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  • Help with design structure choice: Using classes or library of functions

    - by roverred
    So I have GUI Class that will call another class called ImageProcessor that contains a bunch functions that will perform image processing algorithms like edgeDetection, gaussianblur, contourfinding, contour map generations, etc. The GUI passes an image to ImageProcessor, which performs one of those algorithm on it and it returns the image back to the GUI to display. So essentially ImageProcessor is a library of independent image processing functions right now. It is called in the GUI like so Image image = ImageProcessor.EdgeDetection(oldImage); Some of the algorithms procedures require many functions, and some can be done in a single function or even one line. All these functions for the algorithms jam packed into ImageProcessor can be pretty messy, and ImageProcessor doesn't sound it should be a library. So I was thinking about making every algorithm be a class with a shared interface say IAlgorithm. Then I pass the IAlgorithm interface from the GUI to the ImageProcessor. public interface IAlgorithm{ public Image Process(); } public class ImageProcessor{ public Image Process(IAlgorithm TheAlgorithm){ return IAlgorithm.Process(); } } Calling in the GUI like so Image image = ImageProcessor.Process(new EdgeDetection(oldImage)); I think it makes sense in an object point of view, but the problem is I'll end up with some classes that are just one function. What do you think is a better design, or are they both crap and you have a much better idea? Thanks!

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  • OOP Design: relationship between entity classes

    - by beginner_
    I have at first sight a simple issue but can't wrap my head around on how to solve. I have an abstract class Compound. A Compound is made up of Structures. Then there is also a Container which holds 1 Compound. A "special" implementation of Compound has Versions. For that type of Compound I want the Container to hold the Versionof the Compound and not the Compound itself. You could say "just create an interface Containable" and a Container holds 1 Containable. However that won't work. The reason is I'm creating a framework and the main part of that framework is to simplify storing and especially searching for special data type held by Structure objects. Hence to search for Containers which contain a Compound made up of a specific Structure requires that the "Path" from Containerto Structure is well defined (Number of relationships or joins). I hope this was understandable. My question is how to design the classes and relationships to be able to do what I outlined.

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  • Jquery UI Datepicker not displaying

    - by scott
    UPDATE I have reverted back to Jquery 1.3.2 and everything is working, not sure what the problem is/was as I have not changed anything else apart of the jquery and ui library versions. UPDATE END I having an issue with the JQuery UI datepicker. The datepicker is being attached to a class and that part is working but the datepicker is not being displayed. Here is the datepicker code I am using and the inline style that is being generated when I click in the input box that has the class ".datepicker". $('.datepicker').datepicker({dateFormat:'dd/mm/yy'}); display:none; left:418px; position:absolute; top:296px; z-index:1; If I change the display:none to display:block the datepicker works fine except it dosen't close when I select a date. Jquery libraries in use: jQuery JavaScript Library v1.4.2 jQuery UI 1.8 jQuery UI Widget 1.8 jQuery UI Mouse 1.8 jQuery UI Position 1.8 jQuery UI Draggable 1.8 jQuery UI Droppable 1.8 jQuery UI Datepicker 1.8

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  • Pass variable by Post method from JQuery UI Autocomplete to PHP page

    - by Shahriar N Khondokar
    I have two JQuery UI autocomplete input fields. When an option is selected in the first one, the value of the selection will be used as condition for a database query that will send the source data for the second autocomplete field. My problem is how do I send the value of the first selection to the PHP page via Post method? The code so far is shown below (this code is from a tutorial which used the GET method; but I want to use Post): <script> $("input#divisions").autocomplete ({ //this is the first input source : [ { value: "81", label: "City1" }, { value: "82", label: "City2" }, { value: "83", label: "City3" } ], minLength : 0, select: function(event, ui) { $('#divisions').val(ui.item.label); return false; }, focus: function(event, ui){ $('#divisions').val(ui.item.label); return false; }, change: function(event, ui){ //the tutorial has this value sent by variables in the URL; I want the selection value sent by POST. How can I change this? c_t_v_choices = "c_t_v_choices.php?filter=" + ui.item.value; $("#c_t_v").autocomplete("option", "source", c_t_v_choices); } }).focus (function (event) { $(this).autocomplete ("search", ""); }); $("#c_t_v").autocomplete({ source: "", minLength: 2, select: function(event,ui){ //$('#city').val(ui.item.city); } }); </script> Can anyone please help? Dont hesitate to let me know if you have any questions.

