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  • Partial overriding in Java (or dynamic overriding while overloading)

    - by Lie Ryan
    If I have a parent-child that defines some method .foo() like this: class Parent { public void foo(Parent arg) { System.out.println("foo in Function"); } } class Child extends Parent { public void foo(Child arg) { System.out.println("foo in ChildFunction"); } } When I called them like this: Child f = new Child(); Parent g = f; f.foo(new Parent()); f.foo(new Child()); g.foo(new Parent()); g.foo(new Child()); the output is: foo in Parent foo in Child foo in Parent foo in Parent But, I want this output: foo in Parent foo in Child foo in Parent foo in Child I have a Child class that extends Parent class. In the Child class, I want to "partially override" the Parent's foo(), that is, if the argument arg's type is Child then Child's foo() is called instead of Parent's foo(). That works Ok when I called f.foo(...) as a Child; but if I refer to it from its Parent alias like in g.foo(...) then the Parent's foo(..) get called irrespective of the type of arg. As I understand it, what I'm expecting doesn't happen because method overloading in Java is early binding (i.e. resolved statically at compile time) while method overriding is late binding (i.e. resolved dynamically at compile time) and since I defined a function with a technically different argument type, I'm technically overloading the Parent's class definition with a distinct definition, not overriding it. But what I want to do is conceptually "partially overriding" when .foo()'s argument is a subclass of the parent's foo()'s argument. I know I can define a bucket override foo(Parent arg) in Child that checks whether arg's actual type is Parent or Child and pass it properly, but if I have twenty Child, that would be lots of duplication of type-unsafe code. In my actual code, Parent is an abstract class named "Function" that simply throws NotImplementedException(). The children includes "Polynomial", "Logarithmic", etc and .foo() includes things like Child.add(Child), Child.intersectionsWith(Child), etc. Not all combination of Child.foo(OtherChild) are solvable and in fact not even all Child.foo(Child) is solvable. So I'm best left with defining everything undefined (i.e. throwing NotImplementedException) then defines only those that can be defined. So the question is: Is there any way to override only part the parent's foo()? Or is there a better way to do what I want to do?

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  • Overriding Equals method in Structs

    - by devoured elysium
    I've looked for overriding guidelines for structs, but all I can find is for classes. At first I thought I wouldn't have to check to see if the passed object was null, as structs are value types and can't be null. But now that I come to think of it, as equals signature is public bool Equals(object obj) it seems there is nothing preventing the user of my struct to be trying to compare it with an arbitrary reference type. My second point concerns the casting I (think I) have to make before I compare my private fields in my struct. How am I supposed to cast the object to my struct's type? C#'s as keyword seems only suitable for reference types. Thanks

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  • overriding protected internal with protected!

    - by Asad Butt
    This is an extension for this question asked an hour ago. We cannot modify the access modifiers, when overriding a virtual method in derived class. Consider Control class in System.Web.UI namespace public class Control : IComponent, IDisposable,... { protected internal virtual void CreateChildControls() { } . . } Now Consider This public class someClass : System.Web.UI.Control { // This should not compile but it does protected override void CreateChildControls() { } // This should compile but it does not protected internal override void CreateChildControls() { } } can any body explain this ? Thanks

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  • Why does a looser specification in an overriding method compile after the exception specification fo

    - by Everyone
    The code below has an overridden method with a looser exception specification as compared to the method being overridden. //AnotherMain.java public class AnotherMain { public void dummyMethod( String args[] ) throws IOException{ throw new IOException(); } } //SubAnotherMain.java public class SubAnotherMain extends AnotherMain{ @Override public void dummyMethod( String[] args ) throws Exception { // To get this to compile, change the above - throws IOException, Exception super.dummyMethod(args); throw new Exception("This will not compile unless the exception specification has IOException too"); } } Afaik, the overriding method should not compile at all as the looser specification might break substitutability. Why does it compile after the original exception specification is included in the override? What have I misunderstood?

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  • Static and overriding in Java

    - by Abhishek Jain
    public class B { static int i =1; public static int multiply(int a,int b) { return i; } public int multiply1(int a,int b) { return i; } public static void main(String args[]) { B b = new A(); System.out.println(b.multiply(5,2)); System.out.println(b.multiply1(5,2)); } } class A extends B { static int i =8; public static int multiply(int a,int b) { return 5*i; } public int multiply1(int a,int b) { return 5*i; } } Output: 1 40 Why is it so? Please explain.

