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  • Singletons and constants

    - by devoured elysium
    I am making a program which makes use of a couple of constants. At first, each time I needed to use a constant, I'd define it as //C# private static readonly int MyConstant = xxx; //Java private static final int MyConstant = xxx; in the class where I'd need it. After some time, I started to realise that some constants would be needed in more than one class. At this time, I had 3 choises: To define them in the different classes that needed it. This leads to repetition. If by some reason later I need to change one of them, I'd have to check in all classes to replace them everywhere. To define a static class/singleton with all the constants as public. If I needed a constant X in ClassA, ClassB and ClassC, I could just define it in ClassA as public, and then have ClassB and ClassC refer to them. This solution doesn't seem that good to me as it introduces even more dependencies as the classes already have between them. I ended up implementing my code with the second option. Is that the best alternative? I feel I am probably missing some other better alternative. What worries me about using the singleton here is that it is nowhere clear to a user of the class that this class is using the singleton. Maybe I could create a ConstantsClass that held all the constants needed and then I'd pass it in the constructor to the classes that'd need it? Thanks

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  • How do I define my own operators in the Io programming language?

    - by klep
    I'm trying to define my own operator in Io, and I'm having a hard time. I have an object: MyObject := Object clone do( lst := list() !! := method(n, lst at(n)) ) But when I call it, like this: x := MyObject clone do(lst appendSeq(list(1, 2, 3))) x !! 2 But I get an exception that argument 0 to at must not be nil. How can I fix?

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  • One UI for two business objects

    - by JC
    I have an order edit and quote edit screen that are very similar. I want to try to avoid code like this: if (order is Order) SetupScreenForOrder(); if (order is Quote) SetupScreenForQuote(); But maintaining two screens is not good either. If I create some common interface between a Quote and Order then how do you deal with fields like OrderNumber or QuoteDate? What's the best way to handle this?

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  • NSPredicate (Core Data fetch) to filter on an attribute value being present in a supplied set (list)

    - by starbaseweb
    I'm trying to create a fetch predicate that is the analog to the SQL "IN" statement, and the syntax to do so with NSPredicate escapes me. Here's what I have so far (the relevant excerpt from my fetching routine): NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease]; NSEntityDescription *entity = [NSEntityDescription entityForName: @"BodyPartCategory" inManagedObjectContext:_context]; [request setEntity:entity]; NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(name IN %@)", [RPBodyPartCategory defaultBodyPartCategoryNames]]; [request setPredicate:predicate]; The entity "BodyPartCategory" has a string attribute "name". I have a list of names (just NSString objects) in an NSArray as returned by: [RPBodyPartCategory defaultBodyPartCategoryNames] So let's say that array has string such as {@"Liver", @"Kidney", @"Thyroid"} ... etc. I want to fetch all 'BodyPartCategory' instances whose name attribute matches one of the strings in the set provided (technically NSArray but I can make it an NSSet). In SQL, this would be something like: SELECT * FROM BodyPartCategories WHERE name IN ('Liver', 'Kidney', 'Thyroid') I've gone through various portions of the Predicate Programming Guide, but I don't see this simple use case covered. Pointers/help much appreciated!

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  • Is this a good database design?

    - by alokpatil
    I am planning to make a railway reservation project... I am maintaining following tables: trainTable (trainId,trainName,trainFrom,trainTo,trainDate,trainNoOfBoogies)...PK(trainId) Boogie (trainId,boogieId,boogieName,boogieNoOfseats)...CompositeKey(trainId,boogieId)... Seats (trainId,boogieId,seatId,seatStatus,seatType)...CompositeKey(trainId,boogieId,seatId)... user (userId,name...personal details) userBooking (userId,trainId,boogieId,seatId)... Is this good design?

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  • Test if a method is an override?

    - by Water Cooler v2
    Is there a way to tell if a method is an override? For e.g. public class Foo { public virtual void DoSomething() {} public virtual int GimmeIntPleez() { return 0; } } public class BabyFoo: Foo { public override int GimmeIntPleez() { return -1; } } Is it possible to reflect on BabyFoo and tell if GimmeIntPleez is an override?