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  • Defining formula through user interface in user form

    - by BriskLabs Pakistan
    I am a student and developing a simple assignment - windows form application in visual studio 2010. The application is suppose to construct formulas as per user requirement. The process: It has to pick data from columns of Microsoft Access database and the user should be able to pick the data by column name like we do in a drop down menu. and create reusable formulas in it ( configure it once and can change it again). followings are column titles from database that can be picked for example. e.g Col -1 : Marks in Maths Col -2 : Total Marks in Maths Col -3 : Marks in science Col -4 : Total marks in science Finally we should be able to construct any formula in the UI like (Col 1 + Col 3 ) / ( col 2 + col 4) = Formula 1 once this is formula is set saved and a name is assigned to it by user. he/she can use the formula and results shall appear in a window below. i.e He would be able to calculate his desired figures (formula) by only manipulating underlying data on the UI layer....choose the data for a period and apply the formula and get the answer Problem: It looks like I have to create an app where rules are set through UI....... this means no stored procedures are required in SQL.... please suggest the right approach.

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  • Need suggestion for Mutiple Windows application design

    - by King Chan
    This was previously posted in StackOverflow, I just moved to here... I am using VS2008, MVVM, WPF, Prism to make a mutiple window CRM Application. I am using MidWinow in my MainWindow, I want Any ViewModel would able to make request to MainWindow to create/add/close MidChildWindow, ChildWindow(from WPF Toolkit), Window (the Window type). ViewModel can get the DialogResult from the ChildWindow its excutes. MainWindow have control on all opened window types. Here is my current approach: I made Dictionary of each of the windows type and stores them into MainWindow class. For 1, i.e in a CustomerInformationView, its CustomerInformationViewModel can execute EditCommand and use EventAggregator to tell MainWindow to open a new ChildWindow. CustomerInformationViewModel: CustomerEditView ceView = new CustomerEditView (); CustomerEditViewModel ceViewModel = CustomerEditViewModel (); ceView.DataContext = ceViewModel; ChildWindow cWindow = new ChildWindow(); cWindow.Content = ceView; MainWindow.EvntAggregator.GetEvent<NewWindowEvent>().Publish(new WindowEventArgs(ceViewModel.ViewModeGUID, cWindow )); cWindow.Show(); Notice that all my ViewModel will generates a Guid for help identifies the ChildWindow from MainWindow's dictionary. Since I will only be using 1 View 1 ViewModel for every Window. For 2. In CustomerInformationViewModel I can get DialogResult by OnClosing event from ChildWindow, in CustomerEditViewModel can use Guid to tell MainWindow to close the ChildWindow. Here is little question and problems: Is it good idea to use Guid here? Or should I use HashKey from ChildWindow? My MainWindows contains windows reference collections. So whenever window close, it will get notifies to remove from the collection by OnClosing event. But all the Windows itself doesn't know about its associated Guid, so when I remove it, I have to search for every KeyValuePair to compares... I still kind of feel wrong associate ViewModel's Guid for ChildWindow, it would make more sense if ChildWindow has it own ID then ViewModel associate with it... But most important, is there any better approach on this design? How can I improve this better?

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  • Best UI to be shown to User while his request is still in process behind the scenes ?

    - by Rachel
    I am currently involved with an Application where I need to design the UI part of the Application and current I am in the process of implementation of UI which would be displayed to end user while his or her request is being processed behind the scenes. So my question is that: What is the best UI approach/symbol/suggestions to be displayed to end User while his or her request is still being processed behind the scenes ? Thanks.

