static assert - Page 339

Better solution then simple factory method when concrete implementations have different attributes

- by danip

abstract class Animal { function eat() {..} function sleep() {..} function isSmart() } class Dog extends Animal { public $blnCanBark; function isSmart() { return $this->blnCanBark; } } class Cat extends Animal { public $blnCanJumpHigh; function isSmart() { return $this->blnCanJumpHigh; } } .. and so on up to 10-20 animals. Now I created a factory using simple factory method and try to create instances like this: class AnimalFactory { public static function create($strName) { switch($strName) { case 'Dog': return new Dog(); case 'Cat': return new Cat(); default: break; } } } The problem is I can't set the specific attributes like blnCanBark, blnCanJumpHigh in an efficient way. I can send all of them as extra params to create but this will not scale to more then a few classes. Also I can't break the inheritance because a lot of the basic functionality is the same. Is there a better pattern to solve this?

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Trying to use OpenGL in Java on Netbeans but getting an error. Please help [migrated]

- by Steven Rogers

I am on a Mac running Netbeans 6.9. I downloaded and installed LWJGL using this tutorial down to the letter: http://lwjgl.org/wiki/index.php?title=Setting_Up_LWJGL_with_NetBeans I finished the installation and copied sample code to see if my system is working. I got a bug, and was not sure if it was because of faulty code or i was doing something wrong. So i shortened down the code to this little simple bit: package javaopengl; import org.lwjgl.Sys; import org.lwjgl.opengl.Display; //Testing public class Main { public static void main(String[] args) { boolean fullscreen = (args.length == 1 && args[0].equals("-fullscreen")); try { Display.create(); Display.destroy(); } catch (Exception e) { e.printStackTrace(System.err); } System.exit(0); } } But i still get the same error, this is the error that i get: run: Exception in thread "main" java.lang.NoClassDefFoundError: = Caused by: java.lang.ClassNotFoundException: = at java.net.URLClassLoader$1.run(URLClassLoader.java:202) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) Java Result: 1 BUILD SUCCESSFUL (total time: 0 seconds) I am not sure what exactly is going on, Would you please tell me what is going on and how to fix it? It would be greatly appreciated, and thank you. Note: When i am looking at the text in the development environment, it does not show those red lines indicating there are any errors.

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Solved: Operation is not valid due to the current state of the object

- by ChrisD

We use public static methods decorated with [WebMethod] to support our Ajax Postbacks. Recently, I received an error from a UI developing stating he was receiving the following error when attempting his post back: { "Message": "Operation is not valid due to the current state of the object.", "StackTrace": " at System.Web.Script.Serialization.ObjectConverter.ConvertDictionaryToObject(IDictionary`2 dictionary, Type type, JavaScriptSerializer serializer, Boolean throwOnError, Object& convertedObject)\r\n at System.Web.Script.Serialization.ObjectConverter.ConvertObjectToTypeInternal(Object o, Type type, JavaScriptSerializer serializer, Boolean throwOnError, Object& convertedObject)\r\n at System.Web.Script.Serialization.ObjectConverter.ConvertObjectToTypeMain(Object o, Type type, JavaScriptSerializer serializer, Boolean throwOnError, Object& convertedObject)\r\n at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeInternal(Int32 depth)\r\n at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeDictionary(Int32 depth)\r\n at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeInternal(Int32 depth)\r\n at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeDictionary(Int32 depth)\r\n at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeInternal(Int32 depth)\r\n at System.Web.Script.Serialization.JavaScriptObjectDeserializer.BasicDeserialize(String input, Int32 depthLimit, JavaScriptSerializer serializer)\r\n at System.Web.Script.Serialization.JavaScriptSerializer.Deserialize(JavaScriptSerializer serializer, String input, Type type, Int32 depthLimit)\r\n at System.Web.Script.Serialization.JavaScriptSerializer.Deserialize[T](String input)\r\n at System.Web.Script.Services.RestHandler.GetRawParamsFromPostRequest(HttpContext context, JavaScriptSerializer serializer)\r\n at System.Web.Script.Services.RestHandler.GetRawParams(WebServiceMethodData methodData, HttpContext context)\r\n at System.Web.Script.Services.RestHandler.ExecuteWebServiceCall(HttpContext context, WebServiceMethodData methodData)", "ExceptionType": "System.InvalidOperationException" } Goggling this error brought me little support. All the results talked about increasing the aspnet:MaxJsonDeserializerMembers value to handle larger payloads. Since 1) I’m not using the asp.net ajax model and 2) the payload is very small, this clearly was not the cause of my issue. Here’s the payload the UI developer was sending to the endpoint: { "FundingSource": { "__type": "XX.YY.Engine.Contract.Funding.EvidenceBasedFundingSource, XX.YY.Engine.Contract", "MeansType": 13, "FundingMethodName": "LegalTender", }, "AddToProfile": false, "ProfileNickName": "", "FundingAmount": 0 } By tweaking the JSON I’ve found the culprit. Apparently the default JSS Serializer used doesn’t like the assembly name in the __type value. Removing the assembly portion of the type name resolved my issue. { "FundingSource": { "__type": "XX.YY.Engine.Contract.Funding.EvidenceBasedFundingSource", "MeansType": 13, "FundingMethodName": "LegalTender", }, "AddToProfile": false, "ProfileNickName": "", "FundingAmount": 0 }

