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• Override ActiveRecord#save, Method Alias? Trying to mixin functionality into save method...

  - by viatropos

  Here's the situation: I have a User model, and two modules for authentication: Oauth and Openid. Both of them override ActiveRecord#save, and have a fair share of implementation logic. Given that I can tell when the user is trying to login via Oauth vs. Openid, but that both of them have overridden save, how do "finally" override save such that I can conditionally call one of the modules' implementations of it? Here is the base structure of what I'm describing: module UsesOauth def self.included(base) base.class_eval do def save puts "Saving with Oauth!" end def save_with_oauth save end end end end module UsesOpenid def self.included(base) base.class_eval do def save puts "Saving with OpenID!" end def save_with_openid save end end end end module Sequencer def save if using_oauth? save_with_oauth elsif using_openid? save_with_openid else super end end end class User < ActiveRecord::Base include UsesOauth include UsesOpenid include Sequencer end I was thinking about using alias_method like so, but that got too complicated, because I might have 1 or 2 more similar modules. I also tried using those save_with_oauth methods (shown above), which almost works. The only thing that's missing is that I also need to call ActiveRecord::Base#save (the super method), so something like this: def save_with_oauth # do this and that super.save # the rest end But I'm not allowed to do that in ruby. Any ideas for a clever solution to this?

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• Why does Java's invokevirtual need to resolve the called method's compile-time class?

  - by Chris

  Consider this simple Java class: class MyClass { public void bar(MyClass c) { c.foo(); } } I want to discuss what happens on the line c.foo(). At the bytecode level, the meat of c.foo() will be the invokevirtual opcode, and, according to the documentation for invokevirtual, more or less the following will happen: Look up the foo method defined in compile-time class MyClass. (This involves first resolving MyClass.) Do some checks, including: Verify that c is not an initialization method, and verify that calling MyClass.foo wouldn't violate any protected modifiers. Figure out which method to actually call. In particular, look up c's runtime type. If that type has foo(), call that method and return. If not, look up c's runtime type's superclass; if that type has foo, call that method and return. If not, look up c's runtime type's superclass's superclass; if that type has foo, call that method and return. Etc.. If no suitable method can be found, then error. Step #3 alone seems adequate for figuring out which method to call and verifying that said method has the correct argument/return types. So my question is why step #1 gets performed in the first place. Possible answers seem to be: You don't have enough information to perform step #3 until step #1 is complete. (This seems implausible at first glance, so please explain.) The linking or access modifier checks done in #1 and #2 are essential to prevent certain bad things from happening, and those checks must be performed based on the compile-time type, rather than the run-time type hierarchy. (Please explain.)

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• Naming Suggestions For A Function Providing Method Chaining In A Different Way

  - by sid3k

  I've coded an experimental function which makes passed objects chainable by using high order functions. It's name is "chain" for now, and here is a usage example; chain("Hello World") (print) // evaluates print function by passing "Hello World" object. (console.log,"Optional","Parameters") (returnfrom) // returns "Hello World" It looks lispy but behaves very different since it's coded in a C based language, I don't know if there is a name for this idiom and I couldn't any name more suitable than "chain". Any ideas, suggestions?

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• C++ template function specialization using TCHAR on Visual Studio 2005

  - by Eli

  I'm writing a logging class that uses a templatized operator<< function. I'm specializing the template function on wide-character string so that I can do some wide-to-narrow translation before writing the log message. I can't get TCHAR to work properly - it doesn't use the specialization. Ideas? Here's the pertinent code: // Log.h header class Log { public: template <typename T> Log& operator<<( const T& x ); template <typename T> Log& operator<<( const T* x ); template <typename T> Log& operator<<( const T*& x ); ... } template <typename T> Log& Log::operator<<( const T& input ) { printf("ref"); } template <typename T> Log& Log::operator<<( const T* input ) { printf("ptr"); } template <> Log& Log::operator<<( const std::wstring& input ); template <> Log& Log::operator<<( const wchar_t* input ); And the source file // Log.cpp template <> Log& Log::operator<<( const std::wstring& input ) { printf("wstring ref"); } template <> Log& Log::operator<<( const wchar_t* input ) { printf("wchar_t ptr"); } template <> Log& Log::operator<<( const TCHAR*& input ) { printf("tchar ptr ref"); } Now, I use the following test program to exercise these functions // main.cpp - test program int main() { Log log; log << "test 1"; log << L"test 2"; std::string test3( "test3" ); log << test3; std::wstring test4( L"test4" ); log << test4; TCHAR* test5 = L"test5"; log << test4; } Running the above tests reveals the following: // Test results ptr wchar_t ptr ref wstring ref ref Unfortunately, that's not quite right. I'd really like the last one to be "TCHAR", so that I can convert it. According to Visual Studio's debugger, the when I step in to the function being called in test 5, the type is wchar_t*& - but it's not calling the appropriate specialization. Ideas? I'm not sure if it's pertinent or not, but this is on a Windows CE 5.0 device.