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  • Adding interfaces that won't be actually used

    - by devoured elysium
    I currently have two interfaces(that I'll name here IA and IB): interface IA { int Width; int Height; ... } interface IB { int Width; int Height; ... } that share the same two properties: they both have a Width and a Height property. I was thinking if there is any point in defining an IMatrix interface containing a Width and Height properties: interface IMatrix { int Width; int Height; } The thing is that although they share both the same properties, I won't make use of polymorphism with IMatrix in any of my coding: i.e., there won't by any situation where I'll want to use an IMatrix, I'll just want to use IA and IB. Adding an IMatrix seems more like over-engineering than other thing, but I'd like to ask you guys what your opinion is on the matter. Thanks

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  • Website Design Templates

    - by user347834
    I am looking fr someone to make me two website templates for my site for free. Here is a quick design of what I want:(Took me 2 minutes in Paint) http:/ /i50.tinypic.com/33p9aut.jpg (You have to push backspace on the first link to join up the http:/ and the other /)and http://i50.tinypic.com/2qmogoo.jpg Email me at [email protected] or [email protected] for more information

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  • Write a program for a report derived from the data in the data file JEWELRY. The data is to be input

    - by Taylor
    here is the JEWELRY file 0011 Money_Clip 2.000 50.00 Other 0035 Paperweight 1.625 175.00 Other 0457 Cuff_Bracelet 2.375 150.00 Bracelet 0465 Links_Bracelet 7.125 425.00 Bracelet 0585 Key_Chain 1.325 50.00 Other 0595 Cuff_Links 0.625 525.00 Other 0935 Royale_Pendant 0.625 975.00 Pendant 1092 Bordeaux_Cross 1.625 425.00 Cross 1105 Victory_Medallion 0.875 30.00 Pendant 1111 Marquis_Cross 1.375 70.00 Cross 1160 Christina_Ring 0.500 175.00 Ring 1511 French_Clips 0.687 375.00 Other 1717 Pebble_Pendant 1.250 45.00 Pendant 1725 Folded_Pendant 1.250 45.00 Pendant 1730 Curio_Pendant 1.063 275.00 Pendant this is the program i have used #include <iostream> #include <string> #include <iomanip> #include <fstream> using namespace std; struct productJewelry { string name; double amount; int itemCode; double size; string group; }; int main() { // declare variables ifstream inFile; int count=0; int x=0; productJewelry product[50]; inFile.open("jewelry.txt"); // file must be in same folder if (inFile.fail()) cout << "failed"; cout << fixed << showpoint; // fixed format, two decimal places cout << setprecision(2); while (inFile.peek() != EOF) { // cout << count << " : "; count++; inFile>> product[x].itemCode; inFile>> product[x].name; inFile>> product[x].size; inFile>> product[x].amount; inFile>> product[x].group; // cout << product[x].itemCode << ", " << product[x].name << ", "<< product[x].size << ", " << product[x].amount << endl; x++; if (inFile.peek() == '\n') inFile.ignore(1, '\n'); } inFile.close(); string temp; bool swap; do { swap = false; for (int x=0; x<count;x++) { if (product[x].name>product[x+1].name) { //these 3 lines are to swap elements in array temp=product[x].name; product[x].name=product[x+1].name; product[x+1].name=temp; swap=true; } } } while (swap); for (x=0; x< count; x++) { //cout<< product[x].itemCode<<" "; //cout<< product[x].name <<" "; //cout<< product[x].size <<" "; //cout<< product[x].amount<<" "; //cout<< product[x].group<<" "<<endl; } system("pause"); // to freeze Dev-c++ output screen return 0; } // end main

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  • What's the consequence when Core Data detects an optimistic locking failure when trying to save?

    - by dontWatchMyProfile
    I get it: When a managed object context saves, the snapshots of all edited objects are compared against the values in the persistent store to see if the PS has changed since the snapshot was made. If it did change, then there's a conflict and optimistic locking failed, according to Apple. But now, what's the consequence of this? What happens next? What are my options in this case?

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  • Java inheritance question

    - by user247866
    So I have 3 classes. Abstract class A Class B extends class A independent Class C In class D that contains the main method, I create a list of instances of class B List<B> b = method-call();` // the method returns a list of instances of class B Now in class C I have one method that is common to both A and B, and hence I don't want to duplicate it. I want to have one method that takes as input an instance of class A, as follows: public void some-method(LIst<A> a) However, when I do: C c = new C(). c. some-method(b) I get an error that some-method is not applicable for the argument List, instead it's expecting to get List. Is there a good way to fix this problem? Many thanks!

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  • Why are interfaces unusable in PHP?

