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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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• Pattern for managing reference count and object life

  - by Gopalakrishnan Subramani

  We have a serial port which is connected to hundreds of physical devices on the same wire. We have protocols like Modbus and Hart to handle the request and response between the application and devices. The question is related to managing the reference count of the channel. When no device is using the channel, the channel should be closed. public class SerialPortChannel { int refCount = 0; public void AddReference() { refCount++; } public void ReleaseReference() { refCount--; if (refCount <= 0) this.ReleasePort(); //This close the serial port } } For each device connected, we create a object for the device like device = new Device(); device.Attach(channel); //this calls channel.AddReference() When the device disconnect, device.Detach(channel); //this calls channel.ReleaseReference() I am not convinced by the reference count model. Are there any better way to handle this problem in .NET World?

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• How to avoid injecting dependencies into an object so that it can pass them on?

  - by Pheter

  I am interested in applying dependency injection to my current project, which makes use of the MVC pattern. My controllers will call the models and therefore will need to inject the dependencies into the models. To do this, the controller must have the dependencies (such as a database object) in the first place. The controller doesn't need to make use of some of these dependencies (such as the database object), so I feel that it shouldn't be given this dependency. However, it has to have these dependencies if it is to inject them into the model objects. How can I avoid having dependencies injected into an object just so that it can pass them on? Doing so feels wrong and can result in many dependencies being injected into an object. Edit: I am using PHP.

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• Designing a state machine in C++

  - by skyeagle

  I have a little problem that involves modelling a state machine. I have managed to do a little bit of knowledge engineering and 'reverse engineer' a set of primitive deterministic rules that determine state as well as state transitions. I would like to know what the best practises are regarding: How to rigorously test my states and state transitions to make sure that the system cannot end up in an undeetermined state. How to enforce state transition requirements (for example, it should be impossible to go directly from stateFoo to StateFooBar, i.e. to embue each state with 'knowlege' about the states it can transition to. Ideally, I would like to use clean, pattern based design, with templates wherever possible. I do need somewhere to start though and I would be grateful for any pointers (no pun intended), that are sent my way.

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• What is the best database structure for this scenario?

  - by Ricketts

  I have a database that is holding real estate MLS (Multiple Listing Service) data. Currently, I have a single table that holds all the listing attributes (price, address, sqft, etc.). There are several different property types (residential, commercial, rental, income, land, etc.) and each property type share a majority of the attributes, but there are a few that are unique to that property type. My question is the shared attributes are in excess of 250 fields and this seems like too many fields to have in a single table. My thought is I could break them out into an EAV (Entity-Attribute-Value) format, but I've read many bad things about that and it would make running queries a real pain as any of the 250 fields could be searched on. If I were to go that route, I'd literally have to pull all the data out of the EAV table, grouped by listing id, merge it on the application side, then run my query against the in memory object collection. This also does not seem very efficient. I am looking for some ideas or recommendations on which way to proceed. Perhaps the 250+ field table is the only way to proceed. Just as a note, I'm using SQL Server 2012, .NET 4.5 w/ Entity Framework 5, C# and data is passed to asp.net web application via WCF service. Thanks in advance.

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• abstract method signature, inheritance, and "Do" naming convention

  - by T. Webster

  I'm learning about design patterns and in examples of code I've seen a convention where the abstract class declares a method, for example: public abstract class ServiceBase { ... public virtual object GetSomething(); and then protected abstract object DoGetSomething(); My question is on why these two methods exist, since they appear to serve the same purpose. Is this so that the base class GetSomething() method logic cannot be overridden by inherited classes? But then again, the method is marked virtual, so it can be overridden anyway. What is the usefulness here in requiring derived class implementers to implement the abstract method when the virtual method can be called anyway?

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• Storing n-grams in database in < n number of tables.

  - by kurige

  If I was writing a piece of software that attempted to predict what word a user was going to type next using the two previous words the user had typed, I would create two tables. Like so: == 1-gram table == Token | NextWord | Frequency ------+----------+----------- "I" | "like" | 15 "I" | "hate" | 20 == 2-gram table == Token | NextWord | Frequency ---------+------------+----------- "I like" | "apples" | 8 "I like" | "tomatoes" | 12 "I hate" | "tomatoes" | 20 "I hate" | "apples" | 2 Following this example implimentation the user types "I" and the software, using the above database, predicts that the next word the user is going to type is "hate". If the user does type "hate" then the software will then predict that the next word the user is going to type is "tomatoes". However, this implimentation would require a table for each additional n-gram that I choose to take into account. If I decided that I wanted to take the 5 or 6 preceding words into account when predicting the next word, then I would need 5-6 tables, and an exponentially increase in space per n-gram. What would be the best way to represent this in only one or two tables, that has no upper-limit on the number of n-grams I can support?