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• Static method , Abstract method , Interface method comparision ?

  - by programmerist

  When i choose these methods? i can not decide which one i must prefer or when will i use one of them?which one give best performance? First Type Usage public abstract class _AccessorForSQL { public virtual bool Save(string sp, ListDictionary ld, CommandType cmdType); public virtual bool Update(); public virtual bool Delete(); public virtual DataSet Select(); } class GenAccessor : _AccessorForSQL { DataSet ds; DataTable dt; public override bool Save(string sp, ListDictionary ld, CommandType cmdType) { } public override bool Update() { return true; } public override bool Delete() { return true; } public override DataSet Select() { DataSet dst = new DataSet(); return dst; } Second Type Usage Also i can write it below codes: public class GenAccessor { public Static bool Save() { } public Static bool Update() { } public Static bool Delete() { } } Third Type Usage Also i can write it below codes: public interface IAccessorForSQL { bool Delete(); bool Save(string sp, ListDictionary ld, CommandType cmdType); DataSet Select(); bool Update(); } public class _AccessorForSQL : IAccessorForSQL { private DataSet ds; private DataTable dt; public virtual bool Save(string sp, ListDictionary ld, CommandType cmdType) { } } } I can use first one below usage: GenAccessor gen = New GenAccessor(); gen.Save(); I can use second one below usage: GenAccessor.Save(); Which one do you prefer? When will i use them? which time i need override method ? which time i need static method?

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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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• Error in creating template class

  - by Luciano

  I found this vector template class implementation, but it doesn't compile on XCode. Header file: // File: myvector.h #ifndef _myvector_h #define _myvector_h template <typename ElemType> class MyVector { public: MyVector(); ~MyVector(); int size(); void add(ElemType s); ElemType getAt(int index); private: ElemType *arr; int numUsed, numAllocated; void doubleCapacity(); }; #include "myvector.cpp" #endif Implementation file: // File: myvector.cpp #include <iostream> #include "myvector.h" template <typename ElemType> MyVector<ElemType>::MyVector() { arr = new ElemType[2]; numAllocated = 2; numUsed = 0; } template <typename ElemType> MyVector<ElemType>::~MyVector() { delete[] arr; } template <typename ElemType> int MyVector<ElemType>::size() { return numUsed; } template <typename ElemType> ElemType MyVector<ElemType>::getAt(int index) { if (index < 0 || index >= size()) { std::cerr << "Out of Bounds"; abort(); } return arr[index]; } template <typename ElemType> void MyVector<ElemType>::add(ElemType s) { if (numUsed == numAllocated) doubleCapacity(); arr[numUsed++] = s; } template <typename ElemType> void MyVector<ElemType>::doubleCapacity() { ElemType *bigger = new ElemType[numAllocated*2]; for (int i = 0; i < numUsed; i++) bigger[i] = arr[i]; delete[] arr; arr = bigger; numAllocated*= 2; } If I try to compile as is, I get the following error: "Redefinition of 'MyVector::MyVector()'" The same error is displayed for every member function (.cpp file). In order to fix this, I removed the '#include "myvector.h"' on the .cpp file, but now I get a new error: "Expected constructor, destructor, or type conversion before '<' token". A similar error is displayed for every member as well. Interestingly enough, if I move all the .cpp code to the header file, it compiles fine. Does that mean I can't implement template classes in separate files?

