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• Rails: Ajax-enabled form without a model object

  - by Caffeine Coma

  I'm new to Rails and having a hard time figuring out how to create a form that submits over Ajax without having a corresponding model object. My use case is a simple form that collects an email address and sends it an email; there's nothing to be persisted, so no model. In cases where I do have a model, I've had success with form_for(@model, remote: true). I can't seem to find the right helper for the case where there is no model. I tried form_tag(named_path, remote: true) and that works, but does not use Ajax. Pointers to an example with an example with a proper controller, .html.erb and routes.rb would be really appreciated.

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• java string detection of ip

  - by user384706

  Hi, Assume a java string that contains an IP (v4 or v6) or a hostname. What is the best way to detect among these cases? I am not interested so much on whether the IP is in valid range (e.g. 999.999.999.999 for IPv4). I am interested in just a way to detect if a String is a hostname or an IP (v4 or v6). Initially I though this: if(theString.indexOf("@")!=-1){ //Not an Ip } but I am not sure if I should always expect a format containing @ always. Thanks

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• Linux - How do i know the block map of the given file and/or the free space map of the partition.

  - by Inso Reiges

  Hello, I am on Linux and need to know either of the two things: 1) If i have a regular file on some file system on a partition under Linux is there a way to know the set of the physical blocks that this file occupies on the drive from user space? Or at least the set of the file system's clusters? 2) Is there a way to get the same information about the whole free space of the given file system? In both cases i understand that if there is any possible way to extract this info it will probably be totally unsafe and racy (anything could happen to these set of blocks between the time i see them and act on them somehow). I also really don't want an implementation that will have to know a lot about every filesystem.

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• How to create closed areas (convex polygons) from set of line segments ?

  - by Marten

  The following problem is in 2D, so some simplifications can be made when suggesting answers. I need to create closed areas (defined either by line segments or just set of points - convex polygon) from a set of points/line segments. Basically I used Voronoi to generate "roads". Then I changed some of the data. Now I need a way to loop through that data (which is still line segments but doesn't comply with Voronoi anymore) and generate "neigbourhoods" that are bordered with the "roads". I looked at some graph diagrams and shortest path theories, but I could not figure it out. Logically it could be done by starting at left edge from one point, finding the way back to that point using the shortest path with available lines (using only clockwise directions). Then mark this line set down and remove from the data. Then you can repeat the same process and get all the areas like that. I tried to implement that but it did not get me anywhere as I could not figure out a way to write a C++ code that could do that. Problem was with choosing the most counterclockwise line from available lines from a specific point. All angle based math I did gave wrong answers because the way sin/cos are implemented in c++. So to summarize - if you can help me with a totally new approach to the problem its good, if not could you help me find a way to write the part of the code that finds the shortest clockwise path back to the beginning point using the line segment set as paths back. Thank you for your help!

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• How best to associate code with events in jQuery?

  - by Ned Batchelder

  Suppose I have a <select> element on my HTML page, and I want to run some Javascript when the selection is changed. I'm using jQuery. I have two ways to associate the code with the element. Method 1: jQuery .change() <select id='the_select'> <option value='opt1'>One</option> <option value='opt2'>Two</option> </select> <script> $('#the_select').change(function() { alert('Changed!'); }); </script> Method 2: onChange attribute <select id='the_select' onchange='selectChanged();'> <option value='opt1'>One</option> <option value='opt2'>Two</option> </select> <script> function selectChanged() { alert('Changed!'); } </script> I understand the different modularity here: for example, method 1 keeps code references out of the HTML, but method 2 doesn't need to mention HTML ids in the code. What I don't understand is: are there operational differences between these two that would make me prefer one over the other? For example, are there edge-case browsers where one of these works and the other doesn't? Is the integration with jQuery better for either? Does the late-binding of the code to the event make a difference in the behavior of the page? Which do you pick and why?

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• Do you put a super() call a the beginning of your constructors?

