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  • How to build a Django form which requires a delay to be re-submitted ?

    - by pierre-guillaume-degans
    Hey, In order to avoid spamming, I would like to add a waiting time to re-submit a form (i.e. the user should wait a few seconds to submit the form, except the first time that this form is submitted). To do that, I added a timestamp to my form (and a security_hash field containing the timestamp plus the settings.SECRET_KEY which ensures that the timestamp is not fiddled with). This look like: class MyForm(forms.Form): timestamp = forms.IntegerField(widget=forms.HiddenInput) security_hash = forms.CharField(min_length=40, max_length=40, widget=forms.HiddenInput) # + some other fields.. # + methods to build the hash and to clean the timestamp... # (it is based on django.contrib.comments.forms.CommentSecurityForm) def clean_timestamp(self): """Make sure the delay is over (5 seconds).""" ts = self.cleaned_data["timestamp"] if not time.time() - ts > 5: raise forms.ValidationError("Timestamp check failed") return ts # etc... This works fine. However there is still an issue: the timestamp is checked the first time the form is submitted by the user, and I need to avoid this. Any idea to fix it ? Thank you ! :-)

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  • [C++] Multiple inclusion in multiple files

    - by Amumu
    Hi everyone, I am making a small game. In BattleRecord.h: #ifndef _CHARACTER_H_ #define _CHARACTER_H_ #include "Character.h" #endif class BattleRecord { public: Character Attacker; Character Defender; Status status; int DamageDealt; int GoldEarned; int ExpGained; }; In Character.h: #ifndef _EQUIPMENT_H_ #define _EQUIPMENT_H_ #include "Equipment.h" #endif class BattleRecord; class Character { BattleRecord AttackEnemy(Character &Enemy); } In BattleRecord.h: #ifndef _CHARACTER_H_ #define _CHARACTEr_H_ #include "Character.h" #endif #ifndef _BATLE_RECORD_H_ #define _BATLE_RECORD_H_ #include "BattleRecord.h" #endif class GUI { public: //GUI Methods, and two of these: void ViewStats(Character &Player); void Report(BattleRecord Record) } The problem here is, my Character.h and BattleRecord.h need to include each other, and this definitely will cause multiple redefinition problem. Therefore, I used forward declaration in Character.h by adding: class BattleRecord; The problem is sovled. But then, the GUI.h needs BattleRecord.h again for reporting the battle, so I have to include BattleRecord.h into the GUI.h. I also have to include the Character.h in order to pass into the ViewStat function. I got error and stuck with this up to this piont.

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  • How to convert Unicode strings (\u00e2, etc) into NSString for display?

    - by karlbecker_com
    I am trying to support arbitrary unicode from a variety of international users. They have already put a bunch of data into sqlite databases on their iPhones, and now I want to capture the data into a database, then send it back to their device. Right now I am using a php page that is sending data back to from an internet mysql database. The data is saved in the mysql database properly, but when it's sent back it comes out as unicode text, such as Frank\u00e2\u0080\u0099s iPad instead of just Frank's iPad where the apostrophe should really be a curly apostrophe. The answer posted to another question indicates that there is no built-in Cocoa methods to convert the "\u00e2\u0080\u0099" portion of the unicode string from the webserver to an NSString object. Is this correct? That seems really surprising (and scarily disappointing), since Cocoa definitely allows input from many different Unicode characters, and I need to support any arbitrary language that I have never heard of, and all of the possible characters. I save them to and from the local sqlite database just fine now, but once I send it to a web server, then perhaps pull down different data, I want to ensure the data pulled from the web server is correctly formatted.

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  • accessing a method from a button within a class?

