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  • What is better for a student programming in C++ to learn for writing GUI: C# vs QT?

    - by flashnik
    I'm a teacher(instructor) of CS in the university. The course is based on Cormen and Knuth and students program algorithms in C++. But sometimes it is good to show how an algorithm works or just a result of task through GUI. Also in my opinion it's very imporant to be able to write full programs. They will have courses concerning GUI but a three years, later, in fact, before graduatuion. I think that they should be able to write simple GUI applications earlier. So I want to teach them it. How do you think, what is more useful for them to learn: programming GUI with QT or writing GUI in C# and calling unmanaged C++ library? Update. For developing C++ applications students use MS Visual studio, so C# is already installed. But QT AFAIK also can be integrated into VS. I have following pros of C# (some were suggested there in answers): The need to make an additional layer. It's more work, but it forces you explicitly specify contract between GUI and processing data. The border between GUI and algorithms becomes very clear. It's more popular among employers. At least, in Russia where we live. It's rather common to write performance-critical algorithms in C++ and PInvoke them from well-looking C# application/ASP.Net website. Maybe it is not so widespread in the rest of the world but in Russia Windows is very popular, especially in companies and corporations due to some reasons, so most of b2b applications are Windows applications. Rapid development. It's much quicker to code in .Net then in C++ due to many reasons. And the con is that it's a new language with own specific for students. And the mess with invoking calls to library.

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  • PHP download page: file_exists() returns true, but browser returns 'page not found'

    - by Chris
    I'm using PHP for a file download page. Here's a snippet of the problem code: if (file_exists($attachment_location)) { header($_SERVER["SERVER_PROTOCOL"] . " 200 OK"); header("Cache-Control: public"); // needed for i.e. header("Content-Type: application/zip"); header("Content-Transfer-Encoding: Binary"); header("Content-Length:".filesize($attachment_location)); header("Content-Disposition: attachment; filename=file.zip"); readfile($attachment_location); die("Hooray"); } else { die("Error: File not found."); } This code works absolutely fine when testing locally, but after deploying to the live server the browser returns a 'Page not found' error. I thought it might be an .htaccess issue, but all .htaccess files on the live server are identical to their local counterparts. My next guess would be the live server's PHP configuration, but I have no idea what PHP setting might cause this behaviour. The file_exists() function always returns true - I've checked this on the live server and it's always correctly picking up the file, its size etc., so it does have a handle on the file. It just won't perform the download! The main site is a Wordpress site, but this code isn't part of a Wordpress page - it's in a standalone directory within the site root. UPDATE: is_file() and is_readable() are both returning true for the file, so that's not the problem. The specific line that is causing the problem is: readfile($attachment_location) Everything up until that point is super happy.

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  • EXC_BAD_ACCESS in NSURLConnection: how to debug?

    - by baswell
    I have an iPhone app that downloads URLs. (PDFs to display) Easy: self.conn = [NSURLConnection connectionWithRequest:self.request delegate:self]; where self.conn is a retained property. For specific URLs, this throws EXC_BAD_ACCESS. The URL is valid and is constructed in the same way as URLs that do work. (90% of URLs are fine) These ones work: http://www.airservicesaustralia.com/publications/current/ersa/FAC_YARG_11-Mar-2010.pdf http://www.airservicesaustralia.com/publications/current/ersa/FAC_YARK_11-Mar-2010.pdf These don't: http://www.airservicesaustralia.com/publications/current/ersa/FAC_YAMK_11-Mar-2010.pdf http://www.airservicesaustralia.com/publications/current/ersa/FAC_YATN_11-Mar-2010.pdf Spot the difference? Yeah, me neither. Also no difference in response headers from the server for them. To clarify, the ones that work ALWAYS work, the ones that don't NEVER work. So not some random release/retain issue it seems. For the ones that don't work, none of the methods in my delegate are ever called, it fails hard before that. And with no error message, just EXC_BAD_ACCESS. Sooo.... Any way to debug what is going on inside NSURLConnection?

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  • Why can't I create an abstract constructor on an abstract C# class?

