException at: for (Map.Entry<String, DTN> e : curr.children.entries()) How can I find and fix the cause of the NullPointerException of the method so that it returns the longest word in a trie?

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