    - by flo
    #import "GameObject.h" #import "Definitions.h" @implementation GameObject @synthesize owner; @synthesize state; @synthesize mirrored; @synthesize button; @synthesize switcher; - (id) init { if ( self = [super init] ) { [self setOwner: EmptyField]; button = [UIButton buttonWithType:UIButtonTypeCustom]; [self setSwitcher: FALSE]; } return self; } - (UIButton*) display{ button.frame = CGRectMake(0, 0, GO_Width, GO_Height); [button setBackgroundImage:[UIImage imageNamed:BlueStone] forState:UIControlStateNormal]; [button addTarget:self action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside]; return button; } -(void)buttonPressed:(id) sender { //... } } - (void) dealloc { [super dealloc]; } @end Hi! i would like to know if the above is possible somehow within a class (in my case it is called GameObject) or if i HAVE to have the button call a methode in the viewcontroller... the above results with the app crashing. i would call display within a loop on the viewcontroller and id like to change some of the GameObjects instance variables within buttonPressed. Also id like to change some other stuff by calling some other methods from within buttonPressed but i think that will be the lesser of my problems ;) also id like to know how i can pass some variables to the buttonPressed method... cant find it anywhere :( help on this one would be much appreciated ;) thanks flo

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  • Rails helper module undefined method `sort'

    - by Magicked
    I'm trying to create a simple helper module in rails, and I'm stumped on the following error message from my new person form (app/views/people/new.html.erb): undefined method `sort' for 97:Fixnum Extracted source (around line #17): 14: <p> 15: <% nations = { 'United States of America' => 'USA', 'Canada' => 'Canada', 'Mexico' => 'Mexico', 'United Kingdom' => 'UK' } %> 16: <%= f.label :country %><br /> 17: <%= radio_buttons(:person, :country, nations) %> 18: 19: </p> 20: <p> radio_buttons is a helper module I have created for my view. Here it is (app/helpers/people_helper.rb): module PeopleHelper def radio_buttons(model_name, target_property, button_source) html='' list = button_source.sort list.each do |x| html << radio_buttons(model_name, target_property, x[1]) html << h(x[0]) html << '<br />' end return html end end The problem appears to be on the "list = button_source.sort", but I'm not sure why it says the method is undefined. I have been able to use it directly within my view code. Am I not able to use methods like this within helper modules? Do I need to include something? Thanks for any help!

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  • What are Code Smells? What is the best way to correct them?

    - by Rob Cooper
    OK, so I know what a code smell is, and the Wikipedia Article is pretty clear in its definition: In computer programming, code smell is any symptom in the source code of a computer program that indicates something may be wrong. It generally indicates that the code should be refactored or the overall design should be reexamined. The term appears to have been coined by Kent Beck on WardsWiki. Usage of the term increased after it was featured in Refactoring. Improving the Design of Existing Code. I know it also provides a list of common code smells. But I thought it would be great if we could get clear list of not only what code smells there are, but also how to correct them. Some Rules Now, this is going to be a little subjective in that there are differences to languages, programming style etc. So lets lay down some ground rules: ** ONE SMELL PER ANSWER PLEASE! & ADVISE ON HOW TO CORRECT! ** See this answer for a good display of what this thread should be! DO NOT downmod if a smell doesn't apply to your language or development methodology We are all different. DO NOT just quickly smash in as many as you can think of Think about the smells you want to list and get a good idea down on how to work around. DO downmod answers that just look rushed For example "dupe code - remove dupe code". Let's makes it useful (e.g. Duplicate Code - Refactor into separate methods or even classes, use these links for help on these common.. etc. etc.). DO upmod answers that you would add yourself If you wish to expand, then answer with your thoughts linking to the original answer (if it's detailed) or comment if its a minor point. DO format your answers! Help others to be able to read it, use code snippets, headings and markup to make key points stand out!

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  • How do I update a progress bar in Cocoa during a long running loop?

