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  • Website inheritance of ownership question

    - by Adrian Denham
    I paid for a web site for my motel business, then due to my landlord actions I was placed in a position to file for bankrupcy. I asked my IT manager and web developer to close down the web site for the business. He has since then sold my web site to the new owners. I took all the photos myself and I am in at least 4 of the photos on the site. There are no changes to the site as I left it and it now states that it is under the copyright on the new owners? I am not sure what I should do as this happen 10 months ago and I have just found this out. Thank you for your help, I am in Australia.

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  • Website File and Folder Structure

    - by Drummss
    I am having a problem learning how proper website structure should be. And by that I mean how to code the pages and how folder structure should be. Currently I am navigating around my website using GET variables in PHP when you want go to another page, so I am always loading the index.php file. And I would load the page I wanted like so: $page = "error"; if(isset($_GET["page"]) AND file_exists("pages/".$_GET["page"].".php")) { $page = $_GET["page"]; } elseif(!isset($_GET["page"])) { $page = "home"; } And this: <div id="page"> <?php include("pages/".$page.".php"); ?> </div> The reason I am doing this is because it makes making new pages a lot easier as I don't have to link style sheets and javascript in every file like so: <head> <title> Website Name </title> <link href='http://fonts.googleapis.com/css?family=Lato:300,400' rel='stylesheet' type='text/css'> <link rel="stylesheet" href="css/style.css" type="text/css"> <link rel="shortcut icon" href="favicon.png"/> <script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js" type="text/javascript"></script> <script src="//ajax.googleapis.com/ajax/libs/jqueryui/1.10.4/jquery-ui.min.js" type="text/javascript"></script> </head> There is a lot of problems doing it this way as URLs don't look normal ("?page=apanel/app") if I am trying to access a page from inside a folder inside the pages folder to prevent clutter. Obviously this is not the only way to go about it and I can't find the proper way to do it because I'm sure websites don't link style sheets in every file as that would be very bad if you changed a file name or needed to add another file you would have to change it in every file. If anyone could tell me how it is actually done or point me towards a tutorial that would be great. Thanks for your time :)

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  • The Power Of XSL Compared To CSS

    CSS or Cascading Style Sheets is one of the most popular style sheet language used in the market today. This is mainly because of its ease of use as well as with its simplicity which is why CSS was o... [Author: Margarette Mcbride - Web Design and Development - May 17, 2010]

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  • Implenting ActiveRecord with inheritance?

    - by King
    I recently converted an old application that was using XML files as the data store to use SQL instead. To avoid a lot of changes I basically created ActiveRecord style classes that inherited from the original business objects. For example SomeClassRecord :SomeClass //ID Property //Save method I then used this new class in place of the other one, because of polymorphism I didn't need to change any methods that took SomeClass as a parameter. Would this be considered 'Bad'? What would be a better alternative?

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  • Tomcat directly serve static (css, js) files shared by multiple applications

    - by Josvic Zammit
    I'm using the ExtJS framework which has a bulk of js and css files that are used for all apps. I intend to share these between a number of web applications (different war files). For this reason I would like to serve ExtJS js and css directly from the web server, in my case Tomcat6, which can be used to serve static files, as in this helpful link. Therefore I put my files under /var/lib/tomcat6/webapps/ROOT/extjs/. The static files that are directly under that directory are served correctly, e.g. /extjs/ext.js correctly serves the file at /var/lib/tomcat6/webapps/ROOT/extjs/ext.js. However files in lower-level directories, for example /extjs/welcome/css/welcome.css, which should serve the file at /var/lib/tomcat6/webapps/ROOT/extjs/welcome/css/welcome.css, return a 404. TL/DR Tomcat serves static files only at top-level directory. A 404 is returned for files deeper in the hierarchy. Config file contents: server.xml application's web.xml

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  • I have found an inheritance.

    <b>Technology & Life Integration:</b> "You may not know me as I received your attention from a browser link. This is very important so please continue reading. This letter has the possibility of changing your life. With your help we can realise that dream."

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  • Style Sheet Languages Before CSS

    CSS or Cascading Style Sheets is one of the most widely used form of style sheet languages used in the market. According to many professionals, CSS was the perfect move from the use of tables in web ... [Author: Margarette Mcbride - Web Design and Development - May 03, 2010]

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  • Better Than CSS?

    CSS is considered by many as the most popular style sheet language used in the industry. However, aside from CSS, there have also been other style sheet languages in the market which many have said t... [Author: Margarette Mcbride - Web Design and Development - May 02, 2010]

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  • rewrite image URLs

    - by Don
    Hi, I'm writing a Maven plugin that merges CSS files together. So all the CSS files that match /foo/bar/*.css might get merged to /foo/merged.css. A concern is that in a file such as /foo/bar/baz.css there might be a property such as: background: url("images/pic.jpg") So when the file is merged into /foo/merged.css this will need to be changed to background: url("bar/images/pic.jpg") The recalculated URL obviously depends on 3 factors: original URL original CSS file location merged CSS file location Assuming that the original and merged CSS files are both on the same filesystem, is there a general formula (or Java library) that can be used to calculate the new url given these 3 inputs? Thanks, Don

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  • jQuery DataTables is messing op my CSS grids in IE8, how to fix?

