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  • how to create a dynamic class at runtime in Java

    - by Mrityunjay
    hi, is it possible to create a new java file from existing java file after changing some of its attributes at runtime?? Suppose i have a java file pubic class Student{ private int rollNo; private String name; // getters and setters // constructor } is it possible to create something like this, provided that rollNo is key element for the table.. public class Student { private StudentKey key; private String name; //getters and setters //constructor } public class StudentKey { private int rollNo; // getters and setters // construcotors } please help..

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  • Implementation of interface when using child class of a parent class in method of interface

    - by dotnetdev
    I don't have access to my dev environment, but when I write the below: interface IExample void Test (HtmlControl ctrl); class Example : IExample { public void Test (HtmlTextArea area) { } I get an error stating the methods in the class implementation don't match the interface - so this is not possible. HtmlTextArea is a child class of HtmlControl, is there no way this is possible? I tried with .NET 3.5, but .NET 4.0 may be different (I am interested in any solution with either framework). Thanks

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  • C# Function Inheritance--Use Child Class Vars with Base Class Function

    - by Sean O'Connor
    Good day, I have a fairly simple question to experienced C# programmers. Basically, I would like to have an abstract base class that contains a function that relies on the values of child classes. I have tried code similar to the following, but the compiler complains that SomeVariable is null when SomeFunction() attempts to use it. Base class: public abstract class BaseClass { protected virtual SomeType SomeVariable; public BaseClass() { this.SomeFunction(); } protected void SomeFunction() { //DO SOMETHING WITH SomeVariable } } A child class: public class ChildClass:BaseClass { protected override SomeType SomeVariable=SomeValue; } Now I would expect that when I do: ChildClass CC=new ChildClass(); A new instance of ChildClass should be made and CC would run its inherited SomeFunction using SomeValue. However, this is not what happens. The compiler complains that SomeVariable is null in BaseClass. Is what I want to do even possible in C#? I have used other managed languages that allow me to do such things, so I certain I am just making a simple mistake here. Any help is greatly appreciated, thank you.

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  • Create object of unknown class (two inherited classes)

    - by Paul
    I've got the following classes: class A { void commonFunction() = 0; } class Aa: public A { //Some stuff... } class Ab: public A { //Some stuff... } Depending on user input I want to create an object of either Aa or Ab. My imidiate thought was this: A object; if (/*Test*/) { Aa object; } else { Ab object; } But the compiler gives me: error: cannot declare variable ‘object’ to be of abstract type ‘A’ because the following virtual functions are pure within ‘A’: //The functions... Is there a good way to solve this?

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  • Python Class Variables Question

    - by zyq524
    I have some doubt about python's class variables. As my understanding, if I define a class variable, which is declared outside the init() function, this variable will create only once as a static variable in C++. This seems right for some python types, for instance, dict and list type, but for those base type, e.g. int,float, is not the same. For example: class A: dict1={} list1=list() int1=3 def add_stuff(self, k, v): self.dict1[k]=v self.list1.append(k) self.int1=k def print_stuff(self): print self.dict1,self.list1,self.int1 a1 = A() a1.add_stuff(1, 2) a1.print_stuff() a2=A() a2.print_stuff() The output is: {1: 2} [1] 1 {1: 2} [1] 3 I understand the results of dict1 and list1, but why does int1 behavior different?

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  • OBJ-C - Getting a class name from a class hierarchy

    - by mmmilo
    Let's say I have the following headers: @interface SuperClass : NSObject @interface SubClass : SuperClass I'm alloc'ing an instance of the class by doing: SubClass *sc = [[SubClass alloc] init]; In my SuperClass.m: - (id) init { self = [super init]; if (self != nil) { NSString *cString = NSStringFromClass([self class]); } return self; } Simple, right? My question is: how can I get cString to return the SuperClass class, rather than the SubClass class? Since the SubClass is alloc'd/init'd, is this not possible? Thanks!

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  • Singletons and constants

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

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  • ActionScript Custom Class With Return Type?

    - by TheDarkIn1978
    i just know this is a dumb question, so excuse me in advance. i want to essentially classify a simple function in it's own .as file. the function compares integers. but i don't know how to call the class and receive a boolean return. here's my class package { public class CompareInts { public function CompareInts(small:int, big:int) { compare(small, big); } private function compare(small:int, big:int):Boolean { if (small < big) return true; else return false; } } } so now i'd like to write something like this: if (CompareInts(1, 5) == true). or output 'true' by writing trace(CompareInts(1, 5));

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  • PHP: reusing database class

    - by citricsquid
    Hi, I built a class that allows me to do: $db->query($query); and it works perfectly, although if I want to do: $db->query($query); while($row = $db->fetch_assoc()){ $db->query($anotherquery); echo $db->result(); } it "breaks" the class. I don't want to constantly have to redeclare my class (eg: $seconddb = new database()), is there a way to get around this? I want to be able to reuse $db within $db, without overwriting the "outside" db. currently I'm create an array of data (from db-fetch_assoc() then doing a foreach and then doing the db call inside that: $db->query('SELECT * FROM table'); while($row = $db->fetch_assoc()){ $arr[] = $row; } foreach($arr as $a){ $db->query(); // query and processing here } Is this the best method or am I missing the obvious? Should I consider passing a connection link ID with the database connection?

