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  • Getting my head around object oriented programing

    - by nLL
    I am entry level .Net developer and using it to develop web sites. I started with classic asp and last year jumped on the ship with a short C# book. As I developed I learned more and started to see that coming from classic asp I always used C# like scripting language. For example in my last project I needed to encode video on the webserver and wrote a code like public class Encoder { Public static bool Encode(string videopath) { ...snip... return true; } } While searching samples related to my project I’ve seen people doing this public class Encoder { Public static Encode(string videopath) { EncodedVideo encoded = new EncodedVideo(); ...snip... encoded.EncodedVideoPath = outputFile; encoded.Success = true; ...snip... } } public class EncodedVideo { public string EncodedVideoPath { get; set; } public bool Success { get; set; } } As I understand second example is more object oriented but I don’t see the point of using EncodedVideo object. Am I doing something wrong? Does it really necessary to use this sort of code in a web app?

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  • Managing aesthetic code changes in git

    - by Ollie Saunders
    I find that I make a lot of small changes to my source code, often things that have almost no functional effect. For example: Refining or correcting comments. Moving function definitions within a class for a more natural reading order. Spacing and lining up some declarations for readability. Collapsing something using multiple lines on to one. Removing an old piece of commented-out code. Correcting some inconsistent whitespace. I guess I have a formidable attention to detail in my code. But the problem is I don't know what to do about these changes and they make it difficult to switch between branches etc. in git. I find myself not knowing whether to commit the minor changes, stash them, or put them in a separate branch of little tweaks and merge that in later. None those options seems ideal. The main problem is that these sort of changes are unpredictable. If I was to commit these there would be so many commits with the message "Minor code aesthetic change.", because, the second I make such a commit I notice another similar issue. What should I do when I make a minor change, a significant change, and then another minor change? I'd like to merge the three minor changes into one commit. It's also annoying seeing files as modified in git status when the change barely warrants my attention. I know about git commit --amend but I also know that's bad practice as it makes my repo inconsistent with remotes.

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  • How to implement generic callbacks in C++

    - by Kylotan
    Forgive my ignorance in asking this basic question but I've become so used to using Python where this sort of thing is trivial that I've completely forgotten how I would attempt this in C++. I want to be able to pass a callback to a function that performs a slow process in the background, and have it called later when the process is complete. This callback could be a free function, a static function, or a member function. I'd also like to be able to inject some arbitrary arguments in there for context. (ie. Implementing a very poor man's coroutine, in a way.) On top of that, this function will always take a std::string, which is the output of the process. I don't mind if the position of this argument in the final callback parameter list is fixed. I get the feeling that the answer will involve boost::bind and boost::function but I can't work out the precise invocations that would be necessary in order to create arbitrary callables (while currying them to just take a single string), store them in the background process, and invoke the callable correctly with the string parameter.

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  • Suggestions on implementing an iPad magazine app

    - by alku83
    I've been tasked with creating a magazine style app for iPad. Ideally it would look a little something like the Zinio app: http://www.zinio.com/ipad/ . This app is effectively a shell, allowing you to sample magazines (eg. read the first few pages) and select them for download. The magazines appear to have some sort of overlay, allowing you to interact with some things (eg. tap to watch a video). A few questions that come to mind: How would I go about delivering content to the user? In-app purchases aren't really an option, as some content will need to be delivered for free. Is it possible to download a package and make this available within the application? What format would be suitable for displaying the magazine? Sequential images, PDF, ebook? I'll need to have some form of interactivity. I guess I could have some form of lookup table, which would include information such as if the user taps on this page, within these coordinates, then launch this item. Anyone dealt with any similar issues?

