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  • Help me with a solution for what could be solutioned by virtual static fields... in FPC

    - by Gregory Smith
    Hi I'm doing an event manager in Freepascal Each event is an object type TEvent (=object), each kind of event must derive from this class. Events are differentiated by an integer identificator, assigned dynamically. The problem is that i want to retrieve the event id of an instance, and i can't do it well. All instances of a class(object) have a unique id = so it should be static field. All classes have a diferent id = so it should be virtual. Event ids are assignated in run time, and can change = so it can't be a simple method In sum, I can't put all this together. I'm looking for an elegant solution, i don't want to write a hardcoded table, actualizing it in every constructor... etc, i'd prefer something taking advantage of the polymorphism Can anyone help me with another technical or design solution? I remark I don't want to use class instead of object construct.(property doesn't work on objects? :(

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  • Which is the most memory leak safe approach.

    - by MattC
    I have a table of frequently updated information. This is presented using a container div with a div for each row, each row containing 10 divs. I am using setInterval to call a an asmx webservice that returns some json formatted information. On the success callback I call $("#myContainer").empty(); on the container div and recreate the rows and 10 nested divs for each row's columns. This page may be left to run for a whole day, so I am wary of updating the DOM like this as I have noticed that memory does rise for the browser over time (IE8). The other approach I am considering is to add an idea to the row div. When new results process each item of data, look for the corresponding row, if it exists overwrite the data in each div. If it doesn't exist (new data for example), append the row. What approaches have others used for this sort of long lived pseudo realtime information display. TIA

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  • Example with Visitor Pattern

    - by devoured elysium
    public class Song { public string Genre { get; protected set; } public string Name { get; protected set; } public string Band { get; protected set; } public Song(string name, string band, string genre) { Name = name; Genre = genre; Band = band; } } public interface IMusicVisistor { void Visit(List<Song> items); } public class MusicLibrary { List<Song> _songs = new List<Song> { ...songs ... }; public void Accept(IMusicVisitor visitor) { visitor.Visit(_songs); } } and now here's one Visitor I made: public class RockMusicVisitor : IMusicVisitor { public List<Song> Songs { get; protected set; } public void Visit(List<Song> items) { Songs = items.Where(x => x.Genre == "Rock").ToList(); } } Why is this any better than just putting a public property Songs and then letting any kind of class do with it anything that it wants to? This example comes from this post.

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  • python: how to design a container with elements that must reference their container

    - by Luke404
    (the title is admittedly not that great. Please forgive my English, this is the best I could think of) I'm writing a python script that will manage email domains and their accounts, and I'm also a newby at OOP design. My two (related?) issues are: the Domain class must do special work to add and remove accounts, like adding/removing them to the underlying implementation how to manage operations on accounts that must go through their container To solve the former issue I'd add a factory method to the Domain class that'll build an Account instance in that domain, and a 'remove' (anti-factory?) method to handle deletions. For the latter this seems to me "anti-oop" since what would logically be an operation on an Account (eg, change password) must always reference the containing Domain. Seems to me that I must add to the Account a reference back to the Domain and use that to get data (like the domain name) or call methods on the Domain class. Code example (element uses data from the container) that manages an underlying Vpopmail system: class Account: def __init__(self, name, password, domain): self.name = name self.password = password self.domain = domain def set_password(self, password): os.system('vpasswd %s@%s %s' % (self.name, self.domain.name, password) self.password = password class Domain: def __init__(self, domain_name): self.name = domain_name self.accounts = {} def create_account(self, name, password): os.system('vadduser %s@%s %s' % (name, self.name, password)) account = Account(name, password, self) self.accounts[name] = account def delete_account(self, name): os.system('vdeluser %s@%s' % (name, self.name)) del self.accounts[name] another option would be for Account.set_password to call a Domain method that would do the actual work - sounds equally ugly to me. Also note the duplication of data (account name also as dict key), it sounds logical (account names are "primary key" inside a domain) but accounts need to know their own name.

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  • j2ee deployment error

    - by Rajesh
    hi im new to j2ee.. the problem is while deploying a particular project i'm getting deployment error like "module has not been deployed".. but i'm able to deploy other projects... the error shown is as follows In-place deployment at F:\onlineexam_1\build\web deploy?path=F:\onlineexam_1\build\web&name=onlineexam_1&force=true failed on GlassFish v3 Domain F:\onlineexam_1\nbproject\build-impl.xml:577: The module has not been deployed. BUILD FAILED (total time: 3 seconds) pls assist me to overcome this problem Thnx in advance Raj

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  • How can I use data binding in WPF to create a new user control for each element in a list?