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  • Java : Using parent class method to access child class variable

    - by Jayant
    I have the following scenario : public class A { private int x = 5; public void print() { System.out.println(x); } } public class B extends A { private int x = 10; /*public void print() { System.out.println(x); }*/ public static void main(String[] args) { B b = new B(); b.print(); } } On executing the code, the output is : 5. How to access the child class(B's) variable(x) via the parent class method? Could this be done without overriding the print() method (i.e. uncommenting it in B)? [This is important because on overriding we will have to rewrite the whole code for the print() method again]

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  • Preventing SQL injecting in a database class

    - by Josh
    I'm building a database class and thought it'd be a good idea to incorporate some form of SQL injection prevention (duh!). Here's the method that runs a database query: class DB { var $db_host = 'localhost'; var $db_user = 'root'; var $db_passwd = ''; var $db_name = 'whatever'; function query($sql) { $this->result = mysql_query($sql, $this->link); if(!$this->result) { $this->error(mysql_error()); } else { return $this->result; } } } There's more in the class than that but I'm cutting it down just for this. The problem I'm facing is if I just use mysql_real_escape_string($sql, $this->link); then it escapes the entire query and leads to a SQL syntax error. How can I dynamically find the variables that need to be escaped? I want to avoid using mysql_real_escape_string() in my main code blocks, i'd rather have it in a function. Thanks.

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  • C non-trivial constants

    - by user525869
    I want to make several constants in C with #define to speed up computation. Two of them are not simply trivial numbers, where one is a right shift, the other is a power. math.h in C gives the function pow() for doubles, whereas I need powers for integers, so I wrote my own function, ipow, so I wouldn't need to be casting everytime. My question is this: One of the #define constants I want to make is a power, say ipow(M, T), where M and T were also #define constants. ipow is a function in the actual code, so this actually seems to slows things down when I run the code (is it running ipow everytime the constant is mentioned?). However, when I ues the built in pow function and just do (int)pow(M,T), the code is sped up. I'm confused as to why this is, since the ipow and pow functions are just as fast. On a more general note, can I define constants using #define using functions inside the actual code? The above example has me confused on whether this speeds things up or actually slows things down.

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  • Do I need to manually create indexes for a DBIx::Class belongs_to relationship

    - by Dancrumb
    I'm using the DBIx::Class modules for an ORM approach to an application I have. I'm having some problems with my relationships. I have the following package MySchema::Result::ClusterIP; use strict; use warnings; use base qw/DBIx::Class::Core/; our $VERSION = '1.0'; __PACKAGE__->load_components(qw/InflateColumn::Object::Enum Core/); __PACKAGE__->table('cluster_ip'); __PACKAGE__->add_columns( # Columns here ); __PACKAGE__->set_primary_key('objkey'); __PACKAGE__->belongs_to( 'configuration' => 'MySchema::Result::Configuration', 'config_key'); __PACKAGE__->belongs_to( 'cluster' => 'MySchema::Result::Cluster', { 'foreign.config_key' => 'self.config_key', 'foreign.id' => 'self.cluster_id' } ); As well as package MySchema::Result::Cluster; use strict; use warnings; use base qw/DBIx::Class::Core/; our $VERSION = '1.0'; __PACKAGE__->load_components(qw/InflateColumn::Object::Enum Core/); __PACKAGE__->table('cluster'); __PACKAGE__->add_columns( # Columns here ); __PACKAGE__->set_primary_key('objkey'); __PACKAGE__->belongs_to( 'configuration' => 'MySchema::Result::Configuration', 'config_key'); __PACKAGE__->has_many('cluster_ip' => 'MySchema::Result::ClusterIP', { 'foreign.config_key' => 'self.config_key', 'foreign.cluster_id' => 'self.id' }); There are a couple of other modules, but I don't believe that they are relevant. When I attempt to deploy this schema, I get the following error: DBIx::Class::Schema::deploy(): DBI Exception: DBD::mysql::db do failed: Can't create table 'test.cluster_ip' (errno: 150) [ for Statement "CREATE TABLE `cluster_ip` ( `objkey` smallint(5) unsigned NOT NULL auto_increment, `config_key` smallint(5) unsigned NOT NULL, `cluster_id` char(16) NOT NULL, INDEX `cluster_ip_idx_config_key_cluster_id` (`config_key`, `cluster_id`), INDEX `cluster_ip_idx_config_key` (`config_key`), PRIMARY KEY (`objkey`), CONSTRAINT `cluster_ip_fk_config_key_cluster_id` FOREIGN KEY (`config_key`, `cluster_id`) REFERENCES `cluster` (`config_key`, `id`) ON DELETE CASCADE ON UPDATE CASCADE, CONSTRAINT `cluster_ip_fk_config_key` FOREIGN KEY (`config_key`) REFERENCES `configuration` (`config_key`) ON DELETE CASCADE ON UPDATE CASCADE ) ENGINE=InnoDB"] at test_deploy.pl line 18 (running "CREATE TABLE `cluster_ip` ( `objkey` smallint(5) unsigned NOT NULL auto_increment, `config_key` smallint(5) unsigned NOT NULL, `cluster_id` char(16) NOT NULL, INDEX `cluster_ip_idx_config_key_cluster_id` (`config_key`, `cluster_id`), INDEX `cluster_ip_idx_config_key` (`config_key`), PRIMARY KEY (`objkey`), CONSTRAINT `cluster_ip_fk_config_key_cluster_id` FOREIGN KEY (`config_key`, `cluster_id`) REFERENC ES `cluster` (`config_key`, `id`) ON DELETE CASCADE ON UPDATE CASCADE, CONSTRAINT `cluster_ip_fk_config_key` FOREIGN KEY (`config_key`) REFERENCES `configuration` (`conf ig_key`) ON DELETE CASCADE ON UPDATE CASCADE ) ENGINE=InnoDB") at test_deploy.pl line 18 From what I can tell, MySQL is complaining about the FOREIGN KEY constraint, in particular, the REFERENCE to (config_key, id) in the cluster table. From my reading of the MySQL documentation, this seems like a reasonable complaint, especially in regards to the third bullet point on this doc page. Here's my question. Am I missing something in the DBIx::Class module? I realize that I could explicitly create the necessary index to match up with this foreign key constraint, but that seems to be repetitive work. Is there something I should be doing to make this occur implicitly?