    - by Brendan Vogt
    I am using ASP.NET MVC3 with the jQuery Datatable plug in. I am having an issues with my CSS layout when the datatable is on a page. If there is no datatable then everything displays fine. When the datatable is on the screen then it overlaps the footer of my website. I can't seem to get this to display correctly. I have a grid layout using the YUI3, and this is what I all use from YUI3 (in this order): cssreset-min cssfonts-min cssgrids-min cssbase-min This works fine in the latest version of FireFox. I am only testing on IE8, this is a requirement and most of the people at my work uses IE8. I have minified my HTML so that only the bare minimum is available. This is my HTML: <!DOCTYPE html> <html> <head> <title>My Website</title> <meta charset="utf-8" /> <meta http-equiv="X-UA-Compatible" content="IE=Edge" /> <link href="/Assets/Stylesheets/hef2.css" rel="stylesheet" /> <link href="/Assets/Stylesheets/jQuery-DataTables/css/jquery.dataTables.css" rel="stylesheet" /> </head> <body> <div id="hd">Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas sit amet metus. Nunc quam elit, posuere nec, auctor in, rhoncus quis, dui. Aliquam erat volutpat. Ut dignissim, massa sit amet dignissim cursus, quam lacus feugiat.</div> <div id="bd"> <div class="yui3-g"> <div class="yui3-u" id="nav"> <div id="nav-container"> <div class="content"> <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas sit amet metus. Nunc quam elit, posuere nec, auctor in, rhoncus quis, dui. Aliquam erat volutpat. Ut dignissim, massa sit amet dignissim cursus, quam lacus feugiat.</p> </div> <div class="content"> <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas sit amet metus. Nunc quam elit, posuere nec, auctor in, rhoncus quis, dui. Aliquam erat volutpat. Ut dignissim, massa sit amet dignissim cursus, quam lacus feugiat.</p> </div> <div class="content"> <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas sit amet metus. Nunc quam elit, posuere nec, auctor in, rhoncus quis, dui. Aliquam erat volutpat. Ut dignissim, massa sit amet dignissim cursus, quam lacus feugiat.</p> </div> <div class="content"> <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas sit amet metus. Nunc quam elit, posuere nec, auctor in, rhoncus quis, dui. Aliquam erat volutpat. Ut dignissim, massa sit amet dignissim cursus, quam lacus feugiat.</p> </div> </div> </div> <div class="yui3-u" id="main"> <div id="main-container"> <div class="content"> <h1>Banks Dashboard</h1> <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas sit amet metus. Nunc quam elit, posuere nec, auctor in, rhoncus quis, dui. Aliquam erat volutpat. Ut dignissim, massa sit amet dignissim cursus, quam lacus feugiat.</p> </div> <div class="content"> <div id="banks-datatable-wrapper"> <div id="banks-datatable-container"></div> <div style="clear:both;"></div> </div> </div> <div class="content"> <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas sit amet metus. Nunc quam elit, posuere nec, auctor in, rhoncus quis, dui. Aliquam erat volutpat. Ut dignissim, massa sit amet dignissim cursus, quam lacus feugiat.</p> </div> <div class="content"> <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas sit amet metus. Nunc quam elit, posuere nec, auctor in, rhoncus quis, dui. Aliquam erat volutpat. Ut dignissim, massa sit amet dignissim cursus, quam lacus feugiat.</p> </div> <div class="content"> <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas sit amet metus. Nunc quam elit, posuere nec, auctor in, rhoncus quis, dui. Aliquam erat volutpat. Ut dignissim, massa sit amet dignissim cursus, quam lacus feugiat.</p> </div> </div> </div> </div> </div> <div id="ft">Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas sit amet metus. Nunc quam elit, posuere nec, auctor in, rhoncus quis, dui. Aliquam erat volutpat. Ut dignissim, massa sit amet dignissim cursus, quam lacus feugiat.</div> <script src="/Assets/JavaScripts/jQuery/jquery-1.7.2.min.js"></script> <script src="/Assets/JavaScripts/jQuery-DataTables/jquery.dataTables.min.js"></script> <script type="text/javascript"> $(document).ready(function () { $('#banks-datatable-container').html('<table class="display" id="banks-datatable"></table>'); $('#banks-datatable').dataTable({ "aoColumns": [ { "sTitle": "Engine" }, { "sTitle": "Browser" }, { "sTitle": "Platform" }, { "sTitle": "Version", "sClass": "center" }, { "sTitle": "Grade" } ], "bAutoWidth": false, "bFilter": false, "bLengthChange": false, "bProcessing": true, //"bServerSide": true, "bSort": false, "iDisplayLength": 11, "sAjaxSource": '/Administration/Bank/List2' }); }); </script> </body> </html> This is the only CSS that I currently use together with the CSS of YUI3: body { margin: auto; width: 1025px; } #nav { width: 300px; } #main { width: 725px; } Can someone please help me get this sorted out? I have tried tried adding clear:both but it didn't work. Is the an online service like jsbin where I can paste/upload my HTML/CSS code/files? Code can viewed at: http://live.datatables.net/efosuj/3/edit. It displays correctly in the available viewer but when run separate in IE8 then it gives issues. UPDATE 2012-06-12 I managed to add the following and it works, but I would like to add it in a style, tried it but it didn't work: if (navigator.userAgent.toString().indexOf('MSIE') >= 0) { jQuery('#main-container').css('overflow', 'auto'); } This was added after the grid was loaded. Is this the only way to do this?