    - by Joel
    I have a list of objects. For each item in the list, I want to create a new user control bound to that item. From what I've read, doing this programmatically is bad practice with WPF (as well as less than straightforward), so I should use data binding as a solution instead. The problem is, I can't figure out how to do this. I don't know the contents of the list (just the type) at compile-time, so I can't create and bind with XAML for each element. Google and MSDN don't seem to have any answers, so maybe I'm thinking about this the wrong way? What do I need to do? Thanks

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  • Database design for credit based purchases

    - by FreshCode
    I need an elegant way to implement credit-based purchases for an online store with a small variety of products which can be purchased using virtual credit or real currency. Alternatively, products could only be priced in credits. Previous work I have implemented credit-based purchasing before using different product types (eg. Credit, Voucher or Music) with post-order processing to assign purchased credit to users in the form of real currency, which could subsequently be used to discount future orders' charge totals. This worked fairly well as a makeshift solution, but did not succeed in disconnecting the virtual currency from the real currency, which is what I'd like to do, since spending credits is psychologically easier for customers than spending real currency. Design I need guidance on designing the database correctly with support for the simultaneous bulk purchase of credits at a discount along with real currency products. Alternatively, should all products be priced in credits and only credit have a real currency value? Existing Database Design Partial Products table: ProductId Title Type UnitPrice SalePrice Partial Orders table: OrderId UserId (related to Users table, not shown) Status Value Total Partial OrderItems table (similar to CartItems table): OrderItemId OrderId (related to Orders table) ProductId (related to Products table) Quantity UnitPrice SalePrice Prospective UserCredits table: CreditId UserId (related to Users table, not shown) Value (+/- value. Summed over time to determine saldo.) Date I'm using ASP.NET MVC and LINQ-to-SQL on a SQL Server database.

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  • Is there a Standard or Best Practice for Perl Programs, as opposed to Perl Modules?

    - by swestrup
    I've written any number of perl modules in the past, and more than a few stand-alone perl programs, but I've never released a multi-file perl program into the wild before. I have a perl program that is almost at the beta stage and is going to be released open source. It requires a number of data files, as well as some external perl modules -- some I've written myself, and some from CPAN -- that I'll have to bundle with it so as to ensure that someone can just download my program and install it without worrying about hunting for obscure modules. So, it sounds to me like I need to write an installer to copy all the files to standard locations so that a user can easily install everything. The trouble is, I have no idea what the standard practice would be for this. I have found lots of tutorials on perl module standards, but none on perl program standards. Does anyone have any pointers to standard paths, installation proceedures, etc, for perl programs? This is going to be complicated by the fact that the program is multi-platform. I've been testing it in Linux, but its designed to work equally well in Windows.

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  • Need advice to design 'crack-proof' software

    - by alee
    I am currently working on a project where i need to create some architecture, framework or any standards by which i can "at least" increase the cracking method for a software, i.e, to add to software security. There are already different ways to activate a software which includes online activation, keys etc. I am currently studying few research papers as well. But there are still lot of things that i want to discuss. Could someone guide me to some decent forum, mailing list or something like that? or any other help would be appreciated.

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  • where to enlist transaction with parent child delete (repository or bll)?

    - by Caroline Showden
    My app uses a business layer which calls a repository which uses linq to sql. I have an Item class that has an enum type property and an ItemDetail property. I need to implement a delete method that: (1) always delete the Item (2) if the item.type is XYZ and the ItemDetail is not null, delete the ItemDetail as well. My question is where should this logic be housed? If I have it in my business logic which I would prefer, this involves two separate repository calls, each of which uses a separate datacontext. I would have to wrap both calls is a System.Transaction which (in sql 2005) get promoted to a distributed transaction which is not ideal. I can move it all to a single repository call and the transaction will be handled implicitly by the datacontext but feel that this is really business logic so does not belong in the repository. Thoughts? Carrie

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  • Mutex names - best practice?

    - by Argalatyr
    Related to this question, what is the best practice for naming a mutex? I realize this may vary with OS and even with version (esp for Windows), so please specify platform in answering. My interest is in Win XP and Vista. EDIT: I am motivated by curiousity, because in Rob Kennedy's comment under his (excellent) Answer to the above-linked Question, he implied that the choice of mutex name is non-trivial and should be the subject of a separate question. EDIT2: The referenced question's goal was to ensure only a single instance of an app is running.

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  • Is JavaScript 's "new" Keyword Considered Harmful?