    - by Anthony D
    I am creating an abstract class. I want each of my derived classes to be forced to implement a specific signature of constructor. As such, I did what I would have done has I wanted to force them to implement a method, I made an abstract one. public abstract class A { abstract A(int a, int b); } However I get a message saying the abstract modifier is invalid on this item. My goal was to force some code like this. public class B : A { public B(int a, int b) : base(a, b) { //Some other awesome code. } } This is all C# .NET code. Can anyone help me out? Update 1 I wanted to add some things. What I ended up with was this. private A() { } protected A(int a, int b) { //Code } That does what some folks are saying, default is private, and the class needs to implement a constructor. However that doesn't FORCE a constructor with the signature A(int a, int b). public abstract class A { protected abstract A(int a, int b) { } } Update 2 I should be clear, to work around this I made my default constructor private, and my other constructor protected. I am not really looking for a way to make my code work. I took care of that. I am looking to understand why C# does not let you do this.

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  • Memory Management with returning char* function

    - by RageD
    Hello all, Today, without much thought, I wrote a simple function return to a char* based on a switch statement of given enum values. This, however, made me wonder how I could release that memory. What I did was something like this: char* func() { char* retval = new char; // Switch blah blah - will always return some value other than NULL since default: return retval; } I apologize if this is a naive question, but what is the best way to release the memory seeing as I cannot delete the memory after the return and, obviously, if I delete it before, I won't have a returned value. What I was thinking as a viable solution was something like this void func(char*& in) { // blah blah switch make it do something } int main() { char* val = new char; func(val); // Do whatever with func (normally func within a data structure with specific enum set so could run multiple times to change output) val = NULL; delete val; val = NULL; return 0; } Would anyone have anymore insight on this and/or explanation on which to use? Regards, Dennis M.

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  • Preview of code-only WPF controls in VS2010 - how?

    - by Christian
    Hi, I hope I am able to illustrate the problem using a lot of images. First of all, I was no real fan of XAML (Silverlight issues, crashes in Preview, and so on...) Now, with VS2010 the situation has become better. There are still a lot of things I like better in code, but I also want a preview in my VS. So, take a look at the following control: It is really simple, a todo details list. The first screenshot shows the code of the control, pretty straighforward: There is no XAML, so obviously no preview. Of course, I could encapsulate it in another control, like shown in the next screenshot: But, in that case I have an additional file I do not want or need. So I had the idea to move the init stuff inside the contructor of a XAML control. For simplicity, I used simple elements. But they do not show up in the preview... Finally, I know I could use the controls in other parts of my app when creating UIs. But I am using layout manager, PRISM and a lot of other stuff, so I just want an easy preview of some specific control I created (without having to have a XAML wrapper file for each control) Thanks for help, and sorry for the post structure, but I though with images it is better to understand... Chris

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  • How to ensure nginx serves a request from an external IP?

    - by Matt
    I have a strange situation, where my nginx setup stopped handling external requests. I'm pretty stuck. If I hit the domain without a subdomain, I properly get redirected, however, if I request the full url, that fails and doesn't log anything, anywhere. I am able to curl localhost on the server itself, however when I attempt to curl from an external machine, it fails with: curl: (7) couldn't connect to host I've also noticed that bots can get through, I've seen Google hit the log every now and then. My nginx.conf file: upstream mongrels { server 127.0.0.1:5000; } server { listen 80; server_name culini.com; rewrite ^/(.*) http://www.culini.com/$1 permanent; } # the server directive is nginx's virtual host directive. server { # port to listen on. Can also be set to an IP:PORT listen 80; # Set the max size for file uploads to 50Mb client_max_body_size 50M; # sets the domain[s] that this vhost server requests for server_name www.culini.com; # doc root root /var/www/culini/current/public; log_format app '$remote_addr - $remote_user [$time_local] ' '"$request" $status $body_bytes_sent "$http_referer" ' '"$http_user_agent" "$http_x_forwarded_for" [$upstream_addr $upstream_response_time $upstream_status]'; # vhost specific access log access_log /var/www/culini/current/log/nginx.access.log app; error_log /var/www/culini/current/log/nginx.error.log debug; location / { proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header Host $http_host; proxy_redirect false; proxy_max_temp_file_size 0; proxy_intercept_errors on; proxy_ignore_client_abort on; if (-f $request_filename) { break; } if (!-f $request_filename) { proxy_pass http://mongrels; break; } } } Please, please, any help would be greatly appreciated.