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• Template inheritance: X is not a template

  - by user2923917

  I am trying to build a inheritance-structure which looks like: Base - template Grandpa - template Father class Base {}; template <int x> class Grandpa: public Base {}; template <int x> class Father: public Grandpa<x> {}; However, the compiler complains when compiling Father, that Grandpa is not a template. I guess it is just some synthatic issue, however everything I've tried so far led to even more compiler complaints ;) Any idea whats wrong?

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• whats the point of using template?

  - by netrox

  I am under the impression that if I set it as a template in Dreamweaver, any changes made should be saved to a new filename. I've copied the "template" that I made and sometimes I forget to save it as a different file name and it would overwrite previous web content. I just don't get the point of "save as template" if it works just like a document... it doesn't force me to save as a different filename. Common sense in me thinks that the software should evaluate like this, "if this is a template, always save as a different filename when it's modified so nothing is changed to the template, but rather a new file is created with the new content following that template." Am I missing something? Am I always doomed to using Save As...?

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• Fake Template Engine php

  - by user1464822

  i got an idea for making php template engine fast and user friendly but i'm not sure if it's good or bad. the idea is to create a fake template engine: creating a template editor in control panel that let user see something like this: <html> <head> <title>{title}</title> </head> <body> {content} </body> </html> what the editor actually does is to replace all php code like <?php echo $this->title; ?> to user friendly {title} but it's not really replacing it just in the view when the user save the template the template actually saved as fast pure php template. the question is this a good idea or bad ? your answers is highly appreciated.

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• Better solution then simple factory method when concrete implementations have different attributes

  - by danip

  abstract class Animal { function eat() {..} function sleep() {..} function isSmart() } class Dog extends Animal { public $blnCanBark; function isSmart() { return $this->blnCanBark; } } class Cat extends Animal { public $blnCanJumpHigh; function isSmart() { return $this->blnCanJumpHigh; } } .. and so on up to 10-20 animals. Now I created a factory using simple factory method and try to create instances like this: class AnimalFactory { public static function create($strName) { switch($strName) { case 'Dog': return new Dog(); case 'Cat': return new Cat(); default: break; } } } The problem is I can't set the specific attributes like blnCanBark, blnCanJumpHigh in an efficient way. I can send all of them as extra params to create but this will not scale to more then a few classes. Also I can't break the inheritance because a lot of the basic functionality is the same. Is there a better pattern to solve this?

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• Using the Specification Pattern

  - by Kane

  Like any design pattern the Specification Pattern is a great concept but susceptible to overuse by an eager architect/developer. I am about to commence development on a new application (.NET & C#) and really like the concept of the Specification Pattern and am keen to make full use of it. However before I go in all guns blazing I would be really interested in knowing if anyone could share the pain points that experienced when use the Specification Pattern in developing an application. Ideally I'm looking to see if others have had issues in Writing unit tests against the specification pattern Deciding which layer the specifications should live in (Repository, Service, Domain, etc) Using it everywhere when a simple if statement would have done the job etc? Thanks in advance

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• templated method on T inside a templated class on TT : Is that possible/correct.

  - by paercebal

  I have a class MyClass which is templated on typename T. But inside, I want a method which is templated on another type TT (which is unrelated to T). After reading/tinkering, I found the following notation: template <typename T> class MyClass { public : template<typename TT> void MyMethod(const TT & param) ; } ; For stylistic reasons (I like to have my templated class declaration in one header file, and the method definitions in another header file), I won't define the method inside the class declaration. So, I have to write it as: template <typename T> // this is the type of the class template <typename TT> // this is the type of the method void MyClass<T>::MyMethod(const TT & param) { // etc. } I knew I had to "declare" the typenames used in the method, but didn't know how exactly, and found through trials and errors. The code above compiles on Visual C++ 2008, but: Is this the correct way to have a method templated on TT inside a class templated on T? As a bonus: Are there hidden problems/surprises/constraints behind this kind of code? (I guess the specializations can be quite amusing to write)

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• Is component-based design an architectural pattern or design pattern?

