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  • C++ Storing variables and inheritance

    - by Kaa
    Hello Everyone, Here is my situation: I have an event driven system, where all my handlers are derived from IHandler class, and implement an onEvent(const Event &event) method. Now, Event is a base class for all events and contains only the enumerated event type. All actual events are derived from it, including the EventKey event, which has 2 fields: (uchar) keyCode and (bool)isDown. Here's the interesting part: I generate an EventKey event using the following syntax: Event evt = EventKey(15, true); and I ship it to the handlers: EventDispatch::sendEvent(evt); // void EventDispatch::sendEvent(const Event &event); (EventDispatch contains a linked list of IHandlers and calls their onEvent(const Event &event) method with the parameter containing the sent event. Now the actual question: Say I want my handlers to poll the events in a queue of type Event, how do I do that? x Dynamic pointers with reference counting sound like too big of a solution. x Making copies is more difficult than it sounds, since I'm only receiving a reference to a base type, therefore each time I would need to check the type of event, upcast to EventKey and then make a copy to store in a queue. Sounds like the only solution - but is unpleasant since I would need to know every single type of event and would have to check that for every event received - sounds like a bad plan. x I could allocate the events dynamically and then send around pointers to those events, enqueue them in the array if wanted - but other than having reference counting - how would I be able to keep track of that memory? Do you know any way to implement a very light reference counter that wouldn't interfere with the user? What do you think would be a good solution to this design? I thank everyone in advance for your time. Sincerely, Kaa

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  • Migrate Data and Schema from MySQL to SQL Server

    - by colithium
    Are there any free solutions for automatically migrating a database from MySQL to SQL Server Server that "just works"? I've been attempting this simple (at least I thought so) task all day now. I've tried: SQL Server Management Studio's Import Data feature Create an empty database Tasks - Import Data... .NET Framework Data Provider for Odbc Valid DSN (verified it connects) Copy data from one or more tables or views Check 1 VERY simple table Click Preview Get Error: The preview data could not be retrieved. ADDITIONAL INFORMATION: ERROR [42000] [MySQL][ODBC 5.1 Driver][mysqld-5.1.45-community]You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '"table_name"' at line 1 (myodbc5.dll) A similar error occurs if I go through the rest of the wizard and perform the operation. The failed step is "Setting Source Connection" the error refers to retrieving column information and then lists the above error. It can retrieve column information just fine when I modify column mappings so I really don't know what the issue is. I've also tried getting various MySql tools to output ddl statements that SQL Server understand but haven't succeeded. I've tried with MySQL v5.1.11 to SQL Server 2005 and with MySQL v5.1.45 to SQL Server 2008 (with ODBC drivers 3.51.27.00 and 5.01.06.00 respectively)

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  • How to handle array element between int and Integer

    - by masato-san
    First, it is long post so if you need clarification please let me know. I'm new to Java and having difficulty deciding whether I should use int[] or Integer[]. I wrote a function that find odd_number from int[] array. public int[] find_odd(int[] arr) { int[] result = new int[arr.length]; for(int i=0; i<arr.length; i++) { if(arr[i] % 2 != 0) { //System.out.println(arr[i]); result[i] = arr[i]; } } return result; } Then, when I pass the int[] array consisting of some integer like below: int[] myArray = {-1, 0, 1, 2, 3}; int[] result = find_odd(myArray); The array "result" contains: 0, -1, 0, 1, 0, 3 Because in Java you have to define the size of array first, and empty int[] array element is 0 not null. So when I want to test the find_odd() function and expect the array to have odd numbers (which it does) only, it throws the error because the array also includes 0s representing "empty cell" as shown above. My test code: public void testFindOddPassValidIntArray() { int[] arr = {-2, -1, 0, 1, 3}; int[] result = findOddObj.find_odd(arr); //check if return array only contain odd number for(int i=0; i<result.length; i++) { if(result[i] != null) { assert is_odd(result[i]) : result[i]; } } } So, my question is should I use int[] array and add check for 0 element in my test like: if(result[i] != 0) { assert is_odd(result[i] : result[i] } But in this case, if find_odd() function is broken and returning 0 by miscalculation, I can't catch it because my test code would only assume that 0 is empty cell. OR should I use Integer[] array whose default is null? How do people deal with this kind of situation?