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In Djano, why do I get a 500 server error when browsing, but "python mysite.fcgi" from SSH works fin

- by Jim

If I browse to my site, I get a 500 "internal server error." However, if I SSH into my server and go to my site's folder and run "python mysite.fcgi" I see the HTML rendered fine. Obviously, something is wrong, but I'm not sure what. Here is my .htaccess file: AddHandler fastcgi-script .fcgi RewriteEngine On RewriteRule ^(media/.*)$ - [L] RewriteRule ^(static/.*)$ - [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteRule ^(.*)$ mysite.fcgi/$1 [QSA,L] Here is my mysite.fcgi file: #!/usr/bin/python2.5 import sys, os sys.path.insert(0, "/kunden/homepages/34/[mydir]/htdocs/projects/django") sys.path.insert(1, "/kunden/homepages/34/[mydir]/lib/python/site-packages") os.chdir("/kunden/homepages/34/[mydir]/htdocs/projects/django/mysite") os.environ['DJANGO_SETTINGS_MODULE'] = 'mysite.settings' from django.core.servers.fastcgi import runfastcgi runfastcgi(["method=threaded", "daemonize=false"]) I'm setting this up on 1and1. It has been a pain, but I think I'm close.

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How can I making Twitter, Facebook and Reddit share buttons load last?

- by Daniel Bingham

I have a website with a number of pages that sport twitter, facebook and reddit share buttons. They take forever to load and until they do the rest of the page doesn't load. So how I can make them load last? Currently, they are loaded something like this: <div class="item"><a href="http://twitter.com/share" class="twitter-share-button" data-count="vertical" data-via="FridgeToFood" data-related="danielBingham:Recipe and update tweets from Fridge to Food.">Tweet</a><script type="text/javascript" src="http://platform.twitter.com/widgets.js"></script></div> <div class="item"><script src="http://connect.facebook.net/en_US/all.js#xfbml=1"></script><fb:like layout="box_count" width="40"></fb:like></div> <div class="item"> <script type="text/javascript">reddit_target='recipes';</script> <script type="text/javascript" src="http://reddit.com/static/button/button2.js"></script> </div> They are in a div called "shareWrapper" and are loading to one side of the page. The buttons load where ever the script code is placed. As far as I know, I can't place the script code at the bottom of the page and move the resulting buttons after the fact. I want them to appear near the top, which right now means they are stopping everything below them from loading for several seconds. I tried loading them using javascript, but using JQuery's $(document).ready(), but that failed. It seems to leave the page in some sort of loading loop from which it never emerges. Are there other ways to get these to load last?