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  • Selective replication with CouchDB

    - by FRotthowe
    I'm currently evaluating possible solutions to the follwing problem: A set of data entries must be synchonized between multiple clients, where each client may only view (or even know about the existence of) a subset of the data. Each client "owns" some of the elements, and the decision who else can read or modify those elements may only be made by the owner. To complicate this situation even more, each element (and each element revision) must have an unique identifier that is equal for all clients. While the latter sounds like a perfect task for CouchDB (and a document based data model would fit my needs perfectly), I'm not sure if the authentication/authorization subsystem of CouchDB can handle these requirements: While it should be possible to restict write access using validation functions, there doesn't seem to be a way to authorize read access. All solutions I've found for this problem propose to route all CouchDB requests through a proxy (or an application layer) that handles authorization. So, the question is: Is it possible to implement an authorization layer that filters requests to the database so that access is granted only to documents that the requesting client has read access to and still use the replication mechanism of CouchDB? Simplified, this would be some kind of "selective replication" where only some of the documents, and not the whole database is replicated. I would also be thankful for directions to some detailed information about how replication works. The CouchDB wiki and even the "Definite Guide" Book are not too specific about that.

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  • JQuery - Element Selection

    - by user208662
    Hello, I'm relatively new to JQuery. I'm trying to understand how to select a child element. Currently, I have some HTML that is defined as follows: <div id="elem1"> <div class="display">Student 1</div> </div> <div id="elem2"> <div class="display">Student 2</div> </div> <div id="elem3"> <div class="display">Student 3</div> </div> When a user clicks a link, one of the elements (elem1, elem2, or elem3) is going to be passed to a function that is defined as follows: function getNodeDisplay(node) { // NOTE: This does not work as desired return $(node).(#".display").html(); } Unfortunately, this approach does not work. How do I get the HTML associated with an element that has a specific class or a given element? Thank you for your help!

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  • escape exactly what in javascript

    - by Emin
    Hi all, Being a newbie in javascript I came to a situation where I need more information on escaping characters in a string. Basically I know that in order to escape " I need to replace it with \" but what I don't know is for which characters I need to escape a particular string for. Is there a list of these "characters to escape"? or is it any character that is not a-zA-Z0-9 ? In my situation, I don't have control over the content that is being displayed on my page. Users enter some text and save it. I then use a webservice to extract them from the database, build a json array of objects, then iterate the array when I need to display them. In this case, I have - naturally - no idea of what the text the user has entered and therefore for what characters I need to escape. I also use jQuery for this specific project (just in case it has a function I am not aware of, to do what I need) Providing examples would be appreciated but I also want to learn the theory and logic behind it. Hope someone can be of any help.

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  • Faster way to convert from a String to generic type T when T is a valuetype?

    - by Kumba
    Does anyone know of a fast way in VB to go from a string to a generic type T constrained to a valuetype (Of T as Structure), when I know that T will always be some number type? This is too slow for my taste: Return DirectCast(Convert.ChangeType(myStr, GetType(T)), T) But it seems to be the only sane method of getting from a String -- T. I've tried using Reflector to see how Convert.ChangeType works, and while I can convert from the String to a given number type via a hacked-up version of that code, I have no idea how to jam that type back into T so it can be returned. I'll add that part of the speed penalty I'm seeing (in a timing loop) is because the return value is getting assigned to a Nullable(Of T) value. If I strongly-type my class for a specific number type (i.e., UInt16), then I can vastly increase the performance, but then the class would need to be duplicated for each numeric type that I use. It'd almost be nice if there was converter to/from T while working on it in a generic method/class. Maybe there is and I'm oblivious to its existence?

