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  • Detecting/Repairing NSConnection failure

    - by anthony
    I would like to use NSConnection/NSDistributedObject for interprocess communication. I would like the client to be able to handle the case where the server is only occasionally reachable. How can I determine if sending a message to the NSConnection will fail or has failed? Currently if my server (the process that has vended the remote object) dies, the client will crash if it sends a selector to the remote object. Ideally I'd like to have a wrapper for the remote object that can lazily instantiate (or reinstantiate) the connection, and return a default value in the case where the connection could not be instantiated, or the connection has failed. I don't really know the correct way to do this using objective c. Here's some pseudocode representing this logic: if myConnection is null: instantiate myConnection if MyConnection is null: return defaultValue try return [myConnection someMethod] catch myConnection = null return defaultValue

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  • [C#] Async threaded tcp server

    - by mark_dj
    I want to create a high performance server in C# which could take about ~10k clients. Now i started writing a TcpServer with C# and for each client-connection i open a new thread. I also use one thread to accept the connections. So far so good, works fine. The server has to deserialize AMF incoming objects do some logic ( like saving the position of a player ) and send some object back ( serializing objects ). I am not worried about the serializing/deserializing part atm. My main concern is that I will have a lot of threads with 10k clients and i've read somewhere that an OS can only hold like a few hunderd threads. Are there any sources/articles available on writing a decent async threaded server ? Are there other possibilties or will 10k threads work fine ? I've looked on google, but i couldn't find much info about design patterns or ways which explain it clearly

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  • Recommend an algorithms exercise book?

    - by Parappa
    I have a little book called Problems on Algorithms by Ian Parberry which is chock full of exercises related to the study of algorithms. Can anybody recommend similar books? What I am not looking for are recommendations of good books related to algorithms or the theory of computation. Introduction to Algorithms is a good one, and of course there's the Knuth stuff. Ideally I want to know of any books that are light on instructional material and heavy on sample problems. In a nutshell, exercise books. Preferably dedicated to algorithms rather than general logic or other math problems. By the way, the Parberry book does not seem to be in print, but it is available as a PDF dowload.

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  • Auto Increment feature of SQL Server

    - by Rahul Tripathi
    I have created a table named as ABC. It has three columns which are as follows:- The column number_pk (int) is the primary key of my table in which I have made the auto increment feature on for that column. Now I have deleted two rows from that table say Number_pk= 5 and Number_pk =6. The table which I get now is like this:- Now if I again enter two new rows in this table with the same value I get the two new Number_pk starting from 7 and 8 i.e, My question is that what is the logic behind this since I have deleted the two rows from the table. I know that a simple answer is because I have set the auto increment on for the primary key of my table. But I want to know is there any way that I can insert the two new entries starting from the last Number_pk without changing the design of my table? And how the SQL Server manage this record since I have deleted the rows from the database??

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  • What causes a WPF ListCollectionView that uses custom sorting to re-sort its items?

    - by Drew Noakes
    Consider this code (type names genericised for the purposes of example): // Bound to ListBox.ItemsSource _items = new ObservableCollection<Item>(); // ...Items are added here ... // Specify custom IComparer for this collection view _itemsView = CollectionViewSource.GetDefaultView(_items) ((ListCollectionView)_itemsView).CustomSort = new ItemComparer(); When I set CustomSort, the collection is sorted as I expect. However I require the data to re-sort itself at runtime in response to the changing of the properties on Item. The Item class derives from INotifyPropertyChanged and I know that the property fires correctly as my data template updates the values on screen, only the sorting logic is not being called. I have also tried raising INotifyPropertyChanged.PropertyChanged passing an empty string, to see if a generic notification would cause the sorting to be initiated. No bananas. EDIT In response to Kent's suggestion I thought I'd point out that sorting the items using this has the same result, namely that the collection sorts once but does not re-sort as the data changes: _itemsView.SortDescriptions.Add( new SortDescription("PropertyName", ListSortDirection.Ascending));

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  • How does SQL Server treat statements inside stored procedures with respect to transactions?

    - by Sleepless
    Hi All! Say I have a stored procedure consisting of several seperate SELECT, INSERT, UPDATE and DELETE statements. There is no explicit BEGIN TRANS / COMMIT TRANS / ROLLBACK TRANS logic. How will SQL Server handle this stored procedure transaction-wise? Will there be an implicit connection for each statement? Or will there be one transaction for the stored procedure? Also, how could I have found this out on my own using T-SQL and / or SQL Server Management Studio? Thanks!

