C++構造函數後加：的作用

1. 初始化父類

   class Base
   {
       protected:
           int index;
       public :
           Base(int i)
               {
                   index=i;
               }
   };
   
   class Child:public Base
   {
       private:
           string name;
           float age;
       public :
           Child(int i):Base(i)
           {
               
           }
   };

    

2. 初始化引用類型變量

   class Base
   {
       protected:
           int index;
       public :
           Base(int i)
               {
                   index=i;
               }
   };
   
   class Child:public Base
   {
       private:
           string name;
           float age;
       public :
           Child(int i):name("John")
           {
               
           }
   };

    

3. 初始化值類型變量

   class Base
   {
       protected:
           int index;
       public :
           Base(int i)
               {
                   index=i;
               }
   };
   
   class Child:public Base
   {
       private:
           string name;
           float age;
       public :
           Child(int i):age(21)
           {
               
           }
   };