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  • Sorting a list in PHP

    - by Andy
    Alright, so I've just (almost) finished my first little php script. Basically all it does is handling forms. It writes whatever the user put in to the fields of the form to a text file, then I include that text file in the index of the little page I have set up. So, currently it writes to the beginning of the text file (but doesn't overwrite previous data). But, several users wants this list to be alphabetically sorted instead. So what I want to do is make whatever they submit fall into the list in alphabetical order. The thing here is also that all I use in the text file are divs. The list is basically 'divided' into 3 parts. 'Title', 'Link', and 'Poster'. All I have done is positioned them with css. So, can I sort this list (the titles, in this case) alphabetically and still have the 'link' and 'poster' information assigned the way they already are, but just with the titles sorted? It don't use databases at all on my site, so there is no database handling at all used in this script (mainly because I'm not experienced at all in this).

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  • heterogeneous comparisons in python3

    - by Matt Anderson
    I'm 99+% still using python 2.x, but I'm trying to think ahead to the day when I switch. So, I know that using comparison operators (less/greater than, or equal to) on heterogeneous types that don't have a natural ordering is no longer supported in python3.x -- instead of some consistent (but arbitrary) result we raise TypeError instead. I see the logic in that, and even mostly think its a good thing. Consistency and refusing to guess is a virtue. But what if you essentially want the python2.x behavior? What's the best way to go about getting it? For fun (more or less) I was recently implementing a Skip List, a data structure that keeps its elements sorted. I wanted to use heterogeneous types as keys in the data structure, and I've got to compare keys to one another as I walk the data structure. The python2.x way of comparing makes this really convenient -- you get an understandable ordering amongst elements that have a natural ordering, and some ordering amongst those that don't. Consistently using a sort/comparison key like (type(obj).__name__, obj) has the disadvantage of not interleaving the objects that do have a natural ordering; you get all your floats clustered together before your ints, and your str-derived class separates from your strs. I came up with the following: import operator def hetero_sort_key(obj): cls = type(obj) return (cls.__name__+'_'+cls.__module__, obj) def make_hetero_comparitor(fn): def comparator(a, b): try: return fn(a, b) except TypeError: return fn(hetero_sort_key(a), hetero_sort_key(b)) return comparator hetero_lt = make_hetero_comparitor(operator.lt) hetero_gt = make_hetero_comparitor(operator.gt) hetero_le = make_hetero_comparitor(operator.le) hetero_ge = make_hetero_comparitor(operator.gt) Is there a better way? I suspect one could construct a corner case that this would screw up -- a situation where you can compare type A to B and type A to C, but where B and C raise TypeError when compared, and you can end up with something illogical like a > b, a < c, and yet b > c (because of how their class names sorted). I don't know how likely it is that you'd run into this in practice.

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  • How to control the order of module initialization in Prism

    - by Robert Taylor
    I'm using Prism V2 with a DirectoryModuleCatalog and I need the modules to be initialized in a certain order. The desired order is specified with an attribute on each IModule implementation. This is so that as each module is initialized, they add their View into a TabControl region and the order of the tabs needs to be deterministic and controlled by the module author. The order does not imply a dependency, but rather just an order that they should be initialized in. In other words: modules A, B, and C may have priorities of 1, 2, and 3 respectively. B does not have a dependency on A - it just needs to get loaded into the TabControl region after A. So that we have a deterministic and controllable order of the tabs. Also, B might not exist at runtime; so they would load as A, C because the priority should determine the order (1, 3). If i used the ModuleDependency, then module "C" will not be able to load w/o all of it's dependencies. I can manage the logic of how to sort the modules, but i can't figure out where to put said logic.

