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  • Template inheritence c++

    - by Chris Condy
    I have made a template singleton class, I have also made a data structure that is templated. My question is; how do I make my templated data structure inherit from a singleton so you can only have one float type of this structure? I have tested both seperate and have found no problems. Code provided under... (That is the problem) template <class Type> class AbstractRManagers : public Singleton<AbstractRManagers<Type> > The problem is the code above doesn't work I get alot of errors. I cant get it to no matter what I do template a templated singleton class... I was asking for maybe advice or maybe if the code above is incorrect guidence? #ifndef SINGLETON_H #define SINGLETON_H template <class Type> class Singleton { public: virtual ~Singleton(); Singleton(); static Type* m_instance; }; template <class Type> Type* Singleton<Type>::m_instance = 0; #include "Singleton.cpp" #endif #ifndef SINGLETON_CPP #define SINGLETON_CPP #include "Singleton.h" template <class Type> Singleton<Type>::Singleton() { } template <class Type> Singleton<Type>::~Singleton() { } template <class Type> Type* Singleton<Type>::getInstance() { if(m_instance==nullptr) { m_instance = new Type; } return m_instance; } #endif #ifndef ABSTRACTRMANAGERS_H #define ABSTRACTRMANAGERS_H #include <vector> #include <map> #include <stack> #include "Singleton.h" template <class Type> class AbstractRManagers : public Singleton<AbstractRManagers<Type> > { public: virtual ~AbstractRManagers(); int insert(Type* type, std::string name); Type* remove(int i); Type* remove(std::string name); Type* get(int i); Type* getS(std::string name); int get(std::string name); int get(Type* i); bool check(std::string name); int resourceSize(); protected: private: std::vector<Type*> m_resources; std::map<std::string,int> m_map; std::stack<int> m_freePos; }; #include "AbstractRManagers.cpp" #endif #ifndef ABSTRACTRMANAGERS_CPP #define ABSTRACTRMANAGERS_CPP #include "AbstractRManagers.h" template <class Type> int AbstractRManagers<Type>::insert(Type* type, std::string name) { int i=0; if(!check(name)) { if(m_freePos.empty()) { m_resources.push_back(type); i = m_resources.size()-1; m_map[name] = i; } else { i = m_freePos.top(); m_freePos.pop(); m_resources[i] = type; m_map[name] = i; } } else i = -1; return i; } template <class Type> int AbstractRManagers<Type>::resourceSize() { return m_resources.size(); } template <class Type> bool AbstractRManagers<Type>::check(std::string name) { std::map<std::string,int>::iterator it; it = m_map.find(name); if(it==m_map.end()) return false; return true; } template <class Type> Type* AbstractRManagers<Type>::remove(std::string name) { Type* temp = m_resources[m_map[name]]; if(temp!=NULL) { std::map<std::string,int>::iterator it; it = m_map[name]; m_resources[m_map[name]] = NULL; m_freePos.push(m_map[name]); delete (*it).second; delete (*it).first; return temp; } return NULL; } template <class Type> Type* AbstractRManagers<Type>::remove(int i) { if((i < m_resources.size())&&(i > 0)) { Type* temp = m_resources[i]; m_resources[i] = NULL; m_freePos.push(i); std::map<std::string,int>::iterator it; for(it=m_map.begin();it!=m_map.end();it++) { if((*it).second == i) { delete (*it).second; delete (*it).first; return temp; } } return temp; } return NULL; } template <class Type> int AbstractRManagers<Type>::get(Type* i) { for(int i2=0;i2<m_resources.size();i2++) { if(i == m_resources[i2]) { return i2; } } return -1; } template <class Type> Type* AbstractRManagers<Type>::get(int i) { if((i < m_resources.size())&&(i >= 0)) { return m_resources[i]; } return NULL; } template <class Type> Type* AbstractRManagers<Type>::getS(std::string name) { return m_resources[m_map[name]]; } template <class Type> int AbstractRManagers<Type>::get(std::string name) { return m_map[name]; } template <class Type> AbstractRManagers<Type>::~AbstractRManagers() { } #endif #include "AbstractRManagers.h" struct b { float x; }; int main() { b* a = new b(); AbstractRManagers<b>::getInstance()->insert(a,"a"); return 0; } This program produces next errors when compiled : 1> main.cpp 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::stack<_Ty,_Container> &,const std::stack<_Ty,_Container> &)' : could not deduce template argument for 'const std::stack<_Ty,_Container> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\stack(166) : see declaration of 'std::operator <' 1> c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(124) : while compiling class template member function 'bool std::less<_Ty>::operator ()(const _Ty &,const _Ty &) const' 