[C++基础]宏定义中操作符(#,##)的使用

# 和 ## 在宏定义（define）中经常可以看到，是预编译过程中的常用语句

• ##是一个连接符号，用于把参数连在一起
• #是“字符串化”的意思。出现在宏定义中的#是把跟在后面的参数转换成一个字符串

#define CONVERT(name) #name
#define CAT(batman, robin) batman##robin
#define make_friend(index) printf("You and %s are friends.\n", CAT(james, index));
	int
	main()
{
	printf("You and %s are friends.\n", CONVERT(JamesXXX));

	char *james001 = "fake James 001";
	char *james007 = "James Bond";
	char *james110 = "fake James 110";
	make_friend(001);
	make_friend(007);
	make_friend(110);
	return 0;
}
//输出
// You and JamesXXX are friends.
// You and fake James 001 are friends.
// You and James Bond are friends.
// You and fake James 110 are friends.

实际使用实例

类内成员访问

#include <string>
#include <iostream>
#ifndef PROPERTY_INIT
#define PROPERTY_INIT(ptype, fname, proper) \
	void set##fname(ptype val)              \
	{                                       \
		proper = val;                       \
	}                                       \
	ptype get##fname()                      \
	{                                       \
		return proper;                      \
	}
#endif

class OE
{
  public:
	PROPERTY_INIT(const std::string &, Name, name_)
	PROPERTY_INIT(int, Age, age_)
	PROPERTY_INIT(bool, Sex, sex_)
  private:
	int age_ = 18;
	std::string name_ = "chenluyong";
	bool sex_ = true;
};

int main()
{
	OE oe;
	oe.setAge(28);
	std::cout << oe.getName() << std::endl; //chenluyong
	std::cout << oe.getSex() << std::endl;  //1
	std::cout << oe.getAge() << std::endl;  //28
	return 0;
}

优雅的成员变量

// 只读属性
#ifndef PROPERTY_R
#define PROPERTY_R(xtype, xname, proper)         \
  private:                                       \
	void set##xname(xtype val) { proper = val; } \
                                                 \
  public:                                        \
	xtype get##xname() { return proper; }        \
                                                 \
  private:                                       \
	xtype proper;
#endif

// 读写属性
#ifndef PROPERTY_RW
#define PROPERTY_RW(xtype, xname, proper)        \
  public:                                        \
	void set##xname(xtype val) { proper = val; } \
                                                 \
  public:                                        \
	xtype get##xname() { return proper; }        \
                                                 \
  private:                                       \
	xtype proper;
#endif

class OEA
{
	PROPERTY_RW(int, Age, age_);
	PROPERTY_RW(std::string, Name, name_);
};
int main()
{
	OEA oe;
	oe.setAge(78);
	oe.setName("hello");
	std::cout << oe.getName() << std::endl; //hello
	std::cout << oe.getAge() << std::endl;  //78
	return 0;
}