    - by streetparade
    I mean an interface definition without defining the return type makes it unusable? This makes more Clear Interface run { public function getInteger(); } class MyString implements run { public function myNumber() { } public function getInteger() { return "Not a number"; } } In Java every Interface has a return type like Integer,String,Void I know that PHP is unfortunately a loosly typed Language but isnt there a Solution for that Problem? Is it Possible to defining a Interface with a Return type like Integer?

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  • OOP beginner: classB extends classA. classA already object. method in classB needed.. etc.

    - by Yvo
    Hey guys, I'm learning myself to go from function based PHP coding to OOP. And this is the situation: ClassA holds many basic tool methods (functions). it's __construct makes a DB connection. ClassB holds specific methods based on a certain activity (extract widgets). ClassB extends ClassA because it uses some of the basic tools in there e.g. a database call. In a php file I create a $a_class = new ClassA object (thus a new DB connection). Now I need a method in ClassB. I do $b_class = new ClassB; and call a method, which uses a method from it's parent:: ClassA. In this example, i'm having ClassA 'used' twice. Onces as object, and onces via a parent:: call, so ClassA creates another DB connection (or not?). So what is the best setup for this basic classes parent, child (extend) situation? I only want to make one connection of course? I don't like to forward the object to ClassB like this $b_class = new ClassB($a_object); or is that the best way? Thanks for thinking with me, and helping :d

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  • Why is it possible to have an interface without a return type in PHP?

    - by streetparade
    Why is it possible to create an interface without specifying a return type? Why doesn't this make this interface unusable? This makes it more Clear: Interface run { public function getInteger(); } class MyString implements run { public function myNumber() { } public function getInteger() { return "Not a number"; } } In Java every Interface has a return type like Integer, String or Void I know that PHP is unfortunately a loosely typed Language but isn't there a Solution to that Problem? Is it possible to define an Interface with a return type like Integer?

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  • SQL SERVER – Shrinking NDF and MDF Files – Readers’ Opinion