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Cat 6 Only 100mbit speed

- by Stu2000

I tried two different cat6 cables directly connected between my two ubuntu machines. This one I ordered online: http://www.amazon.co.uk/gp/product/B002SQPDXS/ref=wms_ohs_product only achieves 100mbit speeds, but does appear to be supporting cross-talk (direct pc to pc), the other cat 6 cable, worked perfectly and gets the full 1gigabit speed. Both tests were performed using ftp and checking the network monitor with direct pc to pc connection. Did the product from amazon lie to me or do I need to manually set a setting somewhere in ubuntu for some cables? I had thought 10 quid for 20m of gigabit ethernet cable was a bit cheap, you get what you pay for... Regards, Stu Update: It seems that after rebooting, the device is set to 1000mbit sec when looking it up with sudo ethtool eth0 However after a while, this will drop down to just 100, after which to reset it to 1000 again, I have to reboot, and simply unpugging and re-plugging in the cable doesn't do it. I tried setting this in networking config file as suggested here: auto eth0 iface eth0 inet static pre-up /usr/sbin/ethtool -s eth0 speed 1000 duplex full but that resulted in my networking failing to start. Is there a problem with my 'auto-negotiation' or something? Can I manually override a setting to 1000mbit?

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How to make ssh/rsync/etc use a VLAN network interface?

- by Annan

A company I work for has a number of virtual servers with ElasticHosts. They are setup in such a way that eth1 is on a private VLAN connecting them to each other. This is so backups sent between servers are not charged at the same rate as external data transfer. My understanding of how VLANs and network interfaces work is sketchy at best. How can I make ssh, rsync, etc. transfer data through the VLAN? My final solution: I spent a while trying to figure this out, For all servers involved, edit /etc/sysconfig/network-scripts/ifcfg-eth1 DEVICE=eth1 BOOTPROTO=static ONBOOT=yes HWADDR=YOUR_MAC_ADDR IPADDR=192.168.0.100 NETMASK=255.255.255.0 Where HWADDR should already be set and the last octate of IPADDR should be different from each other. Then run, on all servers /etc/init.d/network restart After this the IP addresses specified by IPADDR can be used directly as any other IP address.

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How to fill in the network line in the ubuntu interfaces config file?

- by matnagel

I have to configure an ubuntu hardy server network interface. The service hoster told me that this is the network data for the machine: IP Range: 111.111.200.74 to 111.111.200.78 Netmask: 255.255.255.248 Broadcast: 111.111.200.79 Gateway: 111.111.200.73 Subnet: 111.111.200.72/29 I am only using the first IP address. I will update the /etc/hosts file with 111.111.200.74, but I am still unsure how the /etc/network/interfaces file should be. This is my plan: auto lo iface lo inet loopback auto eth0 iface eth0 inet static address 111.111.200.74 netmask 255.255.255.248 network 111.111.200.??? broadcast 111.111.200.79 gateway 111.111.200.73 As you can see I don't know how to build the network line. How would I calculate the data for the network line and what is the result? (I changed the first 2 octets of the subnet, they are not "111.111" in the real setup.)

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Dynamic procmail filters

- by WombaT

i need procmail to place incoming mail into specific folder depending on some set of rules. I know how i can accomplish this, but i need to write static set of rules in a specific file. What i really need is to configure procmail to use rules stored in mysql database. How i can do this? I've read a bit about that and one solution i found is to pipe message to a php/perl script and return a folder name to place message. But i have completely no i idea how to use php script as a rule and then use its return value.

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How to mange big amount users at server side?

- by Rami

I built a social android application in which users can see other users around them by gps location. at the beginning thing went well as i had low number of users, But now that I have increasing number of users (about 1500 +100 every day) I revealed a major problem in my design. In my Google App Engine servlet I have static HashMap that holding all the users profiles objects, currenty 1500 and this number will increase as more users register. Why I'm doing it Every user that requesting for the users around him compares his gps with other users and check if they are in his 10km radius, this happens every 5 min on average. That is why I can't get the users from db every time because GAE read/write operation quota will tare me apart. The problem with this desgin is As the number of users increased the Hashmap turns to null every 4-6 hours, I thing that this time is getting shorten but I'm not sure. I'm fixing this by reloading the users from the db every time I detect that it became null, But this causes DOS to my users for 30 sec, So I'm looking for better solution. I'm guessing that it happens because the size of the hashmap, Am I right? I have been advised to use spatial database, but that mean that I can't work with GAE any more and that mean that I need to build my big server all over again and lose my existing DB. Is there something I can do with the existing tools? Thanks.