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  • Whose fault is a NullReferenceException?

    - by stefan.at.wpf
    I'm currently working on a class which exposes an internal List through a property. The List shall and can be modified. The problem is, entries in the internal list could be set to null from outside the class. My code actually looks like this: class ClassWithList { List<object> _list = new List<object>(); // get accessor, which however returns the reference to the list, // therefore the list can be modified (this is intended) public List<object> Data { get { return _list; } } private void doSomeWorkWithTheList() { foreach(object obj in _list) // do some work with the objects in the list without checking for null. } } So now in the doSomeWorkWithTheList() I could always check whether the current list entry is null or I could just asume that the person using this class doesn't have the great idea to set entries to null. So finally the questions end up in: Whose fault is a NullReferenceException in this case? Is it the fault of the class developer not checking everything for null (which would make code generally - not only in this class - more complex) or is it the fault of the user of this class, as setting a List entry to null doesn't really make sense? I'd tend to generally not check values for null except in some really special cases. Is this a bad style or de facto standard / standard in praxis? I know there's probably no ultimate answer for this, I'm just missing enough experience for such thing and therefore wondering what other developers think about such cases and want to hear what's done in reality about checking null (or not).

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  • Delphi: How to avoid EIntOverflow underflow when subtracting?

    - by Ian Boyd
    Microsoft already says, in the documentation for GetTickCount, that you could never compare tick counts to check if an interval has passed. e.g.: Incorrect (pseudo-code): DWORD endTime = GetTickCount + 10000; //10 s from now ... if (GetTickCount > endTime) break; The above code is bad because it is suceptable to rollover of the tick counter. For example, assume that the clock is near the end of it's range: endTime = 0xfffffe00 + 10000 = 0x00002510; //9,488 decimal Then you perform your check: if (GetTickCount > endTime) Which is satisfied immediatly, since GetTickCount is larger than endTime: if (0xfffffe01 > 0x00002510) The solution Instead you should always subtract the two time intervals: DWORD startTime = GetTickCount; ... if (GetTickCount - startTime) > 10000 //if it's been 10 seconds break; Looking at the same math: if (GetTickCount - startTime) > 10000 if (0xfffffe01 - 0xfffffe00) > 10000 if (1 > 10000) Which is all well and good in C/C++, where the compiler behaves a certain way. But what about Delphi? But when i perform the same math in Delphi, with overflow checking on ({Q+}, {$OVERFLOWCHECKS ON}), the subtraction of the two tick counts generates an EIntOverflow exception when the TickCount rolls over: if (0x00000100 - 0xffffff00) > 10000 0x00000100 - 0xffffff00 = 0x00000200 What is the intended solution for this problem? Edit: i've tried to temporarily turn off OVERFLOWCHECKS: {$OVERFLOWCHECKS OFF}] delta = GetTickCount - startTime; {$OVERFLOWCHECKS ON} But the subtraction still throws an EIntOverflow exception. Is there a better solution, involving casts and larger intermediate variable types?

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  • has anyone produced an in-memory GIT repository?

    - by Andrew Matthews
    I would like to be able to take advantage of the benefits of GIT (and its workflows), but without the cost of disk access - I just would like to leverage the distributed revision control capabilities of GIT to produce something like a hybrid of memcached and GIT. (preferably in .NET) Is there such a beast out there?