  - by sleske

  This is a question about coding style and recommended practices: As explained in the answers to the question unnecessary to put super() in constructor?, if you write a constructor for a class that is supposed to use the default (no-arg) constructor from the superclass, you may call super() at the beginning of your constructor: public MyClass(int parm){ super(); // leaving this out makes no difference // do stuff... } but you can also omit the call; the compiler will in both cases act as if the super() call were there. So then, do you put the call into your constructors or not? On the one hand, one might argue that including the super() makes things more explicit. OTOH, I always dislike writing redundant code, so personally I tend to leave it out; I do however regularly see it in code from others. What are your experiences? Did you have problems with one or the other approach? Do you have coding guidelines which prescribe one approach?

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• What's the best way to unit test code that generates random output?

  - by Flynn1179

  Specifically, I've got a method picks n items from a list in such a way that a% of them meet one criterion, and b% meet a second, and so on. A simplified example would be to pick 5 items where 50% have a given property with the value 'true', and 50% 'false'; 50% of the time the method would return 2 true/3 false, and the other 50%, 3 true/2 false. Statistically speaking, this means that over 100 runs, I should get about 250 true/250 false, but because of the randomness, 240/260 is entirely possible. What's the best way to unit test this? I'm assuming that even though technically 300/200 is possible, it should probably fail the test if this happens. Is there a generally accepted tolerance for cases like this, and if so, how do you determine what that is?

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• my first shader in WebGL

  - by Diego

  Hello, I am writing my first shader in WebGL. I was wondering if the GLSL language has any way to evaluate if an attribute or a uniform is null. According to the specs it does not support to do something like if (attributeX) { dothis(); } else{ dothat(): } And I think it would be a waste to write a bool attribute for each of these cases would be a waste. Another question: what happen during rendering when you don't pass along the uniforms or attribs to the shader? Thanks!

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• Inline function and calling cost in C

  - by Eonil

  I'm making a vector/matrix library. (GCC, ARM NEON, iPhone) typedef struct{ float v[4]; } Vector; typedef struct{ Vector v[4]; } Matrix; I passed struct data as pointer to avoid performance degrade from data copying when calling function. So I thought designed function like this: void makeTranslation(const Vector* factor, Matrix* restrict result); But, if function is inline, is there any reason to pass values as pointer for performance? Do those variables copied too? How about register and caches? inline Matrix makeTranslation(Vector factor) __attribute__ ((always_inline)); How do you think about calling costs of each cases?

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• Unexpected result when comparing ints

  - by Raghav

  I tried to compare two ints with the following cases and got unexpected results when I did the following, @@@ was printed. class C { static Integer a = 127; static Integer b = 127; public static void main(String args[]){ if(a==b){ System.out.println("@@@"); } } } when I did the following, @@@ was not printed. class C { static Integer a = 145; static Integer b = 145; public static void main(String args[]){ if(a==b){ System.out.println("@@@"); } } } Can anyone tell me what could be the reason.

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• Need help from CSS purist!

  - by Darcy

  I'm beginning to use CSS more and more but I'm not sure if I'm using it as intended in all cases. I have classes named things like 'box' that will wrap the content inside it with a border, which seems like good CSS to me. On the other hand I have classes like 'margin-right-5' and 'float-left' that sets the css to margin-right: 5px and float:left respectively. I'm wondering if this is good practice. Then in my markup I'd do something like: <div class="box float-left margin-right-5"> <!-- CONTENT HERE --> </div> Sometimes I may want to float right or not have a margin at all and still use the 'box' class, so I use several classes in order to make the css more flexible. Am I destroying the principles of CSS?

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• Korn Shell - Test with variable that may be not set

  - by C. Ross

  I have the following code in KornShell FAILURE=1 SUCCESS=0 isNumeric(){ if [ -n "$1" ]; then case $1 in *[!0-9]* | "") return $FAILURE; * ) return $SUCCESS; esac; else return $FAILURE; fi; } #... FILE_EXT=${FILE#*.} if [ isNumeric ${FILE_EXT} ]; then echo "Numbered file." fi #... In some cases the file name not have an extension, and this causes the FILE_EXT variable to be empty, which causes the following error: ./script[37]: test: 0403-004 Specify a parameter with this command. How should I be calling this function so that I do not get this error?

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• Is ActiveMQ unreliable?