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  • Process for beginning a Ruby on Rails project

    - by Daniel Beardsley
    I'm about to begin a Ruby on Rails project and I'd love to hear how others go through the process of starting an application design. I have quite a bit of experience with RoR, but don't have that many starting from scratch with only a vision experiences and would appreciate the wisdom of others who've been there. I'm looking for an order of events, reasons for the order, and maybe why each part is important. I can think of a few starting points, but I'm not sure where it's best to begin Model design and relationships (entities, how they relate, and their attributes) Think of user use-cases (or story-boards) and implement the minimum to get these done Create Model unit-tests then create the necessary migrations and AR models to get the tests to pass Hack out the most basic version of the simplest part of your application and go from there Start with a template for a rails app (like http://github.com/thoughtbot/suspenders) Do the boring gruntwork first (User auth, session management, ...) ...

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  • Improvements to Joshua Bloch's Builder Design Pattern?

    - by Jason Fotinatos
    Back in 2007, I read an article about Joshua Blochs take on the "builder pattern" and how it could be modified to improve the overuse of constructors and setters, especially when an object has a large number of properties, most of which are optional. A brief summary of this design pattern is articled here [http://rwhansen.blogspot.com/2007/07/theres-builder-pattern-that-joshua.html]. I liked the idea, and have been using it since. The problem with it, while it is very clean and nice to use from the client perspective, implementing it can be a pain in the bum! There are so many different places in the object where a single property is reference, and thus creating the object, and adding a new property takes a lot of time. So...I had an idea. First, an example object in Joshua Bloch's style: Josh Bloch Style: public class OptionsJoshBlochStyle { private final String option1; private final int option2; // ...other options here <<<< public String getOption1() { return option1; } public int getOption2() { return option2; } public static class Builder { private String option1; private int option2; // other options here <<<<< public Builder option1(String option1) { this.option1 = option1; return this; } public Builder option2(int option2) { this.option2 = option2; return this; } public OptionsJoshBlochStyle build() { return new OptionsJoshBlochStyle(this); } } private OptionsJoshBlochStyle(Builder builder) { this.option1 = builder.option1; this.option2 = builder.option2; // other options here <<<<<< } public static void main(String[] args) { OptionsJoshBlochStyle optionsVariation1 = new OptionsJoshBlochStyle.Builder().option1("firefox").option2(1).build(); OptionsJoshBlochStyle optionsVariation2 = new OptionsJoshBlochStyle.Builder().option1("chrome").option2(2).build(); } } Now my "improved" version: public class Options { // note that these are not final private String option1; private int option2; // ...other options here public String getOption1() { return option1; } public int getOption2() { return option2; } public static class Builder { private final Options options = new Options(); public Builder option1(String option1) { this.options.option1 = option1; return this; } public Builder option2(int option2) { this.options.option2 = option2; return this; } public Options build() { return options; } } private Options() { } public static void main(String[] args) { Options optionsVariation1 = new Options.Builder().option1("firefox").option2(1).build(); Options optionsVariation2 = new Options.Builder().option1("chrome").option2(2).build(); } } As you can see in my "improved version", there are 2 less places in which we need to add code about any addition properties (or options, in this case)! The only negative that I can see is that the instance variables of the outer class are not able to be final. But, the class is still immutable without this. Is there really any downside to this improvement in maintainability? There has to be a reason which he repeated the properties within the nested class that I'm not seeing?

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  • Design pattern for logging changes in parent/child objects saved to database