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  • Few Basic Questions in Overriding

    - by Dahlia
    I have few problems with my basic and would be thankful if someone can clear this. What does it mean when I say base *b = new derived; Why would one go for this? We very well separately can create objects for class base and class derived and then call the functions accordingly. I know that this base *b = new derived; is called as Object Slicing but why and when would one go for this? I know why it is not advisable to convert the base class object to derived class object (because base class is not aware of the derived class members and methods). I even read in other StackOverflow threads that if this is gonna be the case then we have to change/re-visit our design. I understand all that, however, I am just curious, Is there any way to do this? class base { public: void f(){cout << "In Base";} }; class derived:public base { public: void f(){cout << "In Derived";} }; int _tmain(int argc, _TCHAR* argv[]) { base b1, b2; derived d1, d2; b2 = d1; d2 = reinterpret_cast<derived*>(b1); //gives error C2440 b1.f(); // Prints In Base d1.f(); // Prints In Derived b2.f(); // Prints In Base d1.base::f(); //Prints In Base d2.f(); getch(); return 0; } In case of my above example, is there any way I could call the base class f() using derived class object? I used d1.base()::f() I just want to know if there any way without using scope resolution operator? Thanks a lot for your time in helping me out!

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  • Overriding Built-in Classes (Python)

    - by Yipeng
    How can I view and override the full definition for built in classes? I have seen the library docs but am looking for something more. For e.g. is it possible to override the Array Class such that the base index starts from 1 instead of 0, or to override .sort() of list to a sorting algorithm of my own liking?

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  • overriding implemented base class methods

    - by user793468
    I read somewhere that the chain of inheritance breaks when you alter a behavior from derived class. What does "altering a behavior" mean here? Is overriding an already implemented method in base class considered as "altering behavior"? Or, does the author mean altering method signatures and the output? Also, I ready Duplicating code is not a good practice, and its a maintenance nightmare. Again, does overriding an already implemented method in base class considered "Duplicating code"? If not, what would be considered as "Duplicating code"? I

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  • Overriding component behavior

    - by deft_code
    I was thinking of how to implement overriding of behaviors in a component based entity system. A concrete example, an entity has a heath component that can be damaged, healed, killed etc. The entity also has an armor component that limits the amount of damage a character receives. Has anyone implemented behaviors like this in a component based system before? How did you do it? If no one has ever done this before why do you think that is. Is there anything particularly wrong headed about overriding component behaviors? Below is rough sketch up of how I imagine it would work. Components in an entity are ordered. Those at the front get a chance to service an interface first. I don't detail how that is done, just assume it uses evil dynamic_casts (it doesn't but the end effect is the same without the need for RTTI). class IHealth { public: float get_health( void ) const = 0; void do_damage( float amount ) = 0; }; class Health : public Component, public IHealth { public: void do_damage( float amount ) { m_damage -= amount; } private: float m_health; }; class Armor : public Component, public IHealth { public: float get_health( void ) const { return next<IHealth>().get_health(); } void do_damage( float amount ) { next<IHealth>().do_damage( amount / 2 ); } }; entity.add( new Health( 100 ) ); entity.add( new Armor() ); assert( entity.get<IHealth>().get_health() == 100 ); entity.get<IHealth>().do_damage( 10 ); assert( entity.get<IHealth>().get_health() == 95 ); Is there anything particularly naive about the way I'm proposing to do this?

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  • Customisation / overriding of the Envelop ecs files

    - by Dheeraj Kumar M
    There are few usecases where the requirement is to customise the envelop information (Interchange/Group ecs file). Such scenarios might be required to be used for only few of the customers. Hence, in addition to the default seeded envelop definitions, it also required to upload the customised definitions. Here is the steps for achieving the same. 1. Create only the Interchange ecs and save 2. Create only the group ecs and save 3. Use the same in B2B 1. Create only the Interchange ecs and save :       Open the document editor and select the required version and doctype. During creating new ecs, ensure to select the checkbox for insert envelop.       Once created, delete the group and transactionset nodes and retain only the Interchange ecs nodes, including both header and trailer. Save this file. 2. Create only the group ecs and save       After creating the ecs file as mentioned in steps of Interchange creation, delete the Interchange and transactionset nodes and retain only the group ecs nodes, including both header and trailer. Save this file. 3. Use the same in B2B       These newly created ecs can be used in B2B by 2 ways.              a. By overriding at the trading partner Level:              This will be very useful when the configuration is complete and then need to incorporate the customisation. In this case, just select the Trading partner - document - select the document which need to be customised.              Upload the newly created Interchange and group ECS files under the Interchange and group tabs respectively and re-deply the associated agreement.              The advantage of this approach is              - Flexibility to add customised envelop definitions to the partners              - Save the re-work of design time effort.              b. By adding another document definition in Administration - document screen:              This scenario can be used if there is no configuration done at the trading partner level. Create the required document revision and overtide the Interchange and group ECS files under the Interchange and group tabs respectively. Add the document in Trading partner - document. Create and deploy the agreements

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  • Generic overriding tells me this is the same function. Not agree.