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  • Inheritance Mapping Strategies with Entity Framework Code First CTP5: Part 3 – Table per Concrete Type (TPC) and Choosing Strategy Guidelines

    - by mortezam
    This is the third (and last) post in a series that explains different approaches to map an inheritance hierarchy with EF Code First. I've described these strategies in previous posts: Part 1 – Table per Hierarchy (TPH) Part 2 – Table per Type (TPT)In today’s blog post I am going to discuss Table per Concrete Type (TPC) which completes the inheritance mapping strategies supported by EF Code First. At the end of this post I will provide some guidelines to choose an inheritance strategy mainly based on what we've learned in this series. TPC and Entity Framework in the Past Table per Concrete type is somehow the simplest approach suggested, yet using TPC with EF is one of those concepts that has not been covered very well so far and I've seen in some resources that it was even discouraged. The reason for that is just because Entity Data Model Designer in VS2010 doesn't support TPC (even though the EF runtime does). That basically means if you are following EF's Database-First or Model-First approaches then configuring TPC requires manually writing XML in the EDMX file which is not considered to be a fun practice. Well, no more. You'll see that with Code First, creating TPC is perfectly possible with fluent API just like other strategies and you don't need to avoid TPC due to the lack of designer support as you would probably do in other EF approaches. Table per Concrete Type (TPC)In Table per Concrete type (aka Table per Concrete class) we use exactly one table for each (nonabstract) class. All properties of a class, including inherited properties, can be mapped to columns of this table, as shown in the following figure: As you can see, the SQL schema is not aware of the inheritance; effectively, we’ve mapped two unrelated tables to a more expressive class structure. If the base class was concrete, then an additional table would be needed to hold instances of that class. I have to emphasize that there is no relationship between the database tables, except for the fact that they share some similar columns. TPC Implementation in Code First Just like the TPT implementation, we need to specify a separate table for each of the subclasses. We also need to tell Code First that we want all of the inherited properties to be mapped as part of this table. In CTP5, there is a new helper method on EntityMappingConfiguration class called MapInheritedProperties that exactly does this for us. Here is the complete object model as well as the fluent API to create a TPC mapping: public abstract class BillingDetail {     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } }          public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } }          public class CreditCard : BillingDetail {     public int CardType { get; set; }     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } }      public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; }              protected override void OnModelCreating(ModelBuilder modelBuilder)     {         modelBuilder.Entity<BankAccount>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("BankAccounts");         });         modelBuilder.Entity<CreditCard>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("CreditCards");         });                 } } The Importance of EntityMappingConfiguration ClassAs a side note, it worth mentioning that EntityMappingConfiguration class turns out to be a key type for inheritance mapping in Code First. Here is an snapshot of this class: namespace System.Data.Entity.ModelConfiguration.Configuration.Mapping {     public class EntityMappingConfiguration<TEntityType> where TEntityType : class     {         public ValueConditionConfiguration Requires(string discriminator);         public void ToTable(string tableName);         public void MapInheritedProperties();     } } As you have seen so far, we used its Requires method to customize TPH. We also used its ToTable method to create a TPT and now we are using its MapInheritedProperties along with ToTable method to create our TPC mapping. TPC Configuration is Not Done Yet!We are not quite done with our TPC configuration and there is more into this story even though the fluent API we saw perfectly created a TPC mapping for us in the database. To see why, let's start working with our object model. For example, the following code creates two new objects of BankAccount and CreditCard types and tries to add them to the database: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount();     CreditCard creditCard = new CreditCard() { CardType = 1 };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Running this code throws an InvalidOperationException with this message: The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges. The reason we got this exception is because DbContext.SaveChanges() internally invokes SaveChanges method of its internal ObjectContext. ObjectContext's SaveChanges method on its turn by default calls AcceptAllChanges after it has performed the database modifications. AcceptAllChanges method merely iterates over all entries in ObjectStateManager and invokes AcceptChanges on each of them. Since the entities are in Added state, AcceptChanges method replaces their temporary EntityKey with a regular EntityKey based on the primary key values (i.e. BillingDetailId) that come back from the database and that's where the problem occurs since both the entities have been assigned the same value for their primary key by the database (i.e. on both BillingDetailId = 1) and the problem is that ObjectStateManager cannot track objects of the same type (i.e. BillingDetail) with the same EntityKey value hence it throws. If you take a closer look at the TPC's SQL schema above, you'll see why the database generated the same values for the primary keys: the BillingDetailId column in both BankAccounts and CreditCards table has been marked as identity. How to Solve The Identity Problem in TPC As you saw, using SQL Server’s int identity columns doesn't work very well together with TPC since there will be duplicate entity keys when inserting in subclasses tables with all having the same identity seed. Therefore, to solve this, either a spread seed (where each table has its own initial seed value) will be needed, or a mechanism other than SQL Server’s int identity should be used. Some other RDBMSes have other mechanisms allowing a sequence (identity) to be shared by multiple tables, and something similar can be achieved with GUID keys in SQL Server. While using GUID keys, or int identity keys with different starting seeds will solve the problem but yet another solution would be to completely switch off identity on the primary key property. As a result, we need to take the responsibility of providing unique keys when inserting records to the database. We will go with this solution since it works regardless of which database engine is used. Switching Off Identity in Code First We can switch off identity simply by placing DatabaseGenerated attribute on the primary key property and pass DatabaseGenerationOption.None to its constructor. DatabaseGenerated attribute is a new data annotation which has been added to System.ComponentModel.DataAnnotations namespace in CTP5: public abstract class BillingDetail {     [DatabaseGenerated(DatabaseGenerationOption.None)]     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } } As always, we can achieve the same result by using fluent API, if you prefer that: modelBuilder.Entity<BillingDetail>()             .Property(p => p.BillingDetailId)             .HasDatabaseGenerationOption(DatabaseGenerationOption.None); Working With The Object Model Our TPC mapping is ready and we can try adding new records to the database. But, like I said, now we need to take care of providing unique keys when creating new objects: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount()      {          BillingDetailId = 1                          };     CreditCard creditCard = new CreditCard()      {          BillingDetailId = 2,         CardType = 1     };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Polymorphic Associations with TPC is Problematic The main problem with this approach is that it doesn’t support Polymorphic Associations very well. After all, in the database, associations are represented as foreign key relationships and in TPC, the subclasses are all mapped to different tables so a polymorphic association to their base class (abstract BillingDetail in our example) cannot be represented as a simple foreign key relationship. For example, consider the the domain model we introduced here where User has a polymorphic association with BillingDetail. This would be problematic in our TPC Schema, because if User has a many-to-one relationship with BillingDetail, the Users table would need a single foreign key column, which would have to refer both concrete subclass tables. This isn’t possible with regular foreign key constraints. Schema Evolution with TPC is Complex A further conceptual problem with this mapping strategy is that several different columns, of different tables, share exactly the same semantics. This makes schema evolution more complex. For example, a change to a base class property results in changes to multiple columns. It also makes it much more difficult to implement database integrity constraints that apply to all subclasses. Generated SQLLet's examine SQL output for polymorphic queries in TPC mapping. For example, consider this polymorphic query for all BillingDetails and the resulting SQL statements that being executed in the database: var query = from b in context.BillingDetails select b; Just like the SQL query generated by TPT mapping, the CASE statements that you see in the beginning of the query is merely to ensure columns that are irrelevant for a particular row have NULL values in the returning flattened table. (e.g. BankName for a row that represents a CreditCard type). TPC's SQL Queries are Union Based As you can see in the above screenshot, the first SELECT uses a FROM-clause subquery (which is selected with a red rectangle) to retrieve all instances of BillingDetails from all concrete class tables. The tables are combined with a UNION operator, and a literal (in this case, 0 and 1) is inserted into the intermediate result; (look at the lines highlighted in yellow.) EF reads this to instantiate the correct class given the data from a particular row. A union requires that the queries that are combined, project over the same columns; hence, EF has to pad and fill up nonexistent columns with NULL. This query will really perform well since here we can let the database optimizer find the best execution plan to combine rows from several tables. There is also no Joins involved so it has a better performance than the SQL queries generated by TPT where a Join is required between the base and subclasses tables. Choosing Strategy GuidelinesBefore we get into this discussion, I want to emphasize that there is no one single "best strategy fits all scenarios" exists. As you saw, each of the approaches have their own advantages and drawbacks. Here are some rules of thumb to identify the best strategy in a particular scenario: If you don’t require polymorphic associations or queries, lean toward TPC—in other words, if you never or rarely query for BillingDetails and you have no class that has an association to BillingDetail base class. I recommend TPC (only) for the top level of your class hierarchy, where polymorphism isn’t usually required, and when modification of the base class in the future is unlikely. If you do require polymorphic associations or queries, and subclasses declare relatively few properties (particularly if the main difference between subclasses is in their behavior), lean toward TPH. Your goal is to minimize the number of nullable columns and to convince yourself (and your DBA) that a denormalized schema won’t create problems in the long run. If you do require polymorphic associations or queries, and subclasses declare many properties (subclasses differ mainly by the data they hold), lean toward TPT. Or, depending on the width and depth of your inheritance hierarchy and the possible cost of joins versus unions, use TPC. By default, choose TPH only for simple problems. For more complex cases (or when you’re overruled by a data modeler insisting on the importance of nullability constraints and normalization), you should consider the TPT strategy. But at that point, ask yourself whether it may not be better to remodel inheritance as delegation in the object model (delegation is a way of making composition as powerful for reuse as inheritance). Complex inheritance is often best avoided for all sorts of reasons unrelated to persistence or ORM. EF acts as a buffer between the domain and relational models, but that doesn’t mean you can ignore persistence concerns when designing your classes. SummaryIn this series, we focused on one of the main structural aspect of the object/relational paradigm mismatch which is inheritance and discussed how EF solve this problem as an ORM solution. We learned about the three well-known inheritance mapping strategies and their implementations in EF Code First. Hopefully it gives you a better insight about the mapping of inheritance hierarchies as well as choosing the best strategy for your particular scenario. Happy New Year and Happy Code-Firsting! References ADO.NET team blog Java Persistence with Hibernate book a { color: #5A99FF; } a:visited { color: #5A99FF; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } .exception { background-color: #f0f0f0; font-style: italic; padding-bottom: 5px; padding-left: 5px; padding-top: 5px; padding-right: 5px; }

