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  • Any way to make a generic List where I can add a type AND a subtype?

    - by user383178
    I understand why I cannot do the following: private class Parent { }; private class Child extends Parent { }; private class GrandChild extends Child { }; public void wontCompile(List<? extends Parent> genericList, Child itemToAdd) { genericList.add(itemToAdd); } My question is there ANY practical way to have a typesafe List where you can call add(E) where E is known to be only a Parent or a Child? I vaguely remember some use of the "|" operator as used for wildcard bounds, but I cannot find it in the spec... Thanks!

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  • php query cant figure out the problem

    - by Eat
    I dont get an error but it does not return me the row values as well. How can I address the problem? <?php //DATABASE $dbConn = mysql_connect($host,$username,$password); mysql_select_db($database,$dbConn); $SQL = mysql_query("SELECT N.*, C.CatID FROM News N INNER JOIN Categories C ON N.CatID = C.CatID WHERE N.Active = 1 ORDER BY DateEntered DESC"); while ( $Result = mysql_fetch_array($SQL) or die(mysql_error())) { $CatID[] = $Result[CatID]; $NewsName[] = $Result[NewsName]; $NewsShortDesc[] = $Result[NewsShortDesc]; } // mysql_free_result($Result); ?> <div class="toparticle"> <span class="section"><?=$CatID[0] ?> </span> <span class="headline"><?=$NewsName[0] ?></span> <p><?=$NewsShortDesc[0] ?></p> </div>

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  • @ExceptionHandler doesn't handle the thrown exceptions

    - by Javi
    Hello, I have a method in my controller which will handle the exceptions thrown by the application. So I have a method like this one. @Controller public class ExceptionController { @RequestMapping(value="/error") @ExceptionHandler(value={Exception.class, NullPointerException.class}) public String showError(Exception e, Model model){ return "tiles:error"; } } And to try I if it works I throw a NullPointerException in another method in other method controller: boolean a = true; if(a){ throw new NullPointerException(); } After the exception is thrown it is printed in the JSP, but it doesn't go throw my showError() method (I've set a breakpoint there and it never enters). showError() method will catch the exception and will show different error pages depending on the exception type (though now it always shows the same error page). If I go to the url /error it shows the error page so the showError() method is OK. I'm using Spring 3. What can be the problem? Thanks.

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  • ActiveRecord, has_many, polymorphic and STI

    - by leomayleomay
    I've came into a problem while working with AR and polymorphic, here's the description, class Base < ActiveRecord::Base; end class Subscription < Base set_table_name :subscriptions has_many :posts, :as => :subscriptable end class Post < ActiveRecord::Base belongs_to :subscriptable, :polymorphic => true end in the console, >> s = Subscription.create(:name => 'test') >> s.posts.create(:name => 'foo', :body => 'bar') and it created a Post like: #<Post id: 1, name: "foo", body: "bar", subscriptable_type: "Base", subscriptable_id: 1, created_at: "2010-05-10 12:30:10", updated_at: "2010-05-10 12:30:10"> the subscriptable_type is Base but Subscription, anybody can give me a hand on this?

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  • Where Should Using Statements Be Located [closed]

    - by Bobby Ortiz - DotNetBob
    Possible Duplicate: What is the difference between these two declarations? I recently started working on a project with using statement located inside the NameSpace block. namespace MyApp.Web { using System; using System.Web.Security; using System.Web; public class MyClass { I usually put my using statements above the namespace block. using System; using System.Web.Security; using System.Web; namespace MyApp.Web { public class MyClass { I don't think it matters, but I am currious if someone else had a recommendation and could they explain why one way is better than another. Note: I always have one class per file.

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  • does anyone see any issues with this thread pattern?

    - by prmatta
    Here is a simple thread pattern that I use when writing a class that needs just one thread, and needs to a specific task. The usual requirements for such a class are that it should be startable, stopable and restartable. Does anyone see any issues with this pattern that I use? public class MyThread implements Runnable { private boolean _exit = false; private Thread _thread = null; public void start () { if (_thread == null) { _thread = new Thread(this, "MyThread"); _thread.start(); } } public void run () { while (_exit) { //do something } } public void stop () { _exit = true; if (_thread != null) { _thread.interrupt(); _thread = null; } } } I am looking for comments around if I am missing something, or if there is a better way to write this.

