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  • Objective-C inheritance; calling overriden method from superclass?

    - by anshuchimala
    Hello, I have an Objective-C class that has a method that is meant to be overridden, which is uses in a different method. Something like this: @interface BaseClass - (id)overrideMe; - (void)doAwesomeThings; @end @implementation BaseClass - (id)overrideMe { [self doesNotRecognizeSelector:_cmd]; return nil; } - (void)doAwesomeThings { id stuff = [self overrideMe]; /* do stuff */ } @end @interface SubClass : BaseClass @end @implementation SubClass - (id)overrideMe { /* Actually do things */ return <something>; } @end However, when I create a SubClass and try to use it, it still calls overrideMe on the BaseClass and crashes due to doesNotRecognizeSelector:. (I'm not doing a [super overrideMe] or anything stupid like that). Is there a way to get BaseClass to call the overridden overrideMe?

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  • Javascript: Inherit method from base class and return the subclass's private variable

    - by marisbest2
    I have the following BaseClass defined: function BaseClass (arg1,arg2,arg3) { //constructor code here then - var privateVar = 7500; this.getPrivateVar = function() { return privateVar; }; } I want to have the following subclass which allows changing privateVar like so: function SubClass (arg1,arg2,arg3,privateVar) { //constructor code here then - var privateVar = privateVar; } SubClass.prototype = new BaseClass(); Now I want SubClass to inherit the getPrivateVar method. However, when I try this, it always returns 7500 which is the value in the BaseClass and not the value of privateVar. In other words, is it possible to inherit a BaseClass's public methods but have any references in them refer to the SubClass's properties? And how would I do that?

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  • Class Decorators, Inheritence, super(), and maximum recursion

    - by jamstooks
    I'm trying to figure out how to use decorators on subclasses that use super(). Since my class decorator creates another subclass a decorated class seems to prevent the use of super() when it changes the className passed to super(className, self). Below is an example: def class_decorator(cls): class _DecoratedClass(cls): def __init__(self): return super(_DecoratedClass, self).__init__() return _DecoratedClass class BaseClass(object): def __init__(self): print "class: %s" % self.__class__.__name__ def print_class(self): print "class: %s" % self.__class__.__name__ bc = BaseClass().print_class() class SubClass(BaseClass): def print_class(self): super(SubClass, self).print_class() sc = SubClass().print_class() @class_decorator class SubClassAgain(BaseClass): def print_class(self): super(SubClassAgain, self).print_class() sca = SubClassAgain() # sca.print_class() # Uncomment for maximum recursion The output should be: class: BaseClass class: BaseClass class: SubClass class: SubClass class: _DecoratedClass Traceback (most recent call last): File "class_decorator_super.py", line 34, in <module> sca.print_class() File "class_decorator_super.py", line 31, in print_class super(SubClassAgain, self).print_class() ... ... RuntimeError: maximum recursion depth exceeded while calling a Python object Does anyone know of a way to not break a subclass that uses super() when using a decorator? Ideally I'd like to reuse a class from time to time and simply decorate it w/out breaking it.

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  • LockMode With Subclasses

    - by Lester
    I'm using Fluent Nhibernate with the following query on DerivedClass which extends BaseClass: var query = Session.CreateCriteria<DerivedClass>().SetLockMode(LockMode.Upgrade) What I want is the lock hints (updlock, rowlock) to be applied to both DerivedClass and BaseClass, but the generated SQL only applies the lock hints to DerivedClass: SELECT * FROM DerivedClass this_ with (updlock, rowlock) inner join [BaseClass] this_1_ on this_.Id=this_1_.Id WHERE ... This is the same situation described in http://opensource.atlassian.com/projects/hibernate/browse/HHH-2392 If anyone could point me in the right direction it would be much appreciated.

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  • Getting PDT code completion to recognise runtime return types from base class?

    - by Keith Humm
    Hi guys, I've got an abstract base class: abstract class BaseClass { /** * @return CLASSNAME */ public function fluent() { // do stuff return $this; } } Generally, i would put BaseClass where CLASSNAME is and all would be fine, PDT would pick up the phpdoc return type and happily autocomplete. Until, that is, I subclass BaseClass and add additional methods, and code compete on an instance of the derived class. PDT will only recognise the methods from BaseClass and not those from the derived class. What I need is something like @return self or @return this. Does PDT have such functionality? Or is there an alternate trick without having to declare these methods in every derived class?

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  • Is this a safe/valid hash method implementation?

