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Articles indexed Friday May 28 2010

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  • Rails uniqueness constraint and matching db unique index for null column

    - by Dave
    I have the following in my migration file def self.up create_table :payment_agreements do |t| t.boolean :automatic, :default => true, :null => false t.string :payment_trigger_on_order t.references :supplier t.references :seller t.references :product t.timestamps end end I want to ensure that if a product_id is specified it is unique but I also want to allow null so I have the following in my model: validates :product_id, :uniqueness => true, :allow_nil => true Works great but I should then add an index to the migration file add_index :payment_agreements, :product_id, :unique => true Obviously this will throw an exception when two null values are inserted for product_id. I could just simply omit the index in the migration but then there's the chance that I'll get two PaymentAgreements with the same product_id as shown here: Concurrency and integrity My question is what is the best/most common way to deal with this problem

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  • how to create button in cocos2d?

    - by iPhone Fun
    Hi all, I am new to cocos2d, In that I want to create a button, by touching the same some events should be generated. But I don't know how to make a button in the same. As well as want to save username also. But I am not able to create a text box even. If any one know, kindly help to create both of the things. Thank you in advance.

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  • Krusader on Linux

    - by Guus
    In Krusader you can create a New Network Connection (CTRL-N) How can I save those connections? Now I have to enter all details every time.

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  • Questions about "casting operation" in OOP

    - by rhapsodyn
    When programming, we usually use some type-casting operations. When the casting happens on the objects "on the same level", it feels ok. But when it happens on the ojects "on the different levels"(mainly between father and son), it feels weird. Considering this: Class Son extends Father WhenSon s = (Son)father;, it's absolutely unreasonable. Because a "Son" is not a "Father" anymore, "Son" may grow up with some new properties "Father" doesn't have, the casting operation makes these properties unknown. On the other hand, Father f = (Father)son seems reasonable, but according to LSP "An instance of a derived should be able to replace any instance of its superclass" A "Son" can do anything his "Father" can, so the casting operation seems useless. So can i say that these casting operations are agaisnt OO design principle but necessary?

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  • StreamInsight Licensing

    I cannot help but think that this is currently wrong.  There are two editions of StreamInsight (SI), Premium and Standard.  A link to their differences is here Points to note Developer Edition and Evaluation Edition represent Enterprise Edition in SQL Server but not SI where they represent Datacentre Edition.  Won’t this be confusing when people evaluating SI find that it is not the same animal when they move to Enterprise Edition? If SI Premium is the only thing you want out of the SQL Server box then it is going to be a high cost. The latency rates as well quoted on the site above make Premium Edition essential if you are going to be using this to do Real-Time analytics.

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  • To share a table or not share?

    - by acidzombie24
    Right now on my (beta) site i have a table called user data which stores name, hash(password), ipaddr, sessionkey, email and message number. Now i would like the user to have a profile description, signature, location (optional) and maybe other things. Should i have this in a separate mysql table? or should i share the table? and why?

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  • problem with list return type??

    - by kaushik
    my list has value such as m=[['na','1','2']['ka','31','45']['ra','3','5'] d=0 r=2 t=m[d][r] print t # this is givin number i.e 2 Now when I use this value u=[] u=m[t] I am getting an err msg saying type error list does take str values... i want to use like this how can i convert that t into a integer?? please suggest.. thanks..

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  • UI Testing Tool on linux

    - by Hulk
    Looking for a tool to UI testing on Linux .Platform used for development is django. The idea is that the analysts will capture the tests thru some UI and it will be able to be played back over and over again.

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  • Apache rewriteBase in .htaccess for development subdomains

    - by Das123
    I think I'm missing something and don't think I really understand how rewriteBase works. The problem I have is that I have a production site where the site is in the root directory yet I have my development site in a localhost subdirectory. Eg http://www.sitename.com/ vs http://localhost/sitename/ If I have for example an images folder I want to reference the images from the site root by using the initial slash in the href. Eg Using a relative href (without the initial slash) is not an option. This will work on the production site but the development site is looking for http://localhost/images/imagename.jpg instead of http://localhost/sitename/images/imagename.jpg So I thought all I needed to do was setup the following in my .htaccess file to force the site root to my subdomain within the development environment: Options +FollowSymLinks RewriteEngine On RewriteBase /sitename But this still uses localhost as the site root instead of localhost/sitename. Can anyone please give me some pointers?