    - by Nic
    Hi, I've got a while loop, that runs for many seconds and that's why I want to update a progress bar (NSProgressIndicator) during that process, but it updates only once after the loop has finished. The same happens if I want to update a label text, by the way. I believe, my loop prevents other things of that application to happen. There must be another technique. Does this have to do with threads or something? Am I on the right track? Can someone please give me a simple example, how to “optimize” my application? My application is a Cocoa Application (Xcode 3.2.1) with these two methods in my Example_AppDelegate.m: // This method runs when a start button is clicked. - (IBAction)startIt:(id)sender { [progressbar setDoubleValue:0.0]; [progressbar startAnimation:sender]; running = YES; // this is a instance variable int i = 0; while (running) { if (i++ = processAmount) { // processAmount is something like 1000000 running = NO; continue; } // Update progress bar double progr = (double)i / (double)processAmount; NSLog(@"progr: %f", progr); // Logs values between 0.0 and 1.0 [progressbar setDoubleValue:progr]; [progressbar needsDisplay]; // Do I need this? // Do some more hard work here... } } // This method runs when a stop button is clicked, but as long // as -startIt is busy, a click on the stop button does nothing. - (IBAction)stopIt:(id)sender { NSLog(@"Stop it!"); running = NO; [progressbar stopAnimation:sender]; } I'm really new to Objective-C, Cocoa and applications with a UI. Thank you very much for any helpful answer.

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  • Using memory-based cache together with conventional cache

    - by Industrial
    Hi! Here's the deal. We would have taken the complete static html road to solve performance issues, but since the site will be partially dynamic, this won't work out for us. What we have thought of instead is using memcache + eAccelerator to speed up PHP and take care of caching for the most used data. Here's our two approaches that we have thought of right now: Using memcache on all<< major queries and leaving it alone to do what it does best. Usinc memcache for most commonly retrieved data, and combining with a standard harddrive-stored cache for further usage. The major advantage of only using memcache is of course the performance, but as users increases, the memory usage gets heavy. Combining the two sounds like a more natural approach to us, even though the theoretical compromize in performance. Memcached appears to have some replication features available as well, which may come handy when it's time to increase the nodes. What approach should we use? - Is it stupid to compromize and combine the two methods? Should we insted be focusing on utilizing memcache and instead focusing on upgrading the memory as the load increases with the number of users? Thanks a lot!

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  • How to retrieve view of MultiIndex DataFrame

    - by Henry S. Harrison
    This question was inspired by this question. I had the same problem, updating a MultiIndex DataFrame by selection. The drop_level=False solution in Pandas 0.13 will allow me to achieve the same result, but I am still wondering why I cannot get a view from the MultiIndex DataFrame. In other words, why does this not work?: >>> sat = d.xs('sat', level='day', copy=False) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "C:\Python27\lib\site-packages\pandas\core\frame.py", line 2248, in xs raise ValueError('Cannot retrieve view (copy=False)') ValueError: Cannot retrieve view (copy=False) Of course it could be only because it is not implemented, but is there a reason? Is it somehow ambiguous or impossible to implement? Returning a view is more intuitive to me than returning a copy then later updating the original. I looked through the source and it seems this situation is checked explicitly to raise an error. Alternatively, is it possible to get the same sort of view from any of the other indexing methods? I've experimented but have not been successful. [edit] Some potential implementations are discussed here. I guess with the last question above I'm wondering what the current best solution is to index into arbitrary multiindex slices and cross-sections.

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  • Overriding to_xml for collection of ActiveRecord objects

    - by Chirantan
    Okay, I know you can override the to_xml method for a single instance of ActiveRecord object and it works just fine for me. But how would I go about overriding the to_xml method for collection of objects? Suppose for Task model instance, I implemented to_xml which looks like this. def to_xml super(:methods => [:tag_list], :include => {:project => {:include => {:folder => {}}}, :folder => {}}) end Works just fine when a single task is to be serialized to xml. But when my code runs for collection of tasks, like in the following piece of code render :xml => @tasks.to_xml I get wrong number of arguments (1 for 0) /home/chirantan/.gem/ruby/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/array/conversions.rb:189:in `to_xml' /home/chirantan/.gem/ruby/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/array/conversions.rb:189:in `to_xml' /home/chirantan/.gem/ruby/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/array/conversions.rb:189:in `each' /home/chirantan/.gem/ruby/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/array/conversions.rb:189:in `to_xml' /var/lib/gems/1.8/gems/builder-2.1.2/lib/builder/xmlbase.rb:134:in `call' /var/lib/gems/1.8/gems/builder-2.1.2/lib/builder/xmlbase.rb:134:in `_nested_structures' /var/lib/gems/1.8/gems/builder-2.1.2/lib/builder/xmlbase.rb:58:in `method_missing' /var/lib/gems/1.8/gems/builder-2.1.2/lib/builder/xmlbase.rb:31:in `tag!' /~/blah/app/controllers/tasks_controller.rb:412:in `completed' How do I make this work?