    - by Sean
    I have a set of classes to represent some objects loaded from a database. There are a couple variations of these objects, so I have a common base class and two subclasses to represent the differences. One of the key fields they have in common is an id field. Unfortunately, the id of an object is not unique across all variations, but within a single variation. What I mean is, a single object of type A could have an id between, say, 0 and 1,000,000. An object of type B could have an id between, 25,000 and 1,025,000. This means there's some overlap of id numbers. The objects are just variations of the same kind of thing, though, so I want to think of them as such in my code. (They were assigned ids from different sets for legacy reasons.) So I have classes like this: @class BaseClass @class TypeAClass : BaseClass @class TypeBClass : BaseClass BaseClass has a method (NSNumber *)objectId. However instances of TypeA and TypeB could have overlapping ids as discussed above, so when it comes to equality and putting these into sets, I cannot just use the id alone to check it. The unique key of these instances is, essentially, (class + objectId). So I figured that I could do this by making the following hash function on the BaseClass: -(NSUInteger)hash { return (NSUInteger)[self class] ^ [self.objectId hash]; } I also implemented isEqual like so: - (BOOL)isEqual:(id)object { return (self == object) || ([object class] == [self class] && [self.objectId isEqual:[object objectId]]); } This seems to be working, but I guess I'm just asking here to make sure I'm not overlooking something - especially with the generation of the hash by using the class pointer in that way. Is this safe or is there a better way to do this?

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  • Google App Engine : PolyModel + SelfReferenceProperty

    - by rvandervort
    Is a PolyModel-based class able to be used as a SelfReferenceProperty ? I have the below code : class BaseClass(polymodel.PolyModel): attribute1 = db.IntegerProperty() attribute2 = db.StringProperty() class ParentClass(BaseClass): attribute3 = db.StringProperty() class ChildClass(BaseClass): parent = SelfReferenceProperty(collection_name = 'children') p = ParentClass() p.attribute1 = 1 p.attribute2 = "Parent Description" p.attribute3 = "Parent additional data" p.put() c = ChildClass() c.attribute1 = 5 c.attribute2 = "Child Description" c.parent = p.key() c.put() I execute this code and check the datastore via the development server's admin interface. The parent instance is saved to the datastore class = 'BaseClass,ParentClass', but the child is not. There is no error output to the browser (debug is turned on) and nothing in the launcher's log for my app. Is this possible to do ?

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  • Set property with reflection after Fluent Nhibernates automapping has occured?

    - by Marcus
    I have an abstract baseclass with a collection of details IList that is automapped with fnh. After it has been populated with the correct values i would like to set some properties with reflection on the my class that inherits the abstract baseclass. I have tried to accomplish this in the constructor of my abstract baseclass but obviously my Details collection is empty when the occurs so my question is, what is the recommended way of doing this?

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  • virtual keyword in different scenarios

    - by Mahesh
    I figured out 2 different meanings for virtual based on the situation it is being used. If a baseClass has a function defined virtual, then the derivedClass is going to override the function. The baseClass::~baseClass() should be defined virtual, if there is any class derived from it. Here it means, the derived class destruction first takes place followed by base class destruction. Are there any other situations where virtual hold a different meaning ?

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  • LINQ group one type of item

    - by Nelson
    I have a List that has various derived classes. I may have something like this: List<BaseClass> list = new List<BaseClass>() { new Class1(), new Class2(1), new Class3(), new Class2(2), new Class4() }; I am trying to use LINQ to semi-sort the list so that the natural order is maintained EXCEPT for Class2. All Class2 instances should be grouped together at the place that the first Class2 occurs. Here is what the output should be like: List<BaseClass> list = new List<BaseClass>() { new Class1(), new Class2(1), new Class2(2), new Class3(), new Class4() }; I can't for the life of me figure out how to do this...

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  • Safe to cast pointer to a forward-declared class to its true base class in C++?

    - by Matt DiMeo
    In one header file I have: #include "BaseClass.h" // a forward declaration of DerivedClass, which extends class BaseClass. class DerivedClass ; class Foo { DerivedClass *derived ; void someMethod() { // this is the cast I'm worried about. ((BaseClass*)derived)->baseClassMethod() ; } }; Now, DerivedClass is (in its own header file) derived from BaseClass, but the compiler doesn't know that at the time it's reading the definition above for class Foo. However, Foo refers to DerivedClass pointers and DerivedClass refers to Foo pointers, so they can't both know each other's declaration. First question is whether it's safe (according to C++ spec, not in any given compiler) to cast a derived class pointer to its base class pointer type in the absence of a full definition of the derived class. Second question is whether there's a better approach. I'm aware I could move someMethod()'s body out of the class definition, but in this case it's important that it be inlined (part of an actual, measured hotspot - I'm not guessing).

