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• Fast ArgumentNullException with attributes. It is possible?

  - by Fraga

  Hi. Is there any fast way to verify null arguments via attributes or something? Convert this: public void Method(type arg1,type arg2,type arg3) { if (arg1== null) throw new ArgumentNullException("arg1"); if (arg2== null) throw new ArgumentNullException("arg2"); if (arg3== null) throw new ArgumentNullException("arg3"); //Business Logic } Into something like this: [VerifyNullArgument("arg1","arg2","arg3")] public void Method(type arg1,type arg2,type arg3) { //Business Logic } Ideas? thanks guys.

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• When is it better to use a method versus a property for a class definition?

  - by ccomet

  Partially related to an earlier question of mine, I have a system in which I have to store complex data as a string. Instead of parsing these strings as all kinds of separate objects, I just created one class that contains all of those objects, and it has some parser logic that will encode all properties into strings, or decode a string to get those objects. That's all fine and good. This question is not about the parser itself, but about where I should house the logic for the parser. Is it a better choice to put it as a property, or as a method? In the case of a property, say public string DataAsString, the get accessor would house the logic to encode all of the data into a string, while the set accessor would decode the input value and set all of the data in the class instance. It seems convenient because the input/output is indeed a string. In the case of a method, one method would be Encode(), which returns the encoded string. Then, either the constructor itself would house the logic for the decoding a string and require the string argument, or I write a Decode(string str) method which is called separately. In either case, it would be using a method instead of a property. So, is there a functional difference between these paths, in terms of the actual running of the code? Or are they basically equivalent and it then boils down to a choice of personal preference or which one looks better? And in that kind of question... which would look cleaner anyway?

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• C# reflection instantiation

  - by NickLarsen

  I am currently trying to create a generic instance factory for which takes an interface as the generic parameter (enforced in the constructor) and then lets you get instantiated objects which implement that interface from all types in all loaded assemblies. The current implementation is as follows:     public class InstantiationFactory     {         protected Type Type { get; set; }         public InstantiationFactory()         {             this.Type = typeof(T);             if (!this.Type.IsInterface)             {                 // is there a more descriptive exception to throw?                 throw new ArgumentException(/* Crafty message */);             }         }         public IEnumerable GetLoadedTypes()         {             // this line of code found in other stack overflow questions             var types = AppDomain.CurrentDomain.GetAssemblies()                 .SelectMany(a = a.GetTypes())                 .Where(/* lambda to identify instantiable types which implement this interface */);             return types;         }         public IEnumerable GetImplementations(IEnumerable types)         {             var implementations = types.Where(/* lambda to identify instantiable types which implement this interface */                 .Select(x = CreateInstance(x));             return implementations;         }         public IEnumerable GetLoadedImplementations()         {             var loadedTypes = GetLoadedTypes();             var implementations = GetImplementations(loadedTypes);             return implementations;         }         private T CreateInstance(Type type)         {             T instance = default(T);             var constructor = type.GetConstructor(Type.EmptyTypes);             if (/* valid to instantiate test */)             {                 object constructed = constructor.Invoke(null);                 instance = (T)constructed;             }             return instance;         }     } It seems useful to me to have my CreateInstance(Type) function implemented as an extension method so I can reuse it later and simplify the code of my factory, but I can't figure out how to return a strongly typed value from that extension method. I realize I could just return an object:     public static class TypeExtensions     {         public object CreateInstance(this Type type)         {             var constructor = type.GetConstructor(Type.EmptyTypes);             return /* valid to instantiate test */ ? constructor.Invoke(null) : null;         }     } Is it possible to have an extension method create a signature per instance of the type it extends? My perfect code would be this, which avoids having to cast the result of the call to CreateInstance():     Type type = typeof(MyParameterlessConstructorImplementingType);     MyParameterlessConstructorImplementingType usable = type.CreateInstance();

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• Accessing non-static combbox property in the static method.

  - by Harikrishna

  I have one combobox on the window form and I have one method which is declared with static like private static DataTable ParseTable(HtmlNode table) Now I want to use combobox in that method for using combobox property but I can not access any property of combobox or combobox itself.If I made the combobox declaration as static then it can be accessed in that static method.But any alternative way to access combbox property in that static method because I don't want to make combobox declaration as static.

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• Does Java support default parameter values?

  - by gnavi

  I came across some Java code that had the following structure: public MyParameterizedFunction(String param1, int param2) { this(param1, param2, false); } public MyParameterizedFunction(String param1, int param2, boolean param3) { //use all three parameters here } I know that in C++ I can assign a parameter a default value. For example: void MyParameterizedFunction(String param1, int param2, bool param3=false); Does Java support this kind of syntax? Are there any reasons why this two step syntax is preferable?