    - by pinaldave
    Previously, I had written a blog post about SQL SERVER – Shrinking NDF and MDF Files – A Safe Operation. After that, I have written the following blog post that talks about the advantage and disadvantage of Shrinking and why one should not be Shrinking a file SQL SERVER – SHRINKFILE and TRUNCATE Log File in SQL Server 2008. On this subject, SQL Server Expert Imran Mohammed left an excellent comment. I just feel that his comment is worth a big article itself. For everybody to read his wonderful explanation, I am posting this blog post here. Thanks Imran! Shrinking Database always creates performance degradation and increases fragmentation in the database. I suggest that you keep that in mind before you start reading the following comment. If you are going to say Shrinking Database is bad and evil, here I am saying it first and loud. Now, the comment of Imran is written while keeping in mind only the process showing how the Shrinking Database Operation works. Imran has already explained his understanding and requests further explanation. I have removed the Best Practices section from Imran’s comments, as there are a few corrections. Comments from Imran - Before I explain to you the concept of Shrink Database, let us understand the concept of Database Files. When we create a new database inside the SQL Server, it is typical that SQl Server creates two physical files in the Operating System: one with .MDF Extension, and another with .LDF Extension. .MDF is called as Primary Data File. .LDF is called as Transactional Log file. If you add one or more data files to a database, the physical file that will be created in the Operating System will have an extension of .NDF, which is called as Secondary Data File; whereas, when you add one or more log files to a database, the physical file that will be created in the Operating System will have the same extension as .LDF. The questions now are, “Why does a new data file have a different extension (.NDF)?”, “Why is it called as a secondary data file?” and, “Why is .MDF file called as a primary data file?” Answers: Note: The following explanation is based on my limited knowledge of SQL Server, so experts please do comment. A data file with a .MDF extension is called a Primary Data File, and the reason behind it is that it contains Database Catalogs. Catalogs mean Meta Data. Meta Data is “Data about Data”. An example for Meta Data includes system objects that store information about other objects, except the data stored by the users. sysobjects stores information about all objects in that database. sysindexes stores information about all indexes and rows of every table in that database. syscolumns stores information about all columns that each table has in that database. sysusers stores how many users that database has. Although Meta Data stores information about other objects, it is not the transactional data that a user enters; rather, it’s a system data about the data. Because Primary Data File (.MDF) contains important information about the database, it is treated as a special file. It is given the name Primary Data file because it contains the Database Catalogs. This file is present in the Primary File Group. You can always create additional objects (Tables, indexes etc.) in the Primary data file (This file is present in the Primary File group), by mentioning that you want to create this object under the Primary File Group. Any additional data file that you add to the database will have only transactional data but no Meta Data, so that’s why it is called as the Secondary Data File. It is given the extension name .NDF so that the user can easily identify whether a specific data file is a Primary Data File or a Secondary Data File(s). There are many advantages of storing data in different files that are under different file groups. You can put your read only in the tables in one file (file group) and read-write tables in another file (file group) and take a backup of only the file group that has read the write data, so that you can avoid taking the backup of a read-only data that cannot be altered. Creating additional files in different physical hard disks also improves I/O performance. A real-time scenario where we use Files could be this one: Let’s say you have created a database called MYDB in the D-Drive which has a 50 GB space. You also have 1 Database File (.MDF) and 1 Log File on D-Drive and suppose that all of that 50 GB space has been used up and you do not have any free space left but you still want to add an additional space to the database. One easy option would be to add one more physical hard disk to the server, add new data file to MYDB database and create this new data file in a new hard disk then move some of the objects from one file to another, and put the file group under which you added new file as default File group, so that any new object that is created gets into the new files, unless specified. Now that we got a basic idea of what data files are, what type of data they store and why they are named the way they are, let’s move on to the next topic, Shrinking. First of all, I disagree with the Microsoft terminology for naming this feature as “Shrinking”. Shrinking, in regular terms, means to reduce the size of a file by means of compressing it. BUT in SQL Server, Shrinking DOES NOT mean compressing. Shrinking in SQL Server means to remove an empty space from database files and release the empty space either to the Operating System or to SQL Server. Let’s examine this through an example. Let’s say you have a database “MYDB” with a size of 50 GB that has a free space of about 20 GB, which means 30GB in the database is filled with data and the 20 GB of space is free in the database because it is not currently utilized by the SQL Server (Database); it is reserved and not yet in use. If you choose to shrink the database and to release an empty space to Operating System, and MIND YOU, you can only shrink the database size to 30 GB (in our example). You cannot shrink the database to a size less than what is filled with data. So, if you have a database that is full and has no empty space in the data file and log file (you don’t have an extra disk space to set Auto growth option ON), YOU CANNOT issue the SHRINK Database/File command, because of two reasons: There is no empty space to be released because the Shrink command does not compress the database; it only removes the empty space from the database files and there is no empty space. Remember, the Shrink command is a logged operation. When we perform the Shrink operation, this information is logged in the log file. If there is no empty space in the log file, SQL Server cannot write to the log file and you cannot shrink a database. Now answering your questions: (1) Q: What are the USEDPAGES & ESTIMATEDPAGES that appear on the Results Pane after using the DBCC SHRINKDATABASE (NorthWind, 10) ? A: According to Books Online (For SQL Server 2000): UsedPages: the number of 8-KB pages currently used by the file. EstimatedPages: the number of 8-KB pages that SQL Server estimates the file could be shrunk down to. Important Note: Before asking any question, make sure you go through Books Online or search on the Google once. The reasons for doing so have many advantages: 1. If someone else already has had this question before, chances that it is already answered are more than 50 %. 2. This reduces your waiting time for the answer. (2) Q: What is the difference between Shrinking the Database using DBCC command like the one above & shrinking it from the Enterprise Manager Console by Right-Clicking the database, going to TASKS & then selecting SHRINK Option, on a SQL Server 2000 environment? A: As far as my knowledge goes, there is no difference, both will work the same way, one advantage of using this command from query analyzer is, your console won’t be freezed. You can do perform your regular activities using Enterprise Manager. (3) Q: What is this .NDF file that is discussed above? I have never heard of it. What is it used for? Is it used by end-users, DBAs or the SERVER/SYSTEM itself? A: .NDF File is a secondary data file. You never heard of it because when database is created, SQL Server creates database by default with only 1 data file (.MDF) and 1 log file (.LDF) or however your model database has been setup, because a model database is a template used every time you create a new database using the CREATE DATABASE Command. Unless you have added an extra data file, you will not see it. This file is used by the SQL Server to store data which are saved by the users. Hope this information helps. I would like to as the experts to please comment if what I understand is not what the Microsoft guys meant. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Readers Contribution, Readers Question, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – GUID vs INT – Your Opinion