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  • jquery jstree or dynatree parent node don't get selected

    - by mazhar
    I have used jquery jstree or dynatree using check boxes and found the same logic The thing is that the if for example there is a parent and 4 child. a) i select all the 4 child (parent get auto selected) the 4 child and the parent node id get posted to the controller. b) But if i select less then 4 children (parent get auto selected) only child node ids get posted to the controller. Is there any way even if i select less then 4 children all my selected nodes included the parent get posted to the controller?

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  • IOC - Should util classes with static helper methods be wired up with IOC?

    - by Greg
    Hi, Just trying to still get my head around IOC principles. Q1: Static Methods - Should util classes with static helper methods be wired up with IOC? For example if I have a HttpUtils class with a number of static methods, should I be trying to pass it to other business logic classes via IOC? Follow on questions for this might be: Q2: Singletons - What about things like logging where you may typically get access to it via a Logger.getInstance() type call. Would you normally leave this as is, and NOT use IOC for injecting the logger into business classes that need it? Q3: Static Classes - I haven't really used this concept, but are there any guidelines for how you'd typically handle this if you were moving to an IOC based approach. Thanks in advance.

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  • Nothing = String.Empty (Why are these equal?)

    - by Ek0nomik
    I find it very puzzling that null equals String.Empty in VB.NET. There must be an explanation for it that I'm not understanding. Somehow, when the equality of String.Empty (which has an object type of string) is tested against Nothing (which has no type) the test returns true. It just seems like a turn around in logic to me. In SQL if I were to compare an empty char or varchar against a null value, the test wouldn't return true. A null value is not the same as an empty string in this case. Yet in VB.NET they are equal. I'd love it if someone could provide a good explanation around this.

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  • How to find out all versions of iPad from user-agent string?

    - by User11091981
    I wanted to find out all the version's of iPad (excluding iPhone, iPod) from user agent string, currently while testing I got the following string Mozilla/5.0 (iPad; CPU OS 5_1_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9B206 Safari/7534.48.3 Question: Will the following code works fine for all the iPad's? String userAgentStr = request.getHeader("User-agent"); if (userAgentStr.contains("iPad")) { //do my logic } EDIT: I am using Dolphin browser from iPad but I am getting the following UA string: Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_2_1 like Mac OS X; en_US) AppleWebKit/533.17.9 (KHTML, like Gecko) Mobile/8C148 Safari/6533.18.5 Similarly iBrowser from iPad UA string is: Mozilla/5.0 (iPhone; CPU iPhone OS 5_1_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Mobile/9B206 So my above code is breaking...

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  • Where to place java applet policy file?

    - by makdere
    Hi all, I am working on an artificial intelligence project which is a logic game and aims two user connecting to the server on the network who acts as an Admin and then start to play one by one. In order to create connections, i have a server code which is just listening on localhost:8000 and assigning team values to the clients as they arrive. After connecting, clients make their move under Admin's control. The question is that when i try to put my code to work in the browser it fails with the following error: java.security.AccessControlException: access denied (java.net.SocketPermission 127.0.0.1:8000 connect,resolve) Even though i have created my own policy, first granting only Socket access permission to the codebase of my project folder (file:///home/xxx/projects/-), after it didnt work i granted all permissions from all codebase. I tried placing my policy file both in the home directory and in the same directory where my applet code resides. Appreciate any tips, thanks.

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  • Testing with Qt's QTestLib module

    - by ak
    Hi I started writing some tests with Qt's unit testing system. How do you usually organize the tests? It is one test class per one module class, or do you test the whole module with a single test class? Qt docs (or some podcast that I recently watched) suggested to follow the former strategy. I want to write tests for a module. The module provides only one class that is going to be used by the module user, but there is a lot of logic abstracted in other classes, which I would also like to test, besides testing the public class. The problem is that Qt's proposed way to run tests involved the QTEST_MAIN macro: QTEST_MAIN(TestClass) #include "test_class.moc" and eventually one test program is capable of testing just one test class. And it kinda sucks to create test projects for every single class in the module. Of course, one could take a look at the QTEST_MAIN macro, rewrite it, and run other test classes. But is there something, that works out of the box?

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  • displaying current minute of a soccer match

    - by zurna
    I could not figure out the logic I would need to display a current minute of a soccer match. I have three fields in the database. DateFirstStarted DateSecondStarted DateFullEnded I should enter DateFirstStarted when the game starts and on the website. i.e. game starts at 7:05pm, on 7:25pm it should display '20 on the website. However, it should stop on the 45th minute. Then, I enter DateSecondStarted when the second half starts and should count from 46 to 90 and freeze there. Do I make sense? How can I do it? Is there a better way to do this?