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  • LINQ - group specific types of classes

    - by Nelson
    This question is similar to http://stackoverflow.com/questions/2835192/linq-group-one-type-of-item but handled in a more generic way. I have a List that has various derived classes. I may have something like this: List<BaseClass> list = new List<BaseClass>() { new Class1(1), new Class2(1), new Class1(2), new Class3(1), new Class2(2), new Class4(1), new Class3(2) }; I am trying to use LINQ to semi-sort the list so that the natural order is maintained EXCEPT for certain classes which have base.GroupThisType == true. All classes with GroupThisType should be grouped together at the place that the first class of the same type occurs. Here is what the output should be like: List<BaseClass> list = new List<BaseClass>() { new Class1(1), new Class1(2), new Class2(1), new Class3(1), new Class3(2) new Class2(2), new Class4(1), };

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  • Template Child Class Overriding a Parent Class's Virtual Function

    - by user334066
    The below code compiles with gcc v4.3.3 and the templated child class seems to be overriding a virtual function in the parent, but doesn't that break the rule that you cannot have a virtual template function? Or is something else happening that I don't understand? class BaseClass { public: virtual void Func(int var) { std::cout<<"Base int "<<var<<std::endl; } virtual void Func(double var) { std::cout<<"Base double "<<var<<std::endl; } }; template <class TT> class TemplateClass : public BaseClass { public: using BaseClass::Func; virtual void Func(TT var) { std::cout<<"Child TT "<<var<<std::endl; } }; int main(int argc, char **argv) { BaseClass a; TemplateClass<int> b; BaseClass *c = new TemplateClass<int>; int intVar = 3; double doubleVar = 5.5; a.Func(intVar); a.Func(doubleVar); b.Func(intVar); b.Func(doubleVar); c->Func(intVar); c->Func(doubleVar); delete c; } This then outputs: Base int 3 Base double 5.5 Child TT 3 Base double 5.5 Child TT 3 Base double 5.5 as I hoped, but I'm not sure why it works.

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  • Needs opinions based on design guidelines .

    - by Abu Hamzah
    i am in the process of desigining my domain model and i know its very hard to suggest without knowledge of domain but what i am asking is how to implement or the best way of implementing the baseclass in my domain model. here are few classes: PartialPerson.cs Facilities.cs Visit.cs EntryPoint.cs etc.... my baseclass looks like this: public abstract class BaseClass { public int InfoId { get; } public int PersonId { get; } } here is what i am confused and need help. how do i implement the above baseclass? in the PartialPerson,Facilities,Visit...

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  • Design pattern to use instead of multiple inheritance

    - by mizipzor
    Coming from a C++ background, Im used to multiple inheritance. I like the feeling of a shotgun squarely aimed at my foot. Nowadays, I work more in C# and Java, where you can only inherit one baseclass but implement any number of interfaces (did I get the terminology right?). For example, lets consider two classes that implement a common interface but different (yet required) baseclasses: public class TypeA : CustomButtonUserControl, IMagician { public void DoMagic() { // ... } } public class TypeB : CustomTextUserControl, IMagician { public void DoMagic() { // ... } } Both classes are UserControls so I cant substitute the base class. Both needs to implement the DoMagic function. My problem now is that both implementations of the function are identical. And I hate copy-and-paste code. The (possible) solutions: I naturally want TypeA and TypeB to share a common baseclass, where I can write that identical function definition just once. However, due to having the limit of just one baseclass, I cant find a place along the hierarchy where it fits. One could also try to implement a sort of composite pattern. Putting the DoMagic function in a separate helper class, but the function here needs (and modifies) quite a lot of internal variables/fields. Sending them all as (reference) parameters would just look bad. My gut tells me that the adapter pattern could have a place here, some class to convert between the two when necessery. But it also feels hacky. I tagged this with language-agnostic since it applies to all languages that use this one-baseclass-many-interfaces approach. Also, please point out if I seem to have misunderstood any of the patterns I named. In C++ I would just make a class with the private fields, that function implementation and put it in the inheritance list. Whats the proper approach in C#/Java and the like?

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  • What is wrong with locking non-static fields? What is the correct way to lock a particular instance?