  - by xEnOn

  When using the component-based paradigm in game development with engines like Unity, is component-based design an architectural pattern, or a design pattern? Can I even say that component-based design is my "main" architectural pattern for my game? I see architectural patterns as being more high-level than design pattern. The component-based design in game development's context (like with Unity engine) seems to fit as an architectural pattern to me. However, on some sites, I read that component-based design is a behavioural pattern, much like other behavioural design patterns, and not so much like an architectural pattern like MVC.

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• Calling the same xsl:template for different node names of the same complex type

  - by CraftyFella

  Hi, I'm trying to keep my xsl DRY and as a result I wanted to call the same template for 2 sections of an XML document which happen to be the same complex type (ContactDetails and AltContactDetails). Given the following XML: <?xml version="1.0" encoding="UTF-8"?> <RootNode> <Name>Bob</Name> <ContactDetails> <Address> <Line1>1 High Street</Line1> <Town>TownName</Town> <Postcode>AB1 1CD</Postcode> </Address> <Email>[email protected]</Email> </ContactDetails> <AltContactDetails> <Address> <Line1>3 Market Square</Line1> <Town>TownName</Town> <Postcode>EF2 2GH</Postcode> </Address> <Email>[email protected]</Email> </AltContactDetails> </RootNode> I wrote an XSL Stylesheet as follows: <?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"> <xsl:template match="/"> <PersonsName> <xsl:value-of select="RootNode/Name"/> </PersonsName> <xsl:call-template name="ContactDetails"> <xsl:with-param name="data"><xsl:value-of select="RootNode/ContactDetails"/></xsl:with-param> <xsl:with-param name="elementName"><xsl:value-of select="'FirstAddress'"/></xsl:with-param> </xsl:call-template> <xsl:call-template name="ContactDetails"> <xsl:with-param name="data"><xsl:value-of select="RootNode/AltContactDetails"/></xsl:with-param> <xsl:with-param name="elementName"><xsl:value-of select="'SecondAddress'"/></xsl:with-param> </xsl:call-template> </xsl:template> <xsl:template name="ContactDetails"> <xsl:param name="data"></xsl:param> <xsl:param name="elementName"></xsl:param> <xsl:element name="{$elementName}"> <FirstLine> <xsl:value-of select="$data/Address/Line1"/> </FirstLine> <Town> <xsl:value-of select="$data/Address/Town"/> </Town> <PostalCode> <xsl:value-of select="$data/Address/Postcode"/> </PostalCode> </xsl:element> </xsl:template> </xsl:stylesheet> When i try to run the style sheet it's complaining to me that I need to: To use a result tree fragment in a path expression, either use exsl:node-set() or specify version 1.1 I don't want to go to version 1.1.. So does anyone know how to get the exsl:node-set() working for the above example? Or if someone knows of a better way to apply the same template to 2 different sections then that would also really help me out? Thanks Dave

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• Ajax method within a added method in jQuery validator

  - by nikospkrk

  Hi, I'm kind of stuck with this pretty simple (I'm sure) jQuery/Javascript issue. Here's the code : jQuery.validator.addMethod("emailExists", function(value, element, param) { var email = value || ''; var valid = 0; $.ajax({ type: "POST", url: param, data: "email=" + email, success: function(msg) { if (msg != '' && msg) { valid = 0; } else { valid = 1; } } }); return valid; }, "* Email address already registered, please login."); This function is called where a user type his email address in a registration form, and everything seems to work perfectly, except that my valid variable returned isn't updated, whereas when I use an alert box it is properly done! It looks like it return the value before the AJAX is done, any idea? Cheers, Nicolas.

