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  • If I define a property to prototype appears in the constructor of object, why?

    - by Eduard Florinescu
    I took the example from this question modified a bit: What is the point of the prototype method? function employee(name,jobtitle,born) { this.name=name; this.jobtitle=jobtitle; this.born=born; this.status="single" } employee.prototype.salary=10000000; var fred=new employee("Fred Flintstone","Caveman",1970); console.log(fred.salary); fred.salary=20000; console.log(fred.salary) And the output in console is this: What is the difference salary is in constructor but I still can access it with fred.salary, how can I see if is in constructor from code, status is still employee property how can I tell for example if name is the one of employee or has been touch by initialization? Why is salary in constructor, when name,jobtitle,born where "touched" by employee("Fred Flintstone","Caveman",1970); «constructor»?

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  • Can't I just use all static methods?

    - by Reddy S R
    What's the difference between the two UpdateSubject methods below? I felt using static methods is better if you just want to operate on the entities. In which situations should I go with non-static methods? public class Subject { public int Id {get; set;} public string Name { get; set; } public static bool UpdateSubject(Subject subject) { //Do something and return result return true; } public bool UpdateSubject() { //Do something on 'this' and return result return true; } } I know I will be getting many kicks from the community for this really annoying question but I could not stop myself asking it. Does this become impractical when dealing with inheritance?

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  • When are Getters and Setters Justified

    - by Winston Ewert
    Getters and setters are often criticized as being not proper OO. On the other hand most OO code I've seen has extensive getters and setters. When are getters and setters justified? Do you try to avoid using them? Are they overused in general? If your favorite language has properties (mine does) then such things are also considered getters and setters for this question. They are same thing from an OO methodology perspective. They just have nicer syntax. Sources for Getter/Setter Criticism (some taken from comments to give them better visibility): http://www.javaworld.com/javaworld/jw-09-2003/jw-0905-toolbox.html http://typicalprogrammer.com/?p=23 http://c2.com/cgi/wiki?AccessorsAreEvil http://www.darronschall.com/weblog/2005/03/no-brain-getter-and-setters.cfm http://www.adam-bien.com/roller/abien/entry/encapsulation_violation_with_getters_and To state the criticism simply: Getters and Setters allow you to manipulate the internal state of objects from outside of the object. This violates encapsulation. Only the object itself should care about its internal state. And an example Procedural version of code. struct Fridge { int cheese; } void go_shopping(Fridge fridge) { fridge.cheese += 5; } Mutator version of code: class Fridge { int cheese; void set_cheese(int _cheese) { cheese = _cheese; } int get_cheese() { return cheese; } } void go_shopping(Fridge fridge) { fridge.set_cheese(fridge.get_cheese() + 5); } The getters and setters made the code much more complicated without affording proper encapsulation. Because the internal state is accessible to other objects we don't gain a whole lot by adding these getters and setters. The question has been previously discussed on Stack Overflow: http://stackoverflow.com/questions/565095/java-are-getters-and-setters-evil http://stackoverflow.com/questions/996179

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  • Dependency injection in constructor, method or just use a static class instead?

    - by gaetanm
    What is the best between: $dispatcher = new Dispatcher($request); $dispatcher->dispatch(); and $dispatcher = new Dispatcher(); $dispatcher->dispatch($request); or even Dispatcher::dispatch($request); Knowing that only one method of this class uses the $request instance. I naturally tend to the last solution because the class have no other states, but by I feel that it may not be the best OOP solution.

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  • Which topics should be covered in a basic undergraduate C++ course?

    - by Gulshan
    I have a young lecturer friend who is going to teach the undergraduate C++ course in CS. He asked me for some suggestions regarding how the course should be organized. Now I am asking you. I have seen many trends in universities which leads to a nasty experience of C++. So, please suggest from a professional programmer's point of view. For your information, the students going to take the course, have taken course like "Introduction to programming with C" in previous semester.

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  • how do you read from system.out in Java [closed]

    - by Dan
    I'm trying to create a word scramble game and so far I have taken a vector of randomly assorted strings that contains both words and hints and split them into two vectors. I have randomly scrambled the word and set this all up in text boxes. Right now I'm stuck because I have a text box that takes input but I'm not sure how to read that in? I want the user to type the unscrambled word into the text box and have it calculate as correct and move on to the next word immediately. I also don't know how to get the keys working. I want the "?" character to be the hint button that shows the hint. At the moment the hint box works if I type the question mark in using the System.in but it doesn't work if I type it directly in to the text box. The characters are showing up in the text box but nothing is working after that.