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• Grasp Controller, Does it really need a UI to exist?

  - by dbones

  I have a Domain model which can be in multiple states, and if these states go out of a given range it the domain should automatically react. For example I have a Car which is made of multiple things which have measurements the Engine - Rev counter and Temperature the Fuel Tank - capacity Is is plaseable to have a CarStateController, which observses the engine and the tank, and if these states go out of range IE the engine temperature goes above range, turn the engine fan on?? There is no UI, (you could argue it would show a light on the dash board, but for this case it does not) is this a valid use of a GRASP controller pattern? if not what is this CarStateController Called? Or have I completely missed the point and this should be the State Pattern?

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• overflow-x AND Middle Mouse Button Moving

  - by Rad The Mad

  My Page is 980px in Width, but I have a few design elements (which belong with the background). I positioned them with position: absolute;. This creates a horizontal scrollbar for those who have a =< 1024 resolution. I disabled that scrollbar with overflow-x:hidden on (and for IE7 and etc). However, when I hold my middle mouse button,(i think this applies to laptop touchpads as well) it let's me move around to the right, is it possible to fix this with anything? (javascript, css)? Tested this issues in Chrome, IE, Firefox.

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• What patterns exist for web application development?

  - by DaveDev

  I understand that MVC & MVP are design patterns that are commonly used for web development, as well as ASP.NET WebForms (more of an anti-pattern, really!). What other patterns are used in web application development? I'm not necessarily saying I want to learn/use new patterns just to be different - I do believe there's a lot of value in taking the conventional route - but I think it's good to know what else is out there to be able to properly understand what I'm currently working with. Thanks.

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• How to apply Abstract Factory Pattern ???

  - by Amit

  I am new to Design Pattern and I have a scenario here... and not sure as how to implement the pattern ... We have multiple vendors Philips, Onida... Each vendor (philips, onida...) may have different type of product i.e. Plasma or Normal TV I want specific product of each vendor using Abstract Factory Pattern... Thanks in advance for any help... My implementation so far... public enum TvType { Samsung = 0,LG = 1,Philips = 2, Sony = 3 } public enum Product { Plasma = 0,NormalTV = 1 } concrete class of each vendor.... that returns each product and also the interface that contains ProductInfo i.e. if Vendor is ... then it must have this product....

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• Can we create a class from a xml file ?

  - by panzerschreck

  Hello, Is it possible to create a class dynamically by reading an xml file ( in java preferably) ? if yes, please provide pointers on how to do it. In the process of development, we have come up with a class that has 5 attributes, all these attributes correspond to an entry in the xml file, now if the user adds/modifies the xml entry the object corresponding to it must change automatically, one approach would be generate the source code, before compile time.Is there any other way ? Is there any common pattern to model such changes in the system ? Thanks,

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• How to implement "drag n drop" user interface on website?

  - by Nikkeloodeni

  Hello, I was wondering what would be the best way to implement some kind of "drag n drop" user interface? What i mean is that there would be one main page and every link click (eg. other sections like about, gallery, contact form) would open a new drag n drop element on top of that main page. Something like windows desktop where you can move your application windows around the screen. Would it be best to call different functions with AJAX when a link is clicked? Like "gallery" link would call gallery-function and retrieve dynamically generated contents of that "window" with AJAX call and then just load that stuff on some div? Or would some other type of approach suit better for this? I hope I was able to explain this clearly enough. I'm looking for a proper "design pattern" to implement this. All suggestions are wellcome! :)

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• How to program a connection pool?

  - by the_drow

  Is there a known algorithm for implementing a connection pool? If not what are the known algorithms and what are their trade-offs? What design patterns are common when designing and programming a connection pool? Are there any code examples implement a connection pool using boost.asio? Is it a good idea to use a connection pool for presisting connections (not http)? How is threading related to connection pooling? When do you need a new thread?

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• Is it a good idea to create an interface for each domain objects?

  - by Amitabh

  I was just looking into the source code of an existing project which uses nHibernate and found that there are interfaces created for each entity classes. E.g ICustomer for Customer class. I was just wondering what can be the advantage of this pattern as ICustomer contains mainly the properties and very few methods.

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• Entities used to serialize data have changed. How can the serialized data be upgraded for the new entities?