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• matlab fit exp2

  - by HelloWorld

  I'm unsuccessfully looking for documentation of fit function using exp2 (sum of 2 exponents). How to operate the function is clear: [curve, gof] = fit(x, y,'exp2'); But since there are multiple ways to fit a sum of exponents I'm trying to find out what algorithm is used. Particularly what happens when I'm fitting one exponent (the raw data) with a bit of noise, how the exponents are spread. I've simulated several cases, and it seems that it "drops" all the weight on the second set of coefficients, but row data analysis often shows different behavior. Does anyone have suggestions of documentation?

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• private class calling a method from its outer class

  - by oxinabox.ucc.asn.au

  Ok, so I have a class for a "Advanced Data Structure" (in this case a kinda tree) SO I implimented a Iterator as a private class with in it. So the iterator needs to implement a remove function to remove the last retuirned element. now my ADT already impliments a remove function, and in this case there is very little (thinking about it, i think nothing) to be gain by implimenting a different remove function for the iterator. so how do I go about calling the remove from my ADT sketch of my struture: public class ADT { ... private class ADT_Iterator impliments java.util.Itorator{ ... public void remove(){ //where I want to call the ADT's remove function from } ... public void remove( Object paramFoo ) { ... } ... } So just calling remove(FooInstance) won't work (will it?) and this.remove(FooInstance) is the same thing. what do i call? (and changign the name of the ADT's remove function is not an option, as that AD T has to meet an Interace wich I am note at liberty to change) I could make both of them call a removeHelper functon, I guess...

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• Matlab code help. Backward Euler method.

  - by m0s

  Here is the matlab/freemat code I got to solve ODE numerically using backward Euler method. However the results are inconsistent with my textbook results, and sometimes even ridiculously inconsistent. Please point out what is wrong with the code. I have already asked this question on mathoverflow.com no help there, hope someone here can help. function [x,y]=backEuler(f,xinit,yinit,xfinal,h) %f - this is your y prime %xinit - initial X %yinit - initial Y %xfinal - final X %h - step size n=(xfinal-xinit)/h; %Calculate steps %Inititialize arrays... %1st elements take xinit and yinit corespondigly, the rest fill with 0s x=[xinit zeros(1,n)]; y=[yinit zeros(1,n)]; %Numeric routine for i=1:n x(i+1)=x(i)+h; ynew=y(i)+h*(f(x(i),y(i))); y(i+1)=y(i)+h*f(x(i+1),ynew); end end

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• Lisp, OCaml or what for Runge Kutta?

  - by Eelvex

  Which language would you propose for solving a system with: first order differential equations complex variables N-dimensions using 4th order Runge Kutta or the like. Speed matters a lot but would sacrifice for: Elegant (clean and short) code Flexibility + scalability I'm mostly between a Lisp and OCaml but any other suggestion is welcomed. Thanks!

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• How do i generate a random integer between min and max in java?

  - by David

  What method returns a random int between a min and max? Or does no such method exist? what i'm looking for is something like this: NAMEOFMETHOD (min, max) (where min and max are ints) that returns soemthing like this: 8 (randomly) if such a method does exist could you please link to the relevant documentation with your answer. thanks.

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• Kohana Database Library - How to Execute a Query with the Same Parameters More Than Once?

  - by Noah Goodrich

  With the following bit of code: $builder = ORM::factory('branch')->where('institution_id', $this->institution->id)->orderby('name'); I need to first execute: $count = $builder->count_all(); Then I need to execute: $rs = $builder->find_all($limit, $offset); However, it appears that when I execute the first query the stored query parameters are cleared so that a fresh query can be executed. Is there a way to avoid having the parameters cleared or at least copy them easily without having to reach directly into the Database driver object that stores the query parameters and copy them out? We are using Kohana 2.3.4 and upgrading is not an option.

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• Fatal error: Function name must be a string in.. PHP error

  - by Jonesy

  Hi I have a class called User and a method called insertUser(). function insertUser($first_name, $last_name, $user_name, $password, $email_address, $group_house_id) { $first_name = mysql_real_escape_string($first_name); $last_name = mysql_real_escape_string($last_name); $user_name = mysql_real_escape_string($user_name); $password = mysql_real_escape_string($password); $email_address = mysql_real_escape_string($email_address); $query = "INSERT INTO Users (FirstName,LastName,UserName,Password,EmailAddress, GroupHouseID) VALUES ('$first_name','$last_name','$user_name','$password','$email_address','$group_house_id')"; $mysql_query($query); } And I call it like this: $newUser = new User(); $newUser->insertUser($first_name, $last_name, $user_name, $email, $password, $group_house_id); When I run the code I get this error: Fatal error: Function name must be a string in /Library/WebServer/Documents/ORIOnline/includes/class_lib.php on line 33 Anyone know what I am doing wronly? Also, this is my first attempt at OO PHP. Cheers, Jonesy

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• How do I extend in my class a Dom element, in mootools

  - by Itay Moav

  I want to create a Class, say MyDiv, which inherits from the original DOM DIV element. Later in my code I would like to use it like that: $('a-container').adopt(new MyDiv('my own set of params')); I am missing the exact syntax to do it.