    - by andrew
    I’ve got a 2 database tables in parent/child relationship as one-many. I’ve got three classes representing the data in these two tables: Parent Class { Public int ID {get; set;} .. other properties } Child Class { Public int ID {get;set;} Public int ParentID {get; set;} .. other properties } TogetherClass { Public Parent Parent; Public List<Child> ChildList; } Lastly I’ve got a client and server application – I’m in control of both ends so can make changes to both programs as I need to. Client makes a request for ParentID and receives a Together Class for the matching parent, and all of the child records. The client app may make changes to the children – add new children, remove or modify existing ones. Client app then sends the Together Class back to the server app. Server app needs to update the parent and child records in the database. In addition I would like to be able to log the changes – I’m doing this by having 2 separate tables one for Parent, one for child; each containing the same columns as the original plus date time modified, by whom and a list of the changes. I’m unsure as to the best approach to detect the changes in records – new records, records to be deleted, records with no fields changed, records with some fields changed. I figure I need to read the parent & children records and compare those to the ones in the Together Class. Strategy A: If Together class’s child record has an ID of say 0, that indicates a new record; insert. Any deleted child records are no longer in the Together Class; see if any of the comparison child records are not found in the Together class and delete if not found (Compare using ID). Check each child record for changes and if changed log. Strategy B: Make a new Updated TogetherClass UpdatedClass { Public Parent Parent {get; set} Public List<Child> ListNewChild {get;set;} Public List<Child> DeletedChild {get;set;} Public List<Child> ExistingChild {get;set;} // used for no changes and modified rows } And then process as per the list. The reason why I’m asking for ideas is that both of these solutions don’t seem optimal to me and I suspect this problem has been solved already – some kind of design pattern ? I am aware of one potential problem in this general approach – that where Client App A requests a record; App B requests same record; A then saves changes; B then saves changes which may overwrite changes A made. This is a separate locking issue which I’ll raise a separate question for if I’ve got trouble implementing. The actual implementation is c#, SQL Server and WCF between client and server - sharing a library containing the class implementations. Apologies if this is a duplicate post – I tried searching various terms without finding a match though.

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  • Jquery autocomplete UI - No results on multiple fields

    - by pjammer
    Andrew's answer to my comment has sparked this question. According to his awesome answer in the link above, the code at the bottom of the question will only work for ONE widget. But it's killer nice code and makes sense... I guess I want the best of both worlds. Nice JS, (if that is possible) and to have the zero results show() just the element that we're using at the time. This code snippet is the main crux of my problem, as I see it: source: function (request, response) { jQuery.ajax({ url: "/autocomplete.json", data: { term: request.term }, success: function (data) { if (data.length == 0) { jQuery('span.guest_investor_email').show(); jQuery('span.investor_field_delete_button').show(); } response(data); } }); Currently: I have a button on my page that says "Add more Information" and each time you click it, a new instance of the autocomplete text field appears, complete with some hidden fields and a display:none; on guest_investor_email. If I use the autocomplete text field, say 3 times, and i have 3 autocomplete instances on the page and the third one finds 0 results: The code will show() all 3 instances of the guest_investor_email text field, instead of just this one that is blank. QUESTION: How do i get something like jQuery(this).siblings(('span.guest_investor_email').show(); to work? this is an Object and not an array of elements to select. If it isn't with this I don't mind, as long as I know how to get at it. Thanks. Full Code: jQuery(".auto_search_complete").live("click", function() { jQuery(this).autocomplete({ minLength: 3, source: function (request, response) { jQuery.ajax({ url: "/autocomplete.json", data: { term: request.term }, success: function (data) { if (data.length == 0) { jQuery('span.guest_investor_email').show(); jQuery('span.investor_field_delete_button').show(); } response(data); } }); }, focus: function(event, ui) { jQuery(this).val(ui.item.user ? ui.item.user.name : ui.item.pitch.name); return false; }, select: function(event, ui) { jQuery(this).val(ui.item.user ? ui.item.user.name : ui.item.pitch.name); jQuery(this).siblings('div.hidden_fields').children('.poly_id').val(ui.item.user ? ui.item.user.id : ui.item.pitch.id); jQuery(this).siblings('div.hidden_fields').children('.poly_type').val(ui.item.user ? "User" : "Pitch"); jQuery(this).siblings('span.guest_investor_email').hide(); jQuery(this).siblings('span.investor_field_delete_button').show(); jQuery(this).attr('readonly','readonly'); jQuery(this).attr('id', "investor-selected"); return false; } }).each(function() { jQuery(this).data( "autocomplete" )._renderItem = function( ul, item ) { return jQuery( "" ) .data( "item.autocomplete", item ) .append("" + (item.user ? item.user.name : item.pitch.name) + "" + (item.user ? item.user.investor_type : item.pitch.investor_type) + " - " + (item.user ? item.user.city : item.pitch.city) + "" ) .appendTo( ul ); }; }); });

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  • Surely eAsy but I am not able ... JQUERY UI - WIDGET - HEADER

