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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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• How-to limit feature functionality

  - by ph0enix

  Are there any standard or "best practice" ways of limiting feature functionality for a particular application? Example: We have a product with a variety of features, and our customers can pick and choose which features they would like to use, and the cost of the product varies based on which features they are actually using. In the past, we have distributed along with our software installer an encrypted license file that contains information about the customer, as well as the collection of features that they have enabled. In code, we read from the license file and enable the functionality according to the license file. This seems to work fine, except there a few disadvantages: Upgrading users with new functionality can be sort of a pain If a particular feature shows up in multiple places throughout the application, a developer might not realize that this feature should be licensed, and forget to check the license file before granting functionality to the user If the license file becomes corrupted, deleted, moved, renamed, etc. the application will not run We're getting ready to roll out a new set of features, and I was just curious what others in the community have done to tackle this problem?

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• Should I be relying on WebTests for data validation?

  - by Alexander Kahoun

  I have a suite of web tests created for a web service. I use it for testing a particular input method that updates a SQL Database. The web service doesn't have a way to retrieve the data, that's not its purpose, only to update it. I have a validator that validates the response XML that the web service generates for each request. All that works fine. It was suggested by a teammate that I add data validation so that I check the database to see the data after the initial response validator runs and compare it with what was in the input request. We have a number of services and libraries that are separate from the web service I'm testing that I can use to get the data and compare it. The problem is that when I run the web test the data validation always fails even when the request succeeds. I've tried putting the thread to sleep between the response validation and the data validation but to no avail; It always gets the data from before the response validation. I can set a break point and visually see that the data has been updated in the DB, funny thing is when I step through it in debug with the breakpoint it does validate successfully. Before I get too much more into this issue I have to ask; Is this the purpose of web tests? Should I be able to validate data through service calls in this manner or am I asking too much of a web test and the response validation is as far as I should go?

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• Correctly use dependency injection

  - by Rune

  Me and two other colleagues are trying to understand how to best design a program. For example, I have an interface ISoda and multiple classes that implement that interface like Coke, Pepsi, DrPepper, etc.... My colleague is saying that it's best to put these items into a database like a key/value pair. For example: Key | Name -------------------------------------- Coke | my.namespace.Coke, MyAssembly Pepsi | my.namespace.Pepsi, MyAssembly DrPepper | my.namespace.DrPepper, MyAssembly ... then have XML configuration files that map the input to the correct key, query the database for the key, then create the object. I don't have any specific reasons, but I just feel that this is a bad design, but I don't know what to say or how to correctly argue against it. My second colleague is suggesting that we micro-manage each of these classes. So basically the input would go through a switch statement, something similiar to this: ISoda soda; switch (input) { case "Coke": soda = new Coke(); break; case "Pepsi": soda = new Pepsi(); break; case "DrPepper": soda = new DrPepper(); break; } This seems a little better to me, but I still think there is a better way to do it. I've been reading up on IoC containers the last few days and it seems like a good solution. However, I'm still very new to dependency injection and IoC containers, so I don't know how to correctly argue for it. Or maybe I'm the wrong one and there's a better way to do it? If so, can someone suggest a better method? What kind of arguments can I bring to the table to convince my colleagues to try another method? What are the pros/cons? Why should we do it one way? Unfortunately, my colleagues are very resistant to change so I'm trying to figure out how I can convince them.

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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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• Generating XML Documents from XML Schemas in C++

  - by metdos

  Is there any easy way to create at least a template XML file using XML Schema? My main interest is bounded by C++, but discussions of other programming languages are also welcome.By the way I also use QT framework.

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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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• 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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• 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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• Views performance in MySQL for denormalization

  - by Gianluca Bargelli

  I am currently writing my truly first PHP Application and i would like to know how to project/design/implement MySQL Views properly; In my particular case User data is spread across several tables (as a consequence of Database Normalization) and i was thinking to use a View to group data into one large table: CREATE VIEW `Users_Merged` ( name, surname, email, phone, role ) AS ( SELECT name, surname, email, phone, 'Customer' FROM `Customer` ) UNION ( SELECT name, surname, email, tel, 'Admin' FROM `Administrator` ) UNION ( SELECT name, surname, email, tel, 'Manager' FROM `manager` ); This way i can use the View's data from the PHP app easily but i don't really know how much this can affect performance. For example: SELECT * from `Users_Merged` WHERE role = 'Admin'; Is the right way to filter view's data or should i filter BEFORE creating the view itself? (I need this to have a list of users and the functionality to filter them by role). EDIT Specifically what i'm trying to obtain is Denormalization of three tables into one. Is my solution correct? See Denormalization on wikipedia

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• What's the use of Ant's extension-point if/unless attributes?

