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1.前言

本篇目的：理解模板类重写基类构造函数,子类必须重写。

2.应用实例

v1.0 模板类单个参数

#include<iostream>
#include <typeinfo>
using namespace std;

template<typename SERVICE>
class BaseA{
public:
  //explicit:当基类重写了构造函数函数,子类必须继承重写,否则与基类构造函数的类型不一致,导致报错.
  BaseA(SERVICE *ptr) : mPtr(ptr){
    printf("xxx--------->line = %d, type = %s, name = %s\n",__LINE__,typeid(SERVICE).name(),SERVICE::getName());
  }
  SERVICE *get(){
    printf("xxx--------->%s(), line = %d\n",__FUNCTION__,__LINE__);
    return mPtr;
  }
  void test(){
    printf("xxx--------->%s(), line = %d\n",__FUNCTION__,__LINE__);
  }

  //virtual void tt_01() = 0;
  SERVICE *mPtr;
};

class Parent: public BaseA<Parent>{
public:
  Parent() : BaseA<Parent>(this) {}
  static const char *getName() { return "media.audio"; }
  int value = 100;

  virtual void tt_01(){
    printf("xxx--------->%s(), line = %d\n",__FUNCTION__,__LINE__);
  }
};

class Derived: public Parent{
public:
  int count = 200;
  virtual void tt_01(){
    printf("xxx--------->%s(), line = %d\n",__FUNCTION__,__LINE__);
  }
};

int main(){
  //v1.0
  Parent *dr = new Derived;
  dr->get();
  dr->tt_01();

  //v2.0
  Parent *pt = new Parent;
  pt->tt_01();

}

v2.0 模板类两个参数

#include<iostream>
#include <typeinfo>
using namespace std;

template<typename SERVICE>
class BaseA{
public:
  //当基类重写了构造函数函数,子类必须继承重写,否则与基类构造函数的类型不一致,导致报错.
  //模板函数提供了两个参数.
  BaseA(SERVICE *ptr, int c) : mPtr(ptr),m_c(c){
    printf("xxx--------->line = %d, type = %s, name = %s\n",__LINE__,typeid(SERVICE).name(),SERVICE::getName());
  }
  SERVICE *get(){
    printf("xxx--------->%s(), line = %d\n",__FUNCTION__,__LINE__);
    return mPtr;
  }
  void test(){
    printf("xxx--------->%s(), line = %d\n",__FUNCTION__,__LINE__);
  }

  virtual void tt_01() = 0;
  SERVICE *mPtr;
  int m_c;
};

class Parent: public BaseA<Parent>{
public:
  Parent(int c) : BaseA<Parent>(this, c) {}
  static const char *getName() { return "media.audio"; }
  int value = 100;

  virtual void tt_01(){
    printf("xxx--------->%s(), line = %d\n",__FUNCTION__,__LINE__);
  }
};

class Derived: public Parent{
public:
  Derived(int c) : Parent(c) {}
  int count = 200;
  virtual void tt_01(){
    printf("xxx--------->%s(), line = %d\n",__FUNCTION__,__LINE__);
  }
};

int main(){
  //v1.0
  Parent *dr = new Derived(2);
  dr->get();
  dr->tt_01();

  //v2.0
  Parent *pt = new Parent(1);
  pt->tt_01();

}

3.总结

1.当基类重写了构造函数函数,子类必须继承重写,否则与基类构造函数的类型不一致,导致报错.