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  • Good Hosting Providers With Zend Framework Support

    - by manyxcxi
    I currently use ixwebhosting for my hosting services. They're cheap and work (most of the time). The databases are horribly slow, the servers are horribly slow, and their support (though usually prompt) is tough to deal with. That being said, they're cheap, I've got like 20 domains hosted in my account, none of them are high volume, and they work JUST good enough- until today. This isn't meant to be a condemnation of ixwh though. Their prices are very low for what they do offer and most things work just fine, most of the time. I need to be able to host web apps written with Zend Framework in a fairly easy fashion. The server performance can't be worse than what I've already had (a pretty low hurdle to clear), and I don't want to spend $30/mo. These are not money making websites- they're projects. My requirements are PHP 5.3, ZF support, MySQL databases, multiple domains- not much. Who should I look at, and who should I look out for? Also- I put this on SO instead of SF because of the Zend Framework specific requirement. If I'm wrong, do as you wish.

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  • Implementing IEnumeralbe on Non-Listed Items

    - by Stacey
    I have a class that contains a static number of objects. This class needs to be frequently 'compared' to other classes that will be simple List objects. public partial class Sheet { public Item X{ get; set; } public Item Y{ get; set; } public Item Z{ get; set; } } the items are obviously not going to be "X" "Y" "Z", those are just generic names for example. The problem is that due to the nature of what needs to be done, a List won't work; even though everything in here is going to be of type Item. It is like a checklist of very specific things that has to be tested against in both code and runtime. This works all fine and well; it isn't my issue. My issue is iterating it. For instance I want to do the following... List<Item> UncheckedItems = // Repository Logic Here. UncheckedItems contains all available items; and the CheckedItems is the Sheet class instance. CheckedItems will contain items that were moved from Unchecked to Checked; however due to the nature of the storage system, items moved to Checked CANNOT be REMOVED from Unchecked. I simply want to iterate through "Checked" and remove anything from the list in Unchecked that is already in "Checked". So naturally, that would go like this with a normal list. foreach(Item item in Unchecked) { if( Checked.Contains(item) ) Unchecked.Remove( item ); } But since "Sheet" is not a 'List', I cannot do that. So I wanted to implement IEnumerable so that I could. Any suggestions? I've never implemented IEnumerable directly before and I'm pretty confused as to where to begin.

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  • Database (and ORM) choice for an small-medium size .NET Application

    - by jim
    I have a requirement to develop a .NET-based application whose data requirements are likely to exceed the 4 gig limit of SQL 2005 Express Edition. There may be other customers of the same application (in the future) with a requirement to use a specific DB platform (such as Oracle or SQL Server) due to in-house DBA expertise. Questions What RDBMS would you guys recommend? From the looks of it the major choices are PostGreSQL, MySQL or FireBird. I've only got experience of MYSQL from these. Which ORM tool (if any) would you recommend using - ideally one that can be swapped out between DB platforms with minimal effort? I like the look of the entity framework but unsure as to the degree to which platforms other than SQL Server are supported. If it helps, we'll be using the 3.5 version of the Framework. I'm open to the idea of using a tool such as NHibernate. On the other hand, if it's going to be easier, I'm happy to write my own stored procedures / DAL code - there won't be that many tables (perhaps 30-35).

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  • How to efficiently use LOCK_ESCALATION mssql 2008

    - by Avias
    I'm currently having troubles with frequent deadlocks with a specific user table in MS SQL 2008. Here are some facts about this particular table: Has a large amount of rows (1 to 2 million) All the indexes used on this table only has "use row lock" ticked on its option rows are frequently updated by multiple transactions but are unique (e.g. probably a thousand or more update statements are executed to different unique rows every hour) the table does not use partitions. Upon checking the table on sys.tables, I found that the lock_escalation is set to TABLE I'm very tempted to turn the lock_escalation for this table to DISABLE but I'm not really sure what side effect this would incur. From What I understand, using DISABLE will minimize escalating locks to TABLE level which if combined with the row lock settings of the indexes should theoretically minimize the deadlocks I am encountering.. From what I have read in Determining threshold for lock escalation it seems that locking automatically escalates when a single transaction fetches 5000 rows.. What does a single transaction mean in this sense? A single session/connection getting 5000 rows thru individual update/select statements? Or is it a single sql update/select statement that fetches 5000 or more rows? Any insight is appreciated, btw, n00b DBA here Thanks