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  • Creating Emulated iSCSI Target in a Lab/Testing Environment using Windows Server 2008 R2

    - by Brian McCleary
    We have a single server running Windows Server 2008 with Hyper-V installed running 5 virtual machines. I have purchased a second DELL R805 Server so that we can create a fail-over cluster to our current R805 that is currently in production. Right now, our R805 connects via iSCSI to a MD3000i iSCSI SAN. Before we try to roll out the second server and clustering to our production environment, I want to be able to test and "play with" the clustering features in our lab before rolling it out. The problem is that I don't want to spend a couple thousand dollars on another iSCSI SAN server just for testing. I already have two servers in my lab that are installed with Windows Server 2008 R2 64bit (one is the R805 and another spare desktop that was laying around) and with the Hyper-V roll enabled that should be ready to test with, but I don't have an iSCSI target to use as the Cluster Shared Volume. Is there anyway to install, either on a Hyper-V image or on a external spare computer that we have some sort of emulated iSCSI target? In our lab, we obviously don't need a real SAN, just something that we can test out how to setup the clustering properly outside of our production environment. Any advise is appreciated. FYI - I have read Jose Barret's blog on WUDSS at http://blogs.technet.com/josebda/archive/2008/01/07/installing-the-evaluation-version-of-wudss-2003-refresh-and-the-microsoft-iscsi-software-target-version-3-1-on-a-vm.aspx, but it seems awfully complex. I'm hoping for an easier solution.

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  • Import-Pssession is not importing cmdlets when used in a custom module

    - by Douglas Plumley
    I have a PowerShell script/function that works great when I use it in my PowerShell profile or manually copy/paste the function in the PowerShell window. I'm trying to make the function accessible to other members of my team as a module. I want to have the module stored in a central place so we can all add it to our PSModulePath. Here is a copy of the basic function: Function Connect-O365{ $o365cred = Get-Credential [email protected] $session365 = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://ps.outlook.com/powershell/ -Credential $o365cred -Authentication Basic -AllowRedirection Import-PSSession $session365 -AllowClobber } If I save this function in my PowerShell profile it works fine. I can dot source a *.ps1 script with this function in it and it works as well. The issue is when I save the function as a *.psm1 PowerShell script module. The function runs fine but none of the exported commands from the Import-PSSession are available. I think this may have something to do with the module scope. I'm looking for suggestions on how to get around this. EDIT When I create the following module and run Connect-O365 the imported cmdlets will not be available. $scriptblock = { Function Connect-O365{ $o365cred = Get-Credential [email protected] $session365 = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri "https://ps.outlook.com/powershell/" -Credential $o365cred -Authentication Basic -AllowRedirection Import-PSSession $session365 -AllowClobber } } New-Module -Name "Office 365" -ScriptBlock $scriptblock When I import the next module without the Connect-O365 function the imported cmdlets are available. $scriptblock = { $o365cred = Get-Credential [email protected] $session365 = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri "https://ps.outlook.com/powershell/" -Credential $o365cred -Authentication Basic -AllowRedirection Import-PSSession $session365 -AllowClobber } New-Module -Name "Office 365" -ScriptBlock $scriptblock This appears to be a scope issue of some sort, just not sure how to get around it.

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  • Why doesn't C# do "simple" type inference on generics?

    - by Ken Birman
    Just curious: sure, we all know that the general case of type inference for generics is undecidable. And so C# won't do any kind of subtyping at all: if Foo<T> is a generic, Foo<int> isn't a subtype of Foo<T>, or Foo<Object> or of anything else you might cook up. And sure, we all hack around this with ugly interface or abstract class definitions. But... if you can't beat the general problem, why not just limit the solution to cases that are easy. For example, in my list above, it is OBVIOUS that Foo<int> is a subtype of Foo<T> and it would be trivial to check. Same for checking against Foo<Object>. So is there some other deep horror that would creep forth from the abyss if they were to just say, aw shucks, we'll do what we can? Or is this just some sort of religious purity on the part of the language guys at Microsoft?

