C++ 入门教程（十二）：异常处理、文件 IO 与综合实战

1
// ===== contacts.cpp 完整可编译运行 =====
2
// g++ contacts.cpp -o contacts -std=c++17
3
#include <iostream>
4
#include <fstream>
5
#include <sstream>
6
#include <vector>
7
#include <string>
8
#include <algorithm>
9
#include <iomanip>
10

11
struct Contact {
12
    std::string name;
13
    std::string phone;
14
    std::string group;      // 分组：朋友/家人/同学...
15
};
16

17
class ContactBook {
18
    std::vector<Contact> data_;
19
    const std::string path_ = "contacts.txt";
20

21
public:
22
    class ContactError : public std::runtime_error {
23
    public: using std::runtime_error::runtime_error;
24
    };
25

26
    ContactBook() { load(); }
27
    ~ContactBook() { save(); }
28

29
    void add(const std::string& name, const std::string& phone,
30
             const std::string& group) {
31
        if (name.empty()) throw ContactError("姓名不能为空");
32
        if (find(name))   throw ContactError("联系人已存在: " + name);
33
        data_.push_back({name, phone, group});
34
    }
35

36
    bool remove(const std::string& name) {
37
        auto it = std::remove_if(data_.begin(), data_.end(),
38
            [&](const Contact& c){ return c.name == name; });
39
        if (it == data_.end()) return false;
40
        data_.erase(it, data_.end());            // erase-remove 惯用法
41
        return true;
42
    }
43

44
    const Contact* find(const std::string& name) const {
45
        auto it = std::find_if(data_.begin(), data_.end(),
46
            [&](const Contact& c){ return c.name == name; });
47
        return it == data_.end() ? nullptr : &*it;
48
    }
49

50
    void list_by_group() const {                 // 分组有序输出
51
        std::map<std::string, std::vector<std::string>> groups;
52
        for (const auto& c : data_)
53
            groups[c.group].push_back(c.name + " (" + c.phone + ")");
54

55
        for (const auto& [g, names] : groups) {
56
            std::cout << "【" << g << "】\n";
57
            for (const auto& n : names) std::cout << "  " << n << "\n";
58
        }
59
    }
60

61
    void search(const std::string& keyword) const {   // 模糊查找
62
        std::cout << "搜索 \"" << keyword << "\":\n";
63
        for (const auto& c : data_)
64
            if (c.name.find(keyword) != std::string::npos ||
65
                c.phone.find(keyword) != std::string::npos)
66
                std::cout << "  " << c.name << " " << c.phone
67
                          << " [" << c.group << "]\n";
68
    }
69

70
    size_t size() const { return data_.size(); }
71

72
private:
73
    void load() {                                // 每行: name,phone,group
74
        std::ifstream in(path_);
75
        if (!in) return;
76
        std::string line;
77
        while (std::getline(in, line)) {
78
            std::stringstream ss(line);
79
            std::string n, p, g;
80
            if (std::getline(ss, n, ',') &&
81
                std::getline(ss, p, ',') &&
82
                std::getline(ss, g))
83
                data_.push_back({n, p, g});
84
        }
85
    }
86
    void save() const {
87
        std::ofstream out(path_);                // 覆盖重写
88
        for (const auto& c : data_)
89
            out << c.name << "," << c.phone << "," << c.group << "\n";
90
    }
91
};
92

93
int main() {
94
    ContactBook book;
95

96
    std::cout << "=== 通讯录 ===\n"
97
              << "add 名字 电话 分组 | del 名字 | find 名字 | "
98
                 "search 关键词 | list | quit\n";
99

100
    std::string cmd;
101
    while (true) {
102
        std::cout << "\n> ";
103
        if (!(std::cin >> cmd)) break;
104

105
        try {
106
            if (cmd == "quit") break;
107
            else if (cmd == "add") {
108
                std::string n, p, g;
109
                std::cin >> n >> p >> g;
110
                book.add(n, p, g);
111
                std::cout << "✅ 已添加 " << n << "（共 " << book.size() << " 人）\n";
112
            }
113
            else if (cmd == "del") {
114
                std::string n; std::cin >> n;
115
                std::cout << (book.remove(n) ? "🗑 已删除" : "没找到") << "\n";
116
            }
117
            else if (cmd == "find") {
118
                std::string n; std::cin >> n;
119
                const Contact* c = book.find(n);
120
                if (c) std::cout << c->name << " " << c->phone
121
                                 << " [" << c->group << "]\n";
122
                else   std::cout << "没找到\n";
123
            }
124
            else if (cmd == "search") { std::string k; std::cin >> k; book.search(k); }
125
            else if (cmd == "list")   { book.list_by_group(); }
126
            else std::cout << "未知命令\n";
127
        }
128
        catch (const ContactBook::ContactError& e) {
129
            std::cout << "❌ " << e.what() << "\n";
130
        }
131
    }
132
    std::cout << "数据已保存，再见！\n";      // 析构也会 save
133
}