1> with 1> [ 1> _Ty=std::string 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\map(71) : see reference to class template instantiation 'std::less<_Ty>' being compiled 1> with 1> [ 1> _Ty=std::string 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(451) : see reference to class template instantiation 'std::_Tmap_traits<_Kty,_Ty,_Pr,_Alloc,_Mfl>' being compiled 1> with 1> [ 1> _Kty=std::string, 1> _Ty=int, 1> _Pr=std::less<std::string>, 1> _Alloc=std::allocator<std::pair<const std::string,int>>, 1> _Mfl=false 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(520) : see reference to class template instantiation 'std::_Tree_nod<_Traits>' being compiled 1> with 1> [ 1> _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false> 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(659) : see reference to class template instantiation 'std::_Tree_val<_Traits>' being compiled 1> with 1> [ 1> _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false> 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\map(81) : see reference to class template instantiation 'std::_Tree<_Traits>' being compiled 1> with 1> [ 1> _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false> 1> ] 1> c:\users\chris\desktop\311\ideas\idea1\idea1\abstractrmanagers.h(28) : see reference to class template instantiation 'std::map<_Kty,_Ty>' being compiled 1> with 1> [ 1> _Kty=std::string, 1> _Ty=int 1> ] 1> c:\users\chris\desktop\311\ideas\idea1\idea1\abstractrmanagers.h(30) : see reference to class template instantiation 'AbstractRManagers<Type>' being compiled 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::stack<_Ty,_Container> &,const std::stack<_Ty,_Container> &)' : could not deduce template argument for 'const std::stack<_Ty,_Container> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\stack(166) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::stack<_Ty,_Container> &,const std::stack<_Ty,_Container> &)' : could not deduce template argument for 'const std::stack<_Ty,_Container> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\stack(166) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::deque<_Ty,_Alloc> &,const std::deque<_Ty,_Alloc> &)' : could not deduce template argument for 'const std::deque<_Ty,_Alloc> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\deque(1725) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::deque<_Ty,_Alloc> &,const std::deque<_Ty,_Alloc> &)' : could not deduce template argument for 'const std::deque<_Ty,_Alloc> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\deque(1725) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::deque<_Ty,_Alloc> &,const std::deque<_Ty,_Alloc> &)' : could not deduce template argument for 'const std::deque<_Ty,_Alloc> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\deque(1725) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(1885) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(1885) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(1885) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::vector<_Ty,_Ax> &,const std::vector<_Ty,_Ax> &)' : could not deduce template argument for 'const std::vector<_Ty,_Ax> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\vector(1502) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::vector<_Ty,_Ax> &,const std::vector<_Ty,_Ax> &)' : could not deduce template argument for 'const std::vector<_Ty,_Ax> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\vector(1502) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::vector<_Ty,_Ax> &,const std::vector<_Ty,_Ax> &)' : could not deduce template argument for 'const std::vector<_Ty,_Ax> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\vector(1502) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\memory(2582) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\memory(2582) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\memory(2582) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1356) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1356) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1356) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1179) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1179) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1179) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(318) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(318) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(318) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2676: binary '<' : 'const std::string' does not define this operator or a conversion to a type acceptable to the predefined operator ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

