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  • General ORM design question

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

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  • Why MyModel.all works in Rails ?

    - by AntonAL
    Hi, i don't understand this little thing: Suppose, we have "Person" model class Person < ActiveRecord::Base end Why Person.all works ? Person.all.each { |p| do_something } This syntax tells us, that we have Person class-object instanciated somewhere ? Or is it some convention over configuration case ?

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  • Constructors from extended class in Java

    - by Crystal
    I'm having some trouble with a hw assignment. In one assignment, we had to create a Person class. Mine was: public class Person { String firstName; String lastName; String telephone; String email; public Person() { firstName = ""; lastName = ""; telephone = ""; email = ""; } public Person(String firstName) { this.firstName = firstName; } public Person(String firstName, String lastName, String telephone, String email) { this.firstName = firstName; this.lastName = lastName; this.telephone = telephone; this.email = email; } public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public String getTelephone() { return telephone; } public void setTelephone(String telephone) { this.telephone = telephone; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public boolean equals(Object otherObject) { // a quick test to see if the objects are identical if (this == otherObject) { return true; } // must return false if the explicit parameter is null if (otherObject == null) { return false; } if (!(otherObject instanceof Person)) { return false; } Person other = (Person) otherObject; return firstName.equals(other.firstName) && lastName.equals(other.lastName) && telephone.equals(other.telephone) && email.equals(other.email); } public int hashCode() { return 7 * firstName.hashCode() + 11 * lastName.hashCode() + 13 * telephone.hashCode() + 15 * email.hashCode(); } public String toString() { return getClass().getName() + "[firstName = " + firstName + '\n' + "lastName = " + lastName + '\n' + "telephone = " + telephone + '\n' + "email = " + email + "]"; } } Now we have to extend that class and use that class in our constructor. The function protoype is: public CarLoan(Person client, double vehiclePrice, double downPayment, double salesTax, double interestRate, CAR_LOAN_TERMS length) I'm confused on how I use the Person constructor from the superclass. I cannot necessarily do super(client); in my constructor which is what the book did with some primitive types in their example. Not sure what the correct thing to do is... Any thoughts? Thanks!

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  • ASP.NET Frameworks and Raw Throughput Performance