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  • PHP Code to Generate Simple Flowchart

    - by revbackup
    I am making a flowchart out the subjects in the curriculum of our school. a flowchart is generated through its preRequisite.... for example FIRST YEAR FIRST SEMESTER SUBJECTS ---- PREREQUISITE MATH 1 ---- NONE MATH 2 ---- NONE ENGL 1 ---- NONE SOCIO 1 ----- NONE POLSCI 1 ----- NONE FIRSTE YEAR SECOND SEMESTER SUBJECTS ---- PREREQUISITE MATH 3 ----- MATH 1 MATH 4 ----- MATH 2, MATH 1 ENGL 2 ----- ENGL 1 POLSCI 2 ----- POLSCI 1 So, I must print it this way, just using simple PHP but difficult Logic.: MATH1 -----> MATH3 -----> MATH4 MATH 2 ----->MATH 4 ENGL1 -----> ENGL 2 SOCIO 1 POLSCI 1 -----> POLSCI 2 Can anyone give me a good algorithm for this, because this is really difficult. I am planning to echo the results in an HTML table, and it makes it more complicated. Do you have suggestions how to solve this problem properly and display the results also properly???? Thank you in advance!

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  • Double Negation in C++ code.

    - by Brian Gianforcaro
    I just came onto a project with a pretty huge code base. I'm mostly dealing with C++ and a lot of the code they write uses double negation for their boolean logic. if (!!variable && (!!api.lookup("some-string"))) { do_some_stuff(); } I know these guys are intelligent programmers, it's obvious they aren't doing this by accident. I'm no seasoned C++ expert, my only guess at why they are doing this is that they want to make absolutely positive that the value being evaluated is the actual boolean representation. So they negate it, then negate that again to get it back to its actual boolean value. Is this a correct? or am I missing something else? Thanks, Brian Gianforcaro

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  • prevent _doPostBack getting rendered in button markup

    - by Christo Fur
    Hi Is it possible to prevent the _doPostBack() call getting rendered on a button? I would like add some custom logic prior to calling the postback. I have added an onClick event to the button e.g. <button id="manualSubmit" runat="server" class="manual-submit" onclick="$('#jeweller-form').hide();" /> However, this just gets rendered inline before the _doPostBack() But the postback gets fired before the jQueryHide takes place I would like to call my own JS function then manually trigger the postback any ideas?

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  • ListAdapters and WrapperListAdapter algorithm

    - by Matty F
    This logic is written in a function with signature private void showDialog(final AdapterView<? extends Adapter> parent, String title, String message, final Tag subject) Is there a better way of doing this? // refresh adapter SimpleCursorAdapter adapter; if (parent.getAdapter() instanceof WrapperListAdapter) { adapter = (SimpleCursorAdapter) ((WrapperListAdapter) parent.getAdapter()).getWrappedAdapter(); } else { adapter = (SimpleCursorAdapter) parent.getAdapter(); } adapter.getCursor().requery(); adapter.notifyDataSetChanged(); Also, is there any point in having AdapterView<? extends Adapter> in the signature and not just AdapterView<?>?

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  • Service Layer Patter - Could we avoid the service layer on a specific case?

    - by lidermin
    Hi, we are trying to implement an application using the Service Layer Pattern cause our application needs to connect to other multiple applications too, and googling on the web, we found this link of a demostrative graphic for the "right" way of apply the pattern: martinfowler.com - Service Layer Pattern But now we have a question: what if our system needs to implement some business logic, only for our application (like some maintenance data for the system itself) that we don't need to share with other systems. Based on this graphic: As it seems, it will be unnecesary to implement a service layer just for that; it will be more practical to avoid the service layer, and just go from User Interface to the Business Layer (for example). What should be the right way in this case to implement the Service Layer Pattern? What do you suggest us for a scenario like the one I told you? Thanks in advance.

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  • Service Layer Patter - Could we avoid the service layer on a specific case?

    - by lidermin
    Hi, we are trying to implement an application using the Service Layer Pattern cause our application needs to connect to other multiple applications too, and googling on the web, we found this link of a demostrative graphic for the "right" way of apply the pattern: martinfowler.com - Service Layer Pattern But now we have a question: what if our system needs to implement some business logic, only for our application (like some maintenance data for the system itself) that we don't need to share with other systems. Based on this graphic: As it seems, it will be unnecesary to implement a service layer just for that; it will be more practical to avoid the service layer, and just go from User Interface to the Business Layer (for example). What should be the right way in this case to implement the Service Layer Pattern? What do you suggest us for a scenario like the one I told you? Thanks in advance.