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  • Sort Data in Windows Phone using Collection View Source

    - by psheriff
    When you write a Windows Phone application you will most likely consume data from a web service somewhere. If that service returns data to you in a sort order that you do not want, you have an easy alternative to sort the data without writing any C# or VB code. You use the built-in CollectionViewSource object in XAML to perform the sorting for you. This assumes that you can get the data into a collection that implements the IEnumerable or IList interfaces.For this example, I will be using a simple Product class with two properties, and a list of Product objects using the Generic List class. Try this out by creating a Product class as shown in the following code:public class Product {  public Product(int id, string name)   {    ProductId = id;    ProductName = name;  }  public int ProductId { get; set; }  public string ProductName { get; set; }}Create a collection class that initializes a property called DataCollection with some sample data as shown in the code below:public class Products : List<Product>{  public Products()  {    InitCollection();  }  public List<Product> DataCollection { get; set; }  List<Product> InitCollection()  {    DataCollection = new List<Product>();    DataCollection.Add(new Product(3,        "PDSA .NET Productivity Framework"));    DataCollection.Add(new Product(1,        "Haystack Code Generator for .NET"));    DataCollection.Add(new Product(2,        "Fundamentals of .NET eBook"));    return DataCollection;  }}Notice that the data added to the collection is not in any particular order. Create a Windows Phone page and add two XML namespaces to the Page.xmlns:scm="clr-namespace:System.ComponentModel;assembly=System.Windows"xmlns:local="clr-namespace:WPSortData"The 'local' namespace is an alias to the name of the project that you created (in this case WPSortData). The 'scm' namespace references the System.Windows.dll and is needed for the SortDescription class that you will use for sorting the data. Create a phone:PhoneApplicationPage.Resources section in your Windows Phone page that looks like the following:<phone:PhoneApplicationPage.Resources>  <local:Products x:Key="products" />  <CollectionViewSource x:Key="prodCollection"      Source="{Binding Source={StaticResource products},                       Path=DataCollection}">    <CollectionViewSource.SortDescriptions>      <scm:SortDescription PropertyName="ProductName"                           Direction="Ascending" />    </CollectionViewSource.SortDescriptions>  </CollectionViewSource></phone:PhoneApplicationPage.Resources>The first line of code in the resources section creates an instance of your Products class. The constructor of the Products class calls the InitCollection method which creates three Product objects and adds them to the DataCollection property of the Products class. Once the Products object is instantiated you now add a CollectionViewSource object in XAML using the Products object as the source of the data to this collection. A CollectionViewSource has a SortDescriptions collection that allows you to specify a set of SortDescription objects. Each object can set a PropertyName and a Direction property. As you see in the above code you set the PropertyName equal to the ProductName property of the Product object and tell it to sort in an Ascending direction.All you have to do now is to create a ListBox control and set its ItemsSource property to the CollectionViewSource object. The ListBox displays the data in sorted order by ProductName and you did not have to write any LINQ queries or write other code to sort the data!<ListBox    ItemsSource="{Binding Source={StaticResource prodCollection}}"   DisplayMemberPath="ProductName" />SummaryIn this blog post you learned that you can sort any data without having to change the source code of where the data comes from. Simply feed the data into a CollectionViewSource in XAML and set some sort descriptions in XAML and the rest is done for you! This comes in very handy when you are consuming data from a source where the data is given to you and you do not have control over the sorting.NOTE: You can download this article and many samples like the one shown in this blog entry at my website. http://www.pdsa.com/downloads. Select “Tips and Tricks”, then “Sort Data in Windows Phone using Collection View Source” from the drop down list.Good Luck with your Coding,Paul Sheriff** SPECIAL OFFER FOR MY BLOG READERS **We frequently offer a FREE gift for readers of my blog. Visit http://www.pdsa.com/Event/Blog for your FREE gift!