    - by Rick Strahl
    A few days ago I had a curious thought: With all these different technologies that the ASP.NET stack has to offer, what's the most efficient technology overall to return data for a server request? When I started this it was mere curiosity rather than a real practical need or result. Different tools are used for different problems and so performance differences are to be expected. But still I was curious to see how the various technologies performed relative to each just for raw throughput of the request getting to the endpoint and back out to the client with as little processing in the actual endpoint logic as possible (aka Hello World!). I want to clarify that this is merely an informal test for my own curiosity and I'm sharing the results and process here because I thought it was interesting. It's been a long while since I've done any sort of perf testing on ASP.NET, mainly because I've not had extremely heavy load requirements and because overall ASP.NET performs very well even for fairly high loads so that often it's not that critical to test load performance. This post is not meant to make a point  or even come to a conclusion which tech is better, but just to act as a reference to help understand some of the differences in perf and give a starting point to play around with this yourself. I've included the code for this simple project, so you can play with it and maybe add a few additional tests for different things if you like. Source Code on GitHub I looked at this data for these technologies: ASP.NET Web API ASP.NET MVC WebForms ASP.NET WebPages ASMX AJAX Services  (couldn't get AJAX/JSON to run on IIS8 ) WCF Rest Raw ASP.NET HttpHandlers It's quite a mixed bag, of course and the technologies target different types of development. What started out as mere curiosity turned into a bit of a head scratcher as the results were sometimes surprising. What I describe here is more to satisfy my curiosity more than anything and I thought it interesting enough to discuss on the blog :-) First test: Raw Throughput The first thing I did is test raw throughput for the various technologies. This is the least practical test of course since you're unlikely to ever create the equivalent of a 'Hello World' request in a real life application. The idea here is to measure how much time a 'NOP' request takes to return data to the client. So for this request I create the simplest Hello World request that I could come up for each tech. Http Handler The first is the lowest level approach which is an HTTP handler. public class Handler : IHttpHandler { public void ProcessRequest(HttpContext context) { context.Response.ContentType = "text/plain"; context.Response.Write("Hello World. Time is: " + DateTime.Now.ToString()); } public bool IsReusable { get { return true; } } } WebForms Next I added a couple of ASPX pages - one using CodeBehind and one using only a markup page. The CodeBehind page simple does this in CodeBehind without any markup in the ASPX page: public partial class HelloWorld_CodeBehind : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { Response.Write("Hello World. Time is: " + DateTime.Now.ToString() ); Response.End(); } } while the Markup page only contains some static output via an expression:<%@ Page Language="C#" AutoEventWireup="false" CodeBehind="HelloWorld_Markup.aspx.cs" Inherits="AspNetFrameworksPerformance.HelloWorld_Markup" %> Hello World. Time is <%= DateTime.Now %> ASP.NET WebPages WebPages is the freestanding Razor implementation of ASP.NET. Here's the simple HelloWorld.cshtml page:Hello World @DateTime.Now WCF REST WCF REST was the token REST implementation for ASP.NET before WebAPI and the inbetween step from ASP.NET AJAX. I'd like to forget that this technology was ever considered for production use, but I'll include it here. Here's an OperationContract class: [ServiceContract(Namespace = "")] [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] public class WcfService { [OperationContract] [WebGet] public Stream HelloWorld() { var data = Encoding.Unicode.GetBytes("Hello World" + DateTime.Now.ToString()); var ms = new MemoryStream(data); // Add your operation implementation here return ms; } } WCF REST can return arbitrary results by returning a Stream object and a content type. The code above turns the string result into a stream and returns that back to the client. ASP.NET AJAX (ASMX Services) I also wanted to test ASP.NET AJAX services because prior to WebAPI this is probably still the most widely used AJAX technology for the ASP.NET stack today. Unfortunately I was completely unable to get this running on my Windows 8 machine. Visual Studio 2012  removed adding of ASP.NET AJAX services, and when I tried to manually add the service and configure the script handler references it simply did not work - I always got a SOAP response for GET and POST operations. No matter what I tried I always ended up getting XML results even when explicitly adding the ScriptHandler. So, I didn't test this (but the code is there - you might be able to test this on a Windows 7 box). ASP.NET MVC Next up is probably the most popular ASP.NET technology at the moment: MVC. Here's the small controller: public class MvcPerformanceController : Controller { public ActionResult Index() { return View(); } public ActionResult HelloWorldCode() { return new ContentResult() { Content = "Hello World. Time is: " + DateTime.Now.ToString() }; } } ASP.NET WebAPI Next up is WebAPI which looks kind of similar to MVC. Except here I have to use a StringContent result to return the response: public class WebApiPerformanceController : ApiController { [HttpGet] public HttpResponseMessage HelloWorldCode() { return new HttpResponseMessage() { Content = new StringContent("Hello World. Time is: " + DateTime.Now.ToString(), Encoding.UTF8, "text/plain") }; } } Testing Take a minute to think about each of the technologies… and take a guess which you think is most efficient in raw throughput. The fastest should be pretty obvious, but the others - maybe not so much. The testing I did is pretty informal since it was mainly to satisfy my curiosity - here's how I did this: I used Apache Bench (ab.exe) from a full Apache HTTP installation to run and log the test results of hitting the server. ab.exe is a small executable that lets you hit a URL repeatedly and provides counter information about the number of requests, requests per second etc. ab.exe and the batch file are located in the \LoadTests folder of the project. An ab.exe command line  looks like this: ab.exe -n100000 -c20 http://localhost/aspnetperf/api/HelloWorld which hits the specified URL 100,000 times with a load factor of 20 concurrent requests. This results in output like this:   It's a great way to get a quick and dirty performance summary. Run it a few times to make sure there's not a large amount of varience. You might also want to do an IISRESET to clear the Web Server. Just make sure you do a short test run to warm up the server first - otherwise your first run is likely to be skewed downwards. ab.exe also allows you to specify headers and provide POST data and many other things if you want to get a little more fancy. Here all tests are GET requests to keep it simple. I ran each test: 100,000 iterations Load factor of 20 concurrent connections IISReset before starting A short warm up run for API and MVC to make sure startup cost is mitigated Here is the batch file I used for the test: IISRESET REM make sure you add REM C:\Program Files (x86)\Apache Software Foundation\Apache2.2\bin REM to your path so ab.exe can be found REM Warm up ab.exe -n100 -c20 http://localhost/aspnetperf/MvcPerformance/HelloWorldJsonab.exe -n100 -c20 http://localhost/aspnetperf/api/HelloWorldJson ab.exe -n100 -c20 http://localhost/AspNetPerf/WcfService.svc/HelloWorld ab.exe -n100000 -c20 http://localhost/aspnetperf/handler.ashx > handler.txt ab.exe -n100000 -c20 http://localhost/aspnetperf/HelloWorld_CodeBehind.aspx > AspxCodeBehind.txt ab.exe -n100000 -c20 http://localhost/aspnetperf/HelloWorld_Markup.aspx > AspxMarkup.txt ab.exe -n100000 -c20 http://localhost/AspNetPerf/WcfService.svc/HelloWorld > Wcf.txt ab.exe -n100000 -c20 http://localhost/aspnetperf/MvcPerformance/HelloWorldCode > Mvc.txt ab.exe -n100000 -c20 http://localhost/aspnetperf/api/HelloWorld > WebApi.txt I ran each of these tests 3 times and took the average score for Requests/second, with the machine otherwise idle. I did see a bit of variance when running many tests but the values used here are the medians. Part of this has to do with the fact I ran the tests on my local machine - result would probably more consistent running the load test on a separate machine hitting across the network. I ran these tests locally on my laptop which is a Dell XPS with quad core Sandibridge I7-2720QM @ 2.20ghz and a fast SSD drive on Windows 8. CPU load during tests ran to about 70% max across all 4 cores (IOW, it wasn't overloading the machine). Ideally you can try running these tests on a separate machine hitting the local machine. If I remember correctly IIS 7 and 8 on client OSs don't throttle so the performance here should be Results Ok, let's cut straight to the chase. Below are the results from the tests… It's not surprising that the handler was fastest. But it was a bit surprising to me that the next fastest was WebForms and especially Web Forms with markup over a CodeBehind page. WebPages also fared fairly well. MVC and WebAPI are a little slower and the slowest by far is WCF REST (which again I find surprising). As mentioned at the start the raw throughput tests are not overly practical as they don't test scripting performance for the HTML generation engines or serialization performances of the data engines. All it really does is give you an idea of the raw throughput for the technology from time of request to reaching the endpoint and returning minimal text data back to the client which indicates full round trip performance. But it's still interesting to see that Web Forms performs better in throughput than either MVC, WebAPI or WebPages. It'd be interesting to try this with a few pages that actually have some parsing logic on it, but that's beyond the scope of this throughput test. But what's also amazing about this test is the sheer amount of traffic that a laptop computer is handling. Even the slowest tech managed 5700 requests a second, which is one hell of a lot of requests if you extrapolate that out over a 24 hour period. Remember these are not static pages, but dynamic requests that are being served. Another test - JSON Data Service Results The second test I used a JSON result from several of the technologies. I didn't bother running WebForms and WebPages through this test since that doesn't make a ton of sense to return data from the them (OTOH, returning text from the APIs didn't make a ton of sense either :-) In these tests I have a small Person class that gets serialized and then returned to the client. The Person class looks like this: public class Person { public Person() { Id = 10; Name = "Rick"; Entered = DateTime.Now; } public int Id { get; set; } public string Name { get; set; } public DateTime Entered { get; set; } } Here are the updated handler classes that use Person: Handler public class Handler : IHttpHandler { public void ProcessRequest(HttpContext context) { var action = context.Request.QueryString["action"]; if (action == "json") JsonRequest(context); else TextRequest(context); } public void TextRequest(HttpContext context) { context.Response.ContentType = "text/plain"; context.Response.Write("Hello World. Time is: " + DateTime.Now.ToString()); } public void JsonRequest(HttpContext context) { var json = JsonConvert.SerializeObject(new Person(), Formatting.None); context.Response.ContentType = "application/json"; context.Response.Write(json); } public bool IsReusable { get { return true; } } } This code adds a little logic to check for a action query string and route the request to an optional JSON result method. To generate JSON, I'm using the same JSON.NET serializer (JsonConvert.SerializeObject) used in Web API to create the JSON response. WCF REST   [ServiceContract(Namespace = "")] [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] public class WcfService { [OperationContract] [WebGet] public Stream HelloWorld() { var data = Encoding.Unicode.GetBytes("Hello World " + DateTime.Now.ToString()); var ms = new MemoryStream(data); // Add your operation implementation here return ms; } [OperationContract] [WebGet(ResponseFormat=WebMessageFormat.Json,BodyStyle=WebMessageBodyStyle.WrappedRequest)] public Person HelloWorldJson() { // Add your operation implementation here return new Person(); } } For WCF REST all I have to do is add a method with the Person result type.   ASP.NET MVC public class MvcPerformanceController : Controller { // // GET: /MvcPerformance/ public ActionResult Index() { return View(); } public ActionResult HelloWorldCode() { return new ContentResult() { Content = "Hello World. Time is: " + DateTime.Now.ToString() }; } public JsonResult HelloWorldJson() { return Json(new Person(), JsonRequestBehavior.AllowGet); } } For MVC all I have to do for a JSON response is return a JSON result. ASP.NET internally uses JavaScriptSerializer. ASP.NET WebAPI public class WebApiPerformanceController : ApiController { [HttpGet] public HttpResponseMessage HelloWorldCode() { return new HttpResponseMessage() { Content = new StringContent("Hello World. Time is: " + DateTime.Now.ToString(), Encoding.UTF8, "text/plain") }; } [HttpGet] public Person HelloWorldJson() { return new Person(); } [HttpGet] public HttpResponseMessage HelloWorldJson2() { var response = new HttpResponseMessage(HttpStatusCode.OK); response.Content = new ObjectContent<Person>(new Person(), GlobalConfiguration.Configuration.Formatters.JsonFormatter); return response; } } Testing and Results To run these data requests I used the following ab.exe commands:REM JSON RESPONSES ab.exe -n100000 -c20 http://localhost/aspnetperf/Handler.ashx?action=json > HandlerJson.txt ab.exe -n100000 -c20 http://localhost/aspnetperf/MvcPerformance/HelloWorldJson > MvcJson.txt ab.exe -n100000 -c20 http://localhost/aspnetperf/api/HelloWorldJson > WebApiJson.txt ab.exe -n100000 -c20 http://localhost/AspNetPerf/WcfService.svc/HelloWorldJson > WcfJson.txt The results from this test run are a bit interesting in that the WebAPI test improved performance significantly over returning plain string content. Here are the results:   The performance for each technology drops a little bit except for WebAPI which is up quite a bit! From this test it appears that WebAPI is actually significantly better performing returning a JSON response, rather than a plain string response. Snag with Apache Benchmark and 'Length Failures' I ran into a little snag with Apache Benchmark, which was reporting failures for my Web API requests when serializing. As the graph shows performance improved significantly from with JSON results from 5580 to 6530 or so which is a 15% improvement (while all others slowed down by 3-8%). However, I was skeptical at first because the WebAPI test reports showed a bunch of errors on about 10% of the requests. Check out this report: Notice the Failed Request count. What the hey? Is WebAPI failing on roughly 10% of requests when sending JSON? Turns out: No it's not! But it took some sleuthing to figure out why it reports these failures. At first I thought that Web API was failing, and so to make sure I re-ran the test with Fiddler attached and runiisning the ab.exe test by using the -X switch: ab.exe -n100 -c10 -X localhost:8888 http://localhost/aspnetperf/api/HelloWorldJson which showed that indeed all requests where returning proper HTTP 200 results with full content. However ab.exe was reporting the errors. After some closer inspection it turned out that the dates varying in size altered the response length in dynamic output. For example: these two results: {"Id":10,"Name":"Rick","Entered":"2012-09-04T10:57:24.841926-10:00"} {"Id":10,"Name":"Rick","Entered":"2012-09-04T10:57:24.8519262-10:00"} are different in length for the number which results in 68 and 69 bytes respectively. The same URL produces different result lengths which is what ab.exe reports. I didn't notice at first bit the same is happening when running the ASHX handler with JSON.NET result since it uses the same serializer that varies the milliseconds. Moral: You can typically ignore Length failures in Apache Benchmark and when in doubt check the actual output with Fiddler. Note that the other failure values are accurate though. Another interesting Side Note: Perf drops over Time As I was running these tests repeatedly I was finding that performance steadily dropped from a startup peak to a 10-15% lower stable level. IOW, with Web API I'd start out with around 6500 req/sec and in subsequent runs it keeps dropping until it would stabalize somewhere around 5900 req/sec occasionally jumping lower. For these tests this is why I did the IIS RESET and warm up for individual tests. This is a little puzzling. Looking at Process Monitor while the test are running memory very quickly levels out as do handles and threads, on the first test run. Subsequent runs everything stays stable, but the performance starts going downwards. This applies to all the technologies - Handlers, Web Forms, MVC, Web API - curious to see if others test this and see similar results. Doing an IISRESET then resets everything and performance starts off at peak again… Summary As I stated at the outset, these were informal to satiate my curiosity not to prove that any technology is better or even faster than another. While there clearly are differences in performance the differences (other than WCF REST which was by far the slowest and the raw handler which was by far the highest) are relatively minor, so there is no need to feel that any one technology is a runaway standout in raw performance. Choosing a technology is about more than pure performance but also about the adequateness for the job and the easy of implementation. The strengths of each technology will make for any minor performance difference we see in these tests. However, to me it's important to get an occasional reality check and compare where new technologies are heading. Often times old stuff that's been optimized and designed for a time of less horse power can utterly blow the doors off newer tech and simple checks like this let you compare. Luckily we're seeing that much of the new stuff performs well even in V1.0 which is great. To me it was very interesting to see Web API perform relatively badly with plain string content, which originally led me to think that Web API might not be properly optimized just yet. For those that caught my Tweets late last week regarding WebAPI's slow responses was with String content which is in fact considerably slower. Luckily where it counts with serialized JSON and XML WebAPI actually performs better. But I do wonder what would make generic string content slower than serialized code? This stresses another point: Don't take a single test as the final gospel and don't extrapolate out from a single set of tests. Certainly Twitter can make you feel like a fool when you post something immediate that hasn't been fleshed out a little more <blush>. Egg on my face. As a result I ended up screwing around with this for a few hours today to compare different scenarios. Well worth the time… I hope you found this useful, if not for the results, maybe for the process of quickly testing a few requests for performance and charting out a comparison. Now onwards with more serious stuff… Resources Source Code on GitHub Apache HTTP Server Project (ab.exe is part of the binary distribution)© Rick Strahl, West Wind Technologies, 2005-2012Posted in ASP.NET  Web Api   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • 2010 is gone and Welcome 2011