  - by Robert Menteer

  When you define an extension-point in an Ant build file you can have it conditional by using the if or unless attribute. On a target the if/unless prevent it's tasks from being run. But an extension-point doesn't have any tasks to conditionally run, so what does the condition do? My thought (which proved to be incorrect in Ant 1.8.0) is it would prevent any tasks that extend the extension-point from being run. Here is an example build script showing the problem: <project name = "ext-test" default = "main"> <property name = "do.it" value = "false" /> <extension-point name = "init"/> <extension-point name = "doit" depends = "init" if = "${do.it}" /> <target name = "extend-init" extensionOf = "init"> <echo message = "Doing extend-init." /> </target> <target name = "extend-doit" extensionOf = "doit"> <echo message = "Do It! (${do.it})" /> </target> <target name = "main" depends = "doit"> <echo message = "Doing main." /> </target> </project> Using the command: ant -v Relults in: Apache Ant version 1.8.0 compiled on February 1 2010 Trying the default build file: build.xml Buildfile: /Users/bob/build.xml Detected Java version: 1.6 in: /System/Library/Frameworks/JavaVM.framework/Versions/1.6.0/Home Detected OS: Mac OS X parsing buildfile /Users/bob/build.xml with URI = file:/Users/bob/build.xml Project base dir set to: /Users/bob parsing buildfile jar:file:/Users/bob/Documents/Development/3P-Tools/apache-ant-1.8.0/lib/ant.jar!/org/apache/tools/ant/antlib.xml with URI = jar:file:/Users/bob/Documents/Development/3P-Tools/apache-ant-1.8.0/lib/ant.jar!/org/apache/tools/ant/antlib.xml from a zip file Build sequence for target(s) `main' is [extend-init, init, extend-doit, doit, main] Complete build sequence is [extend-init, init, extend-doit, doit, main, ] extend-init: [echo] Doing extend-init. init: extend-doit: [echo] Do It! (false) doit: Skipped because property 'false' not set. main: [echo] Doing main. BUILD SUCCESSFUL Total time: 0 seconds You will notice the target extend-doit is executed but the extention-point itself is skipped. Since an extention-point doesn't have any tasks exactly what has been skipped? Any targets that depend on the extention-point still get executed since a skipped target is a successful target. What is the value of the if/unless attributes on an extention-point?

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• Should I use comments in code, liberally?

  - by Manav Sharma

  All, To comment liberally or not to?? Pros and Cons. I personally prefer commenting as it leaves nothing to the fancies of the people reading it. Thanks

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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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• 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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• How long do you keep log files?

  - by Alex

  I have an application which writes its log files in a special folder. Now I'd like to add a functionality to delete these logs after a defined period of time automatically. But how long should I keep the log files? What are "good" default values (7 or 180 days)? Or do you prefer other criteria (e.g. max. used disk space)?

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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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• What damage is done by document.write()?

  - by Simon Gibbs

  What bad things happen at the moment document.write() is invoked? I've heard bits and peices about document.write having an adverse impact on the DOM or on the use of Javascript libraries. I have an issue in front of me that I suspect is related, but have not been able to find a concise summary of what damage the method does.

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• Including libraries in project. Best practise.

  - by mridang

  Hi guys, I'm writing a Python open-source app. My app uses some open source Python libraries. These libraries in turn use other open-source libraries. I intend to release my code at Sourceforge or Google Code but do I need to include the sources of the other libraries? Is this a good practice? ...or should I simply write this information into a README file informing the use about the other required libraries. I've placed all these libraries into a libs sub folder in my source directory. When checking my code into SVN, should I use something called svn:externals to link to other sources? Is there a way to dynamically update my libraries to the latest version or is this something I have to do manually when I release a new version. My sincerest apologies if my question sounds vague but I'm pretty lost in this matter and I don't know what to Google for. Thanks all.

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• When to use a routing rule vs query string parameters with asp.net mvc

  - by mwright

  We're considering moving forward with a ASP.NET MVC project and the subject of routing versus parameters came up. Seeing as how you can easily set up either or a combination of both in ASP.NET MVC, are there any considerations that I should be aware of when using one or the other?

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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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• 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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• Is there added overhead to looking up a column in a DataTable by name rather than by index?

  - by Ben McCormack

  In a DataTable object, is there added overhead to looking up a column value by name thisRow("ColumnA") rather than by the column index thisRow(0)? In which scenarios might this be an issue. I work on a team that has lots of experience writing VB6 code and I noticed that didn't do column lookups by name for DataTable objects or data grids. Even in .NET code, we use a set of integer constants to reference column names in these types of objects. I asked our team lead why this was so, and he mentioned that in VB6, there was a lot of overhead in looking up data by column name rather than by index. Is this still true for .NET? Example code (in VB.NET, but same applies to C#): Public Sub TestADOData() Dim dt As New DataTable 'Set up the columns in the DataTable ' dt.Columns.Add(New DataColumn("ID", GetType(Integer))) dt.Columns.Add(New DataColumn("Name", GetType(String))) dt.Columns.Add(New DataColumn("Description", GetType(String))) 'Add some data to the data table ' dt.Rows.Add(1, "Fred", "Pitcher") dt.Rows.Add(3, "Hank", "Center Field") 'Method 1: By Column Name ' For Each r As DataRow In dt.Rows Console.WriteLine( _ "{0,-2} {1,-10} {2,-30}", r("ID"), r("Name"), r("Description")) Next Console.WriteLine() 'Method 2: By Column Name ' For Each r As DataRow In dt.Rows Console.WriteLine("{0,-2} {1,-10} {2,-30}", r(0), r(1), r(2)) Next End Sub Is there an case where method 2 provides a performance advantage over method 1?

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• Use of @keyword in C# -- bad idea?

  - by Robert Fraser

  In my naming convention, I use _name for private member variables. I noticed that if I auto-generate a constructor with ReSharper, if the member is a keyword, it will generate an escaped keyword. For example: class IntrinsicFunctionCall { private Parameter[] _params; public IntrinsicFunctionCall(Parameter[] @params) { _params = @params; } } Is this generally considered bad practice or is it OK? It happens quite frequently with @params and @interface.

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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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• 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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