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  • Problem with sorting NSDictionary

    - by Stas Dmitrenko
    Hello. I need to sort a NSDictionary of dictionaries. It looks like: {//dictionary RU = "110.1"; //key and value SG = "150.2"; //key and value US = "50.3"; //key and value } Result need to be like: {//dictionary SG = "150.2"; //key and value RU = "110.1"; //key and value US = "50.3"; //key and value } I am trying this: @implementation NSMutableDictionary (sorting) -(NSMutableDictionary*)sortDictionary { NSArray *allKeys = [self allKeys]; NSMutableArray *allValues = [NSMutableArray array]; NSMutableArray *sortValues= [NSMutableArray array]; NSMutableArray *sortKeys= [NSMutableArray array]; for(int i=0;i<[[self allValues] count];i++) { [allValues addObject:[NSNumber numberWithFloat:[[[self allValues] objectAtIndex:i] floatValue]]]; } [sortValues addObjectsFromArray:allValues]; [sortKeys addObjectsFromArray:[self allKeys]]; [sortValues sortUsingDescriptors:[NSArray arrayWithObject:[[[NSSortDescriptor alloc] initWithKey:@"floatValue" ascending:NO] autorelease]]]; for(int i=0;i<[sortValues count];i++) { [sortKeys replaceObjectAtIndex:i withObject:[allKeys objectAtIndex:[allValues indexOfObject:[sortValues objectAtIndex:i]]]]; [allValues replaceObjectAtIndex:[allValues indexOfObject:[sortValues objectAtIndex:i]] withObject:[NSNull null]]; } NSLog(@"%@", sortKeys); NSLog(@"%@", sortValues); NSLog(@"%@", [NSMutableDictionary dictionaryWithObjects:sortValues forKeys:sortKeys]); return [NSMutableDictionary dictionaryWithObjects:sortValues forKeys:sortKeys]; } @end This is the result of NSLog: 1) { SG, RU, US } 2) { 150.2, 110.1, 50.3 } 3) { RU = "110.1"; SG = "150.2"; US = "50.3"; } Why is this happening? Can you help me with this problem?

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  • MYSQL not running on Ubuntu OS - Error 2002.

    - by mgj
    Hi, I am a novice to mysql DB. I am trying to run the MYSQL Server on Ubuntu 10.04. Through Synaptic Package Manager I am have installed the mysql version: mysql-client-5.1 I wonder that how was the database password set for the mysql-client software that I installed through the above way.It would be nice if you could enlighten me on this. When I tried running this database, I encountered the error given below: mohnish@mohnish-laptop:/var/lib$ mysql ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) mohnish@mohnish-laptop:/var/lib$ I referred to a similar question posted by another user. I didn't find a solution through the proposed answers. For instance when I tried the solutions posted for the similar question I got the following: mohnish@mohnish-laptop:/var/lib$ service start mysqld start: unrecognized service mohnish@mohnish-laptop:/var/lib$ ps -u mysql ERROR: User name does not exist. ********* simple selection ********* ********* selection by list ********* -A all processes -C by command name -N negate selection -G by real group ID (supports names) -a all w/ tty except session leaders -U by real user ID (supports names) -d all except session leaders -g by session OR by effective group name -e all processes -p by process ID T all processes on this terminal -s processes in the sessions given a all w/ tty, including other users -t by tty g OBSOLETE -- DO NOT USE -u by effective user ID (supports names) r only running processes U processes for specified users x processes w/o controlling ttys t by tty *********** output format ********** *********** long options *********** -o,o user-defined -f full --Group --User --pid --cols --ppid -j,j job control s signal --group --user --sid --rows --info -O,O preloaded -o v virtual memory --cumulative --format --deselect -l,l long u user-oriented --sort --tty --forest --version -F extra full X registers --heading --no-heading --context ********* misc options ********* -V,V show version L list format codes f ASCII art forest -m,m,-L,-T,H threads S children in sum -y change -l format -M,Z security data c true command name -c scheduling class -w,w wide output n numeric WCHAN,UID -H process hierarchy mohnish@mohnish-laptop:/var/lib$ which mysql /usr/bin/mysql mohnish@mohnish-laptop:/var/lib$ mysql ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) I even tried referring to http://forums.mysql.com/read.php?11,27769,84713#msg-84713 but couldn't find anything useful. Please let me know how I could tackle this error. Thank you very much..