    - by anirudha
    last days i spent my week @ firozabadthe town is much small and near to agraso i never forget to see the taj mahal and red fort their even it’s first chance to see them.i make a plan that i go to Agra last Saturday. firstly i go to red fort and i talking with many foreigner and they love to talking with me because their is only one man who with with them who is their GUIDE a person like a  book they never can talk with you but tell you about everything of the location because you buy them. their are many person come from various country such as German , Japan,  Russ , Italy and many other. their is no problem to talk with them perhaps they happen with talk to me. when i completely watch the Red fort at least i see a girl who are look like a foreigner. i talk themselves where they come from they tell me Francewhen i go elsewhere i thing to propose them to be  a friend of mine. i never propose any girl for friendship with me even in school and college. so i propose them to be a friend of mine.  they accept it i put the email ID in their hand whenever they gone. but i still not get their mail. 2ndly i go to Taj mahal the taj experience is not so good i spent 3 or 4 hours in rush. i found their is no security even their are many army force. they all person are too slow to work. they spent 10 minute to check  a person for security . their hands work very slow just like a low configuration computer. i talk many person their too. i talk to a person who tell themselves Jacob and they from Chicago. they speak very fast and i not know what they tell in speech. a another problem i got with some Chinese person. when i talking with them that i found they speak only Chinese language. Wish you a very very happy new year.