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  • Text replacement for multiple script/config files

    - by user343804
    I am doing some sort of science with a combination of Python, bash scripts and configuration files with weird syntaxes from old C programs. To run different tests, I have to tune (open text file, edit and save) a number of these files, but it is getting harder and harder to remember which files to edit. Also, the tasks are very repetitive and I end having a bunch of comment lines, switching on and off the settings for a specific run. I dream of a tool that can keep a list of files (regardless of the file format) and allow me to centrally choose from a predefined list of "profiles", taking care of editing the script/config files. For example lets say I have a config and script file: config.cfg var1 = 1.0 #var1 = 1.5 script.sct function(200.0) #function(300.0) I would like to instead have auxiliary text files: config.cfg.tem var1 = $$var1$$ script.sct.tem function($$par1$$) and in a central script or even better, a GUI, just switch from profile1 (e.g. var1=1.0,par1=200.0) to profile2 (e.g. var1=1.5,par1=300.0), and the tool to automatically update the text files. Any idea if such a tools exists?

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  • Web service failing when installed in seperate project from the website...

    - by Adam
    I am totally new to web services and cannot get mine to work. My setup is on VS 2008 using IIS. I have one solution file with 3 projects in it: website, code, and services. If I put my webservice into my website and call it locally then it will work fine (it's just a hello world web service). I want to put the service into a different location for use from multiple sites. I don't know what I'm doing wrong - i've read so much conflicting info regarding disco files, access files, silverlight, flash, java, etc. I just looking for quick simple steps to create a web service that I can access from javascript and deploy to a seperate website. End goal is to have functionality in webservices so that website will call via JS and run much smoother in the loading time and async calls. Do I need to create a disco file? Do I need to configure security? -- I know this is prob best, i'm just looking to get it working at all. Do I need to allow cross browser access on IIS or on my hosted server? Are there any quick reference websites that you can recommend? Should I be using WCF as new technology? - I saw this on MSDN but seems to be more for windows apps then web apps. I'm not getting any specific error codes. I have installed the firefox debugging tools (firebug) and I can see what the headers are but I don't know how to interpret them and there is no response being passed back. Any help is appreciated!!!

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  • C# Hook Forms / Windows / Dialogs etc. (via HWND?) to Capture Video Buffer (D3D Device?)

    - by Drax
    I am looking to create a very simple C# application which runs Full-Screen in Direct3D, and is able to grab the Desktop 'scene', mapping each Window from the Desktop to a Textured Polygon in my D3D Scene... I'm hoping to create a simplistic "3D Desktop" type of application as an experiment, and I'm wondering if there is a specific method for doing something like the following: 1)Get a list of all the Windows open on the Desktop (List of HWNDs?). 2)Grab the X,Y position of each Window, as well as the Width and Height. 3)Grab the Rendered image of each Window (magic happens here). 4)Create a new Texture/Surface in D3D using the Width and Height of the Window(s), and apply the Image we grabbed as a Texture. Is there an efficient 'best practice' for acquiring the actual image(s) being rendered to the Desktop? Is there also a 'best practice' for "extending the desktop" to a virtual second, third, etc. "desktop" and being able to swap between them, including creating a unique instance of the task-bar for each virtual desktop. Thanks a million for any suggestions!

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  • Can I automate a loop query based on category with the page's title?

    - by jordaninternets
    To explain further, I need to get a page to display posts from a specific category. I want to automate this process so I don't have to make a template for each category. How would I do that? (keep in mind the person I'm building this is for has no coding experience.) The only way I could think off from the top of my head is to use the title or slug. So if the category is named the same thing as the slug, could I filter by category using the slug? Maybe this isn't the best way... what should I do? This is what I came up with, but it doesn't work, I'm sure due to improper use on may part, but I've been pouring over the WP codex and Google with no avail to tell me my problem. <?php $paged = (get_query_var('paged')) ? get_query_var('paged') : 1; $args= array( 'orderby' => 'date', 'order' => 'ASC', 'paged' => $paged, 'category_name' => echo the_title('\'','\'',) ); query_posts($args); ?>

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  • how to compare two tables fields name with another value in mysql?

