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• What elegant method callback design should be used ?

  - by ereOn

  Hi, I'm surprised this question wasn't asked before on SO (well, at least I couldn't find it). Have you ever designed a method-callback pattern (something like a "pointer" to a class method) in C++ and, if so, how did you do it ? I know a method is just a regular function with some hidden this parameter to serve as a context and I have a pretty simple design in mind. However, since things are often more complex than they seem to, I wonder how our C++ gurus would implement this, preferably in an elegant and standard way. All suggestions are welcome !

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• Can jQuery perform a compound select against the top level only? (a.k.a. "How to avoid chaining chil

  - by harpo

  Basically, is there a way to write a.children('.outer').children('.inner') without the intermediate selector? I can't write $('.outer > .inner', a) because I don't want to do full-depth search against a — I know that the .outer elements are immediate children of a. It's partly a matter of "elegance", but partly because I'm trying to avoid "throwaway" element sets. Yes, jQuery may in effect do the same thing, but it has a better chance of optimizing (at least in theory), when it knows the full query's intent.

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• Does a Category applied to NSString also apply to NSCFString via the "toll-free bridge"?

  - by half_brick

  We're integrating a library into an iPhone app which appears to use the google toolbox for iPhone internally. The google toolbox adds a method gtm_stringBySanitizingAndEscapingForXML to NSString. The problem is, whenever we attempt to make a call to this library we get [NSCFString gtm_stringBySanitizingAndEscapingForXML]: unrecognized selector sent to instance 0x272478 So it appears the library is calling that method on a NSCFString, to which the category does not apply. So... is it the case that the category will not apply across the toll-free bridge to CoreFoundation classes? If that's the case then we at least know why it's blowing up. Figuring out how to fix it is a different matter.

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• Accessing individual HABTM records in a form

  - by Pichan

  I'm building a form in my CakePHP project that lets you edit a company's information. Among all other things, every company has at least one geographical area in which the company operates, but it may have more. The areas are selected individually using select dropdowns. The relationship between companies and areas is HABTM, because I need to be able to change the amount of associated areas without modifying the database. Currently the associations and corresponding data are handled separately, which isn't really a problem but I was wondering how it could be done using as much Cake's own 'automagic' functionality as possible?

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• How to add response headers based on Content-type; getting Content-type before the response is commi

  - by Bozho

  I want to set the Expires header for all image/* and text/css. I'm doing this in a Filter. However: before calling chain.doFilter(..) the Content-type is not yet "realized" after calling chain.doFilter(..) the Content-type is set, but so is content-length, which forbids adding new headers (at least in Tomcat implementation) I can use the extensions of the requested resource, but since some of the css files are generated by richfaces by taking them from inside jar-files, the name of the file isn't x.css, but is /xx/yy/zz.xcss/DATB/.... So, is there a way to get the Content-type before the response is committed.

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• ASP.NET/IIS: Tell IIS do not check for file existence

  - by AgileMeansDoAsLittleAsPossible

  In my Global.asax.cs, I have: routes.MapRoute("AssetCss", "css/{*path}", new { controller = "Asset", action = "Index" }); I also have this in a view: <link href="/css/Root/index.css" rel="stylesheet" type="text/css" /> The problem is that the AssetController does not invoke Index when /css/Root/index.css is requested. This is because a file actually exists at the path /css/Root/index.css. If I recall correctly, there's a checkbox setting in IIS that basically says "Do not check that a file actually exists at the request path [instead, let the RouteTable handle it]." (At least there is in IIS 6.) Is there something I can put in my Web.config that sets this IIS setting to true? How do I tell IIS to let my MVC routes handle the path even if a file exists at the path?

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• How can I clear the appcache on the Google Chrome iPad app?

  - by Jannis

  I've written a little HTML5 based web app that I am trying to debug on the iPad using the Chrome for iPad app. I have added a cache.manifest file to my app which has some heavy caching in it of most static resources however since I am now wanting to debug the app I need a way to clear this cache. I know that on Chrome for Mac you can use: chrome://appcache-internals/ however this page does not exist in the iPad app of Chrome. The regular "Clear Browsing Data" does not empty the appcache —at least not in my case. Does anyone know how I can clear the appcache for the Chrome iPad app?