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  • Domain Models (PHP)

    - by Calum Bulmer
    I have been programming in PHP for several years and have, in the past, adopted methods of my own to handle data within my applications. I have built my own MVC, in the past, and have a reasonable understanding of OOP within php but I know my implementation needs some serious work. In the past I have used an is-a relationship between a model and a database table. I now know after doing some research that this is not really the best way forward. As far as I understand it I should create models that don't really care about the underlying database (or whatever storage mechanism is to be used) but only care about their actions and their data. From this I have established that I can create models of lets say for example a Person an this person object could have some Children (human children) that are also Person objects held in an array (with addPerson and removePerson methods, accepting a Person object). I could then create a PersonMapper that I could use to get a Person with a specific 'id', or to save a Person. This could then lookup the relationship data in a lookup table and create the associated child objects for the Person that has been requested (if there are any) and likewise save the data in the lookup table on the save command. This is now pushing the limits to my knowledge..... What if I wanted to model a building with different levels and different rooms within those levels? What if I wanted to place some items in those rooms? Would I create a class for building, level, room and item with the following structure. building can have 1 or many level objects held in an array level can have 1 or many room objects held in an array room can have 1 or many item objects held in an array and mappers for each class with higher level mappers using the child mappers to populate the arrays (either on request of the top level object or lazy load on request) This seems to tightly couple the different objects albeit in one direction (ie. a floor does not need to be in a building but a building can have levels) Is this the correct way to go about things? Within the view I am wanting to show a building with an option to select a level and then show the level with an option to select a room etc.. but I may also want to show a tree like structure of items in the building and what level and room they are in. I hope this makes sense. I am just struggling with the concept of nesting objects within each other when the general concept of oop seems to be to separate things. If someone can help it would be really useful. Many thanks

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  • JavaScript Class Patterns &ndash; In CoffeeScript

    - by Liam McLennan
    Recently I wrote about JavaScript class patterns, and in particular, my favourite class pattern that uses closure to provide encapsulation. A class to represent a person, with a name and an age, looks like this: var Person = (function() { // private variables go here var name,age; function constructor(n, a) { name = n; age = a; } constructor.prototype = { toString: function() { return name + " is " + age + " years old."; } }; return constructor; })(); var john = new Person("John Galt", 50); console.log(john.toString()); Today I have been experimenting with coding for node.js in CoffeeScript. One of the first things I wanted to do was to try and implement my class pattern in CoffeeScript and then see how it compared to CoffeeScript’s built-in class keyword. The above Person class, implemented in CoffeeScript, looks like this: # JavaScript style class using closure to provide private methods Person = (() -> [name,age] = [{},{}] constructor = (n, a) -> [name,age] = [n,a] null constructor.prototype = toString: () -> "name is #{name} age is #{age} years old" constructor )() I am satisfied with how this came out, but there are a few nasty bits. To declare the two private variables in javascript is as simple as var name,age; but in CoffeeScript I have to assign a value, hence [name,age] = [{},{}]. The other major issue occurred because of CoffeeScript’s implicit function returns. The last statement in any function is returned, so I had to add null to the end of the constructor to get it to work. The great thing about the technique just presented is that it provides encapsulation ie the name and age variables are not visible outside of the Person class. CoffeeScript classes do not provide encapsulation, but they do provide nicer syntax. The Person class using native CoffeeScript classes is: # CoffeeScript style class using the class keyword class CoffeePerson constructor: (@name, @age) -> toString: () -> "name is #{@name} age is #{@age} years old" felix = new CoffeePerson "Felix Hoenikker", 63 console.log felix.toString() So now I have a trade-off: nice syntax against encapsulation. I think I will experiment with both strategies in my project and see which works out better.

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  • Business person turned into coder? How and why? Inspire the non-technical.

    - by huisjames
    I graduated with a Business degree. Two years later, I finally realized the power of programming - the power to "invent." I wish I realized this in high school. Nevertheless, I tried to self-teach C# but found it difficult. Then I pivoted to learn PHP two months ago and I have been able to build things I thought was beyond my abilities. Has anyone had the same experience? Or self-taught programming? What lessons did you learn?

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  • SQL SERVER – Enumerations in Relational Database – Best Practice