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  • FFMEPG permission problem, is there any alternative solution instead of FFMPEG?

    - by caglaror
    We have some kind of permenant permission problem on FFMPEG.exe to write JPEG file on to HDD. We are using IIS and try all permission methods to ffmepg.exe, its including folder,folders, cmd.exe and any executable file, related folder, file. Also we tried many many command examples. But never went beyond the "permission denied" error messages. We give up. Do you know another alternative solution to pick images from flv, f4v movie files? Or %100 quaranteed method to achive this permission control on IIS? Thank you. ---last code we try variables etc. aren't shown here. jpegYapKomutu = videoEditorKlasoru &"\ffmpeg.exe -i " & videoEditorKlasoru & "\deneme.flv" &" -s 480×360 -ss 00:00:"&saniyesi&" -vframes 1 -f mjpeg "& "C:\Webhome\normworks\caglarorhan\deneme.jpg" WScript.Run "%COMSPEC% /C dir" & jpegYapKomutu

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  • forward invocation, by hand vs magically?

    - by John Smith
    I have the following two class: //file FruitTree.h @interface FruitTree : NSObject { Fruit * f; Leaf * l; } @end //file FruitTree.m @implementation FruitTree //here I get the number of seeds from the object f @end //file Fruit @interface Fruit : NSObject { int seeds; } -(int) countfruitseeds; @end My question is at the point of how I request the number of seeds from f. I have two choices. Either: Since I know f I can explicitly call it, i.e. I implement the method -(int) countfruitseeds { return [f countfruitseeds]; } Or: I can just use forwardInvocation: - (NSMethodSignature *)methodSignatureForSelector:(SEL)selector { // does the delegate respond to this selector? if ([f respondsToSelector:selector]) return [f methodSignatureForSelector:selector]; else if ([l respondsToSelector:selector]) return [l methodSignatureForSelector:selector]; else return [super methodSignatureForSelector: selector]; } - (void)forwardInvocation:(NSInvocation *)invocation { [invocation invokeWithTarget:f]; } (Note this is only a toy example to ask my question. My real classes have lots of methods, which is why I am asking.) Which is the better/faster method?

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  • Using PHP as template language

    - by Kunal
    I wrote up this quick class to do templating via PHP -- I was wondering if this is easily exploitable if I were ever to open up templating to users (not the immediate plan, but thinking down the road). class Template { private $allowed_methods = array( 'if', 'switch', 'foreach', 'for', 'while' ); private function secure_code($template_code) { $php_section_pattern = '/\<\?(.*?)\?\>/'; $php_method_pattern = '/([a-zA-Z0-9_]+)[\s]*\(/'; preg_match_all($php_section_pattern, $template_code, $matches); foreach (array_unique($matches[1]) as $index => $code_chunk) { preg_match_all($php_method_pattern, $code_chunk, $sub_matches); $code_allowed = true; foreach ($sub_matches[1] as $method_name) { if (!in_array($method_name, $this->allowed_methods)) { $code_allowed = false; break; } } if (!$code_allowed) { $template_code = str_replace($matches[0][$index], '', $template_code); } } return $template_code; } public function render($template_code, $params) { extract($params); ob_start(); eval('?>'.$this->secure_code($template_code).'<?php '); $result = ob_get_contents(); ob_end_clean(); return $result; } } Example usage: $template_code = '<?= $title ?><? foreach ($photos as $photo): ?><img src="<?= $photo ?>"><? endforeach ?>'; $params = array('title' => 'My Title', 'photos' => array('img1.jpg', 'img2.jpg')); $template = new Template; echo $template->render($template_code, $params); The idea here is that I'd store the templates (PHP code) in the database, and then run it through the class which uses regular expressions to only allow permitted methods (if, for, etc.). Anyone see an obvious way to exploit this and run arbitrary PHP? If so, I'll probably go the more standard route of a templating language such as Smarty...

