C++中的类支持声明和实现的分离 - C++中的模块化编程

C++中的类支持声明和实现的分离

1. .h头文中只有类的声明
   成员变量和成员函数的声明

2. .cpp源文件中完成类的其它实现
   成员函数的具体实现

   #ifndef _OPERATOR_H_
   #define _OPERATOR_H_
   
   class Operator
   {
   private:
       char mOp;
       double mP1;
       double mP2;
       
   public:
       bool setOperator(char op);
       void setParameter(double p1, double p2);
       bool result(double& r);
   };
   
   #endif
   #include "Operator.h"
   
   bool Operator::setOperator(char op)
   {
       bool ret = false;
           
       if( (op == '+') || (op == '-') || (op == '*') || (op == '/') )
       {
           ret = true;
           mOp = op;
       }
       else
       {
           mOp = '\0';
       }
           
       return ret;
   }
   
   void Operator::setParameter(double p1, double p2)
   {
       mP1 = p1;
       mP2 = p2;
   }
       
   bool Operator::result(double& r)
   {
       bool ret = true;
           
       switch( mOp )
       {
           case '/':
               if( (-0.000000001 < mP2) && (mP2 < 0.000000001) )
               {
                   ret = false;
               }
               else
               {
                   r = mP1 / mP2;
               }
               break;
           case '+':
               r = mP1 + mP2;
               break;
           case '*':
               r = mP1 * mP2;
               break;
           case '-':
               r = mP1 - mP2;
               break;
           default:
               ret = false;
               break;
       }
           
       return ret;
   }
   

   简化的实验

   #ifndef _TEST_H_ 
   #define _TEST_H_
   #include<iostream>
   
   class Test
   {
       int i;
   public:
       Test();
       Test(int a);
       ~Test();
       int getI();
   };
   
   #endif
   #include<iostream>
   #include"Test.h"
   using namespace std;
   
   Test::Test()
   {
       i = 0;
       cout << "Test() " << endl; 
   }
   
   Test::Test(int a)
   {
       i = a;
       cout << "Test(int a)" << endl;
   }
   
   Test::~Test()
   {
       cout << "~Test()" << endl;
   }
   
   
   int Test::getI()
   {
       return i;
   }
   #include<iostream>
   #include"Test.h"
   using namespace std;
   
   int main(int argc, const char *argv[])
   {
       Test t1;
       Test t2(100);
       Test* tp = new Test;
       delete tp;
          return 0;
   }