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• Subtract displaced mask using OpenCV

  - by dario_ramos

  I want to do: masked = image - mask But I want to "displace" mask. That is, move it vertically and horizontally (as long as the intersection between it and image is not empty, this would be valid). I have some hand-coded assembly (which uses MMX instructions) which does this, embedded in a C++ program, but it's unstable when doing vertical displacemente, so I thought of using OpenCV instead. Would it be possible to do this calling only one OpenCV function? Performance is critical; using OpenCV, time should be at least in the same order of magnitude as the assembly code.

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• Why should "miter" joints be slower than others?

  - by Hanno Fietz

  I'm having a graphics problem on drawing lines in Flash Player, where two lines drawn on top of each other with different thickness don't align properly if I use any other JointStyle than MITER. For pictures of the effect, and for the graphics oriented part of the question, see my post over on doctype. However, there's also a second angle on this problem, which is: why should drawing the "mitered" joints be so much slower than others? This seems to be a problem since at least FP 8, but I couldn't find any detailed info on what the problem might be. Is this just an ordinary bug that didn't get fixed yet, or is there something inherently slower about drawing these joints? For example, they seem to have something to do with square roots, but I seriously lack understanding of what this joint style thing is all about, technically. It just looks like some minor detail a graphic designer might worry about. I'm asking because I'm wondering if I can do something to mitergate, er, mitigate, the problem.

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• How to hash and check for equality of objects with circular references

  - by mfya

  I have a cyclic graph-like structure that is represented by Node objects. A Node is either a scalar value (leaf) or a list of n=1 Nodes (inner node). Because of the possible circular references, I cannot simply use a recursive HashCode() function, that combines the HashCode() of all child nodes: It would end up in an infinite recursion. While the HashCode() part seems at least to be doable by flagging and ignoring already visited nodes, I'm having some troubles to think of a working and efficient algorithm for Equals(). To my surprise I did not find any useful information about this, but I'm sure many smart people have thought about good ways to solve these problems...right? Example (python): A = [ 1, 2, None ]; A[2] = A B = [ 1, 2, None ]; B[2] = B A is equal to B, because it represents exactly the same graph. BTW. This question is not targeted to any specific language, but implementing hashCode() and equals() for the described Node object in Java would be a good practical example.

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• Creating TCP network errors for unit testing

  - by Robert S. Barnes

  I'd like to create various network errors during testing. I'm using the Berkely sockets API directly in C++ on Linux. I'm running a mock server in another thread from within Boost.Test which listens on localhost. For instance, I'd like to create a timeout during connect. So far I've tried not calling accept in my mock server and setting the backlog to 1, then making multiple connections, but all seem to successfully connect. I would think that if there wasn't room in the backlog queue I would at least get a connection refused error if not a timeout. I'd like to do this all programatically if possible, but I'd consider using something external like IPchains to intentionally drop certain packets to certain ports during testing, but I'd need to automate creating and removing rules so I could do it from within my Boost.Test unit tests. I suppose I could mock the various system calls involved, but I'd rather go through a real TCP stack if possible. Ideas?

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• iPhone application build fails with "dyld: Library not loaded: /System/[...]" error? Why?

  - by Andrew J. Brehm

  For my own reasons and not for the app store I am referencing the Apple private framework Apple80211 in an iPhone app. I got the framework from an earlier version of the iPhone SDK. I added the "existing framework", verified that that absolute path to the framework is /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS4.0.sdk/System/Library/PrivateFrameworks/Apple80211.framework and tried to build the app. But the build (to device) fails with the error dyld: Library not loaded: /System/Library/PrivateFrameworks/Apple80211.framework/Apple80211 Referenced from: /var/mobile/Applications/3691587D-87AF-44EA-A505-F73D17F39B3B/iWire2.app/iWire2 Reason: image not found I cannot figure out why Xcode would look for the library in a /System path (instead of using the path given in the frameworks list) or how to change that behaviour. I tried the tricks I found here and elsewhere for similar (and identical) sitiations: Delete the myusername.* files in the xcodeproj bundle Delete the build directory Clean all targets Start new project Result is always the same. How can I add this (or a) framework to an iPhone project AND get Xcode to at least look at the library located where I point to rather than a location in /System?