    - by pinaldave
    I think the title is clear what I am going to write in your post. This is age old problem and I want to compile the list stating advantages and disadvantages of using GUID and INT as a Primary Key or Clustered Index or Both (the usual case). Let me start a list by suggesting one advantage and one disadvantage in each case. INT Advantage: Numeric values (and specifically integers) are better for performance when used in joins, indexes and conditions. Numeric values are easier to understand for application users if they are displayed. Disadvantage: If your table is large, it is quite possible it will run out of it and after some numeric value there will be no additional identity to use. GUID Advantage: Unique across the server. Disadvantage: String values are not as optimal as integer values for performance when used in joins, indexes and conditions. More storage space is required than INT. Please note that I am looking to create list of all the generic comparisons. There can be special cases where the stated information is incorrect, feel free to comment on the same. Please leave your opinion and advice in comment section. I will combine a final list and update this blog after a week. By listing your name in post, I will also give due credit. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Constraint and Keys, SQL Data Storage, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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  • Accessing Server-Side Data from Client Script: Using Ajax Web Services, Script References, and jQuery

    Today's websites commonly exchange information between the browser and the web server using Ajax techniques. In a nutshell, the browser executes JavaScript code typically in response to the page loading or some user action. This JavaScript makes an asynchronous HTTP request to the server. The server processes this request and, perhaps, returns data that the browser can then seamlessly integrate into the web page. Typically, the information exchanged between the browser and server is serialized into JSON, an open, text-based serialization format that is both human-readable and platform independent. Adding such targeted, lightweight Ajax capabilities to your ASP.NET website requires two steps: first, you must create some mechanism on the server that accepts requests from client-side script and returns a JSON payload in response; second, you need to write JavaScript in your ASP.NET page to make an HTTP request to this service you created and to work with the returned results. This article series examines a variety of techniques for implementing such scenarios. In Part 1 we used an ASP.NET page and the JavaScriptSerializer class to create a server-side service. This service was called from the browser using the free, open-source jQuery JavaScript library. This article continues our examination of techniques for implementing lightweight Ajax scenarios in an ASP.NET website. Specifically, it examines how to create ASP.NET Ajax Web Services on the server-side and how to use both the ASP.NET Ajax Library and jQuery to consume them from the client-side. Read on to learn more! Read More >

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  • Data Web Controls Enhancements in ASP.NET 4.0

    Traditionally, developers using Web controls enjoyed increased productivity but at the cost of control over the rendered markup. For instance, many ASP.NET controls automatically wrap their content in <table> for layout or styling purposes. This behavior runs counter to the web standards that have evolved over the past several years, which favor cleaner, terser HTML; sparing use of tables; and Cascading Style Sheets (CSS) for layout and styling. Furthermore, the <table> elements and other automatically-added content makes it harder to both style the Web controls using CSS and to work with the controls from client-side script. One of the aims of ASP.NET version 4.0 is to give Web Form developers greater control over the markup rendered by Web controls. Last week's article, Take Control Of Web Control ClientID Values in ASP.NET 4.0, highlighted how new properties in ASP.NET 4.0 give the developer more say over how a Web control's ID property is translated into a client-side id attribute. In addition to these ClientID-related properties, many Web controls in ASP.NET 4.0 include properties that allow the page developer to instruct the control to not emit extraneous markup, or to use an HTML element other than <table>. This article explores a number of enhancements made to the data Web controls in ASP.NET 4.0. As you'll see, most of these enhancements give the developer greater control over the rendered markup. Read on to learn more! Read More >Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Data Web Controls Enhancements in ASP.NET 4.0

    Traditionally, developers using Web controls enjoyed increased productivity but at the cost of control over the rendered markup. For instance, many ASP.NET controls automatically wrap their content in <table> for layout or styling purposes. This behavior runs counter to the web standards that have evolved over the past several years, which favor cleaner, terser HTML; sparing use of tables; and Cascading Style Sheets (CSS) for layout and styling. Furthermore, the <table> elements and other automatically-added content makes it harder to both style the Web controls using CSS and to work with the controls from client-side script. One of the aims of ASP.NET version 4.0 is to give Web Form developers greater control over the markup rendered by Web controls. Last week's article, Take Control Of Web Control ClientID Values in ASP.NET 4.0, highlighted how new properties in ASP.NET 4.0 give the developer more say over how a Web control's ID property is translated into a client-side id attribute. In addition to these ClientID-related properties, many Web controls in ASP.NET 4.0 include properties that allow the page developer to instruct the control to not emit extraneous markup, or to use an HTML element other than <table>. This article explores a number of enhancements made to the data Web controls in ASP.NET 4.0. As you'll see, most of these enhancements give the developer greater control over the rendered markup. Read on to learn more! Read More >

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