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  • Devise and cancan gems: has_many association

    - by tiktak
    I use devise and cancan gems and have simple model association: user has_many subscriptions, subscription belongs_to :user. Have following SubscriptionsController: class SubscriptionsController < ApplicationController load_and_authorize_resource :user load_and_authorize_resource :subscription, through: :user before_filter :authenticate_user! def index @subscriptions = @user.subscriptions.paginate(:page => params[:page]).order(:created_at) end #other actions end And Cancan Ability.rb: class Ability include CanCan::Ability def initialize(user) user ||=User.new can [:index, :show], [Edition, Kind] if user.admin? can :manage, :all elsif user.id can [:read, :create, :destroy, :pay], Subscription, user_id: user.id can [:delete_from_cart, :add_to_cart, :cart], User, id: user.id end end end The problem is that i cannot use subscriptions actions as a user but can as a admin. And have no problems with UsersController. When i delete following lines from SubscriptionsController: load_and_authorize_resource :user load_and_authorize_resource :subscription, through: :user before_filter :authenticate_user! Have no problems at all. So the issue in these lines or in Ability.rb. Any suggestions?

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  • File Encrypt/Decrypt under load?

    - by chopps
    I found an interesting article about encrypting and decrypting files but since it uses a file.dat to store the key this will run into problems when theres alot of users on the site dealing with alot of files. http://www.codeproject.com/KB/security/VernamEncryption.aspx?display=Print Should a new file be created every time a file needs decrypting or would there be a better way to do this? UPDATE: Here is what im using to avoid the locking problems. using (Mutex FileLock = new Mutex(true, System.Guid.NewGuid().ToString())) { try { FileLock.WaitOne(); using (FileStream fs = new FileStream(keyFile, FileMode.Open)) { keyBytes = new byte[fs.Length]; fs.Read(keyBytes, 0, keyBytes.Length); } } catch (Exception ex) { EventLog.LogEvent(ex); } finally { FileLock.ReleaseMutex(); } } I tested it on 1000 TIFFs doing both encryption and decryption without any errors.

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  • Should class IOException in Java have been an unchecked RuntimeException?

    - by Derek Mahar
    Do you agree that the designers of Java class java.io.IOException should have made it an unchecked run-time exception derived from java.lang.RuntimeException instead of a checked exception derived only from java.lang.Exception? I think that class IOException should have been an unchecked exception because there is little that an application can do to resolve problems like file system errors. However, in When You Can't Throw An Exception, Elliotte Rusty Harold claims that most I/O errors are transient and so you can retry an I/O operation several times before giving up: For instance, an IOComparator might not take an I/O error lying down, but — because many I/O problems are transient — you can retry a few times, as shown in Listing 7: Is this generally the case? Can a Java application correct I/O errors or wait for the system to recover? If so, then it is reasonable for IOException to be checked, but if it is not the case, then IOException should be unchecked so that business logic can delegate handling of this exception to a separate system error handler.

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  • What are some useful SQL statements that should be known by all developers who may touch the Back en

    - by Jian Lin
    What are some useful SQL statements that should be known by all developers who may touch the Back end side of the project? (Update: just like in algorithm, we know there are sorting problems, shuffling problems, and we know some solutions to them. This question is aiming at the same thing). For example, ones I can think of are: Get a list of Employees and their boss. Or one with the employee's salary greater than the boss. (Self-join) Get a list of the most popular Classes registered by students, from the greatest number to the smallest. (Count, group by, order by) Get a list of Classes that are not registered by any students. (Outer join and check whether the match is NULL, or by Get from Classes table, all ClassIDs which are NOT IN (a subquery to get all ClassIDs from the Registrations table)) Are there some SQL statements that should be under the sleeve of all developers that might touch back end data?

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  • Cuda program results are always zero in HW, correct in EMU??

    - by Orion Nebula
    Hi all! I am having a weird problem .. I have written a CUDA code which executes correctly in emulation and all results show up.. however, when executed on hardware "G210" .. the results in the result memory are always 0 I am passing two vectors to the kernel, one with random variables the other is initialized to zero, the code copies the first vector to shared memory, does some swapping and other operations and then writes back the results on the second vector (the one with the initial 0's) I am using double precision, the -arch sm13 flag is used, all memory allocation also use sizeof(double) .. I have checked if the kernel is invoked, it does .. so no problems here .. the cudaMemCpy has no problems .. what could be the problem .. :( why would it work in emulation but not on HW I am quite confused .. any ideas?