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  • Which is the best and appropriate way to write the code in Winforms ?

    - by Harikrishna
    What is the best way to write the code ? (1) Like directly writing the code in the button_click() event. or (2) Make the function of that code which I write in button_click() event and write this function in one class and then that function I should call in the button_Click() event.Like is it called three-tired approach to write the code ? Like in button_Click() event I write the code to save the records in csv file from datatable.So I should write that code in button_Click() event or I should make one new function and one new class and write that code in that function which is the new class and calling that function in button_Click() event. This is only one example but I am talking about all the code written in my application that which is the appropriate and best way to write the code and what are the benefits ? Note that I write the code in Winforms with c#.

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  • [C++] Question on Virtual Methods

    - by bobber205
    IF both methods are declared as virtual, shouldn't both instances of Method1() that are called be the derived class's Method1()? I am seeing BASE then DERIVED called each time. I am doing some review for an interview and I want to make sure I have this straight. xD class BaseClass { public: virtual void Method1() { cout << "Method 1 BASE" << endl; } }; class DerClass: public BaseClass { public: virtual void Method1() { cout << "Method 1 DERVIED" << endl; } }; DerClass myClass; ((BaseClass)myClass).Method1(); myClass.Method1(); Method 1 BASE Method 1 DERVIED

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  • Extension methods on a static object

    - by Max Malygin
    I know (or so I hear) that writing extension methods for a single stand alone .net class (not an implementation of IEnumerable) is potential code smell. However, for the sake of making the life easier I need to attach a method to the ConfigurationManager class in asp.net. It's a static object so this won't work: public static List<string> GetSupportedDomains(this ConfigurationManager manager) { //the manager needs to be static. } So the question is - is it possible to write an extension method for a static class in .net?

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  • Is correct name enough to make it happen?

    - by Knowing me knowing you
    Guys, I've just dipped in to limits.h by MS. I tried to check what's the return type for max() fnc and to my surprise I see something like this: // TEMPLATE CLASS numeric_limits template<class _Ty> class numeric_limits : public _Num_base { // numeric limits for arbitrary type _Ty (say little or nothing) public: static _Ty (__CRTDECL min)() _THROW0() { // return minimum value return (_Ty(0)); } static _Ty (__CRTDECL max)() _THROW0() { // return maximum value return (_Ty(0));//EXACTLY THE SAME WHAT IN min<<------------------ } //... other stuff }; so how is it possiple that in both min and max return does exactly the same? So does it mean if I would write makeSanwich() return (_Ty(0)) it would make a sandwich for me? How is it possible that having this same code just fnc names different we are getting different results?

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  • Programming to interfaces while mapping with Fluent NHibernate.

    - by Lucious
    Fluent Mapping I Have the following scenario public class CustomerMap : ClassMap { public CustomerMap() { Table("Customer"); Id(c = c.Id); Map(c = c.Name); HasMany(c = c.Orders); } } public class OrderMap : ClassMap<IOrder> { public OrderMap() { Table("Orders"); References(o => o.Customer).Access.; Id(o => o.Id); Map(o => o.DateCreated); } } Problems When schema exported the order table has two columns ICustomer_Id,Customer_Id. refers to an unmapped class Order exception Can you please help me out?

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  • What is the definition of a Service object ?

    - by Maskime
    I've been working a lot with PHP. But recently i was sent on a work wich use Java. In PHP i used to do a lot of Singleton object but this pattern has not the same signification in Java that it has in PHP. So i wanted to go for an utility class (a class with static method) but my chief doesn't like this kind of classes and ask me to go for services object. So my guess was that a service object is just a class with a constructor that implement some public methods... Am i right ?

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  • How to instantiate objects of classes that have dependencies injected?

    - by chester89
    Let's say I have some class with dependency injected: public class SomeBusinessCaller { ILogger logger; public SomeBusinessCaller(ILogger logger) { this.logger = logger; } } My question is, how do I instantiate an object of that class? Let's say I have an implementation for this, called AppLogger. After I say ObjectFactory.For<ILogger>().Use<AppLogger>(); how do I call constructor of SomeBusinessCaller? Am I calling SomeBusinessCaller caller = ObjectFactory.GetInstance<SomeBusinessCaller>(); or there is a different strategy for that?