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• What should be contained in a global Subversion ignore pattern for Visual Studio 2010?

  - by Chris Simmons

  After installing and using Visual Studio 2010, I'm seeing some newer file types (at least with C++ projects ... don't know about the other types) as compared to 2008. e.g. .sdf, .opensdf, which I guess are the replacement for ncb files with Intellisense info stored in SQL Server Compact files? I also notice .log files are generated, which appear to be build logs. Given this, what's safe to add to my global ignore pattern? Off the bat, I'd assume .sdf, .opensdf, but what else?

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• Java technologies for web-development.

  - by Alex

  Hello. I'm PHP-programmer, but I'm extremely interested in learning Java. So I decided to change speciality from PHP to Java. At the moment I have an opportunity to try to make quite simple web-application (it should contain 2-3 forms, several pages with information from the database and authorization module) and also I have a chance to choose any technology I want. Besides I have about 3 months for this task. I've decided to develop site with Java technologies for the purpose of studying. I've already read a book about Java ("Java2 Complete Reference" by P.Naughton) and currently I'm reading "Thinking in Java" by B.Eckel. I clearly understand it's not enough for efficient development, but I want, at least, to try. I would be very appreciated for the advises, which framework (for example) or technology to choose (Spring, Grails etc.) and what primary aspects and technologies of Java should I pay attention to? Thank you in advance.

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• Multiple python scripts sending messages to a single central script

  - by Ipsquiggle

  I have a number of scripts written in Python 2.6 that can be run arbitrarily. I would like to have a single central script that collects the output and displays it in a single log. Ideally it would satisfy these requirements: Every script sends its messages to the same "receiver" for display. If the receiver is not running when the first script tries to send a message, it is started. The receiver can also be launched and ended manually. (Though if ended, it will restart if another script tries to send a message.) The scripts can be run in any order, even simultaneously. Runs on Windows. Multiplatform is better, but at least it needs to work on Windows. I've come across some hints: os.pipe() multiprocess Occupying a port mutex From those pieces, I think I could cobble something together. Just wondering if there is an obviously 'right' way of doing this, or if I could learn from anyone's mistakes.

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• Cache images provided through script

  - by Wim Haanstra

  I have a script, which by using several querystring variables provides an image. I am also using URL rewriting within IIS 7.5. So images have an URL like this: http://mydomain/pictures/ajfhajkfhal/44/thumb.jpg or http://mydomain/pictures/ajfhajkfhal/44.jpg This is rewritten to: http://mydomain/Picture.aspx?group=ajfhajkfhal&id=44&thumb=thumb.jpg or http://mydomain/Picture.aspx?group=ajfhajkfhal&id=44 I added caching rules to IIS to cache JPG images when they are requested. This works with my images that are REAL images on the disk. When images are provided through the script, they are somehow always requested through the script, without being cached. The images do not change that often, so if the cache at least is being kept for 30 minutes (or until file change) that would be best. I am using .NET/C# 4.0 for my website. I tried setting several cache options in C#, but I cant seem to find how to cache these images (client-side), while my static images are cached properly.

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• How to host a naked domain on a CDN?

  - by rjw79

  If I have a domain that I wish to serve "naked" eg http://examp.le/, and efficiently with a CDN, what are my options? The issue is that the CDNs I looked at all want you to use a CNAME so that they can do geo ip lookup. CNAMES are not meant to be served at the same level as other records, and this apparently breaks some dns resolvers. You at least need SOA and MX records at the same level for a naked domain. The only solutions are: having A records in your own dns, thus skipping the geo ip, or finding a cdn who will allow delegation of the whole domain so they can do geo ip things for the A record directly. I've tried googling and can't find any Cdn who offers this. Any ideas? I looked closely at Amazon cloudfront and rackspace cloudfiles. I couldn't work it out for those.

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• Package names - impl v internal

  - by Ben J

  In my time of digging around Java APIs I have come across both impl and internal packages. Up until now I never really thought about the difference - as with all enterprisey Java apps, I figured they just meant that "actual implementation in here; you (API user) should be really using the interface. Go away." A little bit of digging around Stack Overflow seems to suggest that the internal package at least can have some security placed around it. So, what is the difference? I don't think it is a matter of taste because I have seen APIs with both.