    - by Pablo Fernandez
    In another question, a user pointed out that the new keyword was dangerous to use and proposed a solution to object creation that did not use new... I didn't believe that was true, mostly because I've used Prototype, Scriptaculous and other excellent JavaScript libraries, and everyone of them used the new keyword... In spite of that, yesterday I was watching Douglas Crockford's talk at YUI theater and he said the exactly same thing, that he didn't use the new keyword anymore in his code. Is it 'bad' to use the new keyword? what are the advantages and disadvantages of using it?

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  • Best Practice for Uploading Many (2000+) Images to A Server

    - by bob
    Hello, I have a general question about this. When you have a gallery, sometimes people need to upload 1000's of images at once. Most likely, it would be done through a .zip file. What is the best way to go about uploading this sort of thing to a server. Many times, server have timeouts etc. that need to be accounted for. I am wondering what kinds of things should I be looking out for and what is the best way to handle a large amount of images being uploaded. I'm guessing that you would allow a user to upload a zip file (assuming the timeout does not effect you), and this zip file is uploaded to a specific directory, lets assume in this case a directory is created for each user in the system. You would then unzip the directory on the server and scan the user's folder for any directories containing .jpg or .png or .gif files (etc.) and then import them into a table accordingly. I'm guessing labeled by folder name. What kind of server side troubles could I run into? I'm aware that there may be many issues. Even general ideas would be could so I can then research further. Thanks! Also, I would be programming in Ruby on Rails but I think this question applies accross any language.

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  • Rails: find by day of week with timestamp

    - by Sleepycat
    I need to grab the records for same day of the week for the preceeding X days of the week. There must be a better way to do it than this: Transaction.find_by_sql "select * from transactions where EXTRACT(DOW from date) = 1 and organisation_id = 4 order by date desc limit 7" It gets me what I need but is Postgres specific and not very "Rails-y". Date is a timestamp. Anyone got suggestions?

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  • Program Structure Design Tools? (Top Down Design)

    - by Lee Olayvar
    I have been looking to expand my methodologies to better involve Unit testing, and i stumbled upon Behavioral Driven Design (Namely Cucumber, and a few others). I am quite intrigued by the concept as i have never been able to properly design top down, only because keeping track of the design gets lost without a decent way to record it. So on that note, in a mostly language agnostic way, are there any useful tools out there i am (probably) unaware of? Eg, i have often been tempted to try building flow charts for my programs, but i am not sure how much that will help, and it seems a bit confusing to me how i could make a complex enough flow chart to handle the logic of a full program, and all its features.. ie, it just seems like flow charts would be limiting in the design scheme.. or possibly grow to an unmaintainable scale. BDD methods are nice, but with a system that is so tied to structure, tying into the language and unit testing seems like a must (for it to be worth it) and it seems to be hard to find something to work well with both Python and Java (my two main languages). So anyway.. on that note, any comments are much appreciated. I have searched around on here and it seems like top down design is a well discussed topic, but i haven't seen too much reference to tools themselves, eg, flow chart programs, etc. I am on Linux, if it matters (in the case of programs).

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  • effective retrieve for a voting system in PHP and MySQL

    - by Adnan
    Hello, I have a system where registered users can vote up/vote down comment for a picture. Something very similar to SO's voting system. I store the votes in a table with values as such; vote_id | vote_comment_id | vote_user_id | vote_date | vote_type Now I have few a question concerned the speed and efficiency for the following; PROB: Once a user opens the picture page with comments I need, if that user has already voted UP/DOWN a comment to show it like; "you voted up" or "you voted down" next to the comment (in SO it the vote image is highlighted) MY POSSIBLE SOL: Right now when I open a picture page for each comment I loop thru, I loop thru my table of votes as well and check if a user has voted and show the status (I compare the vote_user_id with the user's session). How efficient is this? Anyone have a better approach to tackle this kind of problem?

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  • CQRS - The query side

    - by mattcodes
    A lot of the blogsphere articles related to CQRS (command query repsonsibility) seperation seem to imply that all screens/viewmodels are flat. e.g. Name, Age, Location Of Birth etc.. and thus the suggestion that implementation wise we stick them into fast read source etc.. single table per view mySQL etc.. and pull them out with something like primitive SqlDataReader, kick that nasty nhibernate ORM etc.. However, whilst I agree that domain models dont mapped well to most screens, many of the screens that I work with are more dimensional, and Im sure this is pretty common in LOB apps. So my question is how are people handling screen where by for example it displays a summary of customer details and then a list of their orders with a [more detail] link etc.... I thought about keeping with the straight forward SQL query to the Query Database breaking off the outer join so can build a suitable ViewModel to View but it seems like overkill? Alternatively (this is starting to feel yuck) in CustomerSummaryView table have a text/big (whatever the type is in your DB) column called Orders, and the columns for the Order summary screen grid are seperated by , and rows by |. Even with XML datatype it still feeel dirty. Any thoughts on an optimal practice?