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  • What's the difference between these LINQ queries ?

    - by SnAzBaZ
    I use LINQ-SQL as my DAL, I then have a project called DB which acts as my BLL. Various applications then access the BLL to read / write data from the SQL Database. I have these methods in my BLL for one particular table: public IEnumerable<SystemSalesTaxList> Get_SystemSalesTaxList() { return from s in db.SystemSalesTaxLists select s; } public SystemSalesTaxList Get_SystemSalesTaxList(string strSalesTaxID) { return Get_SystemSalesTaxList().Where(s => s.SalesTaxID == strSalesTaxID).FirstOrDefault(); } public SystemSalesTaxList Get_SystemSalesTaxListByZipCode(string strZipCode) { return Get_SystemSalesTaxList().Where(s => s.ZipCode == strZipCode).FirstOrDefault(); } All pretty straight forward I thought. Get_SystemSalesTaxListByZipCode is always returning a null value though, even when it has a ZIP Code that exists in that table. If I write the method like this, it returns the row I want: public SystemSalesTaxList Get_SystemSalesTaxListByZipCode(string strZipCode) { var salesTax = from s in db.SystemSalesTaxLists where s.ZipCode == strZipCode select s; return salesTax.FirstOrDefault(); } Why does the other method not return the same, as the query should be identical ? Note that, the overloaded Get_SystemSalesTaxList(string strSalesTaxID) returns a record just fine when I give it a valid SalesTaxID. Is there a more efficient way to write these "helper" type classes ? Thanks!

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  • Checking for valid email addresses

    - by Roland
    I'm running a website with more than 60 000 registered users. Every week notifications are send to these users via email, now I've noticed some of the mail addresses do not exists anymore eg. the domain address is valid but the email name en asdas@ is not valid anymore since person does not work at a company anymore etc. Now I'm looping through the database and doing some regular expression checks and checking if the MX records exist with the following two functions function verify_email($email){ if(!preg_match('/^[_A-z0-9-]+((\.|\+)[_A-z0-9-]+)*@[A-z0-9-]+(\.[A-z0-9-]+)*(\.[A-z]{2,4})$/',$email)){ return false; } else { return true; } } // Our function to verify the MX records function verify_email_dns($email){ list($name, $domain) = split('@',$email); if(!checkdnsrr($domain,'MX')){ return false; } else { return true; } } If the email address is in an invalid format or the domain does not exists I delete the users account. Are there any methods I could use to check if the email address still exists or not if the domain name is valid and the email address is in the correct format? For example [email protected] does not exist anymore but test.com is a valid domain name.

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  • Convert date to string upon saving a doctrine record

    - by takteek
    Hi, I'm trying to migrate one of my PHP projects to Doctrine. I've never used it before so there are a few things I don't understand. In my current code, I have a class similar to this: class ScheduleItem { private Date start; //A PEAR Date object. private Date end; public function getStart() { return $this-start; } public function setStart($val) { $this-start = $val; } public function getEnd() { return $this-end; } public function setEnd($val) { $this-end= $val; } } I have a ScheduleItemDAO class with methods like save(), getByID(), etc. When loading from and saving to the database, the DAO class converts the Date objects to and from strings so they can be stored in a timestamp field. In my attempt to move to Doctrine, I created a new class like this: class ScheduleItem extends Doctrine_Record { public function setTableDefinition() { $this-hasColumn('start', 'timestamp'); $this-hasColumn('end', 'timestamp'); } } I had hoped I would be able to use Date objects for the start and end times, and have them converted to strings when they are saved to the database. How can I accomplish this?