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  • .Net reflection to get developers comments about class / property etc?

    - by ClarkeyBoy
    Hi, I know its unlikely but I was wondering if there is any way to get the comments (i.e. the bits after the ''') of a class or property..? I have managed to get a list of properties of a class using the PropertyInfo class but I cant find a way to get the comments / description.. I need it for a guide I am writing for the administrators of my site - it would be great if it could automatically update if new properties are added, so there is no need to worry about updating it in the future too much. Anyone know how to do this? Thanks in advance. Regards, Richard

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  • Php code not executing - dies out when trying to create an object of class - no error displayed

    - by Ali
    I'm having some problems with this piece of code. I've included a class declaration and trying to create an object of that class but my code dies out. It doesn't seem to be an include issue as all the files are being included even the files called for inclusion within the class file itself. However the object is not created - I tried to put an echo statement in the __construct function but nothing it just doesn't run infact doesn't create the object and the code won't continue from there - plus no error is reported or displayed and I have error reporting set to E_ALL and display errors set to true WHats happening here :(

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  • Indian school boy never misses a class for 14 years. Applies for Gunnies Records

    - by Gopinath
    If you ask the question “What is the most fun activity?” to school or college kids, most of the kids would say “bunking classes”. Many of us are grown up bunking classes in the name of stomachache, relatives marriage, high fever, rain or some other reason. Here is a wonder kid who is an exception of regular school kids. Mohammed Omar, a 17 year Indian school boy, never skipped his classes for the past 14 years. His attendance records shows 100% for all the 14 years of school he attended so far and it’s an unbelievable track record. Omar lives in Kanpur, a suburban in Uttar Pradesh with parents and a younger brother. He attended school even when the area where he lives was once flooded, had high temperature. When flooded and motor vehicles were not able to run on the streets he loaned a bicycle from neighbors. When he was on high temperature he just popped a tablet and headed towards the school.  Whatever may be the adverse situation, he just found a way to attend school instead of bunking. He recently applied for Guinness Book of World Records. The determination of the boy is incredible and inspiration to many young. I  wish to see this guy soon flashing on TV Channels with Guinness World Records certificates on his hands. Source: NDTV, creative common image: flickr/seeveeaar

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  • How to send a XmlSerializer Class to a WebService and then Deserialize it?

    - by pee2002
    Hi! I want to be able to send a XmlSerializer class (which is generated obvious in remote C# application) over a WebService that will then deserialize it into a class. (I didnt know it its possible either) My class is: SystemInfo I'm serializing it this way: XmlSerializer mySerializer = new XmlSerializer(typeof(SystemInfo)); StreamWriter myWriter = new StreamWriter(textBox1.Text); mySerializer.Serialize(myWriter, sysinfo); How can i build the WebService? [WebMethod] public void Reports(XmlSerializer xmlSerializer) { . . . } Can anyone help me out? Regards

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  • Could the UIHint attribute accept a property of the current class ?

    - by user252160
    I found the follwing code in MSDN . How can I change this "UnitsInStock" with a value that my Product class has. For instance, Product has a FieldType property which has a string property called Name. I'd like to use that FieldType.Name property instead of hardcoding with a string. However, I cannot specify "this", or the current instance as an argument of the UIHint attribute . Please, help using System; using System.Web.DynamicData; using System.ComponentModel.DataAnnotations; [MetadataType(typeof(ProductMetadata))] public partial class Product { } public partial class ProductMetadata { [UIHint("UnitsInStock")] [Range(100, 10000, ErrorMessage = "Units in stock should be between {1} and {2}.")] public object UnitsInStock; }

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  • Why there is perception that VB.NET is good for small to medium size application and not for enterprise class project?

    - by Gens
    I love VB.NET very much. Coding VB.NET with Visual Studio is just like typing messages. Smooth, fast and simple. Any error will be notified instantly. The OO capability of VB.NET is good enough. But often in any .Net languages discussion, there is perception that VB.NET is good for small to medium size application and not for large scale project? Why there is such perception? Or am I missing anything regarding to VB.NET?

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  • How does the Control class, provide the ForeColor, BackColor and Font default values?

    - by Miguel Angelo
    I know that component-model indicates whether a property has a default value or not, by means of ShouldSerializeValue method of PropertyDescriptor. The base windows-forms Control class, has some properties like ForeColor, BackColor and Font, that defaults to the same value of the parent, but I could not find any TypeDescriptor or PropertyDescriptor that provides these default values. The Control class does not implement ICustomTypeDescriptor nor has a TypeDescriptionProviderAttribute. How does the Control class indicates that these properties should be serialized or not? Where does it provide the PropertyDescriptors for these properties?? Thanks!!!

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  • Is windows a "second class citizen" in the django community?

    - by Daniel Upton
    I'm currently doing R&D for a web application which we plan to host ourselves initially and then allow customers to self host. My task has been evaluating web frameworks to see which would give us the biggest productivity initially and ease of maintence while also allowing us to easily support deployment to customer controlled environments. Our team has experience with ASP.NET (MVC and Webforms) and Ruby on Rails. Our experience with rails is that windows deployment is a very taboo subject and any questions on IRC or SO are met with knee jerk "why not linux" responses.. However in this case our target market may be running windows or linux servers. Is this also the case in django land? Is it possible with rubbish performance? Is it possible with lost of pain? Is it seen as reasonable and not treated as a completely stupid idea for not wanting to run linux?