  - by i8abug

  Hi, I have a bunch of simple entity instances that I have serialized to a file. In the future, I know that the structure of these entities (ie, maybe I will rename Name to Header or something). The thing is, I don't want to lose the data that I have saved in all these old files. What is the proper way to either load the data from the old entities into new entities upgrade the old files so that they can be used with new entities Note: I think I am stuck with binary serialization, not xml serialization. Thanks in advance! Edit: So I have an answer for the case I have described. I can use a dataContractSerializer and do something like [DataMember("bar")] private string foo; and change the name in the code and keep the same name that was used for serialization. But what about the following additional cases: The original entity has new members which can be serialized Some serialized members that were in the original entity are removed Some members have actually changed in function (suppose that the original class had a FirstName and LastName member and it has been refactored to have only a FullName member which combines the two) To handle these, I need some sort of interpreter/translator deserialization class but I have no idea what I should use

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• Many-to-many relationship in oop

  - by Manu

  what is best way to model many-to-many relationship? lets say we have a two classes , Team and Player any given Player can be in multiple Team s any Team can have as many Player s as they like I like to call methods like playerX.getTeamList() to get the list of all the Team s he/she is in teamY.getPlayerList() to get the list of all the Player s in the team (or have some other way to do this effectively) I can think of two ways of doing this , but they just don't feels like good oop pattens. can you think of any good ways , perhaps a design patten ?

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• Should I share UI for objects that use common fields?

  - by wb

  I have a parent class that holds all of the fields that are common between all device types. From that, I have a few derived classes that each hold their unique fields. Say I have device type "Switch" and "Transformer". Both derived classes only have 2-3 of their own unique fields. When doing the UI design (windows forms) in this case. Should I create two separate forms for each device type or create a user control with all fields that are shared among all devices? Thank you.

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• Django: Can class-based views accept two forms at a time?

  - by Hooman

  If I have two forms: class ContactForm(forms.Form): name = forms.CharField() message = forms.CharField(widget=forms.Textarea) class SocialForm(forms.Form): name = forms.CharField() message = forms.CharField(widget=forms.Textarea) and wanted to use a class based view, and send both forms to the template, is that even possible? class TestView(FormView): template_name = 'contact.html' form_class = ContactForm It seems the FormView can only accept one form at a time. In function based view though I can easily send two forms to my template and retrieve the content of both within the request.POST back. variables = {'contact_form':contact_form, 'social_form':social_form } return render(request, 'discussion.html', variables) Is this a limitation of using class based view (generic views)? Many Thanks

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• Java(standard, non standard) or Non Java based Web developement [closed]

  - by LivingThing

  I am new to web development. Initially i thought i would be learning LAMP or WAMP to acquire web developement skills but recently i came across Standard Java based (JSP, servlets) and Non standard Java based (GWT). My question is related to if and how LAMP can be compared with Java (standarad or non stadard) technologies. Is LAMP even comparable to Java based tech or it does something else or something more or less ? what requirement for a web developement projects require the choice that which of these 'technologies' should be choosen ? Thank YOu

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• Enable Claims based Auth on a SP2010 website, after it has been provisioned

  - by Sahil Malik

  Ad:: SharePoint 2007 Training in .NET 3.5 technologies (more information). When you provision a web app in SP2010, you can choose it to use Claims Based Auth or Classic Auth right through the GUI.  However, after you have provisioned a web app, there is no GUI to switch from Classic to Claims based. So the below powershell script will let you convert a SP2010 website to claims based auth after it has been provisioned. 1: $w = Get-SPWebApplication "http://sp2010" 2: $w.UseClaimsAuthentication = "True"; 3: $w.Update() The user running the above script should be a member of the SharePoint_Shell_Access role on the config DB, and a member of the WSS_ADMIN_WPG local group. Comment on the article ....

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• Weekend reading: Microsoft/Oracle and SkyDrive based code-editor