    - by I Like PHP
    I have two tables table_school school_open_time|school_close_time|school_day 8:00 AM | 9:00PM | Monday 10:00 AM | 7:00PM | Wednesday table_college college_open_time|college_close_time|college_day 10:00 AM | 8:00PM | Monday 10:00 AM | 9:00PM | Tuesday 10:00 AM | 5:00PM | Wednesday Now I want to select school_open_time school_close time, college_open_time and college_close_time according to today (means college_day=school_day=today), and also if there is no row for a specific day in any of one table then it display blank field ( LEFT JOIN , I think I can use). Please suggest me best and optimized query for this. UPDATE: if there is no open time and close time for school then college_open_time and college_close_time has to be returned( not to be filled in database,just return) as school_open_time and school_close_time. and there always must be college_open_time and college_close_time for a given day MORE UPDATE: i m using below query SELECT college_open_time,college_close_time ,school_open_time, school_close_time FROM tbl_college LEFT JOIN tbl_school ON school_owner_id=college_owner_id WHERE college_owner_id='".$_session['user_id']."' AND college_day='".date('l',time())."'"; it return single row (left hand having some value and right hand having blank value) when there is no row of a given day in table_school, BUT display seven rows with same value on left hand side(college_open_time, college_close_time) and 6 blank row on right hand side (school_open_time and school_close_time) i need only one row when both table have a row of a given day but using above query take only first row of corresponding table_school where school_owner_id is 50(let), it not see the condition that school_day name should be given day

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  • Codeigniter - Active record - sql - complex join

    - by Jack
    I have a function that retrieves all tags from a table: function global_popular_tags() { $this->db->select('tags.*, COUNT(tags.id) AS count'); $this->db->from('tags'); $this->db->join('tags_to_work', 'tags.id = tags_to_work.tag_id'); $this->db->group_by('tags.id'); $this->db->order_by('count', 'desc'); $query = $this->db->get()->result_array(); return $query; } I have another table called 'work'. The 'work' table has a 'draft' column with values of either 1 or 0. I want the COUNT(tags.id) to take into account whether the work with the specific tag is in draft mode (1) or not. Say there are 10 pieces of work tagged with, for example, 'design'. The COUNT will be 10. But 2 of these pieces of work are in draft mode, so the COUNT should really be 8. How do I manage this?

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  • How can I dynamically call the named route in a :partial in rails?

    - by Angela
    I have the following partial. It can be called from three different times in a view as follows: <%= render :partial => "contact_event", :collection => @contacts, :locals => {:event => email} %> Second time: <%= render :partial => "contact_event", :collection => @contacts, :locals => {:event => call} %> Third time: <%= render :partial => "contact_event", :collection => @contacts, :locals => {:event => letter} %> In each instance, call, email, letter refer to a specific instance of a Model Call, Email, or Letter. Here is what I tried to do and conceptually what I'd like to do: assign the route based on the class name that has been passed to the :event from the :partial. What I did was create what the actual url should be. The 'text' of it is correct, but doesn't seem to recognize it as a named route. <% url = "skip_contact_#{event.class.name.tableize.singularize}_url" % <%= link_to_remote "Skip #{url} Remote", :url = skip_contact_email_url(contact_event, event), :update = "update-area-#{contact_event.id}-#{event.id}" % ' My challenge: skip_contact_email_url only works when the event refers to an email. How can I dynamically define skip_contact_email_url to be skip_contact_letter_url if the local variable is letter? Even better, how can I have a single named route that would do the appropriate action?

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  • Please suggest other ways of communicating between server & client.