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  • Problems with ActiveRecord assoc

    - by ciss
    Hello again, so i write my e-commerce shop cms and have some strange error: ActiveRecord::StatementInvalid: Mysql::Error: Unknown column 'id' in 'where clause': DELETE FROM `properties` WHERE `id` = NULL so, i have three models Items: class Item < ActiveRecord::Base has_many :properties, :dependent => :destroy has_many :types, :through => :property end Type: class Type < ActiveRecord::Base has_many :properties, :dependent => :destroy end Properties: class Property < ActiveRecord::Base belongs_to :item belongs_to :type end So, all is okay, but when i try to item.destroy() i have error =( This is my test code: test "should destroy associated properties" do item = Item.create(:name => "Jeans") type = Type.create(:key => "color") property = Property.new property.item = item property.type = type property.save item.destroy() end

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  • Sharing base object with inheritance

    - by max
    I have class Base. I'd like to extend its functionality in a class Derived. I was planning to write: class Derived(Base): def __init__(self, base_arg1, base_arg2, derived_arg1, derived_arg2): super().__init__(base_arg1, base_arg2) # ... def derived_method1(self): # ... Sometimes I already have a Base instance, and I want to create a Derived instance based on it, i.e., a Derived instance that shares the Base object (doesn't re-create it from scratch). I thought I could write a static method to do that: b = Base(arg1, arg2) # very large object, expensive to create or copy d = Derived.from_base(b, derived_arg1, derived_arg2) # reuses existing b object but it seems impossible. Either I'm missing a way to make this work, or (more likely) I'm missing a very big reason why it can't be allowed to work. Can someone explain which one it is? [Of course, if I used composition rather than inheritance, this would all be easy to do. But I was hoping to avoid the delegation of all the Base methods to Derived through __getattr__.]

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  • 'Caching' a large table in ASP.NET

    - by TheNewGuy
    I understand that each page refresh, especially in 'AjaxLand', causes my back-end/code-behind class to be called from scratch... This is a problem because my class (which is a member object in System.Web.UI.Page) contains A LOT of data that it sources from a database. So now every page refresh in AjaxLand is causing me to making large backend DB calls, rather than just to reuse a class object from memory. Any fix for this? Is this where session variables come into play? Are session variables the only option I have to retain an object in memory that is linked to a single-user and a single-session instance?

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  • Global Import/using Aliasing in .NET

    - by Josh Stodola
    Using import aliasing in a single class, we can reference class library namespaces by assigning our own custom alias like this: ' VB Imports Db = Company.Lib.Data.Objects // C# using Db = Company.Lib.Data.Objects; And then we are able to reference the classes inside of Company.Lib.Data.Objects by using the Db alias that we assigned. Is it possible to do this at the global level so that the alias is applied to the entire solution instead of the given file? Currently, we are working with web applications, so I was hoping we could add something to web.config, but I am also interested in whether or not this is possible with windows forms, console apps, and/or class libraries.

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  • Why are Objective-C instance variables declared in an interface?

    - by Chase
    I'm just getting into Objective-C (Java is my primary OO language). Defining an object's instance variables in the interface instead of the class seems strange. I'm used to an interface being a public API definition with nothing besides method signatures (not counting constants here). Is there some reason that state is defined in an interface (even if it is private) and behaviour is defined in a class. It just seems odd that since objects are state+behavior that the definition would be split into two separate places. Is it a design benefit is some way? A pain in the rear issue that you are just forced to deal with in Objective-C? A non-issue, just different? Any background on why it's done this way? Or can you put object state in a class and I just haven't hit that part in my book yet?

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  • app engine's back referencing is too slow. How can I make it faster?