    - by serhio
    base class: Class List(Of T) Function Contains(ByVal value As T) As Boolean derived class: Class Bar : List(Of Exception) ' Exception type as example ' Function Contains(Of U)(ByVal value As U) As Boolean compiler tells me that that two are the same, so I need to declare Overloads/new this second function. But I want use U to differentiate the type (one logic) like NullReferenceException, ArgumentNull Exception, etc. but want to leave the base function(no differentiation by type - other logic) as well.

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  • C# Hiding, overriding and calling function from base class.

    - by Lukasz Lysik
    I'm learning C# and I encountered the following problem. I have two classes: base and derived: class MyBase { public void MyMethod() { Console.WriteLine("MyBase::MyMethod()"); } } class MyDerived: MyBase { public void MyMethod() { Console.WriteLine("MyDerived::MyMethod()"); } } For now, without virtual and override key words. When I compile this I get the warning (which is of course expected) that I try to hide MyMethod from MyBase class. What I want to do is to call the method from the base class having an instance of derived class. I do this like this: MyDerived myDerived = new MyDerived(); ((MyBase)myDerived).MyMethod(); It works fine when I do not specify any virtual, etc. keywords in the methods. I tried to put combination of the keywords and I got the following results: | MyBase::MyMethod | MyDerived::MyMethod | Result printed on the console | | -----------------|---------------------|-------------------------------| | - | - | MyBase::MyMethod() | | - | new | MyBase::MyMethod() | | virtual | new | MyBase::MyMethod() | | virtual | override | MyDerived::MyMethod() | I hope the table is clear to you. I have two questions: Is it the correct way to call the function from the base class (((MyBase)myDerived).MyMethod();)? I know about base keyword, but it can be called only from the inside of the derived class. Is it right? Why in the last case (with virtual and override modifiers) the method which was called came from the derived class? Would you please explain that?

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  • ATI graphics card overriding onboard Intel graphics

    - by Patrick
    I have an ATI graphics card with an AGP connection and a DVI port, and an Intel graphics processor on the motherboard with a VGA port. I have two monitors. When the graphics card is unplugged, I get this from lspci: 00:00.0 Host bridge: Intel Corporation 82G33/G31/P35/P31 Express DRAM Controller (rev 10) 00:02.0 VGA compatible controller: Intel Corporation 82G33/G31 Express Integrated Graphics Controller (rev 10) When it is attached, I get this: 00:00.0 Host bridge: Intel Corporation 82G33/G31/P35/P31 Express DRAM Controller (rev 10) 01:00.0 VGA compatible controller: ATI Technologies Inc RV380 [Radeon X600 (PCIE)] 01:00.1 Display controller: ATI Technologies Inc RV380 [Radeon X600] Note the absence of 00:02.0 - this is apparently causing the VGA monitor to say "No Signal" and the only the DVI display to show up in the list. I checked for problems in xorg.conf... there isn't one. I have no idea how to build one.

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  • Overriding the Pager rendering in Orchard

    - by Bertrand Le Roy
    The Pager shape that is used in Orchard to render pagination is one of those shapes that are built in code rather than in a Razor template. This can make it a little more confusing to override, but nothing is impossible. If we look at the Pager method in CoreShapes, here is what we see: [Shape] public IHtmlString Pager(dynamic Shape, dynamic Display) { Shape.Metadata.Alternates.Clear(); Shape.Metadata.Type = "Pager_Links"; return Display(Shape); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The Shape attribute signals a shape method. All it does is remove all alternates that may exist and replace the type of the shape with “Pager_Links”. In turn, this shape method is rather large and complicated, but it renders as a set of smaller shapes: a List with a “pager” class, and under that Pager_First, Pager_Previous, Pager_Gap, for each page a Pager_Link or a Pager_Current, then Pager_Gap, Pager_Next and Pager_Last. Each of these shapes can be displayed or not depending on the properties of the pager. Each can also be overridden with a Razor template. This can be done by dropping a file into the Views folder of your theme. For example, if you want the current page to appear between square braces, you could drop this Pager-CurrentPage.cshtml into your views folder: <span>[@Model.Value]</span> This overrides the original shape method, which was this: [Shape] public IHtmlString Pager_CurrentPage(HtmlHelper Html, dynamic Display, object Value) { var tagBuilder = new TagBuilder("span"); tagBuilder.InnerHtml = Html.Encode(Value is string ? (string)Value : Display(Value)); return MvcHtmlString.Create(tagBuilder.ToString()); } And here is what it would look like: Now what if we want to completely hide the pager if there is only one page? Well, the easiest way to do that is to override the Pager shape by dropping the following into the Views folder of your theme: @{ if (Model.TotalItemCount > Model.PageSize) { Model.Metadata.Alternates.Clear(); Model.Metadata.Type = "Pager_Links"; @Display(Model) } } And that’s it. The code in this template just adds a check for the number of items to display (in a template, Model is the shape) and only displays the Pager_Links shape if it knows that there’s going to be more than one page.