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  • Float addition promoted to double?

    - by Andreas Brinck
    I had a small WTF moment this morning. Ths WTF can be summarized with this: float x = 0.2f; float y = 0.1f; float z = x + y; assert(z == x + y); //This assert is triggered! (Atleast with visual studio 2008) The reason seems to be that the expression x + y is promoted to double and compared with the truncated version in z. (If i change z to double the assert isn't triggered). I can see that for precision reasons it would make sense to perform all floating point arithmetics in double precision before converting the result to single precision. I found the following paragraph in the standard (which I guess I sort of already knew, but not in this context): 4.6.1. "An rvalue of type float can be converted to an rvalue of type double. The value is unchanged" My question is, is x + y guaranteed to be promoted to double or is at the compiler's discretion? UPDATE: Since many people has claimed that one shouldn't use == for floating point, I just wanted to state that in the specific case I'm working with, an exact comparison is justified. Floating point comparision is tricky, here's an interesting link on the subject which I think hasn't been mentioned.

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  • iPhone: Leak with UIWebView loading Office documents. Any ideas how to avoid it?

    - by Thomas Tempelmann
    While there are already quite a few posts about leaks around UIWebView, mine is a bit more special, I believe, and thus deserves its own post here. I see a reproducible large leak every time I load a Office document such as a Word or Excel file. For instance, every time I display a 180KB .doc file, I get a 100KB leak. And that happens with both the simulator and an actual device, running OS 3.1.3. The leak is not visible with the Leaks instrument but only by looking at the malloc instances via the ObjectAlloc instrument. Here's a picture from the instruments trace: I've also made a demo project, UIWebView-Leak.zip, so you can verify this yourself. To see the leak, use the ObjectAlloc instrument, switch to the view where you see individual allocation objects, and sort by size so that you see the large ones in a group, just like in my picture above. Then view a Office document a few times and find the Malloc objects that keep staying "Live" even after the actual UIWebView has been freed. Is this a known bug? Or is there any way I can avoid these leaks? I.e, have you successfully shown Office documents on an iPhone withing getting such leaks? Note: I've reported this as a bug to Apple now, too (ID 7950594) I am still waiting for someone (including Apple) to confirm this as a true leak or show why it isn't (i.e. that I do something wrong or make wrong assumptions)

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  • How do I send text to a UITextView?

    - by Lee
    I'm new to iphone development. I'm a VB programmer who is trying to convert a VB application to an ipad app. I need some help with sending text to a UITextView. I want to first have a UIPickerView and then once the user hits a UIButton, a UITextView appears and the text is then generated by my source code code, line by line. The code would constantly be concatenating strings to the text. It would sort of go like this-- 1) User makes selections with UIPickerView. 2) User then hits UIButton. 3) UIPickerView is replaced on the screen with a UITextView. 4) The code does stuff. 5) The code adds the 1st line of text into the UITextView. 6) The code does more stuff. 7) The code then adds the 2nd line of text into the UITextView, retaining the 1st line that was already there. Steps 6 and 7 are repeated until the code is done. Does anyone know of any examples of this that I could look at? I am mostly interested in finding something like a youtube video, a webpage that explains the code or even a good book that covers this particular topic. I am finding that the sample codes that Apple has on this site goes over my head. In fact, I could probably benefit from a good book. But, I am looking for one that I would already know covers this particular topic, since it is so essential to the app that I am trying to build.

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  • What's the most efficient query?