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  • OOP concept: is it possible to update the class of an instantiated object?

    - by Federico
    I am trying to write a simple program that should allow a user to save and display sets of heterogeneous, but somehow related data. For clarity sake, I will use a representative example of vehicles. The program flow is like this: The program creates a Garage object, which is basically a class that can contain a list of vehicles objects Then the users creates Vehicles objects, these Vehicles each have a property, lets say License Plate Nr. Once created, the Vehicle object get added to a list within the Garage object --Later on--, the user can specify that a given Vehicle object is in fact a Car object or a Truck object (thus giving access to some specific attributes such as Number of seats for the Car, or Cargo weight for the truck) At first sight, this might look like an OOP textbook question involving a base class and inheritance, but the problem is more subtle because at the object creation time (and until the user decides to give more info), the computer doesn't know the exact Vehicle type. Hence my question: how would you proceed to implement this program flow? Is OOP the way to go? Just to give an initial answer, here is what I've came up until now. There is only one Vehicle class and the various properties/values are handled by the main program (not the class) through a dictionary. However, I'm pretty sure that there must be a more elegant solution (I'm developing using VB.net): Public Class Garage Public GarageAdress As String Private _ListGarageVehicles As New List(Of Vehicles) Public Sub AddVehicle(Vehicle As Vehicles) _ListGarageVehicles.Add(Vehicle) End Sub End Class Public Class Vehicles Public LicensePlateNumber As String Public Enum VehicleTypes Generic = 0 Car = 1 Truck = 2 End Enum Public VehicleType As VehicleTypes Public DictVehicleProperties As New Dictionary(Of String, String) End Class NOTE that in the example above the public/private modifiers do not necessarily reflect the original code

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  • What OO Design to use ( is there a Design Pattern )?

    - by Blundell
    I have two objects that represent a 'Bar/Club' ( a place where you drink/socialise). In one scenario I need the bar name, address, distance, slogon In another scenario I need the bar name, address, website url, logo So I've got two objects representing the same thing but with different fields. I like to use immutable objects, so all the fields are set from the constructor. One option is to have two constructors and null the other fields i.e: class Bar { private final String name; private final Distance distance; private final Url url; public Bar(String name, Distance distance){ this.name = name; this.distance = distance; this.url = null; } public Bar(String name, Url url){ this.name = name; this.distance = null; this.url = url; } // getters } I don't like this as you would have to null check when you use the getters In my real example the first scenario has 3 fields and the second scenario has about 10, so it would be a real pain having two constructors, the amount of fields I would have to declare null and then when the object are in use you wouldn't know which Bar you where using and so what fields would be null and what wouldn't. What other options do I have? Two classes called BarPreview and Bar? Some type of inheritance / interface? Something else that is awesome?

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  • How to maintain encapsulation with composition in C++?