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Remote connection to dynamic public ip & private ip addresses

- by user53864

Many times I connected to windows computer which has static public ip address via remote desktop over wan links. I'm wondering how could I connect to the remote computer that has dynamic public ip address & private ip addresses assigned. I've 2 systems at home: xp system-------connected to internet(dynamic public ip) & allowed other users to connected to the internet on the interface. windows vista system--------enabled dhcp on the interface to access internet from xp. How could I remotely connect from my office to the 'vista system'?. If I've a router/modem at my home it may be possible to allow the ports for the system but I don't. Any tips?

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How can I resolve component types in a way that supports adding new types relatively easily?

- by John

I am trying to build an Entity Component System for an interactive application developed using C++ and OpenGL. My question is quite simple. In my GameObject class I have a collection of Components. I can add and retrieve components. class GameObject: public Object { public: GameObject(std::string objectName); ~GameObject(void); Component * AddComponent(std::string name); Component * AddComponent(Component componentType); Component * GetComponent (std::string TypeName); Component * GetComponent (<Component Type Here>); private: std::map<std::string,Component*> m_components; }; I will have a collection of components that inherit from the base Components class. So if I have a meshRenderer component and would like to do the following GameObject * warship = new GameObject("myLovelyWarship"); MeshRenderer * meshRenderer = warship->AddComponent(MeshRenderer); or possibly MeshRenderer * meshRenderer = warship->AddComponent("MeshRenderer"); I could be make a Component Factory like this: class ComponentFactory { public: static Component * CreateComponent(const std::string &compTyp) { if(compTyp == "MeshRenderer") return new MeshRenderer; if(compTyp == "Collider") return new Collider; return NULL; } }; However, I feel like I should not have to keep updating the Component Factory every time I want to create a new custom Component but it is an option. Is there a more proper way to add and retrieve these components? Is standard templates another solution?

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does ubuntu 11.10 is support ns2.29

- by nasser

I need your help, I'm a beginner on NS2 , and I'm trying to install ns2.29 on ubuntu 11.10 32bits but i can't. This message appear and installation stopped : Build tcl8.4.11 ============================================================ loading cache ./config.cache checking whether to use symlinks for manpages... no checking whether to compress the manpages... no checking whether to add a package name suffix for the manpages... no checking for gcc... gcc checking whether the C compiler (gcc ) works... yes checking whether the C compiler (gcc ) is a cross-compiler... no checking whether we are using GNU C... yes checking whether gcc accepts -g... yes checking for building with threads... no (default) checking if the compiler understands -pipe... yes checking how to run the C preprocessor... gcc -pipe -E checking for sin... no checking for main in -lieee... yes checking for main in -linet... no checking for net/errno.h... no checking for connect... yes checking for gethostbyname... yes checking how to build libraries... static checking for ranlib... ranlib checking if 64bit support is requested... no checking if 64bit Sparc VIS support is requested... no checking system version (for dynamic loading)... ./configure: 1: Syntax error: Unterminated quoted string tcl8.3.2 configuration failed! Exiting ... Tcl is not part of the ns project. Please see www.Scriptics.com to see if they have a fix for your platform. Anyone can help me?

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Functional testing in the verification

- by user970696

Yesterday my question How come verification does not include actual testing? created a lot of controversy, yet did not reveal the answer for related and very important question: does black box functional testing done by testers belong to verification or validation? ISO 12207:12208 here mentiones testing explicitly only as a validation activity, however, it speaks about validation of requirements of the intended use. For me its more high level, like UAT test cases written by business users ISO mentioned above does not mention any specific verification (7.2.4.3.2)except for Requirement verification, Design verification, Document and Code & Integration verification. The last two can be probably thought as unit and integrated testing. But where is then the regular testing done by testers at the end of the phase? The book I mentioned in the original question mentiones that verification is done by static techniques, yet on the V model graph it describes System testing against high level description as a verification, mentioning it includes all kinds of testing like functional, load etc. In the IEEE standard for V&V, you can read this: Even though the tests and evaluations are not part of the V&V processes, the techniques described in this standard may be useful in performing them. So that is different than in ISO, where validation mentiones testing as the activity. Not to mention a lot of contradicting information on the net. I would really appreciate a reference to e.g. a standard in the answer or explanation of what I missed in the ISO. For me, I am unable to tell where the testers work belong.