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  • Python and the self parameter

    - by Svend
    I'm having some issues with the self parameter, and some seemingly inconsistent behavior in Python is annoying me, so I figure I better ask some people in the know. I have a class, Foo. This class will have a bunch of methods, m1, through mN. For some of these, I will use a standard definition, like in the case of m1 below. But for others, it's more convinient to just assign the method name directly, like I've done with m2 and m3. import os def myfun(x, y): return x + y class Foo(): def m1(self, y, z): return y + z + 42 m2 = os.access m3 = myfun f = Foo() print f.m1(1, 2) print f.m2("/", os.R_OK) print f.m3(3, 4) Now, I know that os.access does not take a self parameter (seemingly). And it still has no issues with this type of assignment. However, I cannot do the same for my own modules (imagine myfun defined off in mymodule.myfun). Running the above code yields the following output: 3 True Traceback (most recent call last): File "foo.py", line 16, in <module> print f.m3(3, 4) TypeError: myfun() takes exactly 2 arguments (3 given) The problem is that, due to the framework I work in, I cannot avoid having a class Foo at least. But I'd like to avoid having my mymodule stuff in a dummy class. In order to do this, I need to do something ala def m3(self,a1, a2): return mymodule.myfun(a1,a2) Which is hugely redundant when you have like 20 of them. So, the question is, either how do I do this in a totally different and obviously much smarter way, or how can I make my own modules behave like the built-in ones, so it does not complain about receiving 1 argument too many.

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  • Looping through an List to select an Element in Selenium

    - by ChrisMcLellan
    I'm attempting to write a Page Class for Links within the Header of the website I'm testing. I have the following link structure below <ul> <li><a href="/" title="Home">Home</a></li> <li><a href="/AboutUs" title="About Us">About Us</a> </li> <li><a href="/Account" title="Account">Account</a></li> <li><a href="/Account/Orders" title="Orders">Orders</a></li> <li><a href="/AdministrationPortal" title="Administration Portal">Administration Portal</a></li> </ul> What I want to do is store these into a List, then when a user select one of the links, it will take then to the page they should go to. I have started with the following code below List<IWebElement> headerElements = new List<IWebElement>(); headerElements.Add(WebDriver.FindElement(By.LinkText("Home"))); headerElements.Add(WebDriver.FindElement(By.LinkText("About Us"))); headerElements.Add(WebDriver.FindElement(By.LinkText("Account"))); headerElements.Add(WebDriver.FindElement(By.LinkText("Orders"))); headerElements.Add(WebDriver.FindElement(By.LinkText("Administration Portal"))); headerElements.Add(WebDriver.FindElement(By.LinkText("Log in / Register"))); headerElements.Add(WebDriver.FindElement(By.LinkText("Log off"))); I was thinking for using a for loop to do this, would this be the best way. I'm trying to avoid writting methods like the one below for each link public void SelectCreateNewReferralLink() { var selectAboutUsLink = ( new WebDriverWait(WebDriver, new TimeSpan(50))).Until (ExpectedConditions.ElementExists(By.CssSelector("#main > a:nth-of-type(1)"))); selectCreateNewReferralLink.Click(); } I'm using C#, with WebDriver attempting to write this Any Help would be great Thanks Chris

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  • How to make Solution Explorer behave after clearing search?

    - by stijn
    I currently have a VS installation with no extensions to see how that works out. For navigation that means making heavy use of Ctrl+; aka Search Solution Explorer. While the search itself is ok, it has one major drawback for me that makes it a pain to use for me (both with keyboard and mouse): Solution with two projects, one collapsed, one opened: Use Ctrl+; and start typing until match found from collapsed project What I want now is to simply clear the search and return to the previous view. Seems like a pretty standard requirement, no? But there seems to be no such functionality built in. Problem with the current commands that come close (pressing Esc, clicking Back or Home buttons in Solution Explorer Toolbar) is all the same: they have the extremely annoying behaviour that they insist on suddenly uncollapsing the previously collapsed project and track the match found! (Btw the Track Active Item in Solution Explorer option is turned of in the options). This makes no sense from a UX point of view? You select some kind of 'undo' command, the search box clears which is expected, but then suddenly there's an item visible from a previous search: So if the collapsed project has like 50 items in it, solution explorer is now useless visually since it litters the screen with stuff you don't want to see, and worse you have to manually collapse the project again to return to the previous view. Is there a way around this? I thought maybe keyboard shortcuts for Back/Home would be different, but the commands do not seem to be registered. I looked into EnvDTE80.DTE2.ToolWindows.SolutionExplorer but it has no properties/methods that have anything to do with this issue. And somewhere in the tree there is a Microsoft.VisualStudio.PlatformUI.SolutionPivotNavigator which is probably the class responsible for this behaviour, but I have no idea how to access it?