    - by pinaldave
    Marko Parkkola This article has been submitted by Marko Parkkola, Data systems designer at Saarionen Oy, Finland. Marko is excellent developer and always thinking at next level. You can read his earlier comment which created very interesting discussion here: SQL SERVER- IF EXISTS(Select null from table) vs IF EXISTS(Select 1 from table). I must express my special thanks to Marko for sending this best practice for Enumerations in Relational Database. He has really wrote excellent piece here and welcome comments here. Enumerations in Relational Database This is a subject which is very basic thing in relational databases but often not very well understood and sometimes badly implemented. There are of course many ways to do this but I concentrate only two cases, one which is “the right way” and one which is definitely wrong way. The concept Let’s say we have table Person in our database. Person has properties/fields like Firstname, Lastname, Birthday and so on. Then there’s a field that tells person’s marital status and let’s name it the same way; MaritalStatus. Now MaritalStatus is an enumeration. In C# I would definitely make it an enumeration with values likes Single, InRelationship, Married, Divorced. Now here comes the problem, SQL doesn’t have enumerations. The wrong way This is, in my opinion, absolutely the wrong way to do this. It has one upside though; you’ll see the enumeration’s description instantly when you do simple SELECT query and you don’t have to deal with mysterious values. There’s plenty of downsides too and one would be database fragmentation. Consider this (I’ve left all indexes and constraints out of the query on purpose). CREATE TABLE [dbo].[Person] ( [Firstname] NVARCHAR(100), [Lastname] NVARCHAR(100), [Birthday] datetime, [MaritalStatus] NVARCHAR(10) ) You have nvarchar(20) field in the table that tells the marital status. Obvious problem with this is that what if you create a new value which doesn’t fit into 20 characters? You’ll have to come and alter the table. There are other problems also but I’ll leave those for the reader to think about. The correct way Here’s how I’ve done this in many projects. This model still has one problem but it can be alleviated in the application layer or with CHECK constraints if you like. First I will create a namespace table which tells the name of the enumeration. I will add one row to it too. I’ll write all the indexes and constraints here too. CREATE TABLE [CodeNamespace] ( [Id] INT IDENTITY(1, 1), [Name] NVARCHAR(100) NOT NULL, CONSTRAINT [PK_CodeNamespace] PRIMARY KEY ([Id]), CONSTRAINT [IXQ_CodeNamespace_Name] UNIQUE NONCLUSTERED ([Name]) ) GO INSERT INTO [CodeNamespace] SELECT 'MaritalStatus' GO Then I create a table that holds the actual values and which reference to namespace table in order to group the values under different namespaces. I’ll add couple of rows here too. CREATE TABLE [CodeValue] ( [CodeNamespaceId] INT NOT NULL, [Value] INT NOT NULL, [Description] NVARCHAR(100) NOT NULL, [OrderBy] INT, CONSTRAINT [PK_CodeValue] PRIMARY KEY CLUSTERED ([CodeNamespaceId], [Value]), CONSTRAINT [FK_CodeValue_CodeNamespace] FOREIGN KEY ([CodeNamespaceId]) REFERENCES [CodeNamespace] ([Id]) ) GO -- 1 is the 'MaritalStatus' namespace INSERT INTO [CodeValue] SELECT 1, 1, 'Single', 1 INSERT INTO [CodeValue] SELECT 1, 2, 'In relationship', 2 INSERT INTO [CodeValue] SELECT 1, 3, 'Married', 3 INSERT INTO [CodeValue] SELECT 1, 4, 'Divorced', 4 GO Now there’s four columns in CodeValue table. CodeNamespaceId tells under which namespace values belongs to. Value tells the enumeration value which is used in Person table (I’ll show how this is done below). Description tells what the value means. You can use this, for example, column in UI’s combo box. OrderBy tells if the values needs to be ordered in some way when displayed in the UI. And here’s the Person table again now with correct columns. I’ll add one row here to show how enumerations are to be used. CREATE TABLE [dbo].[Person] ( [Firstname] NVARCHAR(100), [Lastname] NVARCHAR(100), [Birthday] datetime, [MaritalStatus] INT ) GO INSERT INTO [Person] SELECT 'Marko', 'Parkkola', '1977-03-04', 3 GO Now I said earlier that there is one problem with this. MaritalStatus column doesn’t have any database enforced relationship to the CodeValue table so you can enter any value you like into this field. I’ve solved this problem in the application layer by selecting all the values from the CodeValue table and put them into a combobox / dropdownlist (with Value field as value and Description as text) so the end user can’t enter any illegal values; and of course I’ll check the entered value in data access layer also. I said in the “The wrong way” section that there is one benefit to it. In fact, you can have the same benefit here by using a simple view, which I schema bound so you can even index it if you like. CREATE VIEW [dbo].[Person_v] WITH SCHEMABINDING AS SELECT p.[Firstname], p.[Lastname], p.[BirthDay], c.[Description] MaritalStatus FROM [dbo].[Person] p JOIN [dbo].[CodeValue] c ON p.[MaritalStatus] = c.[Value] JOIN [dbo].[CodeNamespace] n ON n.[Id] = c.[CodeNamespaceId] AND n.[Name] = 'MaritalStatus' GO -- Select from View SELECT * FROM [dbo].[Person_v] GO This is excellent write up byMarko Parkkola. Do you have this kind of design setup at your organization? Let us know your opinion. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Best Practices, Database, DBA, Readers Contribution, Software Development, SQL, SQL Authority, SQL Documentation, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Autocompletebox text in Silverlight

    - by Ciaran
    I'm having trouble getting the autocomplete box in System.Windows.Controls.Input working as I wish. When I start typing the dropdown section that displays the filtered list doesn't show the property that I'm binding to, it shows the class name instead. So in the example below, when I type in my - instead of showing 'My Name' it shows MyNamespace.Person. However, when I select the item from the autocomplete list, it displays the FullName property in the textbox. I'm sure I'm just missing a simple autocomplete box property somewhere but I can't see it. Example code: public class Person { public string FirstName { get; set; } public string LastName { get; set; } public string FullName { get { return string.Format("{0} {1}", FirstName, LastName); } } } In my xaml code behind I create some Person objects and store them in a list and bind that list to an autocomplete box List<Person> people = new List<Person>(); people.Add(new Person { FirstName = "My", LastName = "Name" }); people.Add(new Person { FirstName = "Fernando", LastName = "Torres" }); acbNames.ItemsSource = people; My xaml: <my:AutoCompleteBox Name="acbNames" ValueMemberPath="FullName" /> /* after entering 'my', auto complete displays 'MyNamespace.Person' instead of 'My Name', but displays 'My Name' after selecting the item from the list */

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  • How can I pass an arbitrary object to jasper report as parameter?