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  • Connect to QuickBooks from PowerBuilder using RSSBus ADO.NET Data Provider

    - by dataintegration
    The RSSBus ADO.NET providers are easy-to-use, standards based controls that can be used from any platform or development technology that supports Microsoft .NET, including Sybase PowerBuilder. In this article we show how to use the RSSBus ADO.NET Provider for QuickBooks in PowerBuilder. A similar approach can be used from PowerBuilder with other RSSBus ADO.NET Data Providers to access data from Salesforce, SharePoint, Dynamics CRM, Google, OData, etc. In this article we will show how to create a basic PowerBuilder application that performs CRUD operations using the RSSBus ADO.NET Provider for QuickBooks. Step 1: Open PowerBuilder and create a new WPF Window Application solution. Step 2: Add all the Visual Controls needed for the connection properties. Step 3: Add the DataGrid control from the .NET controls. Step 4:Configure the columns of the DataGrid control as shown below. The column bindings will depend on the table. <DataGrid AutoGenerateColumns="False" Margin="13,249,12,14" Name="datagrid1" TabIndex="70" ItemsSource="{Binding}"> <DataGrid.Columns> <DataGridTextColumn x:Name="idColumn" Binding="{Binding Path=ID}" Header="ID" Width="SizeToHeader" /> <DataGridTextColumn x:Name="nameColumn" Binding="{Binding Path=Name}" Header="Name" Width="SizeToHeader" /> ... </DataGrid.Columns> </DataGrid> Step 5:Add a reference to the RSSBus ADO.NET Provider for QuickBooks assembly. Step 6:Optional: Set the QBXML Version to 6. Some of the tables in QuickBooks require a later version of QuickBooks to support updates and deletes. Please check the help for details. Connect the DataGrid: Once the visual elements have been configured, developers can use standard ADO.NET objects like Connection, Command, and DataAdapter to populate a DataTable with the results of a SQL query: System.Data.RSSBus.QuickBooks.QuickBooksConnection conn conn = create System.Data.RSSBus.QuickBooks.QuickBooksConnection(connectionString) System.Data.RSSBus.QuickBooks.QuickBooksCommand comm comm = create System.Data.RSSBus.QuickBooks.QuickBooksCommand(command, conn) System.Data.DataTable table table = create System.Data.DataTable System.Data.RSSBus.QuickBooks.QuickBooksDataAdapter dataAdapter dataAdapter = create System.Data.RSSBus.QuickBooks.QuickBooksDataAdapter(comm) dataAdapter.Fill(table) datagrid1.ItemsSource=table.DefaultView The code above can be used to bind data from any query (set this in command), to the DataGrid. The DataGrid should have the same columns as those returned from the SELECT statement. PowerBuilder Sample Project The included sample project includes the steps outlined in this article. You will also need the QuickBooks ADO.NET Data Provider to make the connection. You can download a free trial here.

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  • How much is modern programming still tied to underyling digital logic?

    - by New Talk
    First of all: I've got no academic background. I'm working primarily with Java and Spring and I'm also fond of web programming and relational databases. I hope I'm using the right terms and I hope that this vague question makes some sense. Today the following question came to my mind: How much is modern programming still tied to the underlying digital logic? With modern programming I mean concepts like OOP, AOP, Java 7, AJAX, … I hope you get the idea. Do they no longer need the digital logic with which computers are working internally? Or is binary logic still ubiquitous when programming this way? If I'd change the inner workings of a computer overnight, would it matter, because my programming techniques are already that abstract? P. S.: With digital logic I mean the physical representation of everything "inside" the computer as zeroes and ones. Changed "binary" to "digital".

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  • Question about SDLC. How to answer this?

    - by pirzada
    I have seen this asked many times in job interviews but I am still not sure how to answer this. I am a web developer for quite some time but I still have problem with explaining OOP and SDLC (Familiar with system development life cycle) . How to prepare for above 2 topics for an interview point of view. Still I use both all the time during development. I am not clear on OOP SDLC Is there any simplest answer to both of these? Thanks

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  • Is it better to load up a class with methods or extend member functionality in a local subclass?