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  • Lightweight HTTP application/server for static content

    - by PartlyCloudy
    Hi, I am in need of a scalable and performant HTTP application/server that will be used for static file serving/uploading. So I only need support for GET and PUT operations. However, there are a few extra features that I need: Custom authentication: I need to check credentials against a database for each request. Thus I must be able to integrate propietary database interaction. Support for signed access keys: The access to resources via PUT should be signed using a key like http://uri/?key=foo The key then contains information about the request like md5(user + path + secret) which allows me to block unwanted requests. The application/server should allow me to check for this. Performance: I'd like to avoid piping content as much as possible. Otherwise the whole application could be implemented in Perl/etc. in a few lines as CGI. Perlbal (in webserver mode) looks nice, however the single-threaded model does not fit with my database lookup and it does also not support query strings. Lighttp/Nginx/… have some modules for these tasks, however it is not feasible putting everything together without ending up writing own extensions/modules. So how would you solve this? Are there other leightweight webservers available for this? Should I implement an application inside of a webserver (i.e. CGI). How can I avoid/speed up piping content between the webserver and my application. Thanks in advance!

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  • Sql compression and backing up in sql server 2005

    - by cagin
    Hi there I want to backup my database with compression. This is my code : BACKUP DATABASE dbbbb TO DISK = N'C:\\dbbb.bak' WITH COMPRESSION this running correctly in Sql Server 2008. But my server has Sql Server 2005 and COMPRESSION is not a recognized BACKUP option in 2005. How can i compress my backup in 2005 Thank you for your helps.

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  • directory resource does not create directory

    - by Dan Tenenbaum
    I have a Vagrantfile that provisions a VM by running a chef recipe. The first resource in the chef recipe is: directory "/downloads" do owner "root" group "root" mode "0755" action :create end # check that it worked: raise "/downloads doesn't exist!" unless File.exists? "/downloads" When I run this at work, it works fine. When I run it at home, it fails, the exception is raised when I check to see if /downloads exists. I'm not sure why this is happening. I would expect it to behave identically, since the underlying Vagrant box is the same both at work and at home. I am a chef newb so perhaps there is something I am not understanding about the order in which the resources are run within my recipe? I would expect them to run in sequential order... I also tried putting a notifies call inside the directory block, where I call another execute block :immediately. That works, but inside the second execute block I test to see whether /downloads has been created and it hasn't. Clearly I'm missing something very basic.

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  • In Perl, how can I wait for threads to end in parallel?

    - by Pmarcoen
    I have a Perl script that launches 2 threads,one for each processor. I need it to wait for a thread to end, if one thread ends a new one is spawned. It seems that the join method blocks the rest of the program, therefore the second thread can't end until everything the first thread does is done which sort of defeats its purpose. I tried the is_joinable method but that doesn't seem to do it either. Here is some of my code : use threads; use threads::shared; @file_list = @ARGV; #Our file list $nofiles = $#file_list + 1; #Real number of files $currfile = 1; #Current number of file to process my %MSG : shared; #shared hash $thr0 = threads->new(\&process, shift(@file_list)); $currfile++; $thr1 = threads->new(\&process, shift(@file_list)); $currfile++; while(1){ if ($thr0->is_joinable()) { $thr0->join; #check if there are files left to process if($currfile <= $nofiles){ $thr0 = threads->new(\&process, shift(@file_list)); $currfile++; } } if ($thr1->is_joinable()) { $thr1->join; #check if there are files left to process if($currfile <= $nofiles){ $thr1 = threads->new(\&process, shift(@file_list)); $currfile++; } } } sub process{ print "Opening $currfile of $nofiles\n"; #do some stuff if(some condition){ lock(%MSG); #write stuff to hash } print "Closing $currfile of $nofiles\n"; } The output of this is : Opening 1 of 4 Opening 2 of 4 Closing 1 of 4 Opening 3 of 4 Closing 3 of 4 Opening 4 of 4 Closing 2 of 4 Closing 4 of 4

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  • how we can save a file as temporary basis

    - by SunilRai86
    how we can save a file as temporary basis i have a xml file it is in encrypted mode i want to decrypt it .but i want it doesn't save on disk rather it save on flash memory. after decryption i have to read values and then it should destroy(decrypted xml file).