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  • Designing a class in such a way that it doesn't become a "God object"

    - by devoured elysium
    I'm designing an application that will allow me to draw some functions on a graphic. Each function will be drawn from a set of points that I will pass to this graphic class. There are different kinds of points, all inheriting from a MyPoint class. For some kind of points it will be just printing them on the screen as they are, others can be ignored, others added, so there is some kind of logic associated to them that can get complex. How to actually draw the graphic is not the main issue here. What bothers me is how to make the code logic such that this GraphicMaker class doesn't become the so called God-Object. It would be easy to make something like this: class GraphicMaker { ArrayList<Point> points = new ArrayList<Point>(); public void AddPoint(Point point) { points.add(point); } public void DoDrawing() { foreach (Point point in points) { if (point is PointA) { //some logic here else if (point is PointXYZ) { //...etc } } } } How would you do something like this? I have a feeling the correct way would be to put the drawing logic on each Point object (so each child class from Point would know how to draw itself) but two problems arise: There will be kinds of points that need to know all the other points that exist in the GraphicObject class to know how to draw themselves. I can make a lot of the methods/properties from the Graphic class public, so that all the points have a reference to the Graphic class and can make all their logic as they want, but isn't that a big price to pay for not wanting to have a God class?

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  • Counting string length in javascript and Ruby on Rails

    - by williamjones
    I've got a text area on a web site that should be limited in length. I'm allowing users to enter 255 characters, and am enforcing that limit with a Rails validation: validates_length_of :body, :maximum => 255 At the same time, I added a javascript char counter like you see on Twitter, to give feedback to the user on how many characters he has already used, and to disable the submit button when over length, and am getting that length in Javascript with a call like this: element.length Lastly, to enforce data integrity, in my Postgres database, I have created this field as a varchar(255) as a last line of defense. Unfortunately, these methods of counting characters do not appear to be directly compatible. Javascript counts the best, in that it counts what users consider as number of characters where everything is a single character. Once the submission hits Rails, however, all of the carriage returns have been converted to \r\n, now taking up 2 characters worth of space, which makes a close call fail Rails validations. Even if I were to handcode a different length validation in Rails, it would still fail when it hits the database I think, though I haven't confirmed this yet. What's the best way for me to make all this work the way the user would want? Best Solution: an approach that would enable me to meet user expectations, where each character of any type is only one character. If this means increasing the length of the varchar database field, a user should not be able to sneakily send a hand-crafted post that creates a row with more than 255 letters. Somewhat Acceptable Solution: a javascript change that enables the user to see the real character count, such that hitting return increments the counter 2 characters at a time, while properly handling all symbols that might have these strange behaviors.

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  • noncopyable static const member class in template class

    - by Dukales
    I have a non-copyable (inherited from boost::noncopyable) class that I use as a custom namespace. Also, I have another class, that uses previous one, as shown here: #include <boost/utility.hpp> #include <cmath> template< typename F > struct custom_namespace : boost::noncopyable { F sqrt_of_half(F const & x) const { using std::sqrt; return sqrt(x / F(2.0L)); } // ... maybe others are not so dummy const/constexpr methods }; template< typename F > class custom_namespace_user { static ::custom_namespace< F > const custom_namespace_; public : F poisson() const { return custom_namespace_.sqrt_of_half(M_PI); } static F square_diagonal(F const & a) { return a * custom_namespace_.sqrt_of_half(1.0L); } }; template< typename F > ::custom_namespace< F > const custom_namespace_user< F >::custom_namespace_(); this code leads to the next error (even without instantiation): error: no 'const custom_namespace custom_namespace_user::custom_namespace_()' member function declared in class 'custom_namespace_user' The next way is not legitimate: template< typename F ::custom_namespace< F const custom_namespace_user< F ::custom_namespace_ = ::custom_namespace< F (); What should I do to declare this two classes (first as noncopyable static const member class of second)? Is this feaseble?