  - by user122991

  Hello, We have been using ActiveMQ 5.2 in our distributed enterprise application for about 3 months. During that time, we have experienced debilitating failures at least twice weekly. In particular, we see: 1) Topic publisher has its connection arbitrarily closed and experiences EOF on attempt to publish. Note well that this issue is not a function of some timeout. It does not correlate reliably with any inactivity. 2) Queue listeners never receive message. Message simply sits on Queue. 2) is much rarer (hardly ever) than 1). In both cases, the failures are highly intermittent-- they cannot be reliably reproduced through any testing usage pattern. Also, there are no errors or warning in the AMQ logs. Have others experienced similar problems? Is there an opinion that some other JMS provider is more reliable? thanks, Joe

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• Organizing multiple embed codes with jQuery

  - by Nimbuz

  I have several embed codes on my website, for example: Embed Code #1: <object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/f8Lp2ssd5A9ErAc&hl=en_US&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/f8Lp2A9ErAc&hl=en_US&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object> Embed Code #2: <script type="text/javascript"> _qoptions={ qacct:"p-3asdb5E0g6" }; </script> <script type="text/javascript" src="http://edge.quantserve.com/quant.js"></script> <noscript> <a href="http://www.quantcast.com/p-3asdb5E0g6" target="_blank"><img src="http://pixel.quantserve.com/pixel/p-3asdb5E0g6.gif" style="display: none;" border="0" height="1" width="1" alt="Quantcast"/></a> </noscript> and so on.. How do organize them and separate them into an external single js file to keep the markup clean? Thanks for your help!

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• Java: is Exception class thread-safe?

  - by Vilius Normantas

  As I understand, Java's Exception class is certainly not immutable (methods like initCause and setStackTrace give some clues about that). So is it at least thread-safe? Suppose one of my classes has a field like this: private final Exception myException; Can I safely expose this field to multiple threads? I'm not willing to discuss concrete cases where and why this situation could occur. My question is more about the principle: can I tell that a class which exposes field of Exception type is thread-safe? Another example: class CustomException extends Exception { ... } Is this class thread-safe?

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• blacklist test requests from google analytics using watir

  - by Anjali

  Hi, I have to automate tests for a web application which runs google analytics script. I have chosen watir for the automation since I can script all the test cases with the same. The only problem is i dont know how to remove my test requests to the web apps from the google analytics report. Can anyone help me with the same? Is it possible to do that with watir? If not watir, is there any other web automation tool which I could use? ~Thanks and Regarads

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• Change text_factory in Django/sqlite

  - by Krumelur

  I have a django project that uses a sqlite database that can be written to by an external tool. The text is supposed to be UTF-8, but in some cases there will be errors in the encoding. The text is from an external source, so I cannot control the encoding. Yes, I know that I could write a "wrapping layer" between the external source and the database, but I prefer not having to do this, especially since the database already contains a lot of "bad" data. The solution in sqlite is to change the text_factory to something like: lambda x: unicode(x, "utf-8", "ignore") However, I don't know how to tell the Django model driver this.

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• Assign multiple Emacs keybindings to a single command?

  - by Dan

  I'm giving ErgoEmacs mode a try to see if I can use Emacs more comfortably. Some of its keybindings are fairly intuitive, but in many cases I don't want to outright replace the defaults. For example, in the context of ErgoEmacs' navigation shortcut structure, M-h makes sense as a replacement for C-a--but I want to be able to use both, not just M-h. I tried simply duplicating the commands: ;; Move to beginning/ending of line (defconst ergoemacs-move-beginning-of-line-key (kbd "C-a")) ; original (defconst ergoemacs-move-end-of-line-key (kbd "C-e")) ; original (defconst ergoemacs-move-beginning-of-line-key (kbd "M-h")) ; ergoemacs (defconst ergoemacs-move-end-of-line-key (kbd "M-H")) ; ergoemacs But Emacs simply overwrites the first keybinding with the second. What's the best way to address this?

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• WPF with code only

  - by rwallace

  I've seen a lot of questions about the merits of WPF here, and essentially every answer says it's the bee's knees, but essentially every answer also talks about things like XAML, in many cases graphic designers and Expression Blend etc. My question is, is it worth getting into WPF if you're a solo coder working in C# only? Specifically, I don't have a graphic designer, nor any great talent in that area myself; I don't use point-and-click tools; I write everything in C#, not XML. Winforms works fine in those conditions. Is the same true of WPF, or does it turn out that important functions can only be done in XAML, the default settings aren't intended for actual use and you have to have a graphic designer on the team to make things look good, etc., and somebody in my position would be better off to stick to Winforms?