    - by alex
    I was making this simple trial, but can anyone tell me why the distance from the border of DIV to the H2 header is so much ? How can I reduce it ? I don't want space ... Prova WIDGET <link rel="stylesheet" href="jquery-ui-1.8.custom/css/smoothness/jquery-ui-1.8.custom.css" type="text/css"> <link rel="stylesheet" href="jquery-ui-1.8.custom/development-bundle/ui/jquery-ui-1.8.custom.css" type="text/css"> <script src="jquery-ui-1.8.custom/development-bundle/jquery-1.4.2.js" type="text/javascript"></script> <script src="jquery-ui-1.8.custom/js/jquery-ui-1.8.custom.min.js" type="text/javascript"></script> <script type="text/javascript"> $(themify); function themify(){ $("div").addClass("ui-widget ui-widget-content ui-corner-all"); $("input").addClass("ui-button ui-button-text"); $(":header").addClass("ui-widget-header ui-corner-all"); //ui-widget } </script> <style>#test{display:none}</style> <script type="text/javascript"> function rendiVisibile(){ if(document.getElementById("test").style.display = "none"){ $("#test").css({"width":"200px","float":"right","text-align":"center"}); $("#test").show("slide",{},1000); } } </script> </head> <body> <h2>Tentativo widget con DIV</h2> <form action=""> <input type="button" value="Submit" id="pulsante" onclick="rendiVisibile()";><br/></br> <div id="test"> <h2>CIAO</h2> Un saluto </div> </form> </body>

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  • C# Design How to Elegantly wrap a DAL class

    - by guazz
    I have an application which uses MyGeneration's dOODads ORM to generate it's Data Access Layer. dOODad works by generating a persistance class for each table in the database. It works like so: // Load and Save Employees emps = new Employees(); if(emps.LoadByPrimaryKey(42)) { emps.LastName = "Just Got Married"; emps.Save(); } // Add a new record Employees emps = new Employees(); emps.AddNew(); emps.FirstName = "Mr."; emps.LastName = "dOOdad"; emps.Save(); // After save the identity column is already here for me. int i = emps.EmployeeID; // Dynamic Query - All Employees with 'A' in thier last name Employees emps = new Employees(); emps.Where.LastName.Value = "%A%"; emps.Where.LastName.Operator = WhereParameter.Operand.Like; emps.Query.Load(); For the above example(i.e. Employees DAL object) I would like to know what is the best method/technique to abstract some of the implementation details on my classes. I don't believe that an Employee class should have Employees(the DAL) specifics in its methods - or perhaps this is acceptable? Is it possible to implement some form of repository pattern? Bear in mind that this is a high volume, perfomacne critical application. Thanks, j

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  • Domain driven design: Manager and service

    - by ryudice
    I'm creating some business logic in the application but I'm not sure how or where to encapsulate it, I've used the repository pattern for data access, I've seen some projects that use DDD that have some classes with the "Service" suffix and the "manager" suffix, what are each of this clases suppose to take care of in DDD?

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  • Repeated properties design pattern

    - by Mark
    I have a DownloadManager class that manages multiple DownloadItem objects. Each DownloadItem has events like ProgressChanged and DownloadCompleted. Usually you want to use the same event handler for all download items, so it's a bit annoying to have to set the event handlers over and over again for each DownloadItem. Thus, I need to decide which pattern to use: Use one DownloadItem as a template and clone it as necessary var dm = DownloadManager(); var di = DownloadItem(); di.ProgressChanged += new DownloadProgressChangedEventHandler(di_ProgressChanged); di.DownloadCompleted += new DownloadProgressChangedEventHandler(di_DownloadCompleted); DownloadItem newDi; newDi = di.Clone(); newDi.Uri = "http://google.com"; dm.Enqueue(newDi); newDi = di.Clone(); newDi.Uri = "http://yahoo.com"; dm.Enqueue(newDi); Set the event handlers on the DownloadManager instead and have it copy the events over to each DownloadItem that is enqeued. var dm = DownloadManager(); dm.ProgressChanged += new DownloadProgressChangedEventHandler(di_ProgressChanged); dm.DownloadCompleted += new DownloadProgressChangedEventHandler(di_DownloadCompleted); dm.Enqueue(new DownloadItem("http://google.com")); dm.Enqueue(new DownloadItem("http://yahoo.com")); Or use some kind of factory var dm = DownloadManager(); var dif = DownloadItemFactory(); dif.ProgressChanged += new DownloadProgressChangedEventHandler(di_ProgressChanged); dif.DownloadCompleted += new DownloadProgressChangedEventHandler(di_DownloadCompleted); dm.Enqueue(dif.Create("http://google.com")); dm.Enqueue(dif.Create("http://yahoo.com")); What would you recommend?