    - by spderosso
    Hi, I would like to pass as a parameter to my .jrxml an arbitrary object of my domain, e.g a Person. InputStream reportFile = MyPage.this.getClass().getResourceAsStream("test.jrxml"); HashMap<String, Person> parameters = new HashMap<String, Person>(); parameters.put("person", new Person("John", "Doe")); ... JasperReport report = JasperCompileManager.compileReport(reportFile); JasperPrint print = JasperFillManager.fillReport(report, parameters, new JREmptyDataSource()); return JasperExportManager.exportReportToPdf(print); And on the .jrxml do something like: <?xml version="1.0" encoding="UTF-8"?> <jasperReport xmlns="http://jasperreports.sourceforge.net/jasperreports" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://jasperreports.sourceforge.net/jasperreports http://jasperreports.sourceforge.net/xsd/jasperreport.xsd" name="test" pageWidth="595" pageHeight="842" columnWidth="555" leftMargin="20" rightMargin="20" topMargin="20" bottomMargin="20"> <property name="ireport.zoom" value="1.0"/> <property name="ireport.x" value="0"/> <property name="ireport.y" value="0"/> <parameter name="PERSON" isForPrompting="false" class="myApp.domain.person"/> <background> <band splitType="Stretch"/> </background> <title> <band height="20"> <staticText> <reportElement x="180" y="0" width="200" height="20"/> <text><![CDATA[$P{PERSON.lastName}]]></text> </staticText> </band> </title> ... Is something like this possible? Where can I find more complex tutorials that show more than just passing a java.lang.String? Thanks

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  • beginning oop php question: do constructors take the place of getter?

    - by Joel
    I'm working through this tutorial: http://www.killerphp.com/tutorials/object-oriented-php/php-objects-page-3.php At first he has you create a setter and getter method in the class: <?php class person{ var $name; function set_name($new_name){ $this->name=$new_name; } function get_name(){ return $this->name; } } php?> And then you create the object and echo the results: <?php $stefan = new person(); $jimmy = new person(); $stefan ->set_name("Stefan Mischook"); $jimmy ->set_name("Nick Waddles"); echo "The first Object name is: ".$stefan->get_name(); echo "The second Object name is: ".$jimmy->get_name(); ?> Works as expected, and I understand. Then he introduces constructors: class person{ var $name; function __construct($persons_name) { $this->name = $persons_name; } function set_name($new_name){ $this->name=$new_name; } function get_name(){ return $this->name; } } And returns like so: <?php $joel = new person("Joel"); echo "The third Object name is: ".$joel->get_name(); ?> This is all fine and makes sense. Then I tried to combine the two and got an error, so I'm curious-is a constructor always taking the place of a "get" function? If you have a constructor, do you always need to include an argument when creating an object? Gives errors: <?php $stefan = new person(); $jimmy = new person(); $joel = new person("Joel Laviolette"); $stefan ->set_name("Stefan Mischook"); $jimmy ->set_name("Nick Waddles"); echo "The first Object name is: ".$stefan->get_name(); echo "The second Object name is: ".$jimmy->get_name(); echo "The third Object name is: ".$joel->get_name(); ?>

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  • How do I eliminate Error 3002?

    - by Andrew
    Say I have the following table definitions in SQL Server 2008: CREATE TABLE Person (PersonId INT IDENTITY NOT NULL PRIMARY KEY, Name VARCHAR(50) NOT NULL, ManyMoreIrrelevantColumns VARCHAR(MAX) NOT NULL) CREATE TABLE Model (ModelId INT IDENTITY NOT NULL PRIMARY KEY, ModelName VARCHAR(50) NOT NULL, Description VARCHAR(200) NULL) CREATE TABLE ModelScore (ModelId INT NOT NULL REFERENCES Model (ModelId), Score INT NOT NULL, Definition VARCHAR(100) NULL, PRIMARY KEY (ModelId, Score)) CREATE TABLE PersonModelScore (PersonId INT NOT NULL REFERENCES Person (PersonId), ModelId INT NOT NULL, Score INT NOT NULL, PRIMARY KEY (PersonId, ModelId), FOREIGN KEY (ModelId, Score) REFERENCES ModelScore (ModelId, Score)) The idea here is that each Person may have only one ModelScore per Model, but each Person may have a score for any number of defined Models. As far as I can tell, this SQL should enforce these constraints naturally. The ModelScore has a particular "meaning," which is contained in the Definition. Nothing earth-shattering there. Now, I try translating this into Entity Framework using the designer. After updating the model from the database and doing some editing, I have a Person object, a Model object, and a ModelScore object. PersonModelScore, being a join table, is not an object but rather is included as an association with some other name (let's say ModelScorePersonAssociation). The mapping details for the association are as follows: - Association - Maps to PersonModelScore - ModelScore ModelId : Int32 <=> ModelId : int Score : Int32 <=> Score : int - Person PersonId : Int32 <=> PersonId : int On the right-hand side, the ModelId and PersonId values have primary key symbols, but the Score value does not. Upon compilation, I get: Error 3002: Problem in Mapping Fragment starting at line 5190: Potential runtime violation of table PersonModelScore's keys (PersonModelScore.ModelId, PersonModelScore.PersonId): Columns (PersonModelScore.PersonId, PersonModelScore.ModelId) are mapped to EntitySet ModelScorePersonAssociation's properties (ModelScorePersonAssociation.Person.PersonId, ModelScorePersonAssociation.ModelScore.ModelId) on the conceptual side but they do not form the EntitySet's key properties (ModelScorePersonAssociation.ModelScore.ModelId, ModelScorePersonAssociation.ModelScore.Score, ModelScorePersonAssociation.Person.PersonId). What have I done wrong in the designer or otherwise, and how can I fix the error? Many thanks!

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  • How do I get google protocol buffer messages over a socket connection without disconnecting the clie

    - by Dan
    Hi there, I'm attempting to send a .proto message from an iPhone application to a Java server via a socket connection. However so far I'm running into an issue when it comes to the server receiving the data; it only seems to process it after the client connection has been terminated. This points to me that the data is getting sent, but the server is keeping its inputstream open and waiting for more data. Would anyone know how I might go about solving this? The current code (or at least the relevant parts) is as follows: iPhone: Person *person = [[[[Person builder] setId:1] setName:@"Bob"] build]; RequestWrapper *request = [[[RequestWrapper builder] setPerson:person] build]; NSData *data = [request data]; AsyncSocket *socket = [[AsyncSocket alloc] initWithDelegate:self]; if (![socket connectToHost:@"192.168.0.6" onPort:6666 error:nil]){ [self updateLabel:@"Problem connecting to socket!"]; } else { [self updateLabel:@"Sending data to server..."]; [socket writeData:data withTimeout:-1 tag:0]; [self updateLabel:@"Data sent, disconnecting"]; //[socket disconnect]; } Java: try { RequestWrapper wrapper = RequestWrapper.parseFrom(socket.getInputStream()); Person person = wrapper.getPerson(); if (person != null) { System.out.println("Persons name is " + person.getName()); socket.close(); } On running this, it seems to hang on the line where the RequestWrapper is processing the inputStream. I did try replacing the socket writedata method with [request writeToOutputStream:[socket getCFWriteStream]]; Which I thought might work, however I get an error claiming that the "Protocol message contained an invalid tag (zero)". I'm fairly certain that it doesn't contain an invalid tag as the message works when sending it via the writedata method. Any help on the matter would be greatly appreciated! Cheers! Dan (EDIT: I should mention, I am using the metasyntactic gpb code; and the cocoaasyncsocket implementation)

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  • Why in this example (got from msdn), in GetEnumerator method , new PeopleEnum returns IEnumerator?