    - by iFreilicht
    I am designing a class Master that is composed from multiple other classes, A, Base, C and D. These four classes have absolutely no use outside of Master and are meant to split up its functionality into manageable and logically divided packages. They also provide extensible functionality as in the case of Base, which can be inherited from by clients. But, how do I maintain encapsulation of Master with this design? So far, I've got two approaches, which are both far from perfect: 1. Replicate all accessors: Just write accessor-methods for all accessor-methods of all classes that Master is composed of. This leads to perfect encapsulation, because no implementation detail of Master is visible, but is extremely tedious and makes the class definition monstrous, which is exactly what the composition should prevent. Also, adding functionality to one of the composees (is that even a word?) would require to re-write all those methods in Master. An additional problem is that inheritors of Base could only alter, but not add functionality. 2. Use non-assignable, non-copyable member-accessors: Having a class accessor<T> that can not be copied, moved or assigned to, but overrides the operator-> to access an underlying shared_ptr, so that calls like Master->A()->niceFunction(); are made possible. My problem with this is that it kind of breaks encapsulation as I would now be unable to change my implementation of Master to use a different class for the functionality of niceFunction(). Still, it is the closest I've gotten without using the ugly first approach. It also fixes the inheritance issue quite nicely. A small side question would be if such a class already existed in std or boost. EDIT: Wall of code I will now post the code of the header files of the classes discussed. It may be a bit hard to understand, but I'll give my best in explaining all of it. 1. GameTree.h The foundation of it all. This basically is a doubly-linked tree, holding GameObject-instances, which we'll later get to. It also has it's own custom iterator GTIterator, but I left that out for brevity. WResult is an enum with the values SUCCESS and FAILED, but it's not really important. class GameTree { public: //Static methods for the root. Only one root is allowed to exist at a time! static void ConstructRoot(seed_type seed, unsigned int depth); inline static bool rootExists(){ return static_cast<bool>(rootObject_); } inline static weak_ptr<GameTree> root(){ return rootObject_; } //delta is in ms, this is used for velocity, collision and such void tick(unsigned int delta); //Interaction with the tree inline weak_ptr<GameTree> parent() const { return parent_; } inline unsigned int numChildren() const{ return static_cast<unsigned int>(children_.size()); } weak_ptr<GameTree> getChild(unsigned int index) const; template<typename GOType> weak_ptr<GameTree> addChild(seed_type seed, unsigned int depth = 9001){ GOType object{ new GOType(seed) }; return addChildObject(unique_ptr<GameTree>(new GameTree(std::move(object), depth))); } WResult moveTo(weak_ptr<GameTree> newParent); WResult erase(); //Iterators for for( : ) loop GTIterator& begin(){ return *(beginIter_ = std::move(make_unique<GTIterator>(children_.begin()))); } GTIterator& end(){ return *(endIter_ = std::move(make_unique<GTIterator>(children_.end()))); } //unloading should be used when objects are far away WResult unloadChildren(unsigned int newDepth = 0); WResult loadChildren(unsigned int newDepth = 1); inline const RenderObject& renderObject() const{ return gameObject_->renderObject(); } //Getter for the underlying GameObject (I have not tested the template version) weak_ptr<GameObject> gameObject(){ return gameObject_; } template<typename GOType> weak_ptr<GOType> gameObject(){ return dynamic_cast<weak_ptr<GOType>>(gameObject_); } weak_ptr<PhysicsObject> physicsObject() { return gameObject_->physicsObject(); } private: GameTree(const GameTree&); //copying is only allowed internally GameTree(shared_ptr<GameObject> object, unsigned int depth = 9001); //pointer to root static shared_ptr<GameTree> rootObject_; //internal management of a child weak_ptr<GameTree> addChildObject(shared_ptr<GameTree>); WResult removeChild(unsigned int index); //private members shared_ptr<GameObject> gameObject_; shared_ptr<GTIterator> beginIter_; shared_ptr<GTIterator> endIter_; //tree stuff vector<shared_ptr<GameTree>> children_; weak_ptr<GameTree> parent_; unsigned int selfIndex_; //used for deletion, this isn't necessary void initChildren(unsigned int depth); //constructs children }; 2. GameObject.h This is a bit hard to grasp, but GameObject basically works like this: When constructing a GameObject, you construct its basic attributes and a CResult-instance, which contains a vector<unique_ptr<Construction>>. The Construction-struct contains all information that is needed to construct a GameObject, which is a seed and a function-object that is applied at construction by a factory. This enables dynamic loading and unloading of GameObjects as done by GameTree. It also means that you have to define that factory if you inherit GameObject. This inheritance is also the reason why GameTree has a template-function gameObject<GOType>. GameObject can contain a RenderObject and a PhysicsObject, which we'll later get to. Anyway, here's the code. class GameObject; typedef unsigned long seed_type; //this declaration magic means that all GameObjectFactorys inherit from GameObjectFactory<GameObject> template<typename GOType> struct GameObjectFactory; template<> struct GameObjectFactory<GameObject>{ virtual unique_ptr<GameObject> construct(seed_type seed) const = 0; }; template<typename GOType> struct GameObjectFactory : GameObjectFactory<GameObject>{ GameObjectFactory() : GameObjectFactory<GameObject>(){} unique_ptr<GameObject> construct(seed_type seed) const{ return unique_ptr<GOType>(new GOType(seed)); } }; //same as with the factories. this is important for storing them in vectors template<typename