    - by smartcaveman
    Why is it considered bad practice to lock non-static fields? And, if I am not locking non-static fields, then how do I lock an instance method without locking the method on all other instances of the same or derived class? I wrote an example to make my question more clear. public abstract class BaseClass { private readonly object NonStaticLockObject = new object(); private static readonly object StaticLockObject = new object(); protected void DoThreadSafeAction<T>(Action<T> action) where T: BaseClass { var derived = this as T; if(derived == null) { throw new Exception(); } lock(NonStaticLockObject) { action(derived); } } } public class DerivedClass :BaseClass { private readonly Queue<object> _queue; public void Enqueue(object obj) { DoThreadSafeAction<DerivedClass>(x=>x._queue.Enqueue(obj)); } } If I make the lock on the StaticLockObject, then the DoThreadSafeAction method will be locked for all instances of all classes that derive from BaseClass and that is not what I want. I want to make sure that no other threads can call a method on a particular instance of an object while it is locked.

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  • Detect modification of variable at runtime in C/C++

    - by YuppieNetworking
    Hello, I am developing a library in C++ where users/programmer will extend a class BaseClass that has a method initArray. This method should be implemented by the user/programmer and it should normally initialize all elements of the array m_arr. Here is a snipplet, modified to this example: class BaseClass { public: BaseClass(int n) { m_arr = new double[n]; size = n; }; virtual ~BaseClass(); int size; double* m_arr; virtual int initArray(); }; Sometimes, the user/programmer implements a initArray that does not initialize some elements of m_arr. What I would like is to create a function in my library that checks if initArray did initialize all elements of m_arr. This function should be called by a sanity-check rutine at runtime. My question: is it possible to detect changes on this array? I can only think of initializing the array with some invalid values (like NaN or Inf), call initArray and check that all values have changed. Thanks for your ideas, David

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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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  • How Can I Accept a Generic Class and Use Its Properties / Methods

    - by Blake Blackwell
    I want to create a class that could hold any of a number of same type of classes. For example lets says I have a base class like follows: public class BaseClass { public string MyBaseString { get; set; } } And then I have a few derived classes like this: public class DerivedClass : BaseClass { public MyDerivedClassString { get; set; } } public class DerivedClass2 : BaseClass { public MyDerivedClass2String { get; set; } } Now I would like a class that accepts one of these implementations and does stuff with it. Here is the only thing I can think of, but there must be a better way: public class ClassA { public object MyClass { get; set; } public ClassA (object myClass) { MyClass = myClass; if (object is BaseClass) { //do something } else if (object is DerivedClass) { //do something specific to derived class } else if (object is DerivedClass2) { //do something specific to derived class 2 } } } I'm not sure really what I'm looking for here. Any ideas would be great!

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  • tc rules block traffic from some hosts at network