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  • manage.py runserver not working

    - by Dan Appleyard
    I am new to django and python in general, so pardon me for any simple mistakes I may be doing. I am trying to setup my first django project on my local windows vista machine. I have created the project successfully with no problems. The issue I am coming across is when my settings.py has values for my database keys, the manage.py runserver command is failing. If I have values in settings before I run the command, as soon as I run it I get errors. If I have already run the command and the server is running, as soon as I edit the settings file with values, the errors show up in my still open command prompt. The inner most exception seems to "Error loading MySQLdb module: No module named MYSQLdb". If I leave the settings.py blank, the command executes with no problems. Any advice would be greatly appreciated! Thanks

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  • Programming language for fast calculations with big integers

    - by sub
    I'm doing Project Euler problems at the moment and I can solve most of them using my own programming language which uses direct C++ integers (so they are bound to 2^32 on my machine). However, at times there are problems which require me to work with very high numbers, I can't do that with native integers. So I implemented a BigInt library in my language which unfortunately gets extremely slow at times. Is there a programming language suitable for very efficient handling of big numbers? I mean that I want to do the things I could do in other programming languages with it (variables, loops, etc.), but in a faster way. If you have got tips for workarounds of the 2^32 limit in my language/C++/other languages, please tell me too!

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  • Managing StringBuilder Resources in C#

    - by Jim Fell
    Hello. My C# (.NET 2.0) application has a StringBuilder variable with a capacity of 2.5MB. Obviously, I do not want to copy such a large buffer to a larger buffer space every time it fills. By that point, there is so much data in the buffer anyways, removing the older data is a viable option. Can anyone see any obvious problems with how I'm doing this (i.e. am I introducing more performance problems than I'm solving), or does it look okay? tText_c = new StringBuilder(2500000, 2500000); private void AppendToText(string text) { if (tText_c.Length * 100 / tText_c.Capacity > 95) { tText_c.Remove(0, tText_c.Length / 2); } tText_c.Append(text); } Thanks.

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  • Help debugging Apache, Passenger and Rails problem

    - by Matt Dressel
    We have an environment running that uses Apache, Passenger and rails. The system is handling most request normally, yet certain requests do not make it to the rails application. For instance, a request to /books is successful, but /books/1 hits apache and passenger, but does not even make it to rails. We set the apache log level to debug and the passenger log level to 3 so that we could monitor all incoming requests. We could see each request coming through and even the /books/1 request is being handled by passenger. But it never gets to rails. Is there any way to determine where the request goes between Passenger and rails or where debugging information might live? Has anyone ever seen any problems with passenger spawning or queuing? We have spawning set to conservative. Also, we have had some permission/ownership problems in the past, so I am not ruling this out yet. Thanks in advance

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  • Efficient algorithm to distribute work?

    - by Zwei Steinen
    It's a bit complicated to explain but here we go. We have problems like this (code is pseudo-code, and is only for illustrating the problem. Sorry it's in java. If you don't understand, I'd be glad to explain.). class Problem { final Set<Integer> allSectionIds = { 1,2,4,6,7,8,10 }; final Data data = //Some data } And a subproblem is: class SubProblem { final Set<Integer> targetedSectionIds; final Data data; SubProblem(Set<Integer> targetedSectionsIds, Data data){ this.targetedSectionIds = targetedSectionIds; this.data = data; } } Work will look like this, then. class Work implements Runnable { final Set<Section> subSections; final Data data; final Result result; Work(Set<Section> subSections, Data data) { this.sections = SubSections; this.data = data; } @Override public void run(){ for(Section section : subSections){ result.addUp(compute(data, section)); } } } Now we have instances of 'Worker', that have their own state sections I have. class Worker implements ExecutorService { final Map<Integer,Section> sectionsIHave; { sectionsIHave = {1:section1, 5:section5, 8:section8 }; } final ExecutorService executor = //some executor. @Override public void execute(SubProblem problem){ Set<Section> sectionsNeeded = fetchSections(problem.targetedSectionIds); super.execute(new Work(sectionsNeeded, problem.data); } } phew. So, we have a lot of Problems and Workers are constantly asking for more SubProblems. My task is to break up Problems into SubProblem and give it to them. The difficulty is however, that I have to later collect all the results for the SubProblems and merge (reduce) them into a Result for the whole Problem. This is however, costly, so I want to give the workers "chunks" that are as big as possible (has as many targetedSections as possible). It doesn't have to be perfect (mathematically as efficient as possible or something). I mean, I guess that it is impossible to have a perfect solution, because you can't predict how long each computation will take, etc.. But is there a good heuristic solution for this? Or maybe some resources I can read up before I go into designing? Any advice is highly appreciated!

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  • What are some useful SQL statements / usage patterns that should be known by all developers who may

    - by Jian Lin
    What are some useful SQL statements that should be known by all developers who may touch the Back end side of the project? (Update: just like in algorithm, we know there are sorting problems, shuffling problems, and we know some solutions to them. This question is aiming at the same thing). For example, ones I can think of are: Get a list of Employees and their boss. Or one with the employee's salary greater than the boss. (Self-join) Get a list of the most popular Classes registered by students, from the greatest number to the smallest. (Count, group by, order by) Get a list of Classes that are not registered by any students. (Outer join and check whether the match is NULL, or by Get from Classes table, all ClassIDs which are NOT IN (a subquery to get all ClassIDs from the Registrations table)) Are there some SQL statements that should be under the sleeve of all developers that might touch back end data?