GOType> struct Construction; template<> struct Construction<GameObject>{ virtual unique_ptr<GameObject> construct() const = 0; }; template<typename GOType> struct Construction : Construction<GameObject>{ Construction(seed_type seed, function<void(GOType*)> func = [](GOType* null){}) : Construction<GameObject>(), seed_(seed), func_(func) {} unique_ptr<GameObject> construct() const{ unique_ptr<GameObject> gameObject{ GOType::factory.construct(seed_) }; func_(dynamic_cast<GOType*>(gameObject.get())); return std::move(gameObject); } seed_type seed_; function<void(GOType*)> func_; }; typedef struct CResult { CResult() : constructions{} {} CResult(CResult && o) : constructions(std::move(o.constructions)) {} CResult& operator= (CResult& other){ if (this != &other){ for (unique_ptr<Construction<GameObject>>& child : other.constructions){ constructions.push_back(std::move(child)); } } return *this; } template<typename GOType> void push_back(seed_type seed, function<void(GOType*)> func = [](GOType* null){}){ constructions.push_back(make_unique<Construction<GOType>>(seed, func)); } vector<unique_ptr<Construction<GameObject>>> constructions; } CResult; //finally, the GameObject class GameObject { public: GameObject(seed_type seed); GameObject(const GameObject&); virtual void tick(unsigned int delta); inline Matrix4f trafoMatrix(){ return physicsObject_->transformationMatrix(); } //getter inline seed_type seed() const{ return seed_; } inline CResult& properties(){ return properties_; } inline const RenderObject& renderObject() const{ return *renderObject_; } inline weak_ptr<PhysicsObject> physicsObject() { return physicsObject_; } protected: virtual CResult construct_(seed_type seed) = 0; CResult properties_; shared_ptr<RenderObject> renderObject_; shared_ptr<PhysicsObject> physicsObject_; seed_type seed_; }; 3. PhysicsObject That's a bit easier. It is responsible for position, velocity and acceleration. It will also handle collisions in the future. It contains three Transformation objects, two of which are optional. I'm not going to include the accessors on the PhysicsObject class because I tried my first approach on it and it's just pure madness (way over 30 functions). Also missing: the named constructors that construct PhysicsObjects with different behaviour. class Transformation{ Vector3f translation_; Vector3f rotation_; Vector3f scaling_; public: Transformation() : translation_{ 0, 0, 0 }, rotation_{ 0, 0, 0 }, scaling_{ 1, 1, 1 } {}; Transformation(Vector3f translation, Vector3f rotation, Vector3f scaling); inline Vector3f translation(){ return translation_; } inline void translation(float x, float y, float z){ translation(Vector3f(x, y, z)); } inline void translation(Vector3f newTranslation){ translation_ = newTranslation; } inline void translate(float x, float y, float z){ translate(Vector3f(x, y, z)); } inline void translate(Vector3f summand){ translation_ += summand; } inline Vector3f rotation(){ return rotation_; } inline void rotation(float pitch, float yaw, float roll){ rotation(Vector3f(pitch, yaw, roll)); } inline void rotation(Vector3f newRotation){ rotation_ = newRotation; } inline void rotate(float pitch, float yaw, float roll){ rotate(Vector3f(pitch, yaw, roll)); } inline void rotate(Vector3f summand){ rotation_ += summand; } inline Vector3f scaling(){ return scaling_; } inline void scaling(float x, float y, float z){ scaling(Vector3f(x, y, z)); } inline void scaling(Vector3f newScaling){ scaling_ = newScaling; } inline void scale(float x, float y, float z){ scale(Vector3f(x, y, z)); } void scale(Vector3f factor){ scaling_(0) *= factor(0); scaling_(1) *= factor(1); scaling_(2) *= factor(2); } Matrix4f matrix(){ return WMatrix::Translation(translation_) * WMatrix::Rotation(rotation_) * WMatrix::Scale(scaling_); } }; class PhysicsObject; typedef void tickFunction(PhysicsObject& self, unsigned int delta); class PhysicsObject{ PhysicsObject(const Transformation& trafo) : transformation_(trafo), transformationVelocity_(nullptr), transformationAcceleration_(nullptr), tick_(nullptr) {} PhysicsObject(PhysicsObject&& other) : transformation_(other.transformation_), transformationVelocity_(std::move(other.transformationVelocity_)), transformationAcceleration_(std::move(other.transformationAcceleration_)), tick_(other.tick_) {} Transformation transformation_; unique_ptr<Transformation> transformationVelocity_; unique_ptr<Transformation> transformationAcceleration_; tickFunction* tick_; public: void tick(unsigned int delta){ tick_ ? tick_(*this, delta) : 0; } inline Matrix4f transformationMatrix(){ return transformation_.matrix(); } } 4. RenderObject RenderObject is a base class for different types of things that could be rendered, i.e. Meshes, Light Sources or Sprites. DISCLAIMER: I did not write this code, I'm working on this project with someone else. class RenderObject { public: RenderObject(float renderDistance); virtual ~RenderObject(); float renderDistance() const { return renderDistance_; } void setRenderDistance(float rD) { renderDistance_ = rD; } protected: float renderDistance_; }; struct NullRenderObject : public RenderObject{ NullRenderObject() : RenderObject(0.f){}; }; class Light : public RenderObject{ public: Light() : RenderObject(30.f){}; }; class Mesh : public RenderObject{ public: Mesh(unsigned int seed) : RenderObject(20.f) { meshID_ = 0; textureID_ = 0; if (seed == 1) meshID_ = Model::getMeshID("EM-208_heavy"); else meshID_ = Model::getMeshID("cube"); }; unsigned int getMeshID() const { return meshID_; } unsigned int getTextureID() const { return textureID_; } private: unsigned int meshID_; unsigned int textureID_; }; I guess this shows my issue quite nicely: You see a few accessors in GameObject which return weak_ptrs to access members of members, but that is not really what I want. Also please keep in mind that this is NOT, by any means, finished or production code! It is merely a prototype and there may be inconsistencies, unnecessary public parts of classes and such.

