具有模板成员变量的C++类

class Diagram
private:
    std::vector<Parameter<T> > v;
};

class ParameterBase
public:
    virtual void setValue() = 0;
    virtual ~ParameterBase() { }
template <typename T>
class Parameter : public ParameterBase
public:
    void setValue() // I want this to be 
                    // void setValue(const T & val)
        // I want this to be 
        // value = val;
private:
    T value;
class Diagram
public:
    std::vector<ParameterBase *> v;
    int type;
};

#include <vector>
#include <memory>
class Parameter
private:
  class ParameterBase {
  public:
    virtual ~ParameterBase() {}
    virtual ParameterBase* copy() = 0;
    virtual void foo() = 0;
  template <typename T>
  class ParameterModel : public ParameterBase {
  public:
    // take by value so we simply move twice, if movable
    ParameterModel(const T& t) : t(t) {}
    ParameterModel(T&& t) : t(t) {}
    void foo() { t.foo(); }
    ParameterModel* copy() { return new ParameterModel(*this); }
  private:
public:
  template <typename T>
  Parameter(T&& t) 
    : pp(new ParameterModel< typename std::remove_reference<T>::type >(std::forward<T>(t))) {}
  // Movable and Copyable only
  Parameter(Parameter&&) = default;
  Parameter& operator=(Parameter&&) = default;
  Parameter(const Parameter& other) : pp(other.pp->copy()) {};
  Parameter operator=(const Parameter& other) {
    pp.reset(other.pp->copy());
    return *this;
  // members
  void foo() { pp->foo(); }
private:
  std::unique_ptr<ParameterBase> pp;
class Diagram
public:
  std::vector<Parameter> v;
  int type;
struct X {
  void foo() {}
struct Y {
  void foo() {}
int main()
  Diagram d;
  d.v.emplace_back(X()); // int
  // parameters are copyable and can be reassigned even with different
  // impls
  Parameter p = d.v.back();
  Parameter other((Y()));
  other = p;
  return 0;
}

class ParameterBase
public:
    virtual ~ParameterBase() {}
    template<class T> const T& get() const; //to be implimented after Parameter
    template<class T, class U> void setValue(const U& rhs); //to be implimented after Parameter
template <typename T>
class Parameter : public ParameterBase
public:
    Parameter(const T& rhs) :value(rhs) {}
    const T& get() const {return value;}
    void setValue(const T& rhs) {value=rhs;}    
private:
    T value;
//Here's the trick: dynamic_cast rather than virtual
template<class T> const T& ParameterBase::get() const
{ return dynamic_cast<const Parameter<T>&>(*this).get(); }
template<class T, class U> void ParameterBase::setValue(const U& rhs)
{ return dynamic_cast<Parameter<T>&>(*this).setValue(rhs); }
class Diagram
public:
    std::vector<ParameterBase*> v;

具有模板成员变量的C++类

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