    - by Calvin Fisher
    Which is better? Class #1: public class SearchClass { public SearchClass (string ProgramName) { /* Searches LocalFile objects, handles exceptions, and puts results into m_Results. */ } DateTime TimeExecuted; bool OperationSuccessful; protected List<LocalFile> m_Results; public ReadOnlyCollection<LocalFile> Results { get { return new ReadOnlyCollection<LocalFile>(m_Results); } } #region Results Filters public DateTime OldestFileModified { get { /* Does what it says. */ } } public ReadOnlyCollection<LocalFile> ResultsWithoutProcessFiles() { return new ReadOnlyCollection<LocalFile> ((from x in m_Results where x.FileTypeID != FileTypeIDs.ProcessFile select x).ToList()); } #endregion } Or class #2: public class SearchClass { public SearchClass (string ProgramName) { /* Searches LocalFile objects, handles exceptions, and puts results into m_Results. */ } DateTime TimeExecuted; bool OperationSuccessful; protected List<LocalFile> m_Results; public ReadOnlyCollection<LocalFile> Results { get { return new ReadOnlyCollection<LocalFile>(m_Results); } } public class SearchResults : ReadOnlyCollection<LocalFile> { public SearchResults(IList<LocalFile> iList) : base(iList) { } #region Results Filters public DateTime OldestFileModified { get { /* Does what it says. */ } } public ReadOnlyCollection<LocalFile> ResultsWithoutProcessFiles() { return new ReadOnlyCollection<LocalFile> ((from x in this where x.FileTypeID != FileTypeIDs.ProcessFile select x).ToList()); } #endregion } } ...with the implication that OperationSuccessful is accompanied by a number of more interesting properties on how the operation went, and OldestFileModified and ResultsWithoutProcessFiles() also have several more siblings in the Results Filters section.

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  • Describe business logic with diagrams

    - by Nikos M.
    I am currently developing a web application for my thesis.I was asked by my professor to make diagrams to describe the business logic. Since I don't have a prior experience, I am pretty confused with all the terminology. I managed to clarify,I think, what business rules and business logic are, but I can't find out how you describe the business logic. Is it something particular or is it something more general? Do I need to learn UML? Does the fact that I use MVC affects the way I'll describe it?

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  • Something similar to Objective-C categories in other languages?

    - by adig
    I understand Objective-C categories and how they become useful, but I always have a hard time explaining the concept to other programmers that are not familiar with Objective C. Maybe I'm just bad at explaining things, but I was thinking at another way to explain it by comparing to similar features offered by other (more popular) languages. (ex : I can explain the similarities between Objective C protocols and Java Interfaces) Any examples similar to Categories ?

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  • Any language where every class instance is a class too?

    - by Dokkat
    Taking inspiration from Javascript prototypes, I had the idea of a language where every instance can be used as a class. Before I potentially reinvent the wheel, I would like to ask if there is a language already using this concept: //To declare a Class, extend the base class (in this case, Type) Type(Weapon,{price:0}); //Same syntax to inherit; simply extend the parent: Weapon(Sword,{price:3}); Weapon(Axe,{price:4}); Sword(Katana,{price:7}); Sword(Dagger,{price:3}); //And the same to create an instance: Katana(myKatana,{nickname:"Leon"}); myKatana.price; // 7 myKatana.nickname; // Leon // An operator to return children of a class; Sword_; // [Katana, Dagger] // An operator to return array of descendants; Sword__; // [Katana, Dagger, myKatana] // An operator to return array of parents; Sword^; // Weapon // Arrays can be used as elements Sword__.price += 1; //increases price of Sword's descendants by 1 mySword.price; //8 // And to access specific element (using its name instead of index) var name = "mySword" Katana_[name]; // [mySword] Katana_[name].nickname; // Leon Has this kind of approach been already studied/implemented?

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  • Design Principles: An Illuminati For Better Solution

    From my earliest memory of programming, I was taught that we should do some level of design before coding. Somewhere around the way I started hearing phrases Dependency Injection, IoC etc., but whenever I asked people the need for these patterns, I seldom got an answer that satisfied me…

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  • What should be allowed inside getters and setters?

    - by Botond Balázs
    I got into an interesting internet argument about getter and setter methods and encapsulation. Someone said that all they should do is an assignment (setters) or a variable access (getters) to keep them "pure" and ensure encapsulation. Am I right that this would completely defeat the purpose of having getters and setters in the first place and validation and other logic (without strange side-effects of course) should be allowed? When should validation happen? When setting the value, inside the setter (to protect the object from ever entering an invalid state - my opinion) Before setting the value, outside the setter Inside the object, before each time the value is used Is a setter allowed to change the value (maybe convert a valid value to some canonical internal representation)?

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  • Is throwing an error in unpredictable subclass-specific circumstances a violation of LSP?