    - by user139430
    I have a problem I can not solve. The script, which sets the rules for traffic shaping is blocking the traffic from some hosts.If I remove all the rules, then it works. I can not understand why? Here is my script... #!/bin/sh cmdTC=/sbin/tc rateLANDl="60mbit" ceilLANDl="60mbit" rateLANUl="40mbit" ceilLANUl="40mbit" quantLAN="1514" # Nowaday bandwidth limit set to 100mbit. # We devide it with 60mbit download and 40mbit upload bandthes. rateHiDl="30mbit" ceilHiDl="60mbit" rateHiUl="20mbit" ceilHiUl="40mbit" quantHi="1514" rateLoDl="30mbit" ceilLoDl="60mbit" rateLoUl="20mbit" ceilLoUl="40mbit" quantLo="1514" devNIF=eth0 devFIF=ifb0 modprobe ifb ip link set $devFIF up 2>/dev/null #exit 0 ################################################################################################ # Remove discuiplines from network and fake interfaces ################################################################################################ $cmdTC qdisc del dev $devNIF root 2>/dev/null $cmdTC qdisc del dev $devFIF root 2>/dev/null $cmdTC qdisc del dev $devNIF ingress 2>/dev/null if [ "$1" = "down" ]; then exit 0 fi ################################################################################################ # Create discuiplines for network interface ################################################################################################ $cmdTC qdisc add dev $devNIF root handle 1:0 htb default 12 # Create classes for network interface $cmdTC class add dev $devNIF parent 1:0 classid 1:1 htb rate ${rateLANDl} ceil ${ceilLANDl} quantum ${quantLAN} $cmdTC class add dev $devNIF parent 1:1 classid 1:11 htb rate ${rateHiDl} ceil ${ceilHiDl} quantum ${quantHi} $cmdTC class add dev $devNIF parent 1:1 classid 1:12 htb rate ${rateLoDl} ceil ${ceilLoDl} quantum ${quantLo} $cmdTC qdisc add dev $devNIF parent 1:11 handle 111: sfq perturb 10 $cmdTC qdisc add dev $devNIF parent 1:12 handle 112: sfq perturb 10 # Create filters for network interface $cmdTC filter add dev $devNIF protocol all parent 1:0 u32 match ip dst 10.252.2.0/24 flowid 1:11 $cmdTC filter add dev $devNIF protocol all parent 111: handle 111 flow hash keys dst divisor 1024 baseclass 1:11 $cmdTC filter add dev $devNIF protocol all parent 112: handle 112 flow hash keys dst divisor 1024 baseclass 1:12 ################################################################################################ # Create discuiplines for fake interface ################################################################################################ $cmdTC qdisc add dev $devFIF root handle 1:0 htb default 12 # Create classes for network interface $cmdTC class add dev $devFIF parent 1:0 classid 1:1 htb rate ${rateLANUl} ceil ${ceilLANUl} quantum ${quantLAN} $cmdTC class add dev $devFIF parent 1:1 classid 1:11 htb rate ${rateHiUl} ceil ${ceilHiUl} quantum ${quantHi} $cmdTC class add dev $devFIF parent 1:1 classid 1:12 htb rate ${rateLoUl} ceil ${ceilLoUl} quantum ${quantLo} $cmdTC qdisc add dev $devFIF parent 1:11 handle 111: sfq perturb 10 $cmdTC qdisc add dev $devFIF parent 1:12 handle 112: sfq perturb 10 # Create filters for network interface $cmdTC filter add dev $devFIF protocol all parent 1:0 u32 match ip src 10.252.2.0/24 flowid 1:11 $cmdTC filter add dev $devFIF protocol all parent 111: handle 111 flow hash keys src divisor 1024 baseclass 1:11 $cmdTC filter add dev $devFIF protocol all parent 112: handle 112 flow hash keys src divisor 1024 baseclass 1:12 ################################################################################################ # Create redirect discuiplines from network to fake interface ################################################################################################ $cmdTC qdisc add dev $devNIF handle ffff:0 ingress $cmdTC filter add dev $devNIF parent ffff:0 protocol all u32 match u32 0 0 action mirred egress redirect dev $devFIF Here is my /etc/modules: loop ifb ppp_mppe nf_conntrack_pptp nt_conntrack_proto_gre nf_nat_pptp nf_nat_proto_gre The system is Linux wall 2.6.32-5-amd64 #1 SMP Sun Sep 23 10:07:46 UTC 2012 x86_64 GNU/Linux

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  • Having a base class function depend on its child class C#

    - by Junk Junk
    I have a Base class with a method that a child class will almost always override. However, instead of replacing the base class' method entirely, I would like for whatever is derived in the child class to be added to what is already in the base class. For Example: class BaseClass public string str() { var string = "Hello my name is" ; } class ChildClass : BaseClass public override string str(){ var string = "Sam"; } The point is that if I want to access the str() method by creating an instance of the ChildClass, the string will print out as "Hello, my name is Sam". I've been looking around and all I have been finding is that this should NOT happen, as the base class shouldn't even know that it is being inherited. So, if the design is false, how would I go about doing this? Keep in mind that there will be multiple child classes inheriting from BaseClass. Thank you

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  • Java CRTP: Works for container but not for methods?

    - by Daniel
    I have a baseclass with a protected static ArrayList. I want to have a seperate ArrayList for each kind of subclass that extends this baseclass. This is when I applied CRTP: public class BaseExample<T> { protected static ArrayList<Integer> data = new ArrayList<Integer>(); } This works just fine. However, when I try to implement the following static method in the same base class, it doesn't adhere to CRTP: public static void clear() { data.clear(); } For example: class SubExample extends BaseExample<SubExample> { // insertion methods accessing 'data' field // these work fine :) } SubExample.clear(); // does not seem to clear data container Do I need to somehow explicitly specify T in my baseclass clear method? Note: These are all pure static classes.

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  • Receive messages for derived types in MVVMLight

    - by Hrvoje
    Shouldn't this test pass: [TestMethod] public void derived_message_subscription() { bool handled = false; Messenger.Default.Register<GenericMessage<baseClass>>(this, true, (msg) => handled = true); Messenger.Default.Send(new GenericMessage<testClass>(new testClass())); Assert.IsTrue(handled); } public abstract class baseClass { } public class testClass : baseClass { } I have to receive all messages for classes that inherits from one base class. MVVMLight has bool property receiveDerivedMessagesToo in Register method, but it seems to me that it isn't working.

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