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• What's an easy way to set up object communication in Obj-C?

  - by seaworthy

  I am trying to send a slider value from a controller object to a method of a model object. The later is implemented in the separate file and I have appropriate headers. I think the problem is that I am not sure how to instantiate the receiver in order to produce a working method for the controller. Here is the controller's method. -(IBAction)setValue:(id)slider {[Model setValue:[slider floatValue]];} @implementation Model -(void)setValue:(float)n{ printf("%f",n); } @end What I get is 'Model' may not respond to '+setValue' warning and no output in my console. Any insight is appreciated.

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• Returning IEnumerable<T> vs IQueryable<T>

  - by stackoverflowuser

  what is the difference between returning iqueryable vs ienumerable. IQueryable<Customer> custs = from c in db.Customers where c.City == "<City>" select c; IEnumerable<Customer> custs = from c in db.Customers where c.City == "<City>" select c; Will both be deferred execution? When should one be preferred over the other?

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• Static method not called

  - by Smile

  I'm trying to call a static method (printABC()) in this class but it's not working. If I uncomment both of the lines marked T_T (1 and 2), it works! Why does it fail with only one of the lines? import java.util.Scanner; class pro0009 { static Scanner in = new Scanner(System.in); static int A,B,C; static void printABC(){ String ABC = in.nextLine(); ABC=ABC.replace("A"," "+A+" "); ABC=ABC.replace("B"," "+B+" "); ABC=ABC.replace("C"," "+C+" "); //System.out.print(ABC.substring(1)); System.out.print(ABC); } public static void main(String[] args){ int x = in.nextInt(); //1 int y = in.nextInt(); //2 int z = in.nextInt(); //3 if(x<y){//1<2 if(x<z){ //1<3 if(y<z){//x<y<z 2<3 //1<2<3 A=x; B=y; C=z; printABC();//T_T 1 System.out.println("Here"); //pro0009.printABC();//T_T 2 //System.out.println("Here2"); }else{ //x<z<y A=x; B=z; C=y; } }else{//z<x<y A=z; B=x; C=y; } }else{//y<x if(y<z){ if(x<z){//y<x<z A=y; B=x; C=z; }else{//y<z<x A=y; B=z; C=x; } }else{//z<y<x A=z; B=y; C=x; } } } }

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• C# extension method doesn't seem to exist

  - by blahblah

  I can't seem to get the following extension method to be found in another class in the same namespace (MyProject.Util). using System.Collections.Specialized; namespace MyProject.Util { public static class Extensions { public static string Get( this NameValueCollection me, string key, string def ) { return me[key] ?? def; } } } As you can see it's basically another version of foo[bar] ?? baz, but I still don't understand why VS2008 fails to compile telling me that no version of Get takes two arguments. Any ideas?

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• Why is my Extension Method not showing up in my test class?

  - by Robert Harvey

  I created an extension method called HasContentPermission on the System.Security.Principal.IIdentity interface: namespace System.Security.Principal { public static bool HasContentPermission (this IIdentity itentity, int contentID) { // I do stuff here return result; } } And I call it like this: bool hasPermission = User.Identity.HasPermission(contentID); Works like a charm. Now I want to unit test it. To do that, all I really need to do is call the extension method directly, so: using System.Security.Principal; namespace MyUnitTests { [TestMethod] public void HasContentPermission_PermissionRecordExists_ReturnsTrue() { IIdentity identity; bool result = identity.HasContentPermission(... But HasContentPermission won't intellisense. I tried creating a stub class that inherits from IIdentity, but that didn't work either. Why? Or am I going about this the wrong way?