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  • Customizing / overriding ComboBox (2 replies)

    Hi, I would override a Windows.Forms.Combobox to have a MyObjectCollection instead of a ObjectCollection as Items property. I've try writing this code, but it seems that items are stored somewhere else (not in Items property). I can add items to collection but when I try to select an item from the combobox (at runtime) an exception tells me that there is no such element in Items (litterally it tel...

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  • nVidia Settings: Overriding anti-aliasing causes delay

    - by Kalle Elmér
    I'm using Google Sketchup on ubuntu 12.04 with Wine 1.4. It works flawlessly out of the box, but anti-aliasing is causing some problems. I can override anti-aliasing settings using the nVidia X Server Settings utility, which results in a great-looking image. However, the view doesn't seem to update properly. It's a bit hard to explain, but if I do something (e.g. zooming) the changes won't appear in the view until I take another action. in other words, there seems to be a delay of one "action". Take this example. The mouse wheel is moved one notch to zoom in one step. Nothing happens. An object is selected by clicking. The new zoom is rendered but the selection box doesn't appear. An empty area is clicked. The selection box appears. Is there something that I can do to solve the problem? Could I force the GPU to redraw that view with a certain interval, or is there some other solution? I really like anti-aliasing, but it's hard to use when drawing stuff.

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  • Customizing / overriding ComboBox (2 replies)

    Hi, I would override a Windows.Forms.Combobox to have a MyObjectCollection instead of a ObjectCollection as Items property. I've try writing this code, but it seems that items are stored somewhere else (not in Items property). I can add items to collection but when I try to select an item from the combobox (at runtime) an exception tells me that there is no such element in Items (litterally it tel...

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  • How to set MANPATH without overriding defaults?

    - by balki
    I have added extra directories to $PATH by exporting PATH=/my/dirs:$PATH But I am not sure if I should do the same to MANPATH. Because default MANPATH is empty yet man command works. I found a command called manpath and its manual says If $MANPATH is set, manpath will simply display its contents and issue a warning.. Does this mean setting MANPATH is not the right way to add directories for man command to search for manual pages?

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  • QML: Overriding a signal handler from other element

    - by user3490458
    Is it possible to override an elements action (eg onTriggered() of a Timer) from within the onClick() of a button? Something like so- Button { id: centerBtn objectName: "button" onClicked: { delaytimer.running = true; delayTimer.onTriggered {}; // override here } Timer { id: delaytimer interval: 1000 running: false repeat: false onTriggered: //something implemented here } }

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  • Overriding a function in an instance [on hold]

    - by MustSeeMelons
    Is it possible to override a function by instance? For example, A and B are both instances of MyClass. I have a function Action(), and I want to specify its implementation for each instance. To be more specific - the class is a Button, and the function is Clicked(). I don't want to derive a class 5 times to create 5 different button actions. Was thinking of something like it's handled in Java Swing: create a button, add code for the button press and use the button.

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  • Inheritance security rules violated while overriding member - SecurityRuleSet.Level2

    - by Page Brooks
    I have a class that inherits from Exception. In .NET 4, I started receiving a runtime error: Inheritance security rules violated while overriding member: MyBusinessException.GetObjectData(System.Runtime.Serialization.SerializationInfo, System.Runtime.Serialization.StreamingContext)'. Security accessibility of the overriding method must match the security accessibility of the method being overriden. I think the issue is caused by the fact that I am overriding GetObjectData. I know one answer for resolving the issue is to set the SecurityRuleSet: [assembly: SecurityRules(SecurityRuleSet.Level1)] This is not an acceptable answer, I'd like to know how to fix the issue without having to relax the default security rules in .NET 4.

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  • Static methods and their overriding

    - by abson
    Java doesn't allow overriding of static methods but, class stat13 { static void show() { System.out.println("Static in base"); } public static void main(String[] ar) { new next().show(); } } class next extends stat13 { static void show() { System.out.println("Static in derived"); } } is not overriding done here?

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  • Wildcard 'A' record overriding CNAME record

    - by user116890
    I have a Wildcard * A record for self-registration of subdomains by users on our web app. All works fine. I now need to set up an alias for support.mydomain.com to point to mydomain.freshdesk.com. I created a CNAME record as per instructions however it appears my Wildcard A record is overriding the CNAME entry. Any thoughts on how to resolve this? I need the wildcard so creating an A record for each user subdomain is not possible. Thanks.

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