    - by Ray Yun
    Google app engine has smart feature named back references and I usually iterate them where the traditional SQL's computed column need to be used. Just imagine that need to accumulate specific force's total hp. class Force(db.Model): hp = db.IntegerProperty() class UnitGroup(db.Model): force = db.ReferenceProperty(reference_class=Force,collection_name="groups") hp = db.IntegerProperty() class Unit(db.Model): group = db.ReferenceProperty(reference_class=UnitGroup,collection_name="units") hp = db.IntegerProperty() When I code like following, it was horribly slow (almost 3s) with 20 forces with single group - single unit. (I guess back-referencing force reload sub entities. Am I right?) def get_hp(self): hp = 0 for group in self.groups: group_hp = 0 for unit in group.units: group_hp += unit.hp hp += group_hp return hp How can I optimize this code? Please consider that there are more properties should be computed for each force/unit-groups and I don't want to save these collective properties to each entities. :)

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  • Remove a DIV using a link

    - by GSTAR
    HTML: <div class="row"> <!-- content --> <a href="#" class="remove">remove</a> </div> JS: $('.remove').click(function(){ $(this).parent().remove(); return false; }); If there is only one DIV it works OK but when there are multiple DIVS (class="row") it won't do anything. No errors are returned either. EDIT: I should add that by default there is only one div - additional divs get dynamically created using a jQuery clone function - perhaps this is why it won't recognise the new link/div?

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  • Force result for empty() test on an object

    - by hsz
    Hello ! Simple class for example: class Foo { protected $_bar; public function setBar( $value ) { $this->_bar = $value; } } And here is the question: $obj = new Foo(); var_dump( empty( $obj ) ); // true $obj->setBar( 'foobar' ); var_dump( empty( $obj ) ); // false Is it possible to change class's behaviour with testing it with empty() function so it will returns true when object is not filled with data ? I know about magic function __isset( $name ) but it is called only when we test specific field like: empty( $obj->someField ); but not when test whole object.

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  • New records added to DataGridView aren't displayed

    - by Ross
    I have a custom Order class, groups of which are stored in List<Order> and a DataGridView. I think the problem is in my implementation so here's how I'm using it: In the form enclosing DataGridView (as OrdersDataGrid): public partial class MainForm : Form { public static List<Order> Orders; public MainForm() { // code to populate Orders with values, otherwise sets Orders to new List<Order>(); OrdersDataGrid.DataSource = Orders; } Then in another form that adds an Order: // Save event public void Save(object sender, EventArgs e) { Order order = BuildOrder(); // method that constructs an order object from form data MainForm.Orders.Add(order); } From what I can tell from the console this is added successfully. I thought the DataGrid would be updated automatically after this since Orders has changed - is there something I'm missing? The DataGrid accepts the class since it generates columns from the members.

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  • Why can't I enforce derived classes to have parameterless constructors?

    - by FrisbeeBen
    I am trying to do the following: public class foo<T> where T : bar, new() { public foo() { _t = new T(); } private T _t; } public abstract class bar { public abstract void someMethod(); // Some implementation } public class baz : bar { public overide someMethod(){//Implementation} } And I am attempting to use it as follows: foo<baz> fooObject = new foo<baz>(); And I get an error explaining that 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. I fully understand why this must be, and also understand that I could pass a pre-initialized object of type 'T' in as a constructor argument to avoid having to 'new' it, but is there any way around this? any way to enforce classes that derive from 'bar' to supply parameterless constructors?

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  • Question on Virtual Methods

    - by bobber205
    IF both methods are declared as virtual, shouldn't both instances of Method1() that are called be the derived class's Method1()? I am seeing BASE then DERIVED called each time. I am doing some review for an interview and I want to make sure I have this straight. xD class BaseClass { public: virtual void Method1() { cout << "Method 1 BASE" << endl; } }; class DerClass: public BaseClass { public: virtual void Method1() { cout << "Method 1 DERVIED" << endl; } }; DerClass myClass; ((BaseClass)myClass).Method1(); myClass.Method1(); Method 1 BASE Method 1 DERVIED

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  • Passing User Data with SetTimer

    - by GJ
    I am calling SetTimer in a function of a Class. SetTimer(NULL, 0, 10000, (TIMERPROC) TimerCallBack); Where TimerCallBack is: static VOID CALLBACK TimerCallBack(HWND, UINT, UINT, DWORD) Now my need is to call one of the method of class which initiated timer, since TimerCallBack is static it has no access to the class object anymore. I cant find any way to pass object pointer along with the SetTimer so that I can receive it back on Callback function. Is there any other way to achieve this, if its not supported using SetTimer then which other way I can implement this.

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