Re: template method gof pattern

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From: Arnaud Debaene (adebaene_at_club-internet.fr)
Date: 12/08/04 

Date: Wed, 8 Dec 2004 19:57:23 +0100

John wrote:
<snip>

You should :
- Call CTest constuctor before CStrategyBase constructor. Although not
strictly necessary in your case, it is a better style to pass a complete,
initialized CTest to CStrategyBase constructor.
- Use an explicit cast to remove the ambiguity about the constructor
overload to call.

Also, if you are not sure about using inheritance vs aggregation for
embedding a CTest into CCompositor, perhaps you should choose private
inheritance instead of public inheritance to avoid the "is-a" relationship
(Liskov principle). However, I cannot say for sure since I don't understand
what is the semantic of your classes.

Arnaud
MVP - VC

Corriged version :

class CTest
{
private:
   int i_;

public:
   int getI() { return i_; }
   void setI(const int rhs) { i_ = rhs; }

   // Construction ------------------------------------------------

   // Copying - no copy allowed, no assignment allowed
private:
   CTest(const CTest& b) {}
   CTest& operator=(const CTest& a) { return *this; }

   // Construction
public:
   CTest() : i_(1) {}
   ~CTest() {}

};

class CStrategyBase
{
private:
   int k_;

protected:
   CTest& test_;

public:
   int getK() { return k_; }
   void setK(const int rhs) { k_ = rhs; }

   // Construction --------------------------------------------------

   // Copying - no copy allowed, no assignment allowed
private:
   CStrategyBase(const CStrategyBase& b) : test_(b.test_) {}
   CStrategyBase& operator=(const CStrategyBase& a) { return *this; }

   // Construction
public:
   CStrategyBase(CTest& t) : test_(t), k_(1) {}
   virtual ~CStrategyBase() {}

};

class CCompositor : private CTest, public CStrategyBase
{
private:
   int m_;

public:
   int getM() { return m_; }
   void setM(const int rhs) { m_ = rhs; }

   // Construction -------------------------------------------------

   // Copying - no copy allowed, no assignment allowed
private:
   CCompositor(const CCompositor& b) : CStrategyBase(b.test_) {}
   CCompositor& operator=(const CCompositor& a) { return *this; }

   // Construction
public:
   CCompositor() : m_(1), CStrategyBase(*static_cast<CTest*>(this)) {}
//call CTest constructor before CStrategyBase constructor.
   virtual ~CCompositor() {}
 

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