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  • jQuery block UI exceptions

    - by Chirantan
    I am using JQuery UI plugin blockUI to block UI for every ajax request. It works like a charm, however, I don't want to block the UI (Or at least not show the "Please wait" message) when I am making ajax calls to fetch autocomplete suggest items. How do I do that? I am using jquery autocomplete plugin for autocomplete functionality. Is there a way I can tell the block UI plug-in to not block UI for autocomplete?

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  • RESTful Question/Answer design?

    - by Kirschstein
    This is a toy project I'm working on at the moment. My app contains questions with multiple choice answers. The question url is in the following format, with GET & POST mapping to different actions on the questions controller. GET: url.com/questions/:category/:difficulty => 'ask' POST: url.com/questions/:category/:difficulty => 'answer' I'm wondering if it's worth redesigning this into a RESTful style. I know I'd need to introduce answers as a resource, but I'm struggling to think of a url that would look natural for answering that question. Would a redesign be worthwhile? How would you go about structuring the urls?

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  • Design Question on when to save

    - by Ben
    Hi, I was just after peoples opinion on when the best time to save an object (or collection of objects) is. I appreciate that it can be completely dependent on the situation that you are in but here is my situation. I have a collection of objects "MyCollection" in a grid. You can open each object "MyObject" in an editor dialogue by double clicking on the grid. Selecting "Cancel" on the dialogue will back out any changes you have made, but should selecting "ok" commit those changes back to the database, or should they commit the changes on that object back to the collection and have a save method that iterates through the collection and saves all changed objects? If i have an object "MyParentObject", that contains a collection of childen "MyChildObjectCollection", none of the changes made to each "MyChildObject" would be commited to the database until the "MyParentObject" was saved - this makes sense. However in my current situation, none of the objects in the collection are linked, therefore should the "Ok" on the dialogue commit the changes to the database? Appreciate any opinions on this. Thanks

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  • User account design and security...

    - by espinet
    Before I begin, I am using Ruby on Rails and the Devise gem for user authentication. Hi, I was doing some research about account security and I found a blog post about the topic awhile ago but I can no longer find it again. I read something about when making a login system you should have 1 model for User, this contains a user's username, encrypted password, and email. You should also have a model for a user's Account. This contains everything else. A User has an Account. I don't know if I'm explaining this correctly since I haven't seen the blog post for several months and I lost my bookmark. Could someone explain how and why I should or shouldn't do this. My application deals with money so I need to cover my bases with security. Thanks.

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  • Schema design: many to many plus additional one to many

    - by chrisj
    Hi, I have this scenario and I'm not sure exactly how it should be modeled in the database. The objects I'm trying to model are: teams, players, the team-player membership, and a list of fees due for each player on a given team. So, the fees depend on both the team and the player. So, my current approach is the following: **teams** id name **players** id name **team_players** id player_id team_id **team_player_fees** id team_players_id amount send_reminder_on Schema layout ERD In this schema, team_players is the junction table for teams and players. And the table team_player_fees has records that belong to records to the junction table. For example, playerA is on teamA and has the fees of $10 and $20 due in Aug and Feb. PlayerA is also on teamB and has the fees of $25 and $25 due in May and June. Each player/team combination can have a different set of fees. Questions: Are there better ways to handle such a scenario? Is there a term for this type of relationship? (so I can google it) Or know of any references with similar structures?