    - by Geo
    I'm writing a TCP chat server ( programming language does not mather ). It's a school project for my nephew, so it won't be released, and all questions I'm asking are just for my knowledge :). . Some of the things it will support: chatting between users ( doh ), it will be multithreaded sending each other files I know I could easily get away with all the stuff above if I go with serialization, and just send objects from client to server and back. But, if I do that, it will be limited to a specific programming language ( meaning clients written in other programming languages may not be able to deserialize the objects ). What would be the way to go so that other clients written in other languages could be supported? One way to go, off the top of my head, would be to go in this direction: the server & the client communicate by sending messages & chunks ( in lieu of other names ). Here's what I mean by this: every time the client/server wants to send something ( text message or file ) it will first send a simple text message ( newline terminated ) with the number of the chunks it will send. Example: command 4,20,30,40,50 Where command would be something like instant-message or file,4 would be the number of chunks to be sent, 20 would be the size in bytes of the first chunk, 30 of the 2nd, and so forth. after the message was sent, the client/server will start sending chunks ( of sizes mentioned in the sent message ). What do you think about implementing the client/server communication this way? What better options are there?

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  • Does ReleaseStringUTF do more than free memory?

    - by Bayou Bob
    Consider the following C code segments. Segment 1: char * getSomeString(JNIEnv *env, jstring jstr) { char * retString; retString = (*env)->GetStringUTFChars(env, jstr, NULL); return retString; } void useSomeString(JNIEnv *env, jobject jobj, char *mName) { jclass cl = (*env)->GetObjectClass(env, jobj); jmethodId mId = (*env)->GetMethodID(env, cl, mName, "()Ljava/lang/String;"); jstring jstr = (*env)->CallObjectMethod(env, obj, id, NULL); char * myString = getSomeString(env, jstr); /* ... use myString without modifing it */ free(myString); } Because myString is freed in useSomeString, I do not think I am creating a memory leak; however, I am not sure. The JNI spec specifically requires the use of ReleaseStringUTFChars. Since I am getting a C style 'char *' pointer from GetStringUTFChars, I believe the memory reference exists on the C stack and not in the JAVA heap so it is not in danger of being Garbage Collected; however, I am not sure. I know that changing getSomeString as follows would be safer (and probably preferable). Segment 2: char * getSomeString(JNIEnv *env, jstring jstr) { char * retString; char * intermedString; intermedString = (*env)->GetStringUTFChars(env, jstr, NULL); retString = strdup(intermedString); (*env)->ReleaseStringUTFChars(env, jstr, intermedString); return retString; } Because of our 'process' I need to build an argument on why getSomeString in Segment 2 is preferable to Segment 1. Is anyone aware of any documentation or references which detail the behavior of GetStringUTFChars and ReleaseStringUTFChars in relation to where memory is allocated or what (if any) additional bookkeeping is done (i.e. local Reference Pointer to the Java Heap being created, etc). What are the specific consequences of ignoring that bookkeeping. Thanks in advance.

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  • Include Multiple Labels and change the value of the same in Iphone, Objective C

    - by user576569
    I m trying to insert label in each row of the cell. Displaying integer. and I m trying to increase the quantity if user click on button add or minus I able to insert button in UITableView Cell as well the function to change the value. But when I click on add button it changes value only for the last row and not on the specific row. //MY code to insert label in each cell txtQty = [[UILabel alloc] initWithFrame:CGRectMake(233,7,20,20)]; txtQty.text = [NSString stringWithFormat:@"%@",[nos objectAtIndex:indexPath.row]]; txtQty.tag = count; txtQty.textColor =[UIColor whiteColor]; txtQty.backgroundColor = [UIColor clearColor]; [cell.contentView addSubview:txtQty]; //Button Creation UIButton *button2 = [[UIButton alloc] initWithFrame:CGRectMake(180,5,30,30)]; [button2 addTarget:self action:@selector(subAddSubQty:) forControlEvents:UIControlEventTouchUpInside]; [button2 setTag:count]; [cell.contentView addSubview:button2]; now what happening is suppose there are 3 rows in table and I click on the 1st row add button the value gets change in the last label i.e at 3rd row and not of the 1st row How to solve these?? please help Thank You

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