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  • Accessing Singleton Instance Variable in Class Methods Throws Warning?

    - by Ross
    Hello, I've using the Objective-C singleton from here at stackoverflow. The singleton in the class method accesses it's instance variable, which works, but throws a complie warning. How should I be doing this? Is there a way to do this without accessing the sharedInstance: in each class method? for example here is my class method: + (NSString *)myClassMethods { [instanceDateFormatter setFormat:@"MM"]; return [instanceDateFormatter stringWithDate:somedate]; } line 2 will have the complie warning. Thanks, Ross

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  • metaclass multiple inheritance inconsistency

    - by Matt Anderson
    Why is this: class MyType(type): def __init__(cls, name, bases, attrs): print 'created', cls class MyMixin: __metaclass__ = MyType class MyList(list, MyMixin): pass okay, and works as expected: created <class '__main__.MyMixin'> created <class '__main__.MyList'> But this: class MyType(type): def __init__(cls, name, bases, attrs): print 'created', cls class MyMixin: __metaclass__ = MyType class MyObject(object, MyMixin): pass Is not okay, and blows up thusly?: created <class '__main__.MyMixin'> Traceback (most recent call last): File "/tmp/junk.py", line 11, in <module> class MyObject(object, MyMixin): pass TypeError: Error when calling the metaclass bases Cannot create a consistent method resolution order (MRO) for bases object, MyMixin

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  • Singleton class design in C#, are these two classes equivalent?

    - by Oskar
    I was reading up on singleton class design in C# on this great resource and decided to go with alternative 4: public sealed class Singleton1 { static readonly Singleton1 _instance = new Singleton1(); static Singleton1() { } Singleton1() { } public static Singleton1 Instance { get { return _instance; } } } Now I wonder if this can be rewritten using auto properties like this? public sealed class Singleton2 { static Singleton2() { Instance = new Singleton2(); } Singleton2() { } public static Singleton2 Instance { get; private set; } } If its only a matter of readability I definitely prefer the second version, but I want to get it right.

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  • When do you use a struct instead of a class?

    - by jkohlhepp
    What are your rules of thumb for when to use structs vs. classes? I'm thinking of the C# definition of those terms but if your language has similar concepts I'd like to hear your opinion as well. I tend to use classes for almost everything, and use structs only when something is very simplistic and should be a value type, such as a PhoneNumber or something like that. But this seems like a relatively minor use and I hope there are more interesting use cases.

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  • Is it safe to lock a static variable in a non-static class?

    - by Dario Solera
    I've got a class that manages a shared resource. Now, since access to the resource depends on many parameters, this class is instantiated and disposed several times during the normal execution of the program. The shared resource does not support concurrency, so some kind of locking is needed. The first thing that came into my mind is having a static instance in the class, and acquire locks on it, like this: // This thing is static! static readonly object MyLock = new object(); // This thing is NOT static! MyResource _resource = ...; public DoSomeWork() { lock(MyLock) { _resource.Access(); } } Does that make sense, or would you use another approach?

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  • Is it Pythonic to have a class keep track of its instances?

    - by Lightbreeze
    Take the following code snippet class Missile: instances = [] def __init__(self): Missile.instances.append(self) Now take the code: class Hero(): ... def fire(self): Missile() When the hero fires, a missile needs to be created and appended to the main list. Thus the hero object needs to reference the list when it fires. Here are a few solutions, although I'm sure there are others: Make the list a global, Use a class variable (as above), or Have the hero object hold a reference to the list. I didn't post this on gamedev because my question is actually more general: Is the previous code considered okay? Given a situation like this, is there a more Pythonic solution?

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  • break dataframe into subsets by factor values, send to function that returns glm class, how to recom

    - by Alex Holcombe
    Thanks to Hadley's plyr package ddply function we can take a dataframe, break it down into subdataframes by factors, send each to a function, and then combine the function results for each subdataframe into a new dataframe. But what if the function returns an object of a class like glm or in my case, a c("glm", "lm"). Then, these can't be combined into a dataframe can they? I get this error instead Error in as.data.frame.default(x[[i]], optional = TRUE, stringsAsFactors = stringsAsFactors) : cannot coerce class 'c("glm", "lm")' into a data.frame Is there some more flexible data structure that will accommodate all the complex glm class results of my function calls, preserving the information regarding the dataframe subsets? Or should this be done in an entirely different way?