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• F# Active Pattern List.filter or equivalent

  - by akaphenom

  I have a records of types type tradeLeg = { id : int ; tradeId : int ; legActivity : LegActivityType ; actedOn : DateTime ; estimates : legComponents ; entryType : ShareOrDollarBased ; confirmedPrice: DollarsPerShare option; actuals : legComponents option ; type trade = { id : int ; securityId : int ; ricCode : string ; tradeActivity : TradeType ; enteredOn : DateTime ; closedOn : DateTime ; tradeLegs : tradeLeg list ; } Obviously the tradeLegs are a type off of a trade. A leg may be settled or unsettled (or unsettled but price confirmed) - thus I have defined the active pattern: let (|LegIsSettled|LegIsConfirmed|LegIsUnsettled|) (l: tradeLeg) = if Helper.exists l.actuals then LegIsSettled elif Helper.exists l.confirmedPrice then LegIsConfirmed else LegIsUnsettled and then to determine if a trade is settled (based on all legs matching LegIsSettled pattern: let (|TradeIsSettled|TradeIsUnsettled|) (t: trade) = if List.exists ( fun l -> match l with | LegIsSettled -> false | _ -> true) t.tradeLegs then TradeIsSettled else TradeIsUnsettled I can see some advantages of this use of active patterns, however i would think there is a more efficient way to see if any item of a list either matches (or doesn't) an actie pattern without having to write a lambda expression specifically for it, and using List.exist. Question is two fold: is there a more concise way to express this? is there a way to abstract the functionality / expression (fun l - match l with | LegIsSettled - false | _ - true) Such that let itemMatchesPattern pattern item = match item with | pattern -> true | _ -> false such I could write (as I am reusing this design-pattern): let curriedItemMatchesPattern = itemMatchesPattern LegIsSettled if List.exists curriedItemMatchesPattern t.tradeLegs then TradeIsSettled else TradeIsUnsettled Thoughts?

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• Print a string that contains a certain pattern in Java

  - by jjpotter

  I am trying to find a regular expression within a line of a .csv file, so I can eventually save all the matches to another file, and lose all the other junk. So a line in my file might look like: MachineName,User,IP,VariableData,Location The VariableData is what I want to match, and if there's a match, print the line. I am using a pattern for this because I only want 3 out of 10 of variations of VariableData, and out of those 3, they are numbered differently(example, "pc104, pccrt102, pccart65"). I am trying to do this using the Scanner Class and keeping it simple as possible so I can understand it. Here is where I was heading with this...(the pattern isn't complete, just have it like this for testing). import java.io.File; import java.util.Scanner; import java.util.regex.Pattern; public class pcv { public static void main(String[] args) { File myFile = new File("c:\\temp\\report.csv"); Pattern myPat = Pattern.compile("pc"); try{ Scanner myScan = new Scanner(myFile); while(myScan.hasNext()){ if(myScan.hasNext(myPat)){ System.out.println("Test"); } } }catch(Exception e){ } } } This code loops, im guessing the .hasNext() methods are resetting themselves. I've played around with the Matcher class a little bit, but only found a way to match the expression but not get the whole line. My other throught was maybe somehow count the line that contains the pattern, then go back and print the line that corresponds to the counts.

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• Does this mimic perfectly a function template specialization?

  - by zeroes00

  Since the function template in the following code is a member of a class template, it can't be specialized without specializing the enclosing class. But if the compiler's full optimizations are on (assume Visual Studio 2010), will the if-else-statement in the following code get optimized out? And if it does, wouldn't it mean that for all practical purposes this IS a function template specialization without any performance cost? template<typename T> struct Holder { T data; template<int Number> void saveReciprocalOf(); }; template<typename T> template<int Number> void Holder<T>::saveReciprocalOf() { //Will this if-else-statement get completely optimized out if(Number == 0) data = (T)0; else data = (T)1 / Number; } //----------------------------------- void main() { Holder<float> holder; holder.saveReciprocalOf<2>(); cout << holder.data << endl; }

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• How can i call an XSL template within a hyperlink in the XSL stylesheet

  - by AdRock

  I am making my own XSL stylesheet which will perform different views on the same XML document Because the XML document is so large, i would like some links at the top of the outputted page to call each template that will be used to display the data. At the moment I can create links that use anchors to a place in the document but it would be better if i just call each template as needed. How can i just call each template in a link? Would i have to use xlink? <?xml version="1.0" encoding="ISO-8859-1"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:template match="folktask"> <html> <body> <a href="folk.xml#organisers">Show all the users</a> <a href="folk.xml#organisers">Show all the festival organisers</a> <xsl:call-template name="show_all_users" /> <xsl:call-template name="show_all_organisers" /> </body> </html> </xsl:template> </xsl:stylesheet>