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  • Help with these warnings. [inheritance].

    - by sil3nt
    Hello there. I have a set of code, which mimics a basic library cataloging system. There is a base class named items, in which the the general id,title and year variables are defined and 3 other derived classes (DVD,Book and CD). Base [Items] Derived [DVD,Book,CD]. The programs runs, however I get the following warnings, I'm not sure how to fix these. "C:\Program Files\gcc\bin/g++" -Os -mconsole -g -Wall -Wshadow -fno-common mainA4.cpp -o mainA4.exe In file included from mainA4.cpp:5: a4.h: In constructor `DVD::DVD(int, std::string, int, std::string)': a4.h:28: warning: `DVD::director' will be initialized after a4.h:32: warning: base `Items' a4.h:32: warning: when initialized here a4.h: In constructor `Book::Book(int, std::string, int, std::string, int)': a4.h:48: warning: `Book::numPages' will be initialized after a4.h:52: warning: base `Items' a4.h:52: warning: when initialized here a4.h: In constructor `CD::CD(int, std::string, int, std::string, int)': a4.h:66: warning: `CD::numSongs' will be initialized after a4.h:70: warning: base `Items' a4.h:70: warning: when initialized here Exit code: 0

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  • Singleton with inheritance, Derived class is not able to get instantiated in parent?

    - by yesraaj
    Below code instantiates a derived singleton object based on environment variable. The compiler errors saying error C2512: 'Dotted' : no appropriate default constructor. I don't understand what the compiler is complaining about. #include <stdlib.h> #include <iostream> #include <string> using namespace std; class Dotted; class Singleton{ public: static Singleton instant(){ if (!instance_) { char * style = getenv("STYLE"); if (!style){ if (strcmp(style,"dotted")==0) { instance_ = new Dotted(); return *instance_; } } else{ instance_ = new Singleton(); return *instance_; } } return *instance_; } void print(){cout<<"Singleton";} ~Singleton(){}; protected: Singleton(){}; private: static Singleton * instance_; Singleton(const Singleton & ); void operator=(const Singleton & ); }; class Dotted:public Singleton{ public: void print(){cout<<"Dotted";} protected: Dotted(); }; Dotted::Dotted():Singleton(){} int main(){ Singleton::instant().print(); cin.get(); }

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  • Why doesn't interface inheritance work when writing shell extensions in c#?

    - by Factor Mystic
    According to this article about writing shell extensions in .Net, inheriting the shell interfaces as you might naturally do when writing code doesn't work. I've observed this in my own code as well. Doesn't work: public interface IPersist { // stuff specific only to IPersist } public interface IPersistFolder : IPersist { // stuff specific only to IPersistFolder } Does work: public interface IPersistFolder { // stuff specific to IPersist only // stuff specific to IPersistFolder only } The article notes this fact: Lo and behold, it worked! Notice that I've abandoned any idea that IPersistFolder is inherited from anything at all and just included the stubs from IPersist right in its definition. In all candor, I can't tell you why this is but it definitely works just fine and shouldn't give you any problems. So my I'll ask the question this guy didn't know; why didn't the original code work?