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Why does explorer restart automatically when I kill it with Process.Kill?

- by Thomas Levesque

If I kill explorer.exe like this: private static void KillExplorer() { var processes = Process.GetProcessesByName("explorer"); Console.Write("Killing Explorer... "); foreach (var process in processes) { process.Kill(); process.WaitForExit(); } Console.WriteLine("Done"); } It restarts immediately. But if I use taskkill /F /IM explorer.exe, or kill it from the task manager, it doesn't restart. Why is that? What's the difference? How can I close explorer.exe from code without restarting it? Sure, I could call taskkill from my code, but I was hoping for a cleaner solution...

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What to do when you're the interviewer and you don't like your job?

- by emcb

I'm in a sorta strange predicament, and I could use some advice. When I was interviewing for my current job, the job description I was given seemed pretty darn nice to me. Without going into the details, the job hasn't quite turned out the way it was advertised. The company is great and takes care of its employees, but for someone who cares about the code they write and the work they do, it's a bad environment - effectively, we operate between 0.5 and 1.0 on the Joel test, and due to political issues we're not going to move beyond that any time soon. Bitter? Maybe. OK...so I'm in the market for a new job. But that's not where my dilemma is. The problem that I see coming is that I will be participating in interviewing some candidates for a position on my team, and I'm not sure what to do. I've heard through the grapevine that we have some really solid, promising, fresh-out-of-college prospects coming in to interview, and I honestly dread the thought of somebody having their first experience of engineering in this department. So I'm wondering: what should I do if/when the interviewee asks me "Do you like your job?" (no) "What kind of projects would I be working on?" (mostly static HTML/CSS changes) Anything else that would elicit a negative answer if told truthfully Do I tell the truth, to give the candidate a real picture of the job? What if this scares them away, and what if it gets blamed on me? Do I fib or lie, saying we work on exciting projects with lots of flexibility, like the pitch my boss will give when the reality is quite different? Should I feel any kind of moral responsibility to let a promising young developer know that this isn't the job for them, or should I shut up and be loyal 100% to the company? Any approaches or advice is appreciated. I hope I don't come across as overly dramatic - I honestly struggle with this question.

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Rolling Back Microsoft CRM during testing

- by npeterson

Process related question: Currently we have a multi-tenant installation of MS CRM 4.0 on three servers, Dev, Test, and Live. We are actively working on customizing one of the tenants, but the others are static. During user testing, we often find it necessary to 'start fresh' in one of the tenants. Is it better to try and delete out the changes from the tenant (created accounts, leads, etc), or just revert the database to a backup from before the testing started? Is there compelling reasons why bulk delete is not advisable for MSCRM or that reverting the database frequently could cause issue?

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Best solution for getting referral information in PHP

- by absentx

I am currently redoing some link structuring on a website. In the past we have used specific php files on the last step to direct the user to the proper place. Example: www.mysite.com/action/go-to-blue.php or www.mysite.com/action/short/go-to-red.php www.mysite.com/action/tall/go-to-red.php We are now restructuring to eliminate the /short/ or /tall/ directory. What this means is now "go-to-blue.php" will be doing some extra processing to make sure it sends the visitor to the proper place. The static method of the past was quite effective, because, well, if they left from that page we knew we had it right. Now since we are 301 redirecting action/short/go-to-red.php to just action/go-to-red.php it is quite important on "go-to-red.php" that we realize a user may have been redirected from /short/ or /tall/. So right now I am using HTTP_REFERRER and of course in my testing that works fine, but after a lot of reading it is clear that this is not a solid solution, so I was starting to brainstorm on other ways to check and make sure we get the proper referral information. If we could check HTTP_REFERRER plus some other test, I would feel confident we have a pretty good system in place to send the visitor to the right place. Some questions/comments: Could I use a session variable or a cookie to accomplish this goal? If so, would that be maintained through the 301 redirect? I don't see why it wouldn't be.. Passing the url in the url is not an option in this case.