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  • 'script/console test' with spork and rspec not loading the whole environment?

    - by TheDeeno
    I'm trying to load up console to interact with some of my rspec mocking helpers. I expected that running script/console test would load an env similar to when I run spec. However, this doesn't appear to be the case. It looks like spec_helper is never loaded. Or, if it is, it's not actually running through the logic because spork has polluted it a bit. In short, is there a quick and easy way to get an interactive rspec party going?

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  • ASP.NET handling button click event before OnPreInit

    - by Phillykins
    Hello, I have a data access layer, a business logic layer and a presentation layer (ie. the pages themselves). I handle the OnPreInit event and populate collections required for the page. All the data comes from an SQL server database and I do not use caching. I handle a button click event to grab values from a form and insert a new object into the database. The problem is that by the time I handle the click event, the collections have already been populated, so the new item which has been inserted into the database has not been retrieved. What is the accepted solution to this? I could insert the new object directly into the collection and re-bind the GridView, but the SQL query selects only a set of objects and the new object could fall outside of this set. Thanks!

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  • Build a JavaScript wrapper for a rails-generated XML API?

    - by Thor Thurn
    I am working with a large website written in Ruby on Rails. Thanks to the support for REST in Rails 2, the site's business logic is all accessible via a consistent XML API. Now I want to be able to easily write one or more JavaScript frontends to the site that interact with the generated Rails XML API. Ideally, an automated wrapper for the API could be created in JavaScript, since this would minimize the effort required in writing XML processing code for the more than 500 API functions. How, then, can I automatically generate a wrapper around a given XML API in JavaScript so that it's more pleasant to work with? I've worked with solutions of this nature for Java that generate classes and methods to wrap an API, so my current thinking is that I want something of that nature for JavaScript. I'd be open to an alternative take on the problem, though.

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  • [C++] Can all/any struct assignment operator be Overloaded? (and specifically struct tm = sql::Resu

    - by Luke Mcneice
    Hi all, Generally, i was wondering if there was any exceptions of types that cant have thier assignment operator overloaded. Specifically, I'm wanting to overload the assignment operator of a tm struct, (time.h) so i can assign a sql::ResultSet to it. I have already have the conversion logic: sscanf(sqlresult->getString("StoredAt").c_str(),"%d-%d-%d %d:%d:%d",&TempTimeStruct->tm_year,&TempTimeStruct->tm_mon,&TempTimeStruct->tm_mday,&TempTimeStruct->tm_hour,&TempTimeStruct->tm_min,&TempTimeStruct->tm_sec); //populating the struct I tried the overload with this: tm& tm::operator=(sql::ResultSet & results) { //CODE return *this; } however VS08 reports: error C2511: 'tm &tm::operator =(sql::ResultSet &)' : overloaded member function not found in 'tm'

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  • Calling UITableViews delegate methods directly.

    - by RickiG
    Hi I was looking for a way to call the edit method directly. - (void)tableView:(UITableView *)theTableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath I have all my logic for animating manipulated cells, removing from my model array etc. in this method. It is getting called when a user swipes, adds or rearranges, but I would like to call it manually/directly as a background thread changes my model. I have constructed an NSIndexPath like so: NSIndexPath *path = [NSIndexPath indexPathForRow:i inSection:1]; I just can't figure out how to call something like: [self.tableview commitEditingStyle:UITableViewCellEditingStyleDelete forRowAtIndexPath:path]; Do I need to gain access to the methods of this plain style UITableView in another way? Thanks:)

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  • Which design pattern should I be using?

    - by Gabriel
    Here's briefly what I'm trying to do. The user supplies me with a link to a photo from one of several photo-sharing websites (such as Flickr, Zooomr, et. al). I then do some processing on the photo using their respective APIs. Right now, I'm only implementing one service, but I will most likely add more in the near future. I don't want to have a bunch of if/else or switch statements to define the logic for the different websites (but maybe that's necessary?) I'd rather just call GetImage(url) and have it get me the image from whatever service the url's domain is from. I'm confused how the GetImage function and classes should be designed. Maybe I need the strategy pattern? I'm still reading and trying to understand the various design patterns and how I could make one fit in this case. I'm doing this in C#, but this question is language-agnostic.

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