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• What is the most suitable for writing a high speed server C, C++ or C# ?

  - by wniroshan

  I'm goint to write a server which does lots of image processing. Server-end processsing is expected to be very tedious. Server will maily have mobile phones as its clients. I am really concerend about speed and effciency. Security is pretty important too. Server will be running on a windows platform. Can anyone tell me what should I use as the language C, C++ or C#? or at least what are the ares that I should be looking at when selecting one of them Thank you.

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• Should the name of my classes begin with 'Q' in Qt?

  - by Venemo

  Hello Everyone, When I first started working with Qt, it was extremely annoying that every class has a name beginning with 'Q', but now I've got used to it. I'm using Qt Creator, and it highlights code quite well. However, it only highlights class names beginning with 'Q'. And it highlights everything beginning with 'Q' even if there is no such type. It doesn't highlight custom class names. That makes me wonder, should I also begin all my class names with 'Q'? Or at least the reusable ones? (I mean, those that I put in a class library, or reuse in another app.) I've seen several places where they named their classes this way. Is it a good thing? I found this page about Qt's naming conventions, but it doesn't deal with this question. Also, I don't understand why Qt doesn't use namespaces.

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• Reference table values in a war against magic numbers

  - by Alex N.

  This question bugged me for years now and can't seem to find good solution still. I working in PHP and Java but it sounds like this maybe language-agnostic :) Say we have a standard status reference table that holds status ids for some kind of entity. Further let's assume the table will have just 5 values, and will remain like this for a long time, maybe edited occasionally with addition of a new status. When you fetch a row and need to see what status it is you have 2 options(as I see it at least) - put it straight ID values(magic numbers that is) or use a named constant. Latter seem much cleaner, the question though is where those named constants should leave? In a model class? In a class that uses this particular constant? Somewhere else?

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• How to Design Programs: An Introduction to Programming and Computing -- teacher guide access

  - by user295683

  Hello -- I'm a biologist switching careers, and trying to learn programming as a result. I stumbled upon the aforementioned book on Amazon, which jived with my liberal arts background. Despite my great satisfaction with the didactic approach, I was frustrated to see that the answers to the exercises are restricted to teachers only. As I am pursuing this endeavor on my own, this restriction dramatically cripples the value of this book. My request to the author's website for access to the answers has not been answered, and I would desperately like to continue with this book. Anyone have any experience dealing with the book's website, or at the very least a torrent of the answers? Otherwise, I suspect I will be relegated to using JavaScript for everything! Thanks!

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• Why jquery.animate on a textarea make the blinking cursor disapears?

  - by Tom S.

  Hello everyone. I have the following code $(document).ready(function() { $("#myTextArea").focus(function() { $("#myTextArea").animate({ "height": "75px"}, "normal"); return false; }); to expand a textbox when it gets focus. The expand occurs, however the blinking cursor disapears, at least in Firefox! Edited: The textarea is still focused, and i can type on it. Why does this happen? Is there a way to show it again? Thanks in advance

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• inheriting scope from a has_many relationship

  - by hb922

  I am using ruby on rails 3.1 and have 2 models, an event and a group. Each event has_many groups, but has to have at least one "master" group, where the column :is_master = true Class Group < ActiveRecord::Base has_many :users belongs_to :event scope :master, where (:is_master => true) end Class Event< ActiveRecord::Base has_many :groups def master_group groups.master end end I want to be able to default all properties of the master group to the event, so for example, event.users.count should be the same as event.master_group.users.count. Is there any way to do something like this? Can I do a has_many :through = master_group? Am I approaching this the wrong way? Thanks!

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• Change update value of property (LINQTOSQL)

  - by Dynde

  Hi... I've got an entity object - Customer, with a property called VATRate. This VATRate is in the form of a decimal (0.25). I wanted to be able to enter a percentage value, and save it in the correct decimal value in the database, so I made this custom property: partial class Customer{ public decimal VatPercent { get{ ... //Get code works fine} set { this.VATRate = (value / 100); } } } And then I just bind this property instead of VATRate in my ASPX editTemplate (formview). This actually works - at least one time, when I debug an update, the value is set correctly one time, and then right after it gets set to the old value. I can't really see why it sets the value twice (and with the old value the second time). Can anyone shed some light on this?

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