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  • Acquiring drive names (as opposed to drive letters) in Java

    - by Mattijs
    Hi, On my Windows machine, my main hard drive has the letter C: and the name "Local disk". To list the drive letters in Java on Windows, the File object has the static listRoots() method. But I can't find a way to acquire the drive names (as opposed to the drive letters) on Windows. Has anyone tried this before? Thanks, Mattijs

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  • Read files via php

    - by Koka
    You all know about restrictions that exist in shared environment, so with that in mind, please suggest me a php function or something with the help of which I could stream my videos and other files. I have a lot of videos on the server, unlimited bandwidth and disk space, but I am limited in ram and cpu.

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  • jQuery ajax returns

    - by Tom
    I think this will be some obvious problem, but I cannot figure it out. I hope someone can help me. So I have a slider with 3 slides - Intro, Question, Submit Now I want to make sure that if the question is answered wrong people cannot slide to Submit. The function to move slide is like this: function changeSlide(slide){ // In case current slide is question check the answer if (jQuery('.modalSteps li.current',base).hasClass('questionStep')){ checkAnswer(jQuery('input[name="question_id"]',base).val(), jQuery('input[name="answer"]:checked',base).val()); } jQuery('.modalSteps li.current',base).fadeOut('fast',function(){ jQuery(this).removeClass('current'); jQuery(slide).fadeIn('fast',function(){ jQuery(slide).addClass('current'); }); }); // In case the new slide is question, load the question if (jQuery(slide).hasClass('questionStep')){ var country = jQuery('input[name="country"]:checked',base).val(); loadQuestion(country); } } Now as you can see on first lines, I am calling function checkAnswer, which takes id of question and id of answer and pass it to the AJAX call. function checkAnswer(question, answer){ jQuery.ajax({ url: window.base_url+'ajax/check_answer/'+question+'/'+answer+'/', success: function(data){ if (!data.success){ jQuery('.question',base).html(data.message); } } }); } The problem i am having is that I cannot say if(checkAnswer(...)){} Because of Ajax it always returns false or undefined. What I need is something like this: function changeSlide(slide){ // In case current slide is question check the answer if (jQuery('.modalSteps li.current',base).hasClass('questionStep')){ if (!checkAnswer(jQuery('input[name="question_id"]',base).val(), jQuery('input[name="answer"]:checked',base).val())){ return false; } } ... So it will prevent the slide from moving on. Now when Im thinking about it, I will probably have slide like "Wrong answer" so I could just move the slide there, but I would like to see the first solution anyway. Thank you for tips

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  • Sharing same properties of ViewController for iPhone Stroryboard and iPad Story Board

    - by Ruhul Amin
    I'm developing a universal application. in the first view, I have the login screen for the user. In iPhone storyBoard, I have added 2 text field and one button( login check). I have added properties in ViewController.h file by dragging those objects(Ctrl key + Dragg) to .h file. I have added code for login check and it is working fine for iPhone. This is the code in ViewController.h @property (strong, nonatomic) IBOutlet UITextField *txtUserId; @property (strong, nonatomic) IBOutlet UITextField *txtUserPwd; @property (strong, nonatomic) IBOutlet UIButton *btnLogin; In the iPad storyBoard, I have added 2 text field( userid and password) and i button for login. So now, I want to bind those objects with the veriable which I declared already in ViewController.h file in case of iPhone. My questions: 1. What is the right way to bind properties for both storyboard? 2. Am I on the right direction or should I think in a different way to do it? I am new with iPhone development. Please help. Thanks. --Amin

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  • Update on: How to model random non-overlapping spheres of non-uniform size in a cube using Matlab?