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  • How do game trainers change an address in memory that's dynamic?

    - by GameTrainersWTF
    Lets assume I am a game and I have a global int* that contains my health. A game trainer's job is to modify this value to whatever in order to achieve god mode. I've looked up tutorials on game trainers to understand how they work, and the general idea is to use a memory scanner to try and find the address of a certain value. Then modify this address by injecting a dll or whatever. But I made a simple program with a global int* and its address changes every time I run the app, so I don't get how game trainers can hard code these addresses? Or is my example wrong? What am I missing?

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  • How can I store data in a table as a trie? (SQL Server)

    - by Matt
    Hi, To make things easier, the table contains all the words in the English dictionary. What I would like to do is be able to store the data as a trie. This way I can traverse the different branches of the trie and return the most relevant result. First, how do I store the data in the table as a trie? Second, how do I traverse the tree? If it helps at all, the suggestion in this previous question is where this question was sparked from. Please make sure it's SQL we're talking about. I understood the Mike Dunlavey's C implementation because of pointers but can't see how this part (The trie itself) works in SQL. Thanks, Matt

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  • fullCalendar: Implementing a custom event fetcher using event as function

    - by Nick-ACNB
    If I specify a json feed, the events are re-fetched everytime and the fetching time shows the item appearing which causes a delay which is undesirable (at least after initial fetch was done). I am using the latest version from gitHub 1.4.6. The lazyFetching property seems to only work when you change views and you previously fetched for example a month and are drilling down to week/day which is unusable since I only use agendaDay. Here is what I am trying to achieve: $("#calendar").fullCalendar({ events: function(start, end, callback) { $.getJSON( "/GetEvents", { start: start.valueOf() }, function(data, textStatus) { $.each(data, function(i, event) { //Goal here is to only add items that aren't already rendered. if ($("#calendar") .fullCalendar('clientEvents', event.id)=="") $("#calendar").fullCalendar('renderEvent', event, true); }); } ); }); The goal is to use the sticky property in the renderEvent method so that on-screen they aren't re-rendered if they we're previously fetched. I omitted a part where I manually delete those that we're deleted and modify those that we're updated since I am in multi-user settings but you get the point. My issue is that they are fetched once and added. But once I change day and come back, they don't render even if I used sticky... has anyone gotten this error or did I code anything wrong? Also, is this a wrong way to go? I will consider any input. :) Thank you very much.

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  • c# im getting an error

    - by vj4u
    double dval = 1; for (int i = 0; i < Cols; i++) { k = 0; dval = 1; for (int j = Cols - 1; j >= 0; j--) { colIndex = (i + j) % 3; val *= dval[colIndex, k]; k++; } det -= dval; } im getting an error Cannot apply indexing with [] to an expression of type 'double' for dval help its urgent

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  • When does a const return type interfere with template instantiation?

    - by Rimo
    From Herb Sutter's GotW #6 Return-by-value should normally be const for non-builtin return types. ... Note: Lakos (pg. 618) argues against returning const value, and notes that it is redundant for builtins anyway (for example, returning "const int"), which he notes may interfere with template instantiation. While Sutter seems to disagree on whether to return a const value or non-const value when returning an object of a non-built type by value with Lakos, he generally agrees that returning a const value of a built-in type (e.g const int) is not a good idea. While I understand why that is useless because the return value cannot be modified as it is an rvalue, I cannot find an example of how that might interfere with template instantiation. Please give me an example of how having a const qualifier for a return type might interfere with template instantiation.

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  • Virtual camera/direct show filter for network stream

    - by Jeje
    Hi guys, i'm working with Flash Live Encoder. It's using camera for streaming video. Support forum say's that i can create custom direct show filter and stream data that i need. I cann't understand how direct show filter will display in the source list of the live encoder. I've tryed to use some commercial virtual camera and it work's fine, but it cann't use source from network stream. Summary. I have a several network streams. I think that i must to create virtual camera for each one. But if i find examples with direct show filter on C#, i cann't find for virtual camera.

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