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Status code in nginx try_files directive

- by Hamish

Is it possible to use the current status code as a parameter in try_files? For example, we try to provide a host specific 503 static response, or a server-wide fallback if it wasn't found: error_page 503 @error503; location @error503 { root /path_to_static_root/; try_files /$host/503.html /503.html =503; } There are a number of these directives, so it would be convenient to do something like: error_page 404 @error error_page 500 @error error_page 503 @error location @error { root /path_to_static_root/; try_files /$host/$status.html /$status.html =$status; } But the Variables documentation doesn't list anything that we could use to do this. Is it possible, or is there an alternative way to do this?

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Cannot execute Java program: UnsupportedClassVersionError

- by Ricko Devian

I have installed JDK 6, but I can't execute a Java program. For example, I have made test.java. I compile it with javac tes.java and there's no error when I compile it, but when I want to execute that program it always displays an error. I execute the Java program with java tes. Exception in thread "main" java.lang.UnsupportedClassVersionError: tes : Unsupported major.minor version 51.0 at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:634) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) at java.net.URLClassLoader.defineClass(URLClassLoader.java:277) at java.net.URLClassLoader.access$000(URLClassLoader.java:73) at java.net.URLClassLoader$1.run(URLClassLoader.java:212) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:205) at java.lang.ClassLoader.loadClass(ClassLoader.java:321) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294) at java.lang.ClassLoader.loadClass(ClassLoader.java:266) Could not find the main class: tes. Program will exit. My javac version is 1.7.0, my java version is 1.6.0. Here is my tes.java code: class tes{ public static void main(String[]args){ System.out.println("hello"); } }

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Code contracts and inheritance

- by DigiMortal

In my last posting about code contracts I introduced you how to force code contracts to classes through interfaces. In this posting I will go step further and I will show you how code contracts work in the case of inherited classes. As a first thing let’s take a look at my interface and code contracts. [ContractClass(typeof(ProductContracts))] public interface IProduct { int Id { get; set; } string Name { get; set; } decimal Weight { get; set; } decimal Price { get; set; } } [ContractClassFor(typeof(IProduct))] internal sealed class ProductContracts : IProduct { private ProductContracts() { } int IProduct.Id { get { return default(int); } set { Contract.Requires(value > 0); } } string IProduct.Name { get { return default(string); } set { Contract.Requires(!string.IsNullOrWhiteSpace(value)); Contract.Requires(value.Length <= 25); } } decimal IProduct.Weight { get { return default(decimal); } set { Contract.Requires(value > 3); Contract.Requires(value < 100); } } decimal IProduct.Price { get { return default(decimal); } set { Contract.Requires(value > 0); Contract.Requires(value < 100); } } } And here is the product class that inherits IProduct interface. public class Product : IProduct { public int Id { get; set; } public string Name { get; set; } public virtual decimal Weight { get; set; } public decimal Price { get; set; } } if we run this code and violate the code contract set to Id we will get ContractException. public class Program { static void Main(string[] args) { var product = new Product(); product.Id = -100; } } Now let’s make Product to be abstract class and let’s define new class called Food that adds one more contract to Weight property. public class Food : Product { public override decimal Weight { get { return base.Weight; } set { Contract.Requires(value > 1); Contract.Requires(value < 10); base.Weight = value; } } } Now we should have the following rules at place for Food: weight must be greater than 1, weight must be greater than 3, weight must be less than 100, weight must be less than 10. Interesting part is what happens when we try to violate the lower and upper limits of Food weight. To see what happens let’s try to violate rules #2 and #4. Just comment one of the last lines out in the following method to test another assignment. public class Program { static void Main(string[] args) { var food = new Food(); food.Weight = 12; food.Weight = 2; } } And here are the results as pictures to see where exceptions are thrown. Click on images to see them at original size. Violation of lower limit. Violation of upper limit. As you can see for both violations we get ContractException like expected. Code contracts inheritance is powerful and at same time dangerous feature. Although you can always narrow down the conditions that come from more general classes it is possible to define impossible or conflicting contracts at different points in inheritance hierarchy.

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How to do dependency Injection and conditional object creation based on type?