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• Getting the name of a child class in the parent class (static context)

  - by Benoit Myard

  Hi everybody, I'm building an ORM library with reuse and simplicity in mind; everything goes fine except that I got stuck by a stupid inheritance limitation. Please consider the code below: class BaseModel { /* * Return an instance of a Model from the database. */ static public function get (/* varargs */) { // 1. Notice we want an instance of User $class = get_class(parent); // value: bool(false) $class = get_class(self); // value: bool(false) $class = get_class(); // value: string(9) "BaseModel" $class = __CLASS__; // value: string(9) "BaseModel" // 2. Query the database with id $row = get_row_from_db_as_array(func_get_args()); // 3. Return the filled instance $obj = new $class(); $obj->data = $row; return $obj; } } class User extends BaseModel { protected $table = 'users'; protected $fields = array('id', 'name'); protected $primary_keys = array('id'); } class Section extends BaseModel { // [...] } $my_user = User::get(3); $my_user->name = 'Jean'; $other_user = User::get(24); $other_user->name = 'Paul'; $my_user->save(); $other_user->save(); $my_section = Section::get('apropos'); $my_section->delete(); Obviously, this is not the behavior I was expecting (although the actual behavior also makes sense).. So my question is if you guys know of a mean to get, in the parent class, the name of child class.

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• Ruby: Alter class static method in a code block

  - by Phuong Nguy?n

  Given the Thread class with it current method. Now inside a test, I want to do this: def test_alter_current_thread Thread.current = a_stubbed_method # do something that involve the work of Thread.current Thread.current = default_thread_current end Basically, I want to alter the method of a class inside a test method and recover it after that. I know it sound complex for another language, like Java & C# (in Java, only powerful mock framework can do it). But it's ruby and I hope such nasty stuff would be available

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• Why can't I pass self as a named argument to an instance method in Python?

  - by Joseph Garvin

  This works: >>> def bar(x, y): ... print x, y ... >>> bar(y=3, x=1) 1 3 And this works: >>> class foo(object): ... def bar(self, x, y): ... print x, y ... >>> z = foo() >>> z.bar(y=3, x=1) 1 3 And even this works: >>> foo.bar(z, y=3, x=1) 1 3 But why doesn't this work? >>> foo.bar(self=z, y=3, x=1) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unbound method bar() must be called with foo instance as first argument (got nothing instead) This makes metaprogramming more difficult, because it requires special case handling. I'm curious if it's somehow necessary by Python's semantics or just an artifact of implementation.

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• Cocos2d: is it good practice to use a shared GameScene when having various levels?

  - by mm24

  In my code (based on the ShootEmUp example in this book, which I highly reccomend, source code in chapter 8 available here) I often use the trick of accessing the GameScene via: +(GameScene*) sharedGameScene; which returns a reference to the static instance of GameScene. Is a static instance of GameScene as in the book still a valid pattern in case I want a MainMenu calling GameScene initialized with different level data each time (e.g. different enemies)? (I have created a sceneWithId:(int) method where I load different level data each time. Or should I pheraps create a GameScene class and then sublcass it? E.g. FirstGameScene : GameScene

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• ControlCollection extension method optimazation

  - by Johan Leino

  Hi, got question regarding an extension method that I have written that looks like this: public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance) where T : class { T control; foreach (Control ctrl in instance) { if ((control = ctrl as T) != null) { yield return control; } foreach (T child in FindControlsOfType<T>(ctrl.Controls)) { yield return child; } } } public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance, Func<T, bool> match) where T : class { return FindControlsOfType<T>(instance).Where(match); } The idea here is to find all controls that match a specifc criteria (hence the Func<..) in the controls collection. My question is: Does the second method (that has the Func) first call the first method to find all the controls of type T and then performs the where condition or does the "runtime" optimize the call to perform the where condition on the "whole" enumeration (if you get what I mean). secondly, are there any other optimizations that I can do to the code to perform better. An example can look like this: var checkbox = this.Controls.FindControlsOfType<MyCustomCheckBox>( ctrl => ctrl.CustomProperty == "Test" ) .FirstOrDefault();

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• php 5.1.6 magic __toString method

  - by NachoF

  In codeigniter Im trying to use this plugin which requires I implement a toString method in my models. My toString method simply does return $this->name On my local machine with php 5.3 everything works just fine but on the production server with php 5.1.6 it shows "Object id#48" where the value of the name property of that object should appear..... I found something about the problem here but I still dont understand... How can I fix this?

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• Predicate<INT> match question

  - by Petr

  Hi, I do not understand how following code works. Specifically, I do not understand using of "return i<3". I would expect return i IF its < than 3. I always though that return just returns value. I could not even find what syntax is it. Second question, it seems to me like using anonymous method (delegate(int i)) but could be possible to write it with normal delegate pointing to method elsewere? Thanks List<int> listOfInts = new List<int> { 1, 2, 3, 4, 5 }; List<int> result = listOfInts.FindAll(delegate(int i) { return i < 3; });

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