    - by user3838079
    I am trying to use MATLAB for generating random locations for non-uniform size spheres (non-overlapping) in a cube. The for loop in the code below never seems to end. I don't know what am missing in the code. I have ran the code for no. of spheres (n) = 10; dims = [ 10 10 10 ] function [ c r ] = randomSphere( dims ) % creating one sphere at random inside [0..dims(1)]x[0..dims(2)]x... % radius and center coordinates are sampled from a uniform distribution % over the relevant domain. % output: c - center of sphere (vector cx, cy,... ) % r - radius of sphere (scalar) r = rand(1); % you might want to scale this w.r.t dims or other consideration c = r + rand( size(dims) )./( dims - 2*r ); % make sure sphere does not exceed boundaries function ovlp = nonOverlapping( centers, rads ) % check if several spheres with centers and rads overlap or not ovlp = false; if numel( rads ) == 1 return; % nothing to check for a single sphere end dst = sqrt( sum( bsxfun( @minus, permute( centers, [1 3 2] ),... permute( centers, [3 1 2] ) ).^2, 3) ); ovlp = dst >= bsxfun( @plus, rads, rads.' ); %' all distances must be smaller than r1+r2 ovlp = any( ovlp(:) ); % all must not overlap function [centers rads] = sampleSpheres( dims, n ) % dims is assumed to be a row vector of size 1-by-ndim % preallocate ndim = numel(dims); centers = zeros( n, ndim ); rads = zeros( n, 1 ); ii = 1; while ii <= n [centers(ii,:), rads(ii) ] = randomSphere( dims ); if nonOverlapping( centers(1:ii,:), rads(1:ii) ) ii = ii + 1; % accept and move on end end

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  • cant open device

    - by yoavstr
    I have a little problem. I install this module into my kernel and its written under /proc When I try to open() it from user mode I get the following message: "Can't open device file: my_dev" static int module_permission(struct inode *inode, int op, struct nameidata *foo) { //if its write if ((op == 2)&&(writer == DOESNT_EXIST)){ writer = EXIST ; return 0; } //if its read if (op == 4 ){ numOfReaders++; return 0; } return -EACCES; } int procfs_open(struct inode *inode, struct file *file) { try_module_get(THIS_MODULE); return 0; } static struct file_operations File_Ops_4_Our_Proc_File = { .read = procfs_read, .write = procfs_write, .open = procfs_open, .release = procfs_close, }; static struct inode_operations Inode_Ops_4_Our_Proc_File = { .permission = module_permission, /* check for permissions */ }; int init_module() { /* create the /proc file */ Our_Proc_File = create_proc_entry(PROC_ENTRY_FILENAME, 0644, NULL); /* check if the /proc file was created successfuly */ if (Our_Proc_File == NULL){ printk(KERN_ALERT "Error: Could not initialize /proc/%s\n", PROC_ENTRY_FILENAME); return -ENOMEM; } Our_Proc_File->owner = THIS_MODULE; Our_Proc_File->proc_iops = &Inode_Ops_4_Our_Proc_File; Our_Proc_File->proc_fops = &File_Ops_4_Our_Proc_File; Our_Proc_File->mode = S_IFREG | S_IRUGO | S_IWUSR; Our_Proc_File->uid = 0; Our_Proc_File->gid = 0; Our_Proc_File->size = 80; //i added init the writewr status writer = DOESNT_EXIST; numOfReaders = 0 ; printk(KERN_INFO "/proc/%s created\n", PROC_ENTRY_FILENAME); return 0; }

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  • Read/Write Excel Files Directly To/From Memory

    - by Corey O.
    Several people have asked, in a roundabout way, but I have yet to see a workable solution. Is there any way to open an excel file from directly memory (like a byte[]) ? Likewise is there a way to write a file directly to memory? I am looking for solutions that will not involve the hard disk or juggling temporary files. Thanks in advance for any suggestions.

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  • Building an 'Activation Key' Generator in JAVA

    - by jax
    I want to develop a Key generator for my phone applications. Currently I am using an external service to do the job but I am a little concerned that the service might go offline one day hence I will be in a bit of a pickle. How authentication works now. Public key stored on the phone. When the user requests a key the 'phone ID' is sent to the "Key Generation Service" and the encrypted key key is returned and stored inside a license file. On the phone I can check if the key is for the current phone by using a method getPhoneId() which I can check with the the current phone and grant or not grant access to features. I like this and it works well, however, I want to create my own "Key Generation Service" from my own website. Requirements: Public and Private Key Encryption:(Bouncy Castle) Written in JAVA Must support getApplicationId() (so that many applications can use the same key generator) and getPhoneId() (to get the phone id out of the encrypted license file) I want to be able to send the ApplicationId and PhoneId to the service for license key generation. Can someone give me some pointers on how to accomplish this? I have dabbled around with some java encryption but am definitely no expert and can't find anything that will help me. A list of the Java classes I would need to instantiate would be helpful.