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  • Passing List (Of ChildClass) as parameter to method expecting List (Of ParentClass)?

    - by Nicholas
    Hi, I have implemented inheritance for two parent classes called Table and Field. Each parent class has several child classes. In the Table parent class, I created a method that expects parameter List(Of Field). I get an error when trying to pass in parameter List(Of ChildField) to the method that expects a parameter of List(Of Field). The error message is as below: Value of type 'System.Collections.Generic.List(Of com.hlb.icisbatch.data.ChildField)' cannot be converted to 'System.Collections.Generic.List(Of com.hlb.icisbatch.data.Field)' My question, is it possible to pass in list of child class as parameter? If it is not a list then it works fine. But somehow it is not possible with lists? Below is sample class structure: Table Field | | ChildTable ChildField I have a method in the parent class: Public Class Table Public Sub New() End Sub Public Overridable Sub setFields(ByVal list As List(Of Field) 'Do work here' End Sub End Class and method in child class: Public Class ChildTable Public Sub New(ByVal list As List(Of ChildField) setFields(ChildField) End Sub End Class

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  • What's an elegant way to conditionally add a class to an HTML element in a view?

    - by ryeguy
    I occasionally have to add a class to an html element based on a condition. The problem is I can't figure out a clean way of doing it. Here's an example of the stuff I've tried: <div <%= if @status = 'success'; "class='ok'"; end %>> some message here </div> OR <% if @status == 'success' %> <div class='success'> <% else %> <div> <% end %> some message here </div> I don't like the first approach because it's crowded looking and hard to read. I don't like the second approach because the nesting is screwed up. It'd be nice to put it in the model, (something like @status.css_class), but that doesn't belong there. What do most people do?

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  • How to hide Amazon webstore default toolbar with Prototype?

    - by melaos
    Hi Guys, after playing around this morning, i've found that there's this default chunk of html code in the amazon webstore which will add a toolbar on top of the page. the html looks like below: <td id="wba_logo_bg"> <table class="logo" border="0" cellpadding="0" cellspacing="0" width="100%"> <tbody><tr><td align="left"></td> <td class="wba_account" style="padding: 5px;" align="right" valign="top"> <table border="0" cellpadding="0" cellspacing="0"> <form action="#" id="searchForm" method="get" name="searchForm"></form> <tbody><tr><td class="wba_account_link"> <a xmlns:xhtml="http://www.w3.org/1999/xhtml" class="myAccountNav" href="#" onclick="return false;">home</a></td> <td class="myAccountDots"></td> <td class="wba_account_link"><a class="myAccountNav" href="#" onclick="return false;">view cart</a></td> <td class="myAccountDots"></td><td class="wba_account_link"><a class="myAccountNav" href="#" onclick="return false;">my account</a></td> <td class="myAccountDots"></td><td class="wba_account_link"><a class="myAccountNav" href="#" onclick="return false;">order status</a></td> <td><img src="pageEditor_files/1_pixel.gif" hspace="7"></td> <td><input name="keyword" tabindex="1" type="text"></td> <td><img alt="Search" class="wba_search_btn" onclick="return false;" onkeyup="if (13==event.keyCode) searchForm.submit();" src="pageEditor_files/btn_search.gif" style="cursor: pointer;" tabindex="2" title="Search" hspace="3"> </td></tr></tbody> </table> </td></tr></tbody> </table> </td> and thus far i was able to use prototype to find those with the class name of wba_account_link and hide them via the codes below: function hideAmazonToolbar() { $("wba_logo_bg").hide(); }//end function but what i really want to do is preferably to hide the whole tbody instead, but with my limited prototype skills, i don't really know how to do this. can anybody point me to the right resources on how to get this done? thanks! EDIT Went higher up and apparently there's a td with an id, and solve it using prototype hide function! man, i love javascript framework :) thanks :)

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  • How can I get VS2008 winforms designer to render a Form that implements an abstract base class

    - by BeowulfOF
    Hi, I engadged a problem with inherited Controls in WinForms, and need some advice on it. I do use a base class for items in a List (selfmade GUI list made of a panel) and some inherited controls that are for each type of data that could be added to the list. There was no problem with it, but I know found out, that it would be right, to make the base-control an abstract class, since it has methods, that need to be implemented in all inherited controls, called from the code inside the base-control, but must not and can not be implemented in the base class. When I mark the base-control as abstract, the VS2008 Designer refuses to load the window. Is there any way to get the Designer work with the base-control made abstract?