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  • Project design / FS layout for large django projects

    - by rcreswick
    What is the best way to layout a large django project? The tutuorials provide simple instructions for setting up apps, models, and views, but there is less information about how apps and projects should be broken down, how much sharing is allowable/necessary between apps in a typical project (obviously that is largely dependent on the project) and how/where general templates should be kept. Does anyone have examples, suggestions, and explanations as to why a certain project layout is better than another? I am particularly interested in the incorporation of large numbers of unit tests (2-5x the size of the actual code base) and string externalization / templates.

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  • General ORM design question

    - by Calvin
    Suppose you have 2 classes, Person and Rabbit. A person can do a number of things to a rabbit, s/he can either feed it, buy it and become its owner, or give it away. A rabbit can have none or at most 1 owner at a time. And if it is not fed for a while, it may die. Class Person { Void Feed(Rabbit r); Void Buy(Rabbit r); Void Giveaway(Person p, Rabbit r); Rabbit[] rabbits; } Class Rabbit { Bool IsAlive(); Person pwner; } There are a couple of observations from the domain model: Person and Rabbit can have references to each other Any actions on 1 object can also change the state of the other object Even if no explicit actions are invoked, there can still be a change of state in the objects (e.g. Rabbit can be starved to death, and that causes it to be removed from the Person.rabbits array) As DDD is concerned, I think the correct approach is to synchronize all calls that may change the states in the domain model. For instance, if a Person buys a Rabbit, s/he would need to acquire a lock in Person to make a change to the rabbits array AND also another lock in Rabbit to change its owner before releasing the first one. This would prevent a race condition where 2 Persons claim to be the owner of the little Rabbit. The other approach is to let the database to handle all these synchronizations. Who makes the first call wins, but then the DB needs to have some kind of business logics to figure out if it is a valid transaction (e.g. if a Rabbit already has an owner, it cannot change its owner unless the Person gives it away). There are both pros/cons in either approach, and I’d expect the “best” solution would be somewhere in-between. How would you do it in real life? What’s your take and experience? Also, is it a valid concern that there can be another race condition the domain model has committed its change but before it is fully committed in the database? And for the 3rd observation (i.e. state change due to time factor). How will you do it?

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  • How to better design it ???

    - by Deepak
    public interface IBasePresenter { } public interface IJobViewPresenter : IBasePresenter { } public interface IActivityViewPresenter : IBasePresenter { } public class BaseView { public IBasePresenter Presenter { get; set; } } public class JobView : BaseView { public IJobViewPresenter JobViewPresenter { get { this.Presenter as IJobViewPresenter;} } } public class ActivityView : BaseView { public IActivityViewPresenter ActivityViewPresenter { get { this.Presenter as IActivityViewPresenter;} } } Lets assume that I need a IBasePresenter property on BaseView. Now this property is inherited by JobView and ActivityView but if I need reference to IJobViewPresenter object in these derived classes then I need to type cast IBasePresenter property to IJobViewPresenter or IActivityPresenter (which I want to avoid) or create JobViewPresenter and ActivityViewPresenter on derived classes (as shown above). I want to avoid type casting in derived classes and still have reference to IJobViewPresenter or IActivityViewPresenter and still have IBasePresenter in BaseView. Is there a way I can achieve it ?

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  • Design issue with ATG CommercePipelineManager

    - by user1339772
    The definition of runProcess() method in PipelineManager is public PipelineResult runProcess(String pChainId, Object pParam) throws RunProcessException This gives me an impression that ANY object can be passed as the second param. However, ATG OOTB has PipelineManager component referring to CommercePipelineManager class which overrides the runProcess() method and downcast pParam to map and adds siteId to it. Basically, this enforces the client code to send only Map. Thus, if one needs to create a new pipeline chain, has to use map as data structure to pass on the data. Offcourse, one can always get around this by creating a new PipelineManager component, but I was just wondering the thought behind explicitly using map in CommercePipelineManager

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  • Exploring the Factory Design Pattern

    - by asksuperuser
    There was an article here: http://msdn.microsoft.com/en-us/library/Ee817667%28pandp.10%29.aspx The first part of tut implemented this pattern with abstract classes. The second part shows an example with Interface class. But nothing in this article discusses why this pattern would rather use abstract or interface. So what explanation (advantages of one over the other) would you give ? Not in general but for this precise pattern.

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