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  • Can one connection get details of another? Or, how can I get the most detailed pending transaction

    - by bob-the-destroyer
    Is there a Mysql statement which provides full details of any other open connection or user? For this particular case, on myisam tables specifically. Looking at Mysql's SHOW TABLE STATUS documentation, it's missing some very important information for my purpose. For example: remote odbc connection one is inserting several thousand records, which due to a slow connection speed can take up to an hour. Tcp connection two, using PHP on the server's localhost, is running select queries with aggregate functions on that data. Before allowing connection two to run those queries, I'd like connection two to first check to make sure there's no pending inserts on any other connection on those specific tables so it can instead wait until all data is available. If the table is currently being written to, I'd like to spit back to the user of connection two an approximation of how much longer to wait based on the number of pending inserts. Ideally by table, I'd like to get back using a query the timestamp when connection one began the write, total inserts left to be done, and total inserts already completed. Instead of insert counts, even knowing number of bytes written and left to write would work just fine here. Obviously since connection two is a tcp connection via a PHP script, all I can really use in that script is some sort of query. I suppose if I have to, since it is on localhost, I can exec() it if the only way is by a mysql command line option that outputs this info, but I'd rather not. I suppose I could simply update a custom-made transaction log before and after this massive insert task which the PHP script can check, but hopefully there's already a built-in Mysql feature I can take advantage of.

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  • Help dealing with data dependency between two registration forms

    - by franko75
    I have a tricky issue here with a registration of both a user and his/her pet. Both the user and the pet are treated as separate entities and both require separate registration forms. However, the user's pet has to be linked to the user via a foreign key in the database. The process is basically that when a new user joins the site, firstly they register their pet, then they register themselves. The reason for this order is to check their pet's eligibility for the site (there are some criteria to be met) first, instead of getting the user to sign up only to then find out their pet is ineligible. It is this ordering of the form submissions which is causing me a bit of a headache, as follows... The site is being developed with an MVC framework, and the User registration process is managed via a method in a User_form controller, while the pet registration process is managed via a method in the Pet_form controller. The pet registration form happens first, and the pet data can be saved without the owner_id at this stage, with the user id possibly being added (e.g by retrieving pet's id from session) following user registration. However, doing it this way could potentially result in redundant data, where pet records would be created in the database, but if the user doesn't actually register themselves too, then the pets will be ownerless records in the DB. Other option is to serialize the new pet's data at the pet registration stage, don't save it to the DB until the user fills out their registration form. Once the user is created, i can pass serialised data AND the owner_id to a method in the Pet Model which can update the DB. However, I also need to set the newly created $pet to $this-pet which I then access for a sequence of other related forms. Should I just set the session variable in the model method? Then in the Pet controller constructor, do a check for pet stored in session, if yes, assign to $this-pet... If this makes any sense to anybody and you have some advice, i'd be grateful to hear it!

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  • logic before dispatcher + controller?

    - by Spoonface
    I believe for a typical MVC web application the router / dispatcher routine is used to decide which controller is loaded based primarily on the area requested in the url by the user. However, in addition to checking the url query string, I also like to use the dispatcher to check whether the user is currently logged in or not to decide which controller is loaded. For example if they are logged in and request the login page, the dispatcher would load their account instead. But is this a fairly non-standard design? Would it violate MVC in any way? I only ask as the examples I've read through this weekend have had no major calculations performed before the dispatcher routine, and commonly check whether the user is logged in or not per controller, and then redirect where necessary. But to me it seems odd to redirect a logged in user from the login area to account area if you could just load the account controller in the first place? I hope I've explained my consternation well enough, but could anyone offer some details on how they handle logged in users, and similar session data?

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