    - by Motti Strom
    Say, I wanted to create a Java List<String> (see spec) implementation that uses a complex subsystem, such as a database or file system, for its store so that it becomes a simple persistent collection rather than an basic in-memory one. (We're limiting it specifically to a List of Strings for the purposes of discussion, but it could extended to automatically de-/serialise any object, with some help. We can also provide persistent Sets, Maps and so on in this way too.) So here's a skeleton implementation: class DbBackedList implements List<String> { private DbBackedList() {} /** Returns a list, possibly non-empty */ public static getList() { return new DbBackedList(); } public String get(int index) { return Db.getTable().getRow(i).asString(); // may throw DbExceptions! } // add(String), add(int, String), etc. ... } My problem lies with the fact that the underlying DB API may encounter connection errors that are not specified in the List interface that it should throw. My problem is whether this violates Liskov's Substitution Principle (LSP). Bob Martin actually gives an example of a PersistentSet in his paper on LSP that violates LSP. The difference is that his newly-specified Exception there is determined by the inserted value and so is strengthening the precondition. In my case the connection/read error is unpredictable and due to external factors and so is not technically a new precondition, merely an error of circumstance, perhaps like OutOfMemoryError which can occur even when unspecified. In normal circumstances, the new Error/Exception might never be thrown. (The caller could catch if it is aware of the possibility, just as a memory-restricted Java program might specifically catch OOME.) Is this therefore a valid argument for throwing an extra error and can I still claim to be a valid java.util.List (or pick your SDK/language/collection in general) and not in violation of LSP? If this does indeed violate LSP and thus not practically usable, I have provided two less-palatable alternative solutions as answers that you can comment on, see below. Footnote: Use Cases In the simplest case, the goal is to provide a familiar interface for cases when (say) a database is just being used as a persistent list, and allow regular List operations such as search, subList and iteration. Another, more adventurous, use-case is as a slot-in replacement for libraries that work with basic Lists, e.g if we have a third-party task queue that usually works with a plain List: new TaskWorkQueue(new ArrayList<String>()).start() which is susceptible to losing all it's queue in event of a crash, if we just replace this with: new TaskWorkQueue(new DbBackedList()).start() we get a instant persistence and the ability to share the tasks amongst more than one machine. In either case, we could either handle connection/read exceptions that are thrown, perhaps retrying the connection/read first, or allow them to throw and crash the program (e.g. if we can't change the TaskWorkQueue code).

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  • Joomla Template Club Makes Your Web Design a Breeze

    Building a new web site will be a lot of trouble when you begin looking at all the minute details. You have to find a company that can provide you with a domain name that is offered and expresses the... [Author: Joel Morrison - Web Design and Development - April 20, 2010]

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  • Should main method be only consists of object creations and method calls?

    - by crucified soul
    A friend of mine told me that, the best practice is class containing main method should be named Main and only contains main method. Also main method should only parse inputs, create other objects and call other methods. The Main class and main method shouldn't do anything else. Basically what he is saying that class containing main method should be like: public class Main { public static void main(String[] args) { //parse inputs //create other objects //call methods } } Is it the best practice?

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  • Explanation on how "Tell, Don't Ask" is considered good OO

    - by Pubby
    This blogpost was posted on Hacker News with several upvotes. Coming from C++, most of these examples seem to go against what I've been taught. Such as example #2: Bad: def check_for_overheating(system_monitor) if system_monitor.temperature > 100 system_monitor.sound_alarms end end versus good: system_monitor.check_for_overheating class SystemMonitor def check_for_overheating if temperature > 100 sound_alarms end end end The advice in C++ is that you should prefer free functions instead of member functions as they increase encapsulation. Both of these are identical semantically, so why prefer the choice that has access to more state? Example 4: Bad: def street_name(user) if user.address user.address.street_name else 'No street name on file' end end versus good: def street_name(user) user.address.street_name end class User def address @address || NullAddress.new end end class NullAddress def street_name 'No street name on file' end end Why is it the responsibility of User to format an unrelated error string? What if I want to do something besides print 'No street name on file' if it has no street? What if the street is named the same thing? Could someone enlighten me on the "Tell, Don't Ask" advantages and rationale? I am not looking for which is better, but instead trying to understand the author's viewpoint.

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  • 5 Steps for Creating a Successful Banner Design

    Banners are supposed to be one of the most effective ways of marketing your products and services. They account for a better visibility and scope for placing your products in the eyes of your custome... [Author: Jessica Woodson - Web Design and Development - March 29, 2010]

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