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  • Why do meshes show up as bones in the Model class?

    - by Itamar Marom
    Right now I'm working on a 3D game and I've come across something very weird. When I created the model in Blender, I added an armature named "MyBone" to the stage and attached a cube ("MyCube") to it, so that when I move the armature, the cube moves with it. I exported this as an FBX and loaded it as a Model object. What I expected to see was: But what I got was this: I'm really confused. Why is the mesh I created showing up in the bone list? And what's Root Node? Here are the .blend and .fbx files: here or here. Thanks.

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  • Tool to generate a GUI (WinForms or WPF) from a class.

    - by Pat
    Say we've got a class like public class Doer { public int Timeout {get;set;} public string DoIt(string input) { string toReturn; // Do something that involves a Timeout return toReturn; } } Is there a tool that would create a Form or Control for prototyping this class? The GUI might have a NumericUpDown control with a label of "Timeout" and a GroupBox with a TextBox for "input" and a button labeled "DoIt" with an eventhandler that calls Doer.DoIt with the Text property of the input TextBox and puts the response in another TextBox.

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  • Is there a better way to create an object-oriented class with jquery?

    - by Devon
    I use the jquery extend function to extend a class prototype. For example: MyWidget = function(name_var) { this.init(name_var); } $.extend(MyWidget.prototype, { // object variables widget_name: '', init: function(widget_name) { // do initialization here this.widget_name = widget_name; }, doSomething: function() { // an example object method alert('my name is '+this.widget_name); } }); // example of using the class built above var widget1 = new MyWidget('widget one'); widget1.doSomething(); Is there a better way to do this? Is there a cleaner way to create the class above with only one statement instead of two?

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  • JQuery: is it possible to instantiate a class on client and pass it to $.ajax to post?

    - by nisardotnet
    what i mean by that is: i have a class called Customer: public class Customer { private string _firstName; private string _lastName; public string FirstName { get { return _firstName; } set { _firstName = value; } } public string LastName { get { return _lastName; } set { _lastName = value; } } } how do i instantitate the class "Customer" on the client code and add the data and post it? (not sure if this is possible) here is my client code: var customer = { "firstName": escape($('#txtFirstName').val()), "lastName": escape($('#txtLastName').val()) }; var jsonText = JSON.stringify({ customer: customer }); $.ajax( { type: "POST", url: "VisitorWS.asmx/AddCustomer", data: jsonText , //data: JSON.stringify(params), contentType: "application/json; charset=utf-8", dataType: "json", ...........

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  • Not able to delete list which dynamically created with jquery.

    - by shin
    I have two html here. The first one is dynamically generated by php and second one is just html to test. I also have the following jquery. When I click a cross with class delete in the second ones(plain html), it works nicely. However when I click a cross in the first ones, it does not work. It redirect me to the home page with # at the end. I am hoping someone point out what I am doing wrong. Thank in advance. HTML First part (dyanmicall generated) <ul style="display: block;" id="message"> <li class="41"> <span class="user"><strong>shin</strong></span> <span class="msg"> delete this as well</span> <span class="date">2010-01-15 07:47:31</span> <a href="#" id="41" class="delete">x</a> <div class="clear"></div></li> <li class="40"> <span class="user"><strong>shin</strong></span> <span class="msg"> delete me as well</span> <span class="date">2010-01-14 16:01:44</span> <a href="#" id="40" class="delete">x</a> <div class="clear"></div></li> ... ...</ul> Second part which is plain html <ul id="another"> <li><a href="#">you can't delete me</a></li> <li><a href="#" class="delete">delete this</a></li> <li><a href="#" class="delete">delete this</a></li> </ul> Here is jquery $(".delete").click(function(event) { event.preventDefault(); loading.fadeIn(); var commentContainer = $(this).parent(); var id = $(this).attr("id"); // var string = 'id='+ id ; $.ajax({ type: "POST", url: "index.php/admin/messages/changestatus/"+id, // data: string, cache: false, success: function(){ commentContainer.slideUp('slow', function() {$(this).remove();}); loading.fadeOut(); } }); return false; }); I am using CodeIgniter by the way.

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