    - by odiseh
    Hi guys, Why in this example (got from msdn), in GetEnumerator method , PeopleEnum returns IEnumerator? public class Person { public Person(string fName, string lName) { this.firstName = fName; this.lastName = lName; } public string firstName; public string lastName; } public class People : IEnumerable { private Person[] _people; public People(Person[] pArray) { _people = new Person[pArray.Length]; for (int i = 0; i < pArray.Length; i++) { _people[i] = pArray[i]; } } //why??? IEnumerator IEnumerable.GetEnumerator() { return (IEnumerator) GetEnumerator(); } public PeopleEnum GetEnumerator() { return new PeopleEnum(_people); } } public class PeopleEnum : IEnumerator { public Person[] _people; // Enumerators are positioned before the first element // until the first MoveNext() call. int position = -1; public PeopleEnum(Person[] list) { _people = list; } public bool MoveNext() { position++; return (position < _people.Length); } public void Reset() { position = -1; } object IEnumerator.Current { get { return Current; } } public Person Current { get { try { return _people[position]; } catch (IndexOutOfRangeException) { throw new InvalidOperationException(); } } } }

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  • Learning Hibernate: too many connections

    - by stivlo
    I'm trying to learn Hibernate and I wrote the simplest Person Entity and I was trying to insert 2000 of them. I know I'm using deprecated methods, I will try to figure out what are the new ones later. First, here is the class Person: @Entity public class Person { private int id; private String name; @Id @GeneratedValue(strategy = GenerationType.TABLE, generator = "person") @TableGenerator(name = "person", table = "sequences", allocationSize = 1) public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } } Then I wrote a small App class that insert 2000 entities with a loop: public class App { private static AnnotationConfiguration config; public static void insertPerson() { SessionFactory factory = config.buildSessionFactory(); Session session = factory.getCurrentSession(); session.beginTransaction(); Person aPerson = new Person(); aPerson.setName("John"); session.save(aPerson); session.getTransaction().commit(); } public static void main(String[] args) { config = new AnnotationConfiguration(); config.addAnnotatedClass(Person.class); config.configure("hibernate.cfg.xml"); //is the default already new SchemaExport(config).create(true, true); //print and execute for (int i = 0; i < 2000; i++) { insertPerson(); } } } What I get after a while is: Exception in thread "main" org.hibernate.exception.JDBCConnectionException: Cannot open connection Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Too many connections Now I know that probably if I put the transaction outside the loop it would work, but mine was a test to see what happens when executing multiple transactions. And since there is only one open at each time, it should work. I tried to add session.close() after the commit, but I got Exception in thread "main" org.hibernate.SessionException: Session was already closed So how to solve the problem?

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  • Using forward declarations for build in datatypes.

    - by bdhar
    I understand that wherever possible we shall use forward declarations instead of includes to speed up the compilation. I have a class Person like this. #pragma once #include <string> class Person { public: Person(std::string name, int age); std::string GetName(void) const; int GetAge(void) const; private: std::string _name; int _age; }; and a class Student like this #pragma once #include <string> class Person; class Student { public: Student(std::string name, int age, int level = 0); Student(const Person& person); std::string GetName(void) const; int GetAge(void) const; int GetLevel(void) const; private: std::string _name; int _age; int _level; }; In Student.h, I have a forward declaration class Person; to use Person in my conversion constructor. Fine. But I have done #include <string> to avoid compilation error while using std::string in the code. How to use forward declaration here to avoid the compilation error? Is it possible? Thanks.

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  • Working with extra fields in an Inline form - save_model, save_formset, can't make sense of the diff

    - by magicrebirth
    Suppose I am in the usual situation where there're extra fields in the many2many relationship: class Person(models.Model): name = models.CharField(max_length=128) class Group(models.Model): name = models.CharField(max_length=128) members = models.ManyToManyField(Person, through='Membership') class Membership(models.Model): person = models.ForeignKey(Person) group = models.ForeignKey(Group) date_joined = models.DateField() invite_reason = models.CharField(max_length=64) # other models which are unrelated to the ones above.. class Trip(models.Model): placeVisited = models.ForeignKey(Place) visitor = models.ForeignKey(Person) pleasuretrip = models.Boolean() class Place(models.Model): name = models.CharField(max_length=128) I want to add some extra fields in the Membership form that gets displayed through the Inline. These fields basically are a shortcut to the instantiation of another model (Trip). Trip can have its own admin views, but these shortcuts are needed because when my project partners are entering 'Membership' data in the system they happen to have also the 'Trip' information handy (and also because some of the info in Membership can just be copied over to Trip etc. etc.). So all I want to have is two extra fields in the Membership Inline - placeVisited and pleasuretrip - which together with the Person instance will let me instantiate the Trip model in the background... I found out I can easily add extra fields to the inline view by defining my own form. But once the data have been entered, how and when to reference to them in order to perform the save operations I need to do? class MyForm(forms.ModelForm): place = forms.ModelChoiceField(required=False, queryset=Place.objects.all(), label="place",) pleasuretrip = forms.BooleanField(required=False, label="...") class MembershipInline(admin.TabularInline): model = Membership form = MyForm def save_model(self, request, obj, form, change): place = form.place pleasuretrip = form.pleasuretrip person = form.person .... # now I can create Trip instances with those data .... obj.save() class GroupAdmin(admin.ModelAdmin): model = Group .... inlines = (MembershipInline,) This doesn't seem to work... I'm also a bit puzzled by the save_formset method... maybe is that the one I should be using? Many thanks in advance for the help!!!!