    - by Aaron Carlino
    I have a table named Projects that has the following relationships: has many Contributions has many Payments In my result set, I need the following aggregate values: Number of unique contributors (DonorID on the Contribution table) Total contributed (SUM of Amount on Contribution table) Total paid (SUM of PaymentAmount on Payment table) Because there are so many aggregate functions and multiple joins, it gets messy do use standard aggregate functions the the GROUP BY clause. I also need the ability to sort and filter these fields. So I've come up with two options: Using subqueries: SELECT Project.ID AS PROJECT_ID, (SELECT SUM(PaymentAmount) FROM Payment WHERE ProjectID = PROJECT_ID) AS TotalPaidBack, (SELECT COUNT(DISTINCT DonorID) FROM Contribution WHERE RecipientID = PROJECT_ID) AS ContributorCount, (SELECT SUM(Amount) FROM Contribution WHERE RecipientID = PROJECT_ID) AS TotalReceived FROM Project; Using a temporary table: DROP TABLE IF EXISTS Project_Temp; CREATE TEMPORARY TABLE Project_Temp (project_id INT NOT NULL, total_payments INT, total_donors INT, total_received INT, PRIMARY KEY(project_id)) ENGINE=MEMORY; INSERT INTO Project_Temp (project_id,total_payments) SELECT `Project`.ID, IFNULL(SUM(PaymentAmount),0) FROM `Project` LEFT JOIN `Payment` ON ProjectID = `Project`.ID GROUP BY 1; INSERT INTO Project_Temp (project_id,total_donors,total_received) SELECT `Project`.ID, IFNULL(COUNT(DISTINCT DonorID),0), IFNULL(SUM(Amount),0) FROM `Project` LEFT JOIN `Contribution` ON RecipientID = `Project`.ID GROUP BY 1 ON DUPLICATE KEY UPDATE total_donors = VALUES(total_donors), total_received = VALUES(total_received); SELECT * FROM Project_Temp; Tests for both are pretty comparable, in the 0.7 - 0.8 seconds range with 1,000 rows. But I'm really concerned about scalability, and I don't want to have to re-engineer everything as my tables grow. What's the best approach?

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  • OOP - Handling Automated Instances of a Class - PHP

    - by dscher
    This is a topic that, as a beginner to PHP and programming, sort of perplexes me. I'm building a stockmarket website and want users to add their own stocks. I can clearly see the benefit of having each stock be a class instance with all the methods of a class. What I am stumped on is the best way to give that instance a name when I instantiate it. If I have: class Stock() { ....doing stuff..... } what is the best way to give my instances of it a name. Obviously I can write: $newStock = new Stock(); $newStock.getPrice(); or whatever, but if a user adds a stock via the app, where can the name of that instance come from? I guess that there is little harm in always creating a new child with $newStock = new Stock() and then storing that to the DB which leads me to my next question! What would be the best way to retrieve 20 user stocks(for example) into instances of class Stock()? Do I need to instantiate 20 new instances of class Stock() every time the user logs in or is there something I'm missing? I hope someone answers this and more important hope a bunch of people answer this and it somehow helps someone else who is having a hard time wrapping their head around what probably leads to a really elegant solution. Thanks guys!

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  • Unable to change background colour for JOptionPane

    - by Sunil Kumar Sahoo
    Hi I have created sample progeam which will give same look and feel of a confirm dialog and set the background colour as red. But I donot know what is the problem that my background colour of option is displayed as the default colour but not red. also i need same look and feel of confirm dialog across all platforms. Here is the code that I have written. please help me to solve the issue public class JOptionPaneBackground { public static void main(String[] args) throws Exception { // UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName()); UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); UIDefaults uiDefaults = UIManager.getLookAndFeelDefaults(); List<Object> keys = new ArrayList<Object>(uiDefaults.keySet()); Collections.sort(keys, new Comparator<Object>() { public int compare(Object o1, Object o2) { return (o1.toString()).compareTo(o2.toString()); } }); for (Object key : keys) { System.out.println(String.format("%-40s = %s", key, uiDefaults.get(key))); } UIManager.put("OptionPane.background", Color.red); UIManager.put("Panel.background", Color.red); JOptionPane.showConfirmDialog(null, "Hello World!"); } }