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  • How to Create VBA Add-In with Shared Codes for All Excels?

    - by StanFish
    I'm writing VBA codes for multiple Excel spreadsheets, which will be shared with others from time to time. At some point I find there are lots of duplications in my works. So I want to find a way to share codes in a sort of Excel add-in, like the .xla file. But when I tried to save the Excel file containing shared codes as .xla file, I got some problems: The file cannot be edit anymore after I save it in the default add-in folder If I move the .xls file to a folder other than the add-in folder, and open it directly - I cannot use its classes - which creates problems for sharing the codes Any ideas to create add-ins in a flexible and powerful way please? Thanks a lot for the help

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  • ClickOnce deployment with VS2008 - prerequisites not installing on Windows 7 (only)

    - by dataft
    I have a VS2008 clickonce application with a custom prerequiste, which I install with the bootstrapper. When deployed online, the prerequisite is downloaded and installed fine. No problems. When deployed via CD to a Windows XP machine, also fine as above. No problems. However, when deployed via CD to a Windows 7 machine: the prerequisite is downloaded - good then the user is asked for permission to the run the file - good then the installation of the prerequiste is just SKIPPED - bad and the ClickOnce application installation begins without the prerequisite - bad Has anyone encountered this weird behaviour? I cannot find a solution anywhere.

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  • How do I make a background thread in Java that allows the main application to exit completely? This

    - by Bob
    I have a Java application that creates a new thread to do some work. I can launch the new thread with no problems. When the "main" program terminates, I want the thread I created to keep running - which it does... But the problem is, when I run the main application from Eclipse or from Ant under Windows, control doesn't return unless the background process is killed. If I fork the main java process in ant, I want control to return to ant once the main thread is done with its work... But as it is, ant continues to wait until both the main process and the created thread are both terminated. How do I launch the thread in the background such that control will return to ant when the "main" application is finished? (By the way, when I run the same application under Linux, I am able to do this with no problems).

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  • Tomcat servlet-api.jar problem

    - by CitadelCSCadet
    I am running a web application using Tomcat and Java Servlets, JSP's, etc. I am aware that in order to use Servlets, it is dependent on the Servlet-api.jar file. Initially I placed this jar file in the WEB-INF/lib/ directory. This has worked fine for me for months during the developmental phase. When we put the application onto the server space we are using, we started seeing wierd problems showing up in the Catalina.out file telling us that there was dependency problems with the servlet-api.jar file. I am aware that tomcat has this jar file in its container, and that I should remove it from the WEB-INF/lib/ directory. I have tried this and it does not work. What do I have to do when I remove this jar file from the local files and allow it to depend on tomcats servlet-api.jar file.

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  • a completely decoupled OO system ?

    - by shrini1000
    To make an OO system as decoupled as possible, I'm thinking of the following approach: 1) we run an RMI/directory like service where objects can register and discover each other. They talk to this service through an interface 2) we run a messaging service to which objects can publish messages, and register subscription callbacks. Again, this happens through interfaces 3) when object A wants to invoke a method on object B, it discovers the target object's unique identity through #1 above, and publishes a message on the message service for object B 4) message services invokes B's callback to give it the message 5) B processes the request and sends the response for A on message service 6) A's callback is called and it gets the response. I feel this system is as decoupled as practically possible, but it has the following problems: 1) communication is typically asynchronous 2) hence it's non real time 3) the system as a whole is less efficient. Are there any other practical problems where this design obviously won't be applicable ? What are your thoughts on this design in general ?

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  • Calling javascript function with arguments using JSNI

    - by jav_000
    I'm trying to integrate Mixpanel with GWT, but I have problems calling an event with a property and one value. My function to track an simple event (without values): public native void trackEvent(String eventName)/*-{ $wnd.mixpanel.track(eventName); }-*/; It works. But when I want to add some properties and values, it doesn't work properly: public native void trackComplexEvent(String eventName, String property, String value)/*-{ $wnd.mixpanel.track(eventName, {property:value}); }-*/; I have 2 problems with this: 1) Mixpanel says the property name is: "property"(yes, the name of the variable that I'm passing, not the value). 2) Mixpanel says the value is:undefined An example from mixpanel web is: mixpanel.track("Video Play", {"age": 13, "gender": "male"}); So, I guess the problem is I'm doing a wrong call or with wrong type of arguments.

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  • MySQL IDE recommendation?