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• C++ explicit template specialization of templated constructor of templated class

  - by Victor Liu

  I have a class like template <class T> struct A{ template <class U> A(U u); }; I would like to write an explicit specialization of this for a declaration like A<int>::A(float); In the following test code, if I comment out the specialization, it compiles with g++. Otherwise, it says I have the wrong number of template parameters: #include <iostream> template <class T> struct A{ template <class U> A(T t, U *u){ *u += U(t); } }; template <> template <> A<int>::A<int,float>(int t, float *u){ *u += U(2*t); } int main(){ float f = 0; int i = 1; A<int>(i, &f); std::cout << f << std::endl; return 0; }

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• Is there a template for curriculum vitae in ms word 2010

  - by user23950

  Is there a template for curriculum vitae in ms word 2010? Please help, thanks

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• C# String.format extension method

  - by Paul Roe

  With the addtion of Extension methods to C# we've seen a lot of them crop up in our group. One debate revolves around extension methods like this one: public static class StringExt { /// <summary> /// Shortcut for string.Format. /// </summary> /// <param name="str"></param> /// <param name="args"></param> /// <returns></returns> public static string Format(this string str, params object[] args) { if (str == null) return null; return string.Format(str, args); } } Does this extension method break any programming best practices that you can name? Would you use it anyway, if not why? If I renamed the function to "F" but left the xml comments would that be epic fail or just a wonderful savings of keystrokes?

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• SQL SERVER – Template Browser – A Very Important and Useful Feature of SSMS

  - by pinaldave

  Let me start today’s blog post with a direction question. How many of you have ever used Template Browser? Template Browser is a very important and useful feature of SQL Server Management Studio (SSMS). Every time when I am talking about SQL Server there is always someone comes up with the question, why there is no step by step procedure included in SSMS for features. Honestly every time I get this question, the question I ask back is How many of you have ever used Template Browser? I think the answer to this question is most of the time either no or we have not heard of the feature. One of the people asked me back – have you ever written about it on your blog? I have not yet written about it. Basically there is nothing much to write about it. It is pretty straight forward feature, like any other feature and it is indeed difficult to elaborate. However, I will try to give a quick introduction to this feature. Templates are like a quick cheat sheet or quick reference. Templates are available to create objects like databases, tables, views, indexes, stored procedures, triggers, statistics, and functions. Templates are also available for Analysis Services as well. The template scripts contain parameters to help you customize the code. You can Replace Template Parameters dialog box to insert values into the script. Additionally users can create new custom templates as well with folder structure. To open a template from Template Explorer Go to View menu >> Template Explorer or type CTRL+ALT+L. You will find a list of categories click on any category and expand the folder structure. For our sample example let us expand Index Folder. In this folder you will notice the various T-SQL Scripts. These scripts can be opened by double click or can be dragged to editor area and modified as needed. Sample template is now available in the query editor area with all the necessary parameter place folder. You can replace the same parameter by typing either CTRL+SHIFT+M or by going to Query Menu >> Specify Values for Template Parameters. In this screen it will show  Specify Values for Template Parameters dialog box, accept the value or replace it with a new value. This will now get your script ready to go. Check it one more time and change the script to fit your requirement. I personally use template explorer for two things. First one is obviously for templates but the hidden one and an important one is for learning new features and T-SQL commands. There is so much to learn and so little time. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology

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• Blogger Template: How is inline style tag getting attached to img? [migrated]

  - by john Smith

  Examining a blogger template's img tag (data:post.thumbnailUrl) i've approached a mystery. An inline style tag controlling the width, margin and heigh perimeters are getting added to my img element. They are auto adjusting the images ratio to fit a smaller size. But I can't figure-out where this style tag script lives and how it's happening in my template. My template has no special javascript or jquery scripts. The full size images in the single posts page don't have this style tag. Is this a css or xml feature? element.style { margin-top: 0px; width: 301.0033444816054px; height: 200px; margin-left: -0.5016722408026908px; }

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