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  • How to avoid multiple, unused has_many associations when using multiple models for the same entity (

    - by mikep
    Hello, I'm looking for a nice, Ruby/Rails-esque solution for something. I'm trying to split up some data using multiple tables, rather than just using one gigantic table. My reasoning is pretty much to try and avoid the performance drop that would come with having a big table. So, rather than have one table called books, I have multiple tables: books1, books2, books3, etc. (I know that I could use a partition, but, for now, I've decided to go the 'multiple tables' route.) Each user has their books placed into a specific table. The actual book table is chosen when the user is created, and all of their books go into the same table. The goal is to try and keep each table pretty much even -- but that's a different issue. One thing I don't particularly want to have is a bunch of unused associations in the User class. Right now, it looks like I'd have to do the following: class User < ActiveRecord::Base has_many :books1, :books2, :books3, :books4, :books5 end class Books1 < ActiveRecord::Base belongs_to :user end class Books2 < ActiveRecord::Base belongs_to :user end First off, for each specific user, only one of the book tables would be usable/applicable, since all of a user's books are stored in the same table. So, only one of the associations would be in use at any time and any other has_many :bookX association that was loaded would be a waste. I don't really know Ruby/Rails does internally with all of those has_many associations though, so maybe it's not so bad. But right now I'm thinking that it's really wasteful, and that there may just be a better, more efficient way of doing this. Is there's some sort of special Ruby/Rails methodology that could be applied here to avoid having to have all of those has_many associations? Also, does anyone have any advice on how to abstract the fact that there's multiple book tables behind a single books model/class?

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  • Risking the exception anti-pattern.. with some modifications

    - by Sridhar Iyer
    Lets say that I have a library which runs 24x7 on certain machines. Even if the code is rock solid, a hardware fault can sooner or later trigger an exception. I would like to have some sort of failsafe in position for events like this. One approach would be to write wrapper functions that encapsulate each api a: returnCode=DEFAULT; try { returnCode=libraryAPI1(); } catch(...) { returnCode=BAD; } return returnCode; The caller of the library then restarts the whole thread, reinitializes the module if the returnCode is bad. Things CAN go horribly wrong. E.g. if the try block(or libraryAPI1()) had: func1(); char *x=malloc(1000); func2(); if func2() throws an exception, x will never be freed. On a similar vein, file corruption is a possible outcome. Could you please tell me what other things can possibly go wrong in this scenario?

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  • Enumerate all paths in a weighted graph from A to B where path length is between C1 and C2

    - by awmross
    Given two points A and B in a weighted graph, find all paths from A to B where the length of the path is between C1 and C2. Ideally, each vertex should only be visited once, although this is not a hard requirement. I supose I could use a heuristic to sort the results of the algorithm to weed out "silly" paths (e.g. a path that just visits the same two nodes over and over again) I can think of simple brute force algorithms, but are there any more sophisticed algorithms that will make this more efficient? I can imagine as the graph grows this could become expensive. In the application I am developing, A & B are actually the same point (i.e. the path must return to the start), if that makes any difference. Note that this is an engineering problem, not a computer science problem, so I can use an algorithm that is fast but not necessarily 100% accurate. i.e. it is ok if it returns most of the possible paths, or if most of the paths returned are within the given length range.

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  • How to use the LINQ where expression?

    - by NullReference
    I'm implementing the service \ repository pattern in a new project. I've got a base interface that looks like this. Everything works great until I need to use the GetMany method. I'm just not sure how to pass a LINQ expression into the GetMany method. For example how would I simply sort a list of objects of type name? nameRepository.GetMany( ? ) public interface IRepository<T> where T : class { void Add(T entity); void Update(T entity); void Delete(T entity); void Delete(Expression<Func<T, bool>> where); T GetById(long Id); T GetById(string Id); T Get(Expression<Func<T, bool>> where); IEnumerable<T> GetAll(); IEnumerable<T> GetMany(Expression<Func<T, bool>> where); } public virtual IEnumerable<T> GetMany(Expression<Func<T, bool>> where) { return dbset.Where(where).ToList(); }

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  • How do I design a Wizard-based system with SoC in mind?

