C++ 靜態成員變數與靜態成員函數完整實作範例

需求

• 靜態 char ServerName 保存伺服器名稱
• 靜態 int ClientNum 記錄客戶數量
• 靜態函數 ChangeServerName() 修改名稱
• 分離宣告 (client.h)、實作 (client.cpp)、測試 (test.cpp)

client.h

#ifndef CLIENT_H
#define CLIENT_H

class CLIENT {
public:
    CLIENT(char name, int num); // 建構子同步更新靜態成員 (示範用)
    ~CLIENT();
    static void ChangeServerName(char newName);
    static char GetServerName();
    static int GetClientNum();
private:
    static char ServerName; // 僅宣告
    static int ClientNum;
};

#endif

client.cpp (關鍵：定義靜態成員)

#include "client.h"
#include 

// 靜態成員必須在全域/命名空間範圍定義並初始化
char CLIENT::ServerName = 'I';
int  CLIENT::ClientNum = 0;

CLIENT::CLIENT(char name, int num) {
    ServerName = name;
    ClientNum = num;
}
CLIENT::~CLIENT() {}

void CLIENT::ChangeServerName(char newName) {
    ServerName = newName;
}
char CLIENT::GetServerName() { return ServerName; }
int  CLIENT::GetClientNum() { return ClientNum; }

test.cpp

#include "client.h"
#include 

int main() {
    CLIENT n('W', 7); // 建構子更新靜態值
    std::cout << "Server: " << CLIENT::GetServerName() << "\n";
    std::cout << "Clients: " << CLIENT::GetClientNum() << "\n";

    CLIENT::ChangeServerName('X');
    std::cout << "After change: " << CLIENT::GetServerName() << "\n";
    return 0;
}

編譯指令

g++ client.cpp test.cpp -o test
./test

關鍵知識點