  - by jamiet

  A couple of news item caught my eye this weekend that I think are worthy of comment. Microsoft/Oracle partnership to be announced tomorrow (24/06/2013) According to many news site Microsoft and Oracle are about to announce a partnership (Oracle set for major Microsoft, Salesforce, Netsuite partnerships) and they all seem to be assuming that it will be something to do with “the cloud”. I wouldn’t disagree with that assessment, Microsoft are heavily pushing Azure and Oracle seem (to me anyway) to be rather lagging behind in the cloud game. More specifically folks seem to be assuming that Oracle’s forthcoming 12c database release will be offered on Azure. I did a bit of reading about Oracle 12c and one of its key pillars appears to be that it supports multi-tenant topologies and multi-tenancy is a common usage scenario for databases in the cloud. I’m left wondering then, if Microsoft are willing to push a rival’s multi-tenant solution what is happening to its own cloud-based multi-tenant offering – SQL Azure Federations. We haven’t heard anything about federations for what now seems to be a long time and moreover the main Program Manager behind the technology, Cihan Biyikoglu, recently left Microsoft to join Twitter. Furthermore, a Principle Architect for SQL Server, Conor Cunningham, recently presented the opening keynote at SQLBits 11 where he talked about multi-tenant solutions on SQL Azure and not once did he mention federations. All in all I don’t have a warm fuzzy feeling about the future of SQL Azure Federations so I hope that that question gets asked at some point following the Microsoft/Oracle announcement. Text Editor on SkyDrive with coding-specific features Liveside.net got a bit of a scoop this weekend with the news (Exclusive: SkyDrive.com to get web-based text file editing features) that Microsoft’s consumer-facing file storage service is going to get a new feature – a web-based code editor. Here’s Liveside’s screenshot: I’ve long had a passing interest in online code editors, indeed back in December 2009 I wondered out loud on this blog site: I started to wonder when the development tools that we use would also become cloud-based. After all, if we’re using cloud-based services does it not make sense to have cloud-based tools that work with them? I think it does. Project Houston Since then the world has moved on. Cloud 9 IDE (https://c9.io/) have blazed a trail in the fledgling world of online code editors and I have been wondering when Microsoft were going to start playing catch-up. I had no doubt that an online code editor was in Microsoft’s future; its an obvious future direction, why would I want to have to download and install a bloated text editor (which, arguably, is exactly what Visual Studio amounts to) and have to continually update it when I can simply open a web browser and have ready access to all of my code from wherever I am. There are signs that Microsoft is already making moves in this direction, after all the URL for their new offering Team Foundation Service doesn’t mention TFS at all – my own personalised URL for Team Foundation Service is http://jamiet.visualstudio.com – using “Visual Studio” as the domain name for a service that isn’t strictly speaking part of Visual Studio leads me to think that there’s a much bigger play here and that one day http://visualstudio.com will house an online code editor. With that in mind then I find Liveside’s revelation rather intriguing, why would a code editing tool show up in Skydrive? Perhaps SkyDrive is going to get integrated more tightly into TFS, I’m very interested to see where this goes. The larger question playing on my mind though is whether an online code editor from Microsoft will support SQL Server developers. I have opined before (see The SQL developer gap) about the shoddy treatment that SQL Server developers have to experience from Microsoft and I haven’t seen any change in Microsoft’s attitude in the three and a half years since I wrote that post. I’m constantly bewildered by the lack of investment in SQL Server developer productivity compared to the riches that are lavished upon our appdev brethren. When you consider that SQL Server is Microsoft’s third biggest revenue stream it is, frankly, rather insulting. SSDT was a step in the right direction but the hushed noises I hear coming out of Microsoft of late in regard to SSDT don’t bode fantastically well for its future. So, will an online code editor from Microsoft support T-SQL development? I have to assume not given the paucity of investment on us lowly SQL Server developers over the last few years, but I live in hope! Your thoughts in the comments section please. I would be very interested in reading them. @Jamiet

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• New Silverligh-based Protal for Windows Azure AppFabric Labs

  - by Shaun

  Wade Wegner introduced a good news about the Windows Azure platform, which is the new Silverlight-based portal for Windows Azure AppFabric Labs had been launched. You can have a look here. As we know the new Silverlight-based portal of Windows Azure had been published on the Nov of last year but the AppFabric part still not changed. (Clicked the AppFabric link will direct to the old portal.) Now the Silverlight-based AppFabric portal is available for Labs. For more information about this new portal and new features with the latest Windows Azure AppFabric CTP please refer to Wade’s blob post.   Hope this helps, Shaun All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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• The New My Oracle Support User Interface (HTML-based)

  - by user793553

  A single source for learning about the latest enhancements to the My Oracle Support User Interface... On January 27, 2012, we launched a new My Oracle Support HTML-based user interface (UI). The new user interface is built using Oracle’s Application Development Framework and is our first step towards providing a single online support portal for our customers and partners; one that all users will transition to in the coming months. Further enhancements to the HTML-based user interface are planned for April 13, 2012. We will transition users of the standard Flash-based interface in the coming months. To help facilitate a smooth transition, we invite you to preview and begin using the new My Oracle Support interface by going to supporthtml.oracle.com and sign in using your Single Sign-on username and password For full information regarding functionality, supported browsers and links to quick and easy videos on how to navigate the new UI, please check out Doc ID 1385682.1 

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• On-line Based Conferencing For Admin Panel

  - by Tim Marshall

  Working on my admin panels work station section which will allow the admin to use simple office tools such as word editors, calculators and whatnot. Under this section of the admin panel, I would like to add a conferencing feature which will allow any administrator to connect with another administrator 1-2-1 under the 1-2-1 Conferencing section, or to join a meeting under 'live meeting' section. Upon my search for on-line based, I found there are all these, what seem to be great applications out there, however not all of them are on-line based, and come with a price! I would like to a purely on-line based conferencing/meeting/1-2-1 feature which will allow administrators to communicate via text or sound, stream their video, share their screen and sending of files. I know this sounds like a big feature, and I am not asking for someone to answer by programming one for my website! Does anyone know my best solution to progress to having this feature on my website, any tutorials or free to use, free to modify web plugins? Thank you for your help, Best Regards, Tim

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