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  • CSS precedence order? My lecture slides are correct or not?

    - by Michael Mao
    Hi all: I've noticed that there are a couple of similar questions and answers at SO already, but let me clarify my specific question here first: I've got lecture slides which states like this: To be frank, I haven't heard of this rule of css precedence myself, and I googled to find something with similar topic but not quite like that : here To have a test myself, I've made a test page on my own server here After running it on FireFox 3.6.3, I am sure it does not show the way as it should be, according to the statement in lecture slides: imported stylesheet ? am I doing it wrong? I cannot see its effect using FireBug it says that embedded stylesheet has a higher precedence over linked/imported stylesheets, however, it doesn't work, if I put the linked/imported tag AFTER that. inline style vs html attributes ? I've got an image where I firstly set its inline style to control the width and height, then use direct html attributes width/height to try modifying that, but failed... Below is the source code : <html> <head> <style type="text/css"> #target { border : 2px solid green; color : green; } </style> <link rel="stylesheet" href="./linked.css" type="text/css" media="screen" /> </head> <body> <div id="target">A targeted div tag on page.</div> <img src="cat.jpg" alt="" style="width : 102px; height : 110px;" width="204px" height="220px" /> </body> </html> Can any experienced CSS guys help me figure out if the slide is correct or not? Frankly speaking, I am puzzled myself, as I can clearly see some other "incorrect" statements here and there amongst the slides, such as JavaScript is on client-side (how about server-side JavaScript?) and "Embedded styles are in the head section of a web page "(what the heck? I am not allowed to put it inside the body tag?) Sorry about this silly question, the exam is on TOMORROW, and I now see a lot of things to think about :)

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  • Class inheritance in PHP 5.2: Overriding static variable in extension class?

    - by Christoffer
    Hi, I need to bea be able to use a static variable set in a class that extends a base class... from the base class. Consider this: class Animal { public static $color = 'black'; public static function get_color() { return self::$color; } } class Dog { public static $color = 'brown'; } echo Animal::get_color(); // prints 'black' echo Dog::get_color(); // also prints 'black' This works wonderfully in PHP 5.3.x (Dog::get_color() prints 'brown') since it has late static binding. But my production server runs PHP 5.2.11 and so I need to adapt my script. Is there a somewhat pretty workaround to solve this issue? Cheers! Christoffer

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  • How is it possible the class inheritance in namespaces using Ruby on Rails 3?

    - by user502052
    In my RoR3 application I have a namespace called NS1 so that I have this filesystem structure: ROOT_RAILS/controllers/ ROOT_RAILS/controllers/application_controller.rb ROOT_RAILS/controllers/ns/ ROOT_RAILS/controllers/ns/ns_controller.rb ROOT_RAILS/controllers/ns/names_controller.rb ROOT_RAILS/controllers/ns/surnames_controller.rb I wuold like that 'ns_controller.rb' inherits from application controller, so in 'ns_controller.rb' file I have: class Ns::NsController < ApplicationController ... end Is this the right approach? Anyway if I have this situation... in 'application_controller.rb' class ApplicationController < ActionController::Base @profile = Profile.find(1) end in 'ns_controller.rb' class Ns::NsController < ApplicationController @name = @profile.name @surname = @profile.surname end ... '@name' and '@surname' variables are not set. Why?

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  • Is there a mean to specify specialization-genralization (inheritance) of actors in UML?

    - by Ivan
    I am just starting to use UML and have came to the following question: Some actors clearly are specialized versions of a natural entity. For example I've got Administrator and User actors which are clearly nothing but different roles of a user, Authorizer and Dispatcher which are services (and are going to be implemented this way). Should I just ignore these facts while modelling actors and use cases or specify it some way? I think I could make good use of such a specification to facilitate code generation.

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  • Is it possible to use CSS to align these divs/spans in a table-like manner?

    - by Justin L.
    I have <div class='line'> <div class='chord_line'> <span class='chord_block'></span> <span class='chord_block'>E</span> <span class='chord_block'>B</span> <span class='chord_block'>C#m</span> <span class='chord_block'>A</span> </div> <div class='lyric_line'> <span class='lyric_block'></span> <span class='lyric_block'>Just a</span> <span class='lyric_block'>small-town girl</span> <span class='lyric_block'>living in a</span> <span class='lyric_block'>lonely world</span> </div> </div> (Excuse me for not being too familiar with proper css conventions for when to use div/spans) I want to be able to display them so that each chord_block span and lyric_block span is aligned vertically, as if they were left-aligned and on the same row of a table. For example: E B C#m A Just a small-town girl living in a lonely world (There will often be cases where an empty chord block is matched up to non-empty lyric block, and vice-versa.) I'm completely new to using CSS to align things, and have had no real understanding/experience of CSS aside from changing background colors and link styles. Is this possible in CSS? If not, how could the div/class nesting structure be revised to make this possible? I could change the spans to divs if necessary. Some things I cannot use: I can't change the structure to group things by a chord_and_lyric_block div (and have their width stretch to the length of the lyric, and stack them horizontally), because I couldn't really copy/select the lyrical lines continuously in their entirety, which is extremely critical. I'm trying to avoid a table-like solution, because this data is not tabular at all. The chord line and the lyric line are meant to be read as one continuous line, not a set of cells. Also, apart from the design philosophy reasons, I think it might have the same problems as the previous thing bullet point. If this is possible, what div/span attributes should I be using? Can you provide sample css? If this is not possible, can it be done with javascript?

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