    - by Erik Forbes
    I'm building a Windows Forms system (in C# if it matters to anyone) that provides an application automation service. As this application is targeted at users who are not computer savvy, I've decided to break up the functions of the application into various tasks, and provide these tasks via a wizard UI. I'd like to avoid coupling the views and view engine (from which the Wizard will be built) to the automation engine. The problem I'm having is that the automation engine, which runs on a separate thread while it does its thing, needs to report status information back to the user, as well as listen for cancel or pause events from the user. Since I don't want the view engine or the automation engine to rely on each other, I'm having a hard time figuring out how to provide for this information conduit. Any insights into this issue I'm having would be greatly appreciated. I've been wracking my brain for a couple weeks now on this point, and I really don't want to give up and just couple everything together. If anyone needs additional details to help come up with some sort of idea please let me know and I'll be happy to provide them.

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  • How can I make a family of singletons?

    - by Jay
    I want to create a set of classes that share a lot of common behavior. Of course in OOP when you think that you automatically think "abstract class with subclasses". But among the things I want these classes to do is to each have a static list of instances of the class. The list should function as sort of a singleton within the class. I mean each of the sub-classes has a singleton, not that they share one. "Singleton" to that subclass, not a true singleton. But if it's a static, how can I inherit it? Of course code like this won't work: public abstract A { static List<A> myList; public static List getList() { if (myList==null) myList=new ArrayList<A>(10); return myList; } public static A getSomethingFromList() { List listInstance=getList(); ... do stuff with list ... } public int getSomethingFromA() { ... regular code acting against current instance ... } } public class A1 extends A { ... } public class A2 extends A { ... } A1 somethingfromA1List=(A1) A1.getSomethingFromList(); A2 somethingfromA2List=(A2) A2.getSomethingFromList(); The contents of the list for each subclass would be different, but all the code to work on the lists would be the same. The problem with the above code is that I'd only have one list for all the subclasses, and I want one for each. Yes, I could replicate the code to declare the static list in each of the subclasses, but then I'd also have to replicate all the code that adds to the lists and searches the list, etc, which rather defeats the purpose of subclassing. Any ideas on how to do this without replicating code?

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  • What is wrong with the JavaScript event handling in this example? (Using click() and hover() jQuery

    - by Bungle
    I'm working on a sort of proof-of-concept for a project that approximates Firebug's inspector tool. For more details, please see this related question. Here is the example page. I've only tested it in Firefox: http://troy.onespot.com/static/highlight.html The idea is that, when you're mousing over any element that can contain text, it should "highlight" with a light gray background to indicate the boundaries of that element. When you then click on the element, it should alert() a CSS selector that matches it. This is somewhat working in the example linked above. However, there's one fundamental problem. When mousing over from the top of the page to the bottom, it will pick up the paragraphs, <h1> element, etc. But, it doesn't get the <div>s that encompass those paragraphs. However, for example, if you "sneak up" on the <div> that contains the two paragraphs "The area was settled..." and "Austin was selected..." from the left - tracing down the left edge of the page and entering the <div> just between the two paragraphs (see this screenshot) - then it is picked up. I assume this has something to do with the fact that I haven't attached an event handler to the <body> element (where you're entering the <div> from if you enter from the left), but I have attached handlers to the <p>s (where you're entering from if you come from the top or bottom). There are also other issues with mousing in and out elements - background colors that "stick" and the like - that I think are also related. As indicated in the related question posted above, I suspect there is something about event bubbling that I don't understand that is causing unexpected behavior. Can anyone spot what's wrong with my code? Thanks in advance for any help!

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