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• Is Work Stealing always the most appropriate user-level thread scheduling algorithm?

  - by Il-Bhima

  I've been investigating different scheduling algorithms for a thread pool I am implementing. Due to the nature of the problem I am solving I can assume that the tasks being run in parallel are independent and do not spawn any new tasks. The tasks can be of varying sizes. I went immediately for the most popular scheduling algorithm "work stealing" using lock-free deques for the local job queues, and I am relatively happy with this approach. However I'm wondering whether there are any common cases where work-stealing is not the best approach. For this particular problem I have a good estimate of the size of each individual task. Work-stealing does not make use of this information and I'm wondering if there is any scheduler which will give better load-balancing than work-stealing with this information (obviously with the same efficiency). NB. This question ties up with a previous question.

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• SQL Server Query Editors - any that warn of number of rows to be changed?

  - by ciaranarcher

  We're using SQL Server 2000 Query Analyser, and one issue we have is that very occasionally, when a user is updating our live database, they insert the incorrect/no(!) where clause. I know, not good, but it happens. Are there any editors that will warn of the number of rows that might be changed (if that is even possible) or even a way to configure an editor, if it is connected to a certain database, to prompt for confirmation before the query is run? We have a way to recover our data in the cases where we run an incorrect query, but it takes time, and I'm just seeing if there are any ways to catch the error, or at least give the user a second chance. Thanks in advance.

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• C++ Testing framework integrated with Eclipse

  - by Mike

  I'm writing a C++ unit testing framework and I would like it if it could be integrated with Eclipse CDT. In other testing suites that work with Eclipse, JUnit for example, the user is provided a graphical list of all test cases and their results. Something like this would be the ideal. I'm just getting into this, so I need some advice on getting started. There are two approaches I see Use an existing Eclipse testing plugin (such as JUnit) and make the framework return output in the same format as the plugin's input. Write a plugin from scratch that can work with my framework (seems like it would take a lot of time) Thoughts appreciated

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• To Show a Continuous ProgressBar using ExtJS

  - by UIDreamer

  Hi, Problem:- I need to embed a progressbar that will run continuously until the completion of the operation. ExtJS provides a Progressbar Ext.Progressbar which will:- a) Run Continuously using wait method b) Run after updating the updateProgress method. In both the cases output of the progressbar will be The solution that i am trying for is:- Step 1 : Step 2 : Step 3 : Kindly suggest me a solution or a approach. The JavaScript library that i am using is ExtJS. Thanks in Advance. Links Referred for the example:- http://dev.sencha.com/deploy/dev/examples/simple-widgets/progress-bar.html

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• Retain, alloc, properties ... Topic to make your Obj-c life easier !

  - by gotye

  Hey everyone, The more I code, the more I get lost ... so I decided to create a topic entirely dedicated to the memory management for me (and others) not to waste hours understanding obj-c basics ... I'll update it as new questions are asked ! Okay below is some examples : // myArray is property (retain) myArray = otherArray; //myArray isn't a property myArray = otherArray; //myArray is a property (retain) myArray = [[NSArray alloc] init]; //myArray isn't a property myArray = [[NSArray alloc] init]; Could you explain to me what happens in every cases ? And especially the number 3 ;) Thanks for the time. Gotye.

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• java methods and race condition in a jsp/servlets application.

  - by A.S al-shammari

  Hi. Suppose that I have a method called doSomething() and I want to use this method in a multithreaded application (each servlet inherits from HttpServlet).I'm wondering if it is possible that a race condition will occur in the following cases: doSomething() is not staic method and it writes values to a database. doSomething() is static method but it does not write values to a database. what I have noticed that many methods in my application may lead to a race condition or dirty read/write. for example , I have a Poll System , and for each voting operation, a certain method will change a single cell value for that poll as the following: [poll_id | poll_data ] [1 | {choice_1 : 10, choice_2 : 20}] will the JSP/Servlets app solve these issues by itself, or I have to solve all that by myself? Thanks..

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