    - by Maxim Veksler
    Hello, I've been wondering what you guys are using to write,debug,test your SQL queries there days? The requirements are quite simple: Auto-complete Syntax Highlighting SQL Hisotry Good UI There are some tools which are common for this task, each with his own problems. To name a few Mysql Query Browser MySQL Workbench (GA?, Beta?) Eclipse Database development perspective Oracle SQL Developer with Connector/J I won't go into why none of them is perfect, trust me they all have their problems. So, what are you guys using?

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  • CVS in cmd/gui works only the third time I run a command.

    - by Somebody still uses you MS-DOS
    I'm using CVS in the command line. I'm in my repository folder. When I call a CVS command, I get... cvs [log aborted]: unrecognized auth response from localhost: -f [pserver aborted]: /opt/cvs/XXXXXX: no such repository ...2 times. The third time I run the command, it works with no problems. I tried to use a GUI client (CrossVC) and the same problem occurs. I tried inside gVim and Vim using VCSCommand and I'm having the same issues as well. I've tested with different times between each command, but I still have the same problems. I'm using a CVS configuration with stunnel. Why am I having problem with this setup? Why every time just the third time that I try to run the command that actually works?

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  • APC not recommended for production?

    - by solomongaby
    I have started having problems with my VPS in the way that it would faill to serve the pages on all the websites. It just showed a blank page, or offered to download the php file ( luckily the code was not in the download file :) ). The server was still running, but this seemed to be a problem with PHP, since i could login into WHM. If i did a apache restart, the sites would work again. After some talks with the server support they told me this is a problem with the APC extension witch they considered to be old and not recommended for production servers. So they removed it for now, to see if the same kind of fails would continue to appear. I haven't read anywhere that APC could have some problems or that its not always recommended to use, quite the contrary ... everywhere people are saying to always use it. The APC extension was installed ssh and is the latest version. Edit: They also dont recomend MemCache and say that a more reliable extension would be eAccelerator

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  • Have you ever derived a programming solution from nature?

    - by Ryu
    When you step back and look at ... the nature of animals, insects, plants and the problems they have organically solved perhaps even the nature and balance of the universe Have you ever been able to solve a problem by deriving an approach from nature? I've heard of Ant Colony Algorithms being able to optimize supply chain amongst other things. Also Fractal's being the "geometry of nature" have been applied to a wide range of problems. Now that spring is here again and the world is coming back to life I'm wondering if anybody has some experiences they can share. Thanks PS I would recommend watching the "Hunting the Hidden Dimension" Nova episode on fractals.

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  • How to handle recurring execution?

    - by ShaneC
    I am trying to validate the solution I came up for what I think is a fairly typical problem. I have a service running and every 10 minutes it should do something. I've ended up with the following: private bool isRunning = true; public void Execute() { while(isRunning) { if(isRunning) { DoSomething(); m_AutoResetEvent.WaitOne(new Timespan(0, 10, 0)); } } } public void Stop() { isRunning = false; m_AutoResetEvent.Set(); } The immediate potential problems I can see is that I'm not doing any sort of locking around the isRunning modification in Stop() which gets called by another thread but I'm not sure I really need to? The worst that I think could happen is that it runs one extra cycle. Beyond that are there any obvious problems with this code? Is there a better way to solve this problem that I'm unaware of?

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  • Google Pie Chart and Bar Chart (both Interactive) not showing labels.

    - by iRubens
    I'm trying to put Google's BarChart and PieChart both the client side version, and i'm experiencing some problems with the labels over the pie and the labels on the left of the vertical axis (of the bar chart). I checked the code a lot of times and it seems to be like that you can see in the examples. I've tried the same page on Firefox and Chrome and it shows the labels without problems. If i try the examples on IE8 the labels are shown but not in my page. Sincerely I've not any idea where to start to fix this thing. Someone can help me or give me an advice? Thanks in advance.

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  • QLocale, what is the scope of the global QLocale::setDefault()?

    - by ALoopingIcon
    Problem: I have a QT based multiplatform (win,mac,*nix) application that parses ascii files containing decimal numbers. parsing is done using a variety of different code pieces that use anything from qt string stuff, c++ stdin, oldstyle scanf, etc. ascii files have always the '.' (dot) as separated decimal (e.g. in the file to be parsed 1/10 is written 0.1 as standard in many countries). people using the application within a OS localized for using comma separated decimal encounter a lot of problems (e.g. for french users scanf expect to find 0,1 as a valid textual representation of 1/10 and if they find 0.1 scanf will parse it as 0) How can I be sure that the OS Locale indication of how decimal point has to be written is always ignored? Is it safe assuming that adding QLocale::setDefault(QLocale(QLocale::English,QLocale::UnitedStates)); is enough to get rid of all these problems? Any suggestion for portable ways of setting the locale globally?

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