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  • Reduce function calls

    - by Curious2learn
    Hello, I profiled my python program and found that the following function was taking too long to run. Perhaps, I can use a different algorithm and make it run faster. However, I have read that I can also possibly increase the speed by reducing function calls, especially when it gets called repeatedly within a loop. I am a python newbie and would like to learn how to do this and see how much faster it can get. Currently, the function is: def potentialActualBuyers(setOfPeople,theCar,price): count=0 for person in setOfPeople: if person.getUtility(theCar) >= price and person.periodCarPurchased==None: count += 1 return count where setOfPeople is a list of person objects. I tried the following: def potentialActualBuyers(setOfPeople,theCar,price): count=0 Utility=person.getUtility for person in setOfPeople: if Utility(theCar) >= price and person.periodCarPurchased==None: count += 1 return count This, however, gives me an error saying local variable 'person' referenced before assignment Any suggestions, how I can reduce function calls or any other changes that can make the code faster. Again, I am a python newbie and even though I may possibly be able to use a better algorithm, it is still worthwhile learning the answer to the above question. Thanks very much.

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  • XSLT: generate multiple object by incrementing attribute and value

    - by Daniel
    Hi, I have a xml as below that I'd like to copy n times while incrementing one of its element and one of its attribute. XML input: <Person position=1> <name>John</name> <number>1</number> <number>1</number> </Person> and I'd like something like below with the number of increment to be a variable. XML output: <Person position=1> <name>John</name> <number>1</number> </Person> <Person position=2> <name>John</name> <number>2</number> </Person> .... <Person position=n> <name>John</name> <number>n</number> </Person> Any clue

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  • Serialization in C#

    - by anjansaha
    My class structure is as follows. [Serializable] [XmlRootAttribute("person", Namespace = "", IsNullable = false)] public class Person : IDisposable { Private int _id; Private string _name; [XmlElement(“id”)] Public int Id { Get{ return _id;} Set{ _id = value;} } [XmlElement(“name”)] Public string Name { Get{return _name;} Set{_name = value;} } } I am getting the following xml when I serialize the above class <person> <id>1</id> <name>Test</name> </person> Now, I would like to serialize the above class as follows i.e. I would like append “type” attribute for each public property that is serialized as xml element. I can append “type” attribute to “person” node by declaring another public property “type” with “[XmlAttribute(“type”)]” but I would like to achieve the same for each public property that is serialized as xml element. Any idea to achieve below: <person type=”Person”> <id type=”int”>1</id> <name type=”string”>Test</name> </person>

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  • How do repos (SVN, GIT) work?

    - by masfenix
    I read SO nearly everyday and mostly there is a thread about source control. I have a few questions. I am going to use SVN as example. 1) There is a team (small, large dosnt matter). In the morning everyone checks out the code to start working. At noon Person A commits, while person B still works on it. What happens when person B commits? how will person B know that there is an updated file? 2) I am assuming the answer to the first question is "run an update command which tells you", ok so person B finds out that the file they have been working on all morning in changed. When they see the udpated file, it seems like person A has REWRITTEN the file for better performance. What does person B do? Seems like there whole day was a waste of time. Or if they commit their version then its a waste of person A's time? 3) What are branches? thanks, and if anyone knows a laymen terms pdf or something that explains it that would be awesome.

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  • How can I bind to a helper property in Silverlight

    - by Matt
    For the sake of argument, here's a simple person class public class Person : DependencyObject, INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; public static readonly DependencyProperty FirstNameProperty = DependencyProperty.Register( "FirstName", typeof ( string ), typeof ( Person ), null ); public static readonly DependencyProperty LastNameProperty = DependencyProperty.Register( "LastName", typeof( string ), typeof( Person ), null ); public string FirstName { get { return ( string ) GetValue( FirstNameProperty ); } set { SetValue( FirstNameProperty, value ); if(PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs( "FirstName" )); } } public string LastName { get { return ( string ) GetValue( LastNameProperty ); } set { SetValue( LastNameProperty, value ); if ( PropertyChanged != null ) PropertyChanged( this, new PropertyChangedEventArgs( "LastName" ) ); } } } I want to go about creating a readonly property like this public string FullName { get { return FirstName + " " + LastName; } } How does binding work in this scenario? I've tried adding a DependancyProperty and raised the PropertyChanged event for the fullname. Basically I just want to have a property that I can bind to that returns the fullname of a user whenever the first or last name changes. Here's the final class I'm using with the modifications. public class Person : DependencyObject, INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; public static readonly DependencyProperty FirstNameProperty = DependencyProperty.Register( "FirstName", typeof ( string ), typeof ( Person ), null ); public static readonly DependencyProperty LastNameProperty = DependencyProperty.Register( "LastName", typeof( string ), typeof( Person ), null ); public static readonly DependencyProperty FullNameProperty = DependencyProperty.Register( "FullName", typeof( string ), typeof( Person ), null ); public string FirstName { get { return ( string ) GetValue( FirstNameProperty ); } set { SetValue( FirstNameProperty, value ); if ( PropertyChanged != null ) { PropertyChanged( this, new PropertyChangedEventArgs( "FirstName" ) ); PropertyChanged( this, new PropertyChangedEventArgs( "FullName" ) ); } } } public string LastName { get { return ( string ) GetValue( LastNameProperty ); } set { SetValue( LastNameProperty, value ); if ( PropertyChanged != null ) { PropertyChanged( this, new PropertyChangedEventArgs( "LastName" ) ); PropertyChanged( this, new PropertyChangedEventArgs( "FullName" ) ); } } } public string FullName { get { return GetValue( FirstNameProperty ) + " " + GetValue( LastNameProperty ); } } }

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  • Question About Fk refrence in The Collection

    - by Ahmed
    Hi , i have 2 entities : ( person ) & (Address) with follwing mapping : <class name="Adress" table="Adress" lazy="false"> <id name="Id" column="Id"> <generator class="native" /> </id> <many-to-one name="Person" class="Person"> <column name="PersonId" /> </many-to-one> </class> <class name="Person" table="Person" lazy="false"> <id name="PersonId" column="PersonId"> <generator class="native" /> </id> <property name="Name" column="Name" type="String" not-null="true" /> <set name="Adresses" lazy="true" inverse="true" cascade="save-update"> <key> <column name="PersonId" /> </key> <one-to-many class="Adress" /> </set> </class> my propblem is that when i set Adrees.Person with new object of person ,The collection person.Adresses doesn't update itself . should i update every end role of the association to be updated in the two both? another thing : if i updated the Fk manually like this : Adress.PersonId it doesn't break or change association. does this is Nhibernte behavior ? thanks in advance , i am waiting for your experiencies

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