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  • How to learn how to program?

    - by twinbornJoint
    I would like to know the best methods for learning to program. I've been directed towards the Python language because I was told it is good for beginners. I ultimately want to make games for OS X/iPhone. My problem is that I understand what I read but I can't apply my knowledge to anything. I am a programming noob. Should I stick with Python? (is there a better language I should be learning?) Where can I learn programming theory? I get very hyper when reading my book sometimes, any tips on staying calm and focusing? What are effective ways to learn how to program? Are there standard exercises for programming? (I feel solving problems helps my understanding immensely) Ultimately I feel like I am in a never ending tunnel that leads me no where. It feels like I am just completely unable to pursue anything in the world of programming, yet it is something I want to do very much. Thanks.

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  • .NET: How to pass value when subscribing to event and obtain it when the event is triggered (Dynamic

    - by Entrase
    The task is to create event handlers in runtime. I need the one method to be called with different parameter value for different events. The events and their number are only known in runtime. So I'm trying to generate dynamic methods, each of which will be assigned to some event, but in general they all just pass some value to an instance method and call it. It would be great if something similar could be done the easier way. I mean passing some value at subscribing stage and then obtaining it when the event is triggered. This is what I'm trying to do now: public class EventSource { public event EventHandler eventOne; public event EventHandler eventTwO; public event EventHandler eventThree; } public class EventListener { SubscribeForEvents() { BindingFlags flags = BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.Instance; // Suppose we've already got EventInfo // and target source somewhere // so we can do eventInfo.AddEventHandler(target, delegate) // Now we need a delegate. int value = 42; Type tDelegate = eventInfo.EventHandlerType; // http://msdn.microsoft.com/en-us/library/ms228976(VS.95).aspx Type returnType = GetDelegateReturnType(tDelegate); DynamicMethod listener = new DynamicMethod("", null, GetDelegateParameterTypes(tDelegate), this.GetType()); ///////// Type[] callParameters = { typeof(int) }; MethodInfo method = this.GetType().GetMethod("ToCallFromDelegate", flags); ILGenerator generator = listener.GetILGenerator(); // No success in this mess. What's wrong? generator.Emit(OpCodes.Ldc_I4, value); generator.Emit(OpCodes.Call, method); generator.Emit(OpCodes.Pop); generator.Emit(OpCodes.Ret); ///////////// Delegate delegate = listener.CreateDelegate(tDelegate); eventInfo.AddEventHandler(target, delegate); // When triggered, there is InvalidProgramException } void ToCallFromDelegate(int value) { doSomething(); } }

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  • Lookup table size reduction

    - by Ryan
    Hello: I have an application in which I have to store a couple of millions of integers, I have to store them in a Look up table, obviously I cannot store such amount of data in memory and in my requirements I am very limited I have to store the data in an embebedded system so I am very limited in the space, so I would like to ask you about recommended methods that I can use for the reduction of the look up table. I cannot use function approximation such as neural networks, the values needs to be in a table. The range of the integers is not known at the moment. When I say integers I mean a 32 bit value. Basically the idea is use some copmpression method to reduce the amount of memory but without losing many precision. This thing needs to run in hardware so the computation overhead cannot be very high. In my algorithm I have to access to one value of the table do some operations with it and after update the value. In the end what I should have is a function which I pass an index to it and then I get a value, and after I have to use another function to write a value in the table. I found one called tile coding http://www.cs.ualberta.ca/~sutton/book/8/node6.html, this one is based on several look up tables, does anyone know any other method?. Thanks.

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