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  • How to get actual type of an derived class from its parent interface

    - by Tarik
    Hello people, Lets say we have a code portion like this : IProduct product = ProductCreator.CreateProduct(); //Factory Method we have here SellThisProduct(product); //... private void SellThisProduct(IProduct product) { //..do something here } //... internal class Soda : IProduct {} internal class Book : IProduct {} How can I infer which product is actually passed into SellThisProduct() method in the method? I think if I say GetType() or something it will probably return the IProduct type. Thanks...

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  • Generating Class Diagram

    - by GustlyWind
    HI All I am at the end of the release of my project.So in order to keep working our manger asked us to generate Class Diagrams for the code we had written.Its medium project with 3500 java files .So I think we need to generate class diagrams.First I need to know how reverse engineering works here. Also I looked for some tools in Google(Green, Violet) but not sure whether they are of any help.Please suggest me how to proceed.Also a good beginning tutorial is appreciated.

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  • Append class="external" to external links.

    - by K3
    What is the php code to append class="external" to links that are posted and are not the domain. For example my site is www.mysite.com and you post a link to www.mysite.com/news and a link to www.yoursite.com How do I set it so only non "mysite.com" links have the class specified?

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  • Best way to define an immutable class in Objective C

    - by Patrick Marty
    Hi, I am a newbie in Objective C and I was wondering what is the best way to define an immutable class in Objective-C (like NSString for example). I want to know what are the basic rules one has to follow to make a class immutable. I think that : setters shouldn't be provided if properties are used, they should be readonly accessInstanceVariablesDirectly must be override and return NO Did I forget something ? Thanks

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  • Pear PHP UML Class Diagrams

    - by bigstylee
    Hi, I am trying to create graphical representations of existing code. I have tried to use VS.PHP (with Visual Studios 2010) but cant seem to generate class diagrams from this. I have tried to use Pear's PHP UML package which has produced a lot of JavaDoc style documentation and an XMI document. From what I have read, this can be used to create class diagrams? If so, how? Are there other "easier" alternatives? Thanks in advance

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  • Looking to write a Tag class

    - by Austin Schneider
    I'm looking to write a Tag class (a tag is a string with no spaces). My first thought is to inherit from String: class Tag < String def initialize(str) raise ArgumentError if str =~ /\s/ super end end Does this look correct? Are there any other methods I should redefine?

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  • Class for move, scale and rotate, of a uiimageview

    - by David
    Hi Everyone, I'm creating a subclass of UIImageView that detects touches, and will move, rotate and scale the image based on the touches. However, I really feel like I'm reinventing the wheel here, and it's driving me nuts. Shouldn't this already exist somewhere? Does anyone have any examples, or links to a class that is already doing this? Or if you have a class you've written, that'd be helpful too. Thanks a lot in advance.

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  • Instance variables vs. class variables in Python

    - by deamon
    I have Python classes, of which I need only one instance at runtime, so it would be sufficient to have the attributes only once per class and not per instance. If there would be more than one instance (what won't happen), all instance should have the same configuration. I wonder which of the following options would be better or more "idiomatic" Python. Class variables: MyController(Controller): path = "something/" childs = [AController, BController] def action(request): pass Instance ariables: MyController(Controller): def __init__(self): self.path = "something/" self.childs = [AController, BController] def action(self, request): pass

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  • Ruby is already using the class name of my model

    - by Octopus Inc
    I'm making a forum application with various levels of authorization, one of which is a Monitor. I am doing this by extending my User class, and I plan on fine tuning this with "-ship" classes (e.g. administratorship, authorship, moderatorship, etc.). Apparently the Monitor class is part of ruby mixin. How do I keep my resource name without the collisions?

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