- by Pradeep

I have a service endpoint initialized using DI. It is of the following style. This end point is used across the app. public class CustomerService : ICustomerService { private IValidationService ValidationService { get; set; } private ICustomerRepository Repository { get; set; } public CustomerService(IValidationService validationService,ICustomerRepository repository) { ValidationService = validationService; Repository = repository; } public void Save(CustomerDTO customer) { if (ValidationService.Valid(customer)) Repository.Save(customer); } Now, With the changing requirements, there are going to be different types of customers (Legacy/Regular). The requirement is based on the type of the customer I have to validate and persist the customer in a different way (e.g. if Legacy customer persist to LegacyRepository). The wrong way to do this will be to break DI and do somthing like public void Save(CustomerDTO customer) { if(customer.Type == CustomerTypes.Legacy) { if (LegacyValidationService.Valid(customer)) LegacyRepository.Save(customer); } else { if (ValidationService.Valid(customer)) Repository.Save(customer); } } My options to me seems like DI all possible IValidationService and ICustomerRepository and switch based on type, which seems wrong. The other is to change the service signature to Save(IValidationService validation, ICustomerRepository repository, CustomerDTO customer) which is an invasive change. Break DI. Use the Strategy pattern approach for each type and do something like: validation= CustomerValidationServiceFactory.GetStratedgy(customer.Type); validation.Valid(customer) but now I have a static method which needs to know how to initialize different services. I am sure this is a very common problem, What is the right way to solve this without changing service signatures or breaking DI?

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What is the point of dynamic allocation in C++?

- by Aerovistae

I really have never understood it at all. I can do it, but I just don't get why I would want to. For instance, I was programming a game yesterday, and I set up an array of pointers to dynamically allocated little enemies in the game, then passed it to a function which updates their positions. When I ran the game, I got one of those nondescript assertion errors, something about a memory block not existing, I don't know. It was a run-time error, so it didn't say where the problem was. So I just said screw it and rewrote it with static instantiation, i.e.: while(n<4) { Enemy tempEnemy = Enemy(3, 4); enemyVector.push_back(tempEnemy); n++; } updatePositions(&enemyVector); And it immediately worked perfectly. Now sure, some of you may be thinking something to the effect of "Maybe if you knew what you were doing," or perhaps "n00b can't use pointers L0L," but frankly, you really can't deny that they make things way overcomplicated, hence most modern languages have done away with them entirely. But please-- someone -- What IS the point of dynamic allocation? What advantage does it afford? Why would I ever not do what I just did in the above example?

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What is the safest and least expensive way to store 10 terabytes of data?

- by Josh T

I'm a member of a production company and we're preparing for our first feature film. We've been discussing methods of data storage to keep all of our original content safe (for as long as possible). While we understand data is never 100% safe, we'd like to find the safest solution for us. We've considered: 16TB NAS for on-site storage 4-5 2TB hard drives (cheap, but not redundant), copy original footage to drives then seal in static free bag Burn data to Blu-Ray disks (time consuming and expensive: 200 disks == $5000) Tape drive(s)? I know the least about tape drives, except the fact that they're more reliable than disks. Any experience/knowledge with this amount of data is hugely appreciated.

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Library Organization in .NET

- by Greg Ros

I've written a .NET bitwise operations library as part of my projects (stuff ranging from get MSB set to some more complicated bitwise transformations) and I mean to release it as free software. I'm a bit confused about a design aspect of the library, though. Many of the methods/transformations in the library come with different endianness. A simple example is a getBitAt method that regards index 0 as the least significant bit, or the most significant bit, depending on the version used. In practice, I've found that using separate functions for different endianness results in much more comprehensible and reusable code than assuming all operations are little-endian or something. I'm really stumped regarding how best to package the library. Should I have methods that have LE and BE versions take an enum parameter in their signature, e.g. Endianness.Little, Endianness.Big? Should I have different static classes with identically named methods? such as MSB.GetBit and LSB.GetBit On a much wider note, is there a standard I could use in cases like this? Some guide? Is my design issue trivial? I have a perfectionist bent, and I sometimes get stuck on tricky design issues like this... Note: I've sort of realized I'm using endianness somewhat colloquially to refer to the order/place value of digital component parts (be they bits, bytes, or words) in a larger whole, in any setting. I'm not talking about machine-level endianness or serial transmission endianness. Just about place-value semantics in general. So there isn't a context of targeting different machines/transmission techniques or something.

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