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  • Looking for exercises to learn SQL, using the Northwind database

    - by MedicineMan
    I am trying to become more familiar with SQL by writing queries against the Northwind database. I am looking for some exercises that would help me to learn SQL and features of SQL Server. It is important that the exercises have solutions, and in complicated cases, it would be great if there was an explanation for the query. Thanks for the answers so far but I still have not found what I am looking for: Is there any free resource, available online, without registration, that I can find a list of these exercises?

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  • html & javascript: How to store data referring to html elements

    - by Dan
    Hello, I'm working on a web application that uses ajax to communicate to the server. My specific situation is the following: I have a list of users lined out in the html page. On each of these users i can do the following: change their 'status' or 'remove' them from the account. What's a good practice for storing information in the page about the following: the user id the current status of the user P.S.: I'm using jQuery.

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  • Should I store generated code in source control

    - by Ron Harlev
    This is a debate I'm taking a part in. I would like to get more opinions and points of view. We have some classes that are generated in build time to handle DB operations (in This specific case, with SubSonic, but I don't think it is very important for the question). The generation is set as a pre-build step in Visual Studio. So every time a developer (or the official build process) runs a build, these classes are generated, and then compiled into the project. Now some people are claiming, that having these classes saved in source control could cause confusion, in case the code you get, doesn't match what would have been generated in your own environment. I would like to have a way to trace back the history of the code, even if it is usually treated as a black box. Any arguments or counter arguments? UPDATE: I asked this question since I really believed there is one definitive answer. Looking at all the responses, I could say with high level of certainty, that there is no such answer. The decision should be made based on more than one parameter. Reading the answers below could provide a very good guideline to the types of questions you should be asking yourself when having to decide on this issue. I won't select an accepted answer at this point for the reasons mentioned above.

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  • Automatically create tag based on the string

    - by Gautam
    Hello, I am new to ruby on rails. Lets say i have this text.. Ashley Cole and Cheryl Cole Split. Is there a way to automatically tag this above text to Ashley Cole, Cheryl Code, ChelseaFC ( Ashley Cole plays football (Soccer) for that club. Please help.. Also which is the best tagging gem available? Looking forward for your help Thanks Gautam

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  • How do I remove a folder from Windows Distributed File System?

    - by digiguru
    We recently moved to a webfarm and setup dfs, only to find a beta application was creating files like there was no tomorrow. 1.2 million files were replicated across the farm, and since then we have prevented the application from creating new files, but every time we try to remove the files, it replaces them on each server because of replication. The process of replacing them actually causes to server to run slowly and in some cases stall. Is there any way we can stop replication at a folder level?

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  • Unit Testing in ASP.NET MVC: Minimising the number of asserts per test

    - by Neil Barnwell
    I'm trying out TDD on a greenfield hobby app in ASP.NET MVC, and have started to get test methods such as the following: [Test] public void Index_GetRequest_ShouldReturnPopulatedIndexViewModel() { var controller = new EmployeeController(); controller.EmployeeService = GetPrePopulatedEmployeeService(); var actionResult = (ViewResult)controller.Index(); var employeeIndexViewModel = (EmployeeIndexViewModel)actionResult.ViewData.Model; EmployeeDetailsViewModel employeeViewModel = employeeIndexViewModel.Items[0]; Assert.AreEqual(1, employeeViewModel.ID); Assert.AreEqual("Neil Barnwell", employeeViewModel.Name); Assert.AreEqual("ABC123", employeeViewModel.PayrollNumber); } Now I'm aware that ideally tests will only have one Assert.xxx() call, but does that mean I should refactor the above to separate tests with names such as: Index_GetRequest_ShouldReturnPopulatedIndexViewModelWithCorrectID Index_GetRequest_ShouldReturnPopulatedIndexViewModelWithCorrectName Index_GetRequest_ShouldReturnPopulatedIndexViewModelWithCorrectPayrollNumber ...where the majority of the test is duplicated code (which therefore is being tested more than once and violates the "keep tests fast" advice)? That seems to be taking it to the extreme to me, so